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28
vendor/github.com/chai2010/image/qrencoder/hello.go generated vendored Normal file
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// Copyright 2015 <chaishushan{AT}gmail.com>. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build ingore
package main
import (
"fmt"
"io/ioutil"
"log"
qr "github.com/chai2010/image/qrencoder"
)
func main() {
c, err := qr.Encode("hello, world", qr.L)
if err != nil {
log.Fatal(err)
}
err = ioutil.WriteFile("zz_qrout.png", c.PNG(), 0666)
if err != nil {
log.Fatal(err)
}
fmt.Print("output: zz_qrout.png\n")
}

149
vendor/github.com/chai2010/image/qrencoder/internal/coding/gen.go generated vendored Normal file
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// +build ignore
package main
import "fmt"
// tables from qrencode-3.1.1/qrspec.c
var capacity = [41]struct {
width int
words int
remainder int
ec [4]int
}{
{0, 0, 0, [4]int{0, 0, 0, 0}},
{21, 26, 0, [4]int{7, 10, 13, 17}}, // 1
{25, 44, 7, [4]int{10, 16, 22, 28}},
{29, 70, 7, [4]int{15, 26, 36, 44}},
{33, 100, 7, [4]int{20, 36, 52, 64}},
{37, 134, 7, [4]int{26, 48, 72, 88}}, // 5
{41, 172, 7, [4]int{36, 64, 96, 112}},
{45, 196, 0, [4]int{40, 72, 108, 130}},
{49, 242, 0, [4]int{48, 88, 132, 156}},
{53, 292, 0, [4]int{60, 110, 160, 192}},
{57, 346, 0, [4]int{72, 130, 192, 224}}, //10
{61, 404, 0, [4]int{80, 150, 224, 264}},
{65, 466, 0, [4]int{96, 176, 260, 308}},
{69, 532, 0, [4]int{104, 198, 288, 352}},
{73, 581, 3, [4]int{120, 216, 320, 384}},
{77, 655, 3, [4]int{132, 240, 360, 432}}, //15
{81, 733, 3, [4]int{144, 280, 408, 480}},
{85, 815, 3, [4]int{168, 308, 448, 532}},
{89, 901, 3, [4]int{180, 338, 504, 588}},
{93, 991, 3, [4]int{196, 364, 546, 650}},
{97, 1085, 3, [4]int{224, 416, 600, 700}}, //20
{101, 1156, 4, [4]int{224, 442, 644, 750}},
{105, 1258, 4, [4]int{252, 476, 690, 816}},
{109, 1364, 4, [4]int{270, 504, 750, 900}},
{113, 1474, 4, [4]int{300, 560, 810, 960}},
{117, 1588, 4, [4]int{312, 588, 870, 1050}}, //25
{121, 1706, 4, [4]int{336, 644, 952, 1110}},
{125, 1828, 4, [4]int{360, 700, 1020, 1200}},
{129, 1921, 3, [4]int{390, 728, 1050, 1260}},
{133, 2051, 3, [4]int{420, 784, 1140, 1350}},
{137, 2185, 3, [4]int{450, 812, 1200, 1440}}, //30
{141, 2323, 3, [4]int{480, 868, 1290, 1530}},
{145, 2465, 3, [4]int{510, 924, 1350, 1620}},
{149, 2611, 3, [4]int{540, 980, 1440, 1710}},
{153, 2761, 3, [4]int{570, 1036, 1530, 1800}},
{157, 2876, 0, [4]int{570, 1064, 1590, 1890}}, //35
{161, 3034, 0, [4]int{600, 1120, 1680, 1980}},
{165, 3196, 0, [4]int{630, 1204, 1770, 2100}},
{169, 3362, 0, [4]int{660, 1260, 1860, 2220}},
{173, 3532, 0, [4]int{720, 1316, 1950, 2310}},
{177, 3706, 0, [4]int{750, 1372, 2040, 2430}}, //40
}
var eccTable = [41][4][2]int{
{{0, 0}, {0, 0}, {0, 0}, {0, 0}},
{{1, 0}, {1, 0}, {1, 0}, {1, 0}}, // 1
{{1, 0}, {1, 0}, {1, 0}, {1, 0}},
{{1, 0}, {1, 0}, {2, 0}, {2, 0}},
{{1, 0}, {2, 0}, {2, 0}, {4, 0}},
{{1, 0}, {2, 0}, {2, 2}, {2, 2}}, // 5
{{2, 0}, {4, 0}, {4, 0}, {4, 0}},
{{2, 0}, {4, 0}, {2, 4}, {4, 1}},
{{2, 0}, {2, 2}, {4, 2}, {4, 2}},
{{2, 0}, {3, 2}, {4, 4}, {4, 4}},
{{2, 2}, {4, 1}, {6, 2}, {6, 2}}, //10
{{4, 0}, {1, 4}, {4, 4}, {3, 8}},
{{2, 2}, {6, 2}, {4, 6}, {7, 4}},
{{4, 0}, {8, 1}, {8, 4}, {12, 4}},
{{3, 1}, {4, 5}, {11, 5}, {11, 5}},
{{5, 1}, {5, 5}, {5, 7}, {11, 7}}, //15
{{5, 1}, {7, 3}, {15, 2}, {3, 13}},
{{1, 5}, {10, 1}, {1, 15}, {2, 17}},
{{5, 1}, {9, 4}, {17, 1}, {2, 19}},
{{3, 4}, {3, 11}, {17, 4}, {9, 16}},
{{3, 5}, {3, 13}, {15, 5}, {15, 10}}, //20
{{4, 4}, {17, 0}, {17, 6}, {19, 6}},
{{2, 7}, {17, 0}, {7, 16}, {34, 0}},
{{4, 5}, {4, 14}, {11, 14}, {16, 14}},
{{6, 4}, {6, 14}, {11, 16}, {30, 2}},
{{8, 4}, {8, 13}, {7, 22}, {22, 13}}, //25
{{10, 2}, {19, 4}, {28, 6}, {33, 4}},
{{8, 4}, {22, 3}, {8, 26}, {12, 28}},
{{3, 10}, {3, 23}, {4, 31}, {11, 31}},
{{7, 7}, {21, 7}, {1, 37}, {19, 26}},
{{5, 10}, {19, 10}, {15, 25}, {23, 25}}, //30
{{13, 3}, {2, 29}, {42, 1}, {23, 28}},
{{17, 0}, {10, 23}, {10, 35}, {19, 35}},
{{17, 1}, {14, 21}, {29, 19}, {11, 46}},
{{13, 6}, {14, 23}, {44, 7}, {59, 1}},
{{12, 7}, {12, 26}, {39, 14}, {22, 41}}, //35
{{6, 14}, {6, 34}, {46, 10}, {2, 64}},
{{17, 4}, {29, 14}, {49, 10}, {24, 46}},
{{4, 18}, {13, 32}, {48, 14}, {42, 32}},
{{20, 4}, {40, 7}, {43, 22}, {10, 67}},
{{19, 6}, {18, 31}, {34, 34}, {20, 61}}, //40
}
var align = [41][2]int{
{0, 0},
{0, 0}, {18, 0}, {22, 0}, {26, 0}, {30, 0}, // 1- 5
{34, 0}, {22, 38}, {24, 42}, {26, 46}, {28, 50}, // 6-10
{30, 54}, {32, 58}, {34, 62}, {26, 46}, {26, 48}, //11-15
{26, 50}, {30, 54}, {30, 56}, {30, 58}, {34, 62}, //16-20
{28, 50}, {26, 50}, {30, 54}, {28, 54}, {32, 58}, //21-25
{30, 58}, {34, 62}, {26, 50}, {30, 54}, {26, 52}, //26-30
{30, 56}, {34, 60}, {30, 58}, {34, 62}, {30, 54}, //31-35
{24, 50}, {28, 54}, {32, 58}, {26, 54}, {30, 58}, //35-40
}
var versionPattern = [41]int{
0,
0, 0, 0, 0, 0, 0,
0x07c94, 0x085bc, 0x09a99, 0x0a4d3, 0x0bbf6, 0x0c762, 0x0d847, 0x0e60d,
0x0f928, 0x10b78, 0x1145d, 0x12a17, 0x13532, 0x149a6, 0x15683, 0x168c9,
0x177ec, 0x18ec4, 0x191e1, 0x1afab, 0x1b08e, 0x1cc1a, 0x1d33f, 0x1ed75,
0x1f250, 0x209d5, 0x216f0, 0x228ba, 0x2379f, 0x24b0b, 0x2542e, 0x26a64,
0x27541, 0x28c69,
}
func main() {
fmt.Printf("\t{},\n")
for i := 1; i <= 40; i++ {
apos := align[i][0] - 2
if apos < 0 {
apos = 100
}
astride := align[i][1] - align[i][0]
if astride < 1 {
astride = 100
}
fmt.Printf("\t{%v, %v, %v, %#x, [4]level{{%v, %v}, {%v, %v}, {%v, %v}, {%v, %v}}}, // %v\n",
apos, astride, capacity[i].words,
versionPattern[i],
eccTable[i][0][0]+eccTable[i][0][1],
float64(capacity[i].ec[0])/float64(eccTable[i][0][0]+eccTable[i][0][1]),
eccTable[i][1][0]+eccTable[i][1][1],
float64(capacity[i].ec[1])/float64(eccTable[i][1][0]+eccTable[i][1][1]),
eccTable[i][2][0]+eccTable[i][2][1],
float64(capacity[i].ec[2])/float64(eccTable[i][2][0]+eccTable[i][2][1]),
eccTable[i][3][0]+eccTable[i][3][1],
float64(capacity[i].ec[3])/float64(eccTable[i][3][0]+eccTable[i][3][1]),
i,
)
}
}

815
vendor/github.com/chai2010/image/qrencoder/internal/coding/qr.go generated vendored Normal file
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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package coding implements low-level QR coding details.
package coding
import (
"fmt"
"strconv"
"strings"
"github.com/chai2010/image/qrencoder/internal/gf256"
)
// Field is the field for QR error correction.
var Field = gf256.NewField(0x11d, 2)
// A Version represents a QR version.
// The version specifies the size of the QR code:
// a QR code with version v has 4v+17 pixels on a side.
// Versions number from 1 to 40: the larger the version,
// the more information the code can store.
type Version int
const MinVersion = 1
const MaxVersion = 40
func (v Version) String() string {
return strconv.Itoa(int(v))
}
func (v Version) sizeClass() int {
if v <= 9 {
return 0
}
if v <= 26 {
return 1
}
return 2
}
// DataBytes returns the number of data bytes that can be
// stored in a QR code with the given version and level.
func (v Version) DataBytes(l Level) int {
vt := &vtab[v]
lev := &vt.level[l]
return vt.bytes - lev.nblock*lev.check
}
// Encoding implements a QR data encoding scheme.
// The implementations--Numeric, Alphanumeric, and String--specify
// the character set and the mapping from UTF-8 to code bits.
// The more restrictive the mode, the fewer code bits are needed.
type Encoding interface {
Check() error
Bits(v Version) int
Encode(b *Bits, v Version)
}
type Bits struct {
b []byte
nbit int
}
func (b *Bits) Reset() {
b.b = b.b[:0]
b.nbit = 0
}
func (b *Bits) Bits() int {
return b.nbit
}
func (b *Bits) Bytes() []byte {
if b.nbit%8 != 0 {
panic("fractional byte")
}
return b.b
}
func (b *Bits) Append(p []byte) {
if b.nbit%8 != 0 {
panic("fractional byte")
}
b.b = append(b.b, p...)
b.nbit += 8 * len(p)
}
func (b *Bits) Write(v uint, nbit int) {
for nbit > 0 {
n := nbit
if n > 8 {
n = 8
}
if b.nbit%8 == 0 {
b.b = append(b.b, 0)
} else {
m := -b.nbit & 7
if n > m {
n = m
}
}
b.nbit += n
sh := uint(nbit - n)
b.b[len(b.b)-1] |= uint8(v >> sh << uint(-b.nbit&7))
v -= v >> sh << sh
nbit -= n
}
}
// Num is the encoding for numeric data.
// The only valid characters are the decimal digits 0 through 9.
type Num string
func (s Num) String() string {
return fmt.Sprintf("Num(%#q)", string(s))
}
func (s Num) Check() error {
for _, c := range s {
if c < '0' || '9' < c {
return fmt.Errorf("non-numeric string %#q", string(s))
}
}
return nil
}
var numLen = [3]int{10, 12, 14}
func (s Num) Bits(v Version) int {
return 4 + numLen[v.sizeClass()] + (10*len(s)+2)/3
}
func (s Num) Encode(b *Bits, v Version) {
b.Write(1, 4)
b.Write(uint(len(s)), numLen[v.sizeClass()])
var i int
for i = 0; i+3 <= len(s); i += 3 {
w := uint(s[i]-'0')*100 + uint(s[i+1]-'0')*10 + uint(s[i+2]-'0')
b.Write(w, 10)
}
switch len(s) - i {
case 1:
w := uint(s[i] - '0')
b.Write(w, 4)
case 2:
w := uint(s[i]-'0')*10 + uint(s[i+1]-'0')
b.Write(w, 7)
}
}
// Alpha is the encoding for alphanumeric data.
// The valid characters are 0-9A-Z$%*+-./: and space.
type Alpha string
const alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:"
func (s Alpha) String() string {
return fmt.Sprintf("Alpha(%#q)", string(s))
}
func (s Alpha) Check() error {
for _, c := range s {
if strings.IndexRune(alphabet, c) < 0 {
return fmt.Errorf("non-alphanumeric string %#q", string(s))
}
}
return nil
}
var alphaLen = [3]int{9, 11, 13}
func (s Alpha) Bits(v Version) int {
return 4 + alphaLen[v.sizeClass()] + (11*len(s)+1)/2
}
func (s Alpha) Encode(b *Bits, v Version) {
b.Write(2, 4)
b.Write(uint(len(s)), alphaLen[v.sizeClass()])
var i int
for i = 0; i+2 <= len(s); i += 2 {
w := uint(strings.IndexRune(alphabet, rune(s[i])))*45 +
uint(strings.IndexRune(alphabet, rune(s[i+1])))
b.Write(w, 11)
}
if i < len(s) {
w := uint(strings.IndexRune(alphabet, rune(s[i])))
b.Write(w, 6)
}
}
// String is the encoding for 8-bit data. All bytes are valid.
type String string
func (s String) String() string {
return fmt.Sprintf("String(%#q)", string(s))
}
func (s String) Check() error {
return nil
}
var stringLen = [3]int{8, 16, 16}
func (s String) Bits(v Version) int {
return 4 + stringLen[v.sizeClass()] + 8*len(s)
}
func (s String) Encode(b *Bits, v Version) {
b.Write(4, 4)
b.Write(uint(len(s)), stringLen[v.sizeClass()])
for i := 0; i < len(s); i++ {
b.Write(uint(s[i]), 8)
}
}
// A Pixel describes a single pixel in a QR code.
type Pixel uint32
const (
Black Pixel = 1 << iota
Invert
)
func (p Pixel) Offset() uint {
return uint(p >> 6)
}
func OffsetPixel(o uint) Pixel {
return Pixel(o << 6)
}
func (r PixelRole) Pixel() Pixel {
return Pixel(r << 2)
}
func (p Pixel) Role() PixelRole {
return PixelRole(p>>2) & 15
}
func (p Pixel) String() string {
s := p.Role().String()
if p&Black != 0 {
s += "+black"
}
if p&Invert != 0 {
s += "+invert"
}
s += "+" + strconv.FormatUint(uint64(p.Offset()), 10)
return s
}
// A PixelRole describes the role of a QR pixel.
type PixelRole uint32
const (
_ PixelRole = iota
Position // position squares (large)
Alignment // alignment squares (small)
Timing // timing strip between position squares
Format // format metadata
PVersion // version pattern
Unused // unused pixel
Data // data bit
Check // error correction check bit
Extra
)
var roles = []string{
"",
"position",
"alignment",
"timing",
"format",
"pversion",
"unused",
"data",
"check",
"extra",
}
func (r PixelRole) String() string {
if Position <= r && r <= Check {
return roles[r]
}
return strconv.Itoa(int(r))
}
// A Level represents a QR error correction level.
// From least to most tolerant of errors, they are L, M, Q, H.
type Level int
const (
L Level = iota
M
Q
H
)
func (l Level) String() string {
if L <= l && l <= H {
return "LMQH"[l : l+1]
}
return strconv.Itoa(int(l))
}
// A Code is a square pixel grid.
type Code struct {
Bitmap []byte // 1 is black, 0 is white
Size int // number of pixels on a side
Stride int // number of bytes per row
}
func (c *Code) Black(x, y int) bool {
return 0 <= x && x < c.Size && 0 <= y && y < c.Size &&
c.Bitmap[y*c.Stride+x/8]&(1<<uint(7-x&7)) != 0
}
// A Mask describes a mask that is applied to the QR
// code to avoid QR artifacts being interpreted as
// alignment and timing patterns (such as the squares
// in the corners). Valid masks are integers from 0 to 7.
type Mask int
// http://www.swetake.com/qr/qr5_en.html
var mfunc = []func(int, int) bool{
func(i, j int) bool { return (i+j)%2 == 0 },
func(i, j int) bool { return i%2 == 0 },
func(i, j int) bool { return j%3 == 0 },
func(i, j int) bool { return (i+j)%3 == 0 },
func(i, j int) bool { return (i/2+j/3)%2 == 0 },
func(i, j int) bool { return i*j%2+i*j%3 == 0 },
func(i, j int) bool { return (i*j%2+i*j%3)%2 == 0 },
func(i, j int) bool { return (i*j%3+(i+j)%2)%2 == 0 },
}
func (m Mask) Invert(y, x int) bool {
if m < 0 {
return false
}
return mfunc[m](y, x)
}
// A Plan describes how to construct a QR code
// with a specific version, level, and mask.
type Plan struct {
Version Version
Level Level
Mask Mask
DataBytes int // number of data bytes
CheckBytes int // number of error correcting (checksum) bytes
Blocks int // number of data blocks
Pixel [][]Pixel // pixel map
}
// NewPlan returns a Plan for a QR code with the given
// version, level, and mask.
func NewPlan(version Version, level Level, mask Mask) (*Plan, error) {
p, err := vplan(version)
if err != nil {
return nil, err
}
if err := fplan(level, mask, p); err != nil {
return nil, err
}
if err := lplan(version, level, p); err != nil {
return nil, err
}
if err := mplan(mask, p); err != nil {
return nil, err
}
return p, nil
}
func (b *Bits) Pad(n int) {
if n < 0 {
panic("qr: invalid pad size")
}
if n <= 4 {
b.Write(0, n)
} else {
b.Write(0, 4)
n -= 4
n -= -b.Bits() & 7
b.Write(0, -b.Bits()&7)
pad := n / 8
for i := 0; i < pad; i += 2 {
b.Write(0xec, 8)
if i+1 >= pad {
break
}
b.Write(0x11, 8)
}
}
}
func (b *Bits) AddCheckBytes(v Version, l Level) {
nd := v.DataBytes(l)
if b.nbit < nd*8 {
b.Pad(nd*8 - b.nbit)
}
if b.nbit != nd*8 {
panic("qr: too much data")
}
dat := b.Bytes()
vt := &vtab[v]
lev := &vt.level[l]
db := nd / lev.nblock
extra := nd % lev.nblock
chk := make([]byte, lev.check)
rs := gf256.NewRSEncoder(Field, lev.check)
for i := 0; i < lev.nblock; i++ {
if i == lev.nblock-extra {
db++
}
rs.ECC(dat[:db], chk)
b.Append(chk)
dat = dat[db:]
}
if len(b.Bytes()) != vt.bytes {
panic("qr: internal error")
}
}
func (p *Plan) Encode(text ...Encoding) (*Code, error) {
var b Bits
for _, t := range text {
if err := t.Check(); err != nil {
return nil, err
}
t.Encode(&b, p.Version)
}
if b.Bits() > p.DataBytes*8 {
return nil, fmt.Errorf("cannot encode %d bits into %d-bit code", b.Bits(), p.DataBytes*8)
}
b.AddCheckBytes(p.Version, p.Level)
bytes := b.Bytes()
// Now we have the checksum bytes and the data bytes.
// Construct the actual code.
c := &Code{Size: len(p.Pixel), Stride: (len(p.Pixel) + 7) &^ 7}
c.Bitmap = make([]byte, c.Stride*c.Size)
crow := c.Bitmap
for _, row := range p.Pixel {
for x, pix := range row {
switch pix.Role() {
case Data, Check:
o := pix.Offset()
if bytes[o/8]&(1<<uint(7-o&7)) != 0 {
pix ^= Black
}
}
if pix&Black != 0 {
crow[x/8] |= 1 << uint(7-x&7)
}
}
crow = crow[c.Stride:]
}
return c, nil
}
// A version describes metadata associated with a version.
type version struct {
apos int
astride int
bytes int
pattern int
level [4]level
}
type level struct {
nblock int
check int
}
var vtab = []version{
{},
{100, 100, 26, 0x0, [4]level{{1, 7}, {1, 10}, {1, 13}, {1, 17}}}, // 1
{16, 100, 44, 0x0, [4]level{{1, 10}, {1, 16}, {1, 22}, {1, 28}}}, // 2
{20, 100, 70, 0x0, [4]level{{1, 15}, {1, 26}, {2, 18}, {2, 22}}}, // 3
{24, 100, 100, 0x0, [4]level{{1, 20}, {2, 18}, {2, 26}, {4, 16}}}, // 4
{28, 100, 134, 0x0, [4]level{{1, 26}, {2, 24}, {4, 18}, {4, 22}}}, // 5
{32, 100, 172, 0x0, [4]level{{2, 18}, {4, 16}, {4, 24}, {4, 28}}}, // 6
{20, 16, 196, 0x7c94, [4]level{{2, 20}, {4, 18}, {6, 18}, {5, 26}}}, // 7
{22, 18, 242, 0x85bc, [4]level{{2, 24}, {4, 22}, {6, 22}, {6, 26}}}, // 8
{24, 20, 292, 0x9a99, [4]level{{2, 30}, {5, 22}, {8, 20}, {8, 24}}}, // 9
{26, 22, 346, 0xa4d3, [4]level{{4, 18}, {5, 26}, {8, 24}, {8, 28}}}, // 10
{28, 24, 404, 0xbbf6, [4]level{{4, 20}, {5, 30}, {8, 28}, {11, 24}}}, // 11
{30, 26, 466, 0xc762, [4]level{{4, 24}, {8, 22}, {10, 26}, {11, 28}}}, // 12
{32, 28, 532, 0xd847, [4]level{{4, 26}, {9, 22}, {12, 24}, {16, 22}}}, // 13
{24, 20, 581, 0xe60d, [4]level{{4, 30}, {9, 24}, {16, 20}, {16, 24}}}, // 14
{24, 22, 655, 0xf928, [4]level{{6, 22}, {10, 24}, {12, 30}, {18, 24}}}, // 15
{24, 24, 733, 0x10b78, [4]level{{6, 24}, {10, 28}, {17, 24}, {16, 30}}}, // 16
{28, 24, 815, 0x1145d, [4]level{{6, 28}, {11, 28}, {16, 28}, {19, 28}}}, // 17
{28, 26, 901, 0x12a17, [4]level{{6, 30}, {13, 26}, {18, 28}, {21, 28}}}, // 18
{28, 28, 991, 0x13532, [4]level{{7, 28}, {14, 26}, {21, 26}, {25, 26}}}, // 19
{32, 28, 1085, 0x149a6, [4]level{{8, 28}, {16, 26}, {20, 30}, {25, 28}}}, // 20
{26, 22, 1156, 0x15683, [4]level{{8, 28}, {17, 26}, {23, 28}, {25, 30}}}, // 21
{24, 24, 1258, 0x168c9, [4]level{{9, 28}, {17, 28}, {23, 30}, {34, 24}}}, // 22
{28, 24, 1364, 0x177ec, [4]level{{9, 30}, {18, 28}, {25, 30}, {30, 30}}}, // 23
{26, 26, 1474, 0x18ec4, [4]level{{10, 30}, {20, 28}, {27, 30}, {32, 30}}}, // 24
{30, 26, 1588, 0x191e1, [4]level{{12, 26}, {21, 28}, {29, 30}, {35, 30}}}, // 25
{28, 28, 1706, 0x1afab, [4]level{{12, 28}, {23, 28}, {34, 28}, {37, 30}}}, // 26
{32, 28, 1828, 0x1b08e, [4]level{{12, 30}, {25, 28}, {34, 30}, {40, 30}}}, // 27
{24, 24, 1921, 0x1cc1a, [4]level{{13, 30}, {26, 28}, {35, 30}, {42, 30}}}, // 28
{28, 24, 2051, 0x1d33f, [4]level{{14, 30}, {28, 28}, {38, 30}, {45, 30}}}, // 29
{24, 26, 2185, 0x1ed75, [4]level{{15, 30}, {29, 28}, {40, 30}, {48, 30}}}, // 30
{28, 26, 2323, 0x1f250, [4]level{{16, 30}, {31, 28}, {43, 30}, {51, 30}}}, // 31
{32, 26, 2465, 0x209d5, [4]level{{17, 30}, {33, 28}, {45, 30}, {54, 30}}}, // 32
{28, 28, 2611, 0x216f0, [4]level{{18, 30}, {35, 28}, {48, 30}, {57, 30}}}, // 33
{32, 28, 2761, 0x228ba, [4]level{{19, 30}, {37, 28}, {51, 30}, {60, 30}}}, // 34
{28, 24, 2876, 0x2379f, [4]level{{19, 30}, {38, 28}, {53, 30}, {63, 30}}}, // 35
{22, 26, 3034, 0x24b0b, [4]level{{20, 30}, {40, 28}, {56, 30}, {66, 30}}}, // 36
{26, 26, 3196, 0x2542e, [4]level{{21, 30}, {43, 28}, {59, 30}, {70, 30}}}, // 37
{30, 26, 3362, 0x26a64, [4]level{{22, 30}, {45, 28}, {62, 30}, {74, 30}}}, // 38
{24, 28, 3532, 0x27541, [4]level{{24, 30}, {47, 28}, {65, 30}, {77, 30}}}, // 39
{28, 28, 3706, 0x28c69, [4]level{{25, 30}, {49, 28}, {68, 30}, {81, 30}}}, // 40
}
func grid(siz int) [][]Pixel {
m := make([][]Pixel, siz)
pix := make([]Pixel, siz*siz)
for i := range m {
m[i], pix = pix[:siz], pix[siz:]
}
return m
}
// vplan creates a Plan for the given version.
func vplan(v Version) (*Plan, error) {
p := &Plan{Version: v}
if v < 1 || v > 40 {
return nil, fmt.Errorf("invalid QR version %d", int(v))
}
siz := 17 + int(v)*4
m := grid(siz)
p.Pixel = m
// Timing markers (overwritten by boxes).
const ti = 6 // timing is in row/column 6 (counting from 0)
for i := range m {
p := Timing.Pixel()
if i&1 == 0 {
p |= Black
}
m[i][ti] = p
m[ti][i] = p
}
// Position boxes.
posBox(m, 0, 0)
posBox(m, siz-7, 0)
posBox(m, 0, siz-7)
// Alignment boxes.
info := &vtab[v]
for x := 4; x+5 < siz; {
for y := 4; y+5 < siz; {
// don't overwrite timing markers
if (x < 7 && y < 7) || (x < 7 && y+5 >= siz-7) || (x+5 >= siz-7 && y < 7) {
} else {
alignBox(m, x, y)
}
if y == 4 {
y = info.apos
} else {
y += info.astride
}
}
if x == 4 {
x = info.apos
} else {
x += info.astride
}
}
// Version pattern.
pat := vtab[v].pattern
if pat != 0 {
v := pat
for x := 0; x < 6; x++ {
for y := 0; y < 3; y++ {
p := PVersion.Pixel()
if v&1 != 0 {
p |= Black
}
m[siz-11+y][x] = p
m[x][siz-11+y] = p
v >>= 1
}
}
}
// One lonely black pixel
m[siz-8][8] = Unused.Pixel() | Black
return p, nil
}
// fplan adds the format pixels
func fplan(l Level, m Mask, p *Plan) error {
// Format pixels.
fb := uint32(l^1) << 13 // level: L=01, M=00, Q=11, H=10
fb |= uint32(m) << 10 // mask
const formatPoly = 0x537
rem := fb
for i := 14; i >= 10; i-- {
if rem&(1<<uint(i)) != 0 {
rem ^= formatPoly << uint(i-10)
}
}
fb |= rem
invert := uint32(0x5412)
siz := len(p.Pixel)
for i := uint(0); i < 15; i++ {
pix := Format.Pixel() + OffsetPixel(i)
if (fb>>i)&1 == 1 {
pix |= Black
}
if (invert>>i)&1 == 1 {
pix ^= Invert | Black
}
// top left
switch {
case i < 6:
p.Pixel[i][8] = pix
case i < 8:
p.Pixel[i+1][8] = pix
case i < 9:
p.Pixel[8][7] = pix
default:
p.Pixel[8][14-i] = pix
}
// bottom right
switch {
case i < 8:
p.Pixel[8][siz-1-int(i)] = pix
default:
p.Pixel[siz-1-int(14-i)][8] = pix
}
}
return nil
}
// lplan edits a version-only Plan to add information
// about the error correction levels.
func lplan(v Version, l Level, p *Plan) error {
p.Level = l
nblock := vtab[v].level[l].nblock
ne := vtab[v].level[l].check
nde := (vtab[v].bytes - ne*nblock) / nblock
extra := (vtab[v].bytes - ne*nblock) % nblock
dataBits := (nde*nblock + extra) * 8
checkBits := ne * nblock * 8
p.DataBytes = vtab[v].bytes - ne*nblock
p.CheckBytes = ne * nblock
p.Blocks = nblock
// Make data + checksum pixels.
data := make([]Pixel, dataBits)
for i := range data {
data[i] = Data.Pixel() | OffsetPixel(uint(i))
}
check := make([]Pixel, checkBits)
for i := range check {
check[i] = Check.Pixel() | OffsetPixel(uint(i+dataBits))
}
// Split into blocks.
dataList := make([][]Pixel, nblock)
checkList := make([][]Pixel, nblock)
for i := 0; i < nblock; i++ {
// The last few blocks have an extra data byte (8 pixels).
nd := nde
if i >= nblock-extra {
nd++
}
dataList[i], data = data[0:nd*8], data[nd*8:]
checkList[i], check = check[0:ne*8], check[ne*8:]
}
if len(data) != 0 || len(check) != 0 {
panic("data/check math")
}
// Build up bit sequence, taking first byte of each block,
// then second byte, and so on. Then checksums.
bits := make([]Pixel, dataBits+checkBits)
dst := bits
for i := 0; i < nde+1; i++ {
for _, b := range dataList {
if i*8 < len(b) {
copy(dst, b[i*8:(i+1)*8])
dst = dst[8:]
}
}
}
for i := 0; i < ne; i++ {
for _, b := range checkList {
if i*8 < len(b) {
copy(dst, b[i*8:(i+1)*8])
dst = dst[8:]
}
}
}
if len(dst) != 0 {
panic("dst math")
}
// Sweep up pair of columns,
// then down, assigning to right then left pixel.
// Repeat.
// See Figure 2 of http://www.pclviewer.com/rs2/qrtopology.htm
siz := len(p.Pixel)
rem := make([]Pixel, 7)
for i := range rem {
rem[i] = Extra.Pixel()
}
src := append(bits, rem...)
for x := siz; x > 0; {
for y := siz - 1; y >= 0; y-- {
if p.Pixel[y][x-1].Role() == 0 {
p.Pixel[y][x-1], src = src[0], src[1:]
}
if p.Pixel[y][x-2].Role() == 0 {
p.Pixel[y][x-2], src = src[0], src[1:]
}
}
x -= 2
if x == 7 { // vertical timing strip
x--
}
for y := 0; y < siz; y++ {
if p.Pixel[y][x-1].Role() == 0 {
p.Pixel[y][x-1], src = src[0], src[1:]
}
if p.Pixel[y][x-2].Role() == 0 {
p.Pixel[y][x-2], src = src[0], src[1:]
}
}
x -= 2
}
return nil
}
// mplan edits a version+level-only Plan to add the mask.
func mplan(m Mask, p *Plan) error {
p.Mask = m
for y, row := range p.Pixel {
for x, pix := range row {
if r := pix.Role(); (r == Data || r == Check || r == Extra) && p.Mask.Invert(y, x) {
row[x] ^= Black | Invert
}
}
}
return nil
}
// posBox draws a position (large) box at upper left x, y.
func posBox(m [][]Pixel, x, y int) {
pos := Position.Pixel()
// box
for dy := 0; dy < 7; dy++ {
for dx := 0; dx < 7; dx++ {
p := pos
if dx == 0 || dx == 6 || dy == 0 || dy == 6 || 2 <= dx && dx <= 4 && 2 <= dy && dy <= 4 {
p |= Black
}
m[y+dy][x+dx] = p
}
}
// white border
for dy := -1; dy < 8; dy++ {
if 0 <= y+dy && y+dy < len(m) {
if x > 0 {
m[y+dy][x-1] = pos
}
if x+7 < len(m) {
m[y+dy][x+7] = pos
}
}
}
for dx := -1; dx < 8; dx++ {
if 0 <= x+dx && x+dx < len(m) {
if y > 0 {
m[y-1][x+dx] = pos
}
if y+7 < len(m) {
m[y+7][x+dx] = pos
}
}
}
}
// alignBox draw an alignment (small) box at upper left x, y.
func alignBox(m [][]Pixel, x, y int) {
// box
align := Alignment.Pixel()
for dy := 0; dy < 5; dy++ {
for dx := 0; dx < 5; dx++ {
p := align
if dx == 0 || dx == 4 || dy == 0 || dy == 4 || dx == 2 && dy == 2 {
p |= Black
}
m[y+dy][x+dx] = p
}
}
}

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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This file contains a straightforward implementation of
// Reed-Solomon encoding, along with a benchmark.
// It goes with http://research.swtch.com/field.
//
// For an optimized implementation, see gf256.go.
package gf256
import (
"bytes"
"fmt"
"testing"
)
// BlogECC writes to check the error correcting code bytes
// for data using the given Reed-Solomon parameters.
func BlogECC(rs *RSEncoder, m []byte, check []byte) {
if len(check) < rs.c {
panic("gf256: invalid check byte length")
}
if rs.c == 0 {
return
}
// The check bytes are the remainder after dividing
// data padded with c zeros by the generator polynomial.
// p = data padded with c zeros.
var p []byte
n := len(m) + rs.c
if len(rs.p) >= n {
p = rs.p
} else {
p = make([]byte, n)
}
copy(p, m)
for i := len(m); i < len(p); i++ {
p[i] = 0
}
gen := rs.gen
// Divide p by gen, leaving the remainder in p[len(data):].
// p[0] is the most significant term in p, and
// gen[0] is the most significant term in the generator.
for i := 0; i < len(m); i++ {
k := f.Mul(p[i], f.Inv(gen[0])) // k = pi / g0
// p -= k·g
for j, g := range gen {
p[i+j] = f.Add(p[i+j], f.Mul(k, g))
}
}
copy(check, p[len(m):])
rs.p = p
}
func BenchmarkBlogECC(b *testing.B) {
data := []byte{0x10, 0x20, 0x0c, 0x56, 0x61, 0x80, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0x10, 0x20, 0x0c, 0x56, 0x61, 0x80, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11}
check := []byte{0x29, 0x41, 0xb3, 0x93, 0x8, 0xe8, 0xa3, 0xe7, 0x63, 0x8f}
out := make([]byte, len(check))
rs := NewRSEncoder(f, len(check))
for i := 0; i < b.N; i++ {
BlogECC(rs, data, out)
}
b.SetBytes(int64(len(data)))
if !bytes.Equal(out, check) {
fmt.Printf("have %#v want %#v\n", out, check)
}
}
func TestBlogECC(t *testing.T) {
data := []byte{0x10, 0x20, 0x0c, 0x56, 0x61, 0x80, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11}
check := []byte{0xa5, 0x24, 0xd4, 0xc1, 0xed, 0x36, 0xc7, 0x87, 0x2c, 0x55}
out := make([]byte, len(check))
rs := NewRSEncoder(f, len(check))
BlogECC(rs, data, out)
if !bytes.Equal(out, check) {
t.Errorf("have %x want %x", out, check)
}
}

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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package gf256 implements arithmetic over the Galois Field GF(256).
package gf256
import "strconv"
// A Field represents an instance of GF(256) defined by a specific polynomial.
type Field struct {
log [256]byte // log[0] is unused
exp [510]byte
}
// NewField returns a new field corresponding to the polynomial poly
// and generator α. The Reed-Solomon encoding in QR codes uses
// polynomial 0x11d with generator 2.
//
// The choice of generator α only affects the Exp and Log operations.
func NewField(poly, α int) *Field {
if poly < 0x100 || poly >= 0x200 || reducible(poly) {
panic("gf256: invalid polynomial: " + strconv.Itoa(poly))
}
var f Field
x := 1
for i := 0; i < 255; i++ {
if x == 1 && i != 0 {
panic("gf256: invalid generator " + strconv.Itoa(α) +
" for polynomial " + strconv.Itoa(poly))
}
f.exp[i] = byte(x)
f.exp[i+255] = byte(x)
f.log[x] = byte(i)
x = mul(x, α, poly)
}
f.log[0] = 255
for i := 0; i < 255; i++ {
if f.log[f.exp[i]] != byte(i) {
panic("bad log")
}
if f.log[f.exp[i+255]] != byte(i) {
panic("bad log")
}
}
for i := 1; i < 256; i++ {
if f.exp[f.log[i]] != byte(i) {
panic("bad log")
}
}
return &f
}
// nbit returns the number of significant in p.
func nbit(p int) uint {
n := uint(0)
for ; p > 0; p >>= 1 {
n++
}
return n
}
// polyDiv divides the polynomial p by q and returns the remainder.
func polyDiv(p, q int) int {
np := nbit(p)
nq := nbit(q)
for ; np >= nq; np-- {
if p&(1<<(np-1)) != 0 {
p ^= q << (np - nq)
}
}
return p
}
// mul returns the product x*y mod poly, a GF(256) multiplication.
func mul(x, y, poly int) int {
z := 0
for x > 0 {
if x&1 != 0 {
z ^= y
}
x >>= 1
y <<= 1
if y&0x100 != 0 {
y ^= poly
}
}
return z
}
// reducible reports whether p is reducible.
func reducible(p int) bool {
// Multiplying n-bit * n-bit produces (2n-1)-bit,
// so if p is reducible, one of its factors must be
// of np/2+1 bits or fewer.
np := nbit(p)
for q := 2; q < 1<<(np/2+1); q++ {
if polyDiv(p, q) == 0 {
return true
}
}
return false
}
// Add returns the sum of x and y in the field.
func (f *Field) Add(x, y byte) byte {
return x ^ y
}
// Exp returns the base-α exponential of e in the field.
// If e < 0, Exp returns 0.
func (f *Field) Exp(e int) byte {
if e < 0 {
return 0
}
return f.exp[e%255]
}
// Log returns the base-α logarithm of x in the field.
// If x == 0, Log returns -1.
func (f *Field) Log(x byte) int {
if x == 0 {
return -1
}
return int(f.log[x])
}
// Inv returns the multiplicative inverse of x in the field.
// If x == 0, Inv returns 0.
func (f *Field) Inv(x byte) byte {
if x == 0 {
return 0
}
return f.exp[255-f.log[x]]
}
// Mul returns the product of x and y in the field.
func (f *Field) Mul(x, y byte) byte {
if x == 0 || y == 0 {
return 0
}
return f.exp[int(f.log[x])+int(f.log[y])]
}
// An RSEncoder implements Reed-Solomon encoding
// over a given field using a given number of error correction bytes.
type RSEncoder struct {
f *Field
c int
gen []byte
lgen []byte
p []byte
}
func (f *Field) gen(e int) (gen, lgen []byte) {
// p = 1
p := make([]byte, e+1)
p[e] = 1
for i := 0; i < e; i++ {
// p *= (x + Exp(i))
// p[j] = p[j]*Exp(i) + p[j+1].
c := f.Exp(i)
for j := 0; j < e; j++ {
p[j] = f.Mul(p[j], c) ^ p[j+1]
}
p[e] = f.Mul(p[e], c)
}
// lp = log p.
lp := make([]byte, e+1)
for i, c := range p {
if c == 0 {
lp[i] = 255
} else {
lp[i] = byte(f.Log(c))
}
}
return p, lp
}
// NewRSEncoder returns a new Reed-Solomon encoder
// over the given field and number of error correction bytes.
func NewRSEncoder(f *Field, c int) *RSEncoder {
gen, lgen := f.gen(c)
return &RSEncoder{f: f, c: c, gen: gen, lgen: lgen}
}
// ECC writes to check the error correcting code bytes
// for data using the given Reed-Solomon parameters.
func (rs *RSEncoder) ECC(data []byte, check []byte) {
if len(check) < rs.c {
panic("gf256: invalid check byte length")
}
if rs.c == 0 {
return
}
// The check bytes are the remainder after dividing
// data padded with c zeros by the generator polynomial.
// p = data padded with c zeros.
var p []byte
n := len(data) + rs.c
if len(rs.p) >= n {
p = rs.p
} else {
p = make([]byte, n)
}
copy(p, data)
for i := len(data); i < len(p); i++ {
p[i] = 0
}
// Divide p by gen, leaving the remainder in p[len(data):].
// p[0] is the most significant term in p, and
// gen[0] is the most significant term in the generator,
// which is always 1.
// To avoid repeated work, we store various values as
// lv, not v, where lv = log[v].
f := rs.f
lgen := rs.lgen[1:]
for i := 0; i < len(data); i++ {
c := p[i]
if c == 0 {
continue
}
q := p[i+1:]
exp := f.exp[f.log[c]:]
for j, lg := range lgen {
if lg != 255 { // lgen uses 255 for log 0
q[j] ^= exp[lg]
}
}
}
copy(check, p[len(data):])
rs.p = p
}

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vendor/github.com/chai2010/image/qrencoder/internal/gf256/gf256_test.go generated vendored Normal file
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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gf256
import (
"bytes"
"fmt"
"testing"
)
var f = NewField(0x11d, 2) // x^8 + x^4 + x^3 + x^2 + 1
func TestBasic(t *testing.T) {
if f.Exp(0) != 1 || f.Exp(1) != 2 || f.Exp(255) != 1 {
panic("bad Exp")
}
}
func TestECC(t *testing.T) {
data := []byte{0x10, 0x20, 0x0c, 0x56, 0x61, 0x80, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11}
check := []byte{0xa5, 0x24, 0xd4, 0xc1, 0xed, 0x36, 0xc7, 0x87, 0x2c, 0x55}
out := make([]byte, len(check))
rs := NewRSEncoder(f, len(check))
rs.ECC(data, out)
if !bytes.Equal(out, check) {
t.Errorf("have %x want %x", out, check)
}
}
func TestLinear(t *testing.T) {
d1 := []byte{0x00, 0x00}
c1 := []byte{0x00, 0x00}
out := make([]byte, len(c1))
rs := NewRSEncoder(f, len(c1))
if rs.ECC(d1, out); !bytes.Equal(out, c1) {
t.Errorf("ECBytes(%x, %d) = %x, want 0", d1, len(c1), out)
}
d2 := []byte{0x00, 0x01}
c2 := make([]byte, 2)
rs.ECC(d2, c2)
d3 := []byte{0x00, 0x02}
c3 := make([]byte, 2)
rs.ECC(d3, c3)
cx := make([]byte, 2)
for i := range cx {
cx[i] = c2[i] ^ c3[i]
}
d4 := []byte{0x00, 0x03}
c4 := make([]byte, 2)
rs.ECC(d4, c4)
if !bytes.Equal(cx, c4) {
t.Errorf("ECBytes(%x, 2) = %x\nECBytes(%x, 2) = %x\nxor = %x\nECBytes(%x, 2) = %x",
d2, c2, d3, c3, cx, d4, c4)
}
}
func TestGaussJordan(t *testing.T) {
rs := NewRSEncoder(f, 2)
m := make([][]byte, 16)
for i := range m {
m[i] = make([]byte, 4)
m[i][i/8] = 1 << uint(i%8)
rs.ECC(m[i][:2], m[i][2:])
}
if false {
fmt.Printf("---\n")
for _, row := range m {
fmt.Printf("%x\n", row)
}
}
b := []uint{0, 1, 2, 3, 12, 13, 14, 15, 20, 21, 22, 23, 24, 25, 26, 27}
for i := 0; i < 16; i++ {
bi := b[i]
if m[i][bi/8]&(1<<(7-bi%8)) == 0 {
for j := i + 1; ; j++ {
if j >= len(m) {
t.Errorf("lost track for %d", bi)
break
}
if m[j][bi/8]&(1<<(7-bi%8)) != 0 {
m[i], m[j] = m[j], m[i]
break
}
}
}
for j := i + 1; j < len(m); j++ {
if m[j][bi/8]&(1<<(7-bi%8)) != 0 {
for k := range m[j] {
m[j][k] ^= m[i][k]
}
}
}
}
if false {
fmt.Printf("---\n")
for _, row := range m {
fmt.Printf("%x\n", row)
}
}
for i := 15; i >= 0; i-- {
bi := b[i]
for j := i - 1; j >= 0; j-- {
if m[j][bi/8]&(1<<(7-bi%8)) != 0 {
for k := range m[j] {
m[j][k] ^= m[i][k]
}
}
}
}
if false {
fmt.Printf("---\n")
for _, row := range m {
fmt.Printf("%x", row)
out := make([]byte, 2)
if rs.ECC(row[:2], out); !bytes.Equal(out, row[2:]) {
fmt.Printf(" - want %x", out)
}
fmt.Printf("\n")
}
}
}
func BenchmarkECC(b *testing.B) {
data := []byte{0x10, 0x20, 0x0c, 0x56, 0x61, 0x80, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0x10, 0x20, 0x0c, 0x56, 0x61, 0x80, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11, 0xec, 0x11}
check := []byte{0x29, 0x41, 0xb3, 0x93, 0x8, 0xe8, 0xa3, 0xe7, 0x63, 0x8f}
out := make([]byte, len(check))
rs := NewRSEncoder(f, len(check))
for i := 0; i < b.N; i++ {
rs.ECC(data, out)
}
b.SetBytes(int64(len(data)))
if !bytes.Equal(out, check) {
fmt.Printf("have %#v want %#v\n", out, check)
}
}
func TestGen(t *testing.T) {
for i := 0; i < 256; i++ {
_, lg := f.gen(i)
if lg[0] != 0 {
t.Errorf("#%d: %x", i, lg)
}
}
}
func TestReducible(t *testing.T) {
var count = []int{1, 2, 3, 6, 9, 18, 30, 56, 99, 186} // oeis.org/A1037
for i, want := range count {
n := 0
for p := 1 << uint(i+2); p < 1<<uint(i+3); p++ {
if !reducible(p) {
n++
}
}
if n != want {
t.Errorf("#reducible(%d-bit) = %d, want %d", i+2, n, want)
}
}
}
func TestExhaustive(t *testing.T) {
for poly := 0x100; poly < 0x200; poly++ {
if reducible(poly) {
continue
}
α := 2
for !generates(α, poly) {
α++
}
f := NewField(poly, α)
for p := 0; p < 256; p++ {
for q := 0; q < 256; q++ {
fm := int(f.Mul(byte(p), byte(q)))
pm := mul(p, q, poly)
if fm != pm {
t.Errorf("NewField(%#x).Mul(%#x, %#x) = %#x, want %#x", poly, p, q, fm, pm)
}
}
}
}
}
func generates(α, poly int) bool {
x := α
for i := 0; i < 254; i++ {
if x == 1 {
return false
}
x = mul(x, α, poly)
}
return true
}

400
vendor/github.com/chai2010/image/qrencoder/png.go generated vendored Normal file
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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package qrcode
// PNG writer for QR codes.
import (
"bytes"
"encoding/binary"
"hash"
"hash/crc32"
)
// PNG returns a PNG image displaying the code.
//
// PNG uses a custom encoder tailored to QR codes.
// Its compressed size is about 2x away from optimal,
// but it runs about 20x faster than calling png.Encode
// on c.Image().
func (c *Code) PNG() []byte {
var p pngWriter
return p.encode(c)
}
type pngWriter struct {
tmp [16]byte
wctmp [4]byte
buf bytes.Buffer
zlib bitWriter
crc hash.Hash32
}
var pngHeader = []byte("\x89PNG\r\n\x1a\n")
func (w *pngWriter) encode(c *Code) []byte {
scale := c.Scale
siz := c.Size
w.buf.Reset()
// Header
w.buf.Write(pngHeader)
// Header block
binary.BigEndian.PutUint32(w.tmp[0:4], uint32((siz+8)*scale))
binary.BigEndian.PutUint32(w.tmp[4:8], uint32((siz+8)*scale))
w.tmp[8] = 1 // 1-bit
w.tmp[9] = 0 // gray
w.tmp[10] = 0
w.tmp[11] = 0
w.tmp[12] = 0
w.writeChunk("IHDR", w.tmp[:13])
// Comment
w.writeChunk("tEXt", comment)
// Data
w.zlib.writeCode(c)
w.writeChunk("IDAT", w.zlib.bytes.Bytes())
// End
w.writeChunk("IEND", nil)
return w.buf.Bytes()
}
var comment = []byte("Software\x00QR-PNG <chaishushan{AT}gmail.com>")
func (w *pngWriter) writeChunk(name string, data []byte) {
if w.crc == nil {
w.crc = crc32.NewIEEE()
}
binary.BigEndian.PutUint32(w.wctmp[0:4], uint32(len(data)))
w.buf.Write(w.wctmp[0:4])
w.crc.Reset()
copy(w.wctmp[0:4], name)
w.buf.Write(w.wctmp[0:4])
w.crc.Write(w.wctmp[0:4])
w.buf.Write(data)
w.crc.Write(data)
crc := w.crc.Sum32()
binary.BigEndian.PutUint32(w.wctmp[0:4], crc)
w.buf.Write(w.wctmp[0:4])
}
func (b *bitWriter) writeCode(c *Code) {
const ftNone = 0
b.adler32.Reset()
b.bytes.Reset()
b.nbit = 0
scale := c.Scale
siz := c.Size
// zlib header
b.tmp[0] = 0x78
b.tmp[1] = 0
b.tmp[1] += uint8(31 - (uint16(b.tmp[0])<<8+uint16(b.tmp[1]))%31)
b.bytes.Write(b.tmp[0:2])
// Start flate block.
b.writeBits(1, 1, false) // final block
b.writeBits(1, 2, false) // compressed, fixed Huffman tables
// White border.
// First row.
b.byte(ftNone)
n := (scale*(siz+8) + 7) / 8
b.byte(255)
b.repeat(n-1, 1)
// 4*scale rows total.
b.repeat((4*scale-1)*(1+n), 1+n)
for i := 0; i < 4*scale; i++ {
b.adler32.WriteNByte(ftNone, 1)
b.adler32.WriteNByte(255, n)
}
row := make([]byte, 1+n)
for y := 0; y < siz; y++ {
row[0] = ftNone
j := 1
var z uint8
nz := 0
for x := -4; x < siz+4; x++ {
// Raw data.
for i := 0; i < scale; i++ {
z <<= 1
if !c.Black(x, y) {
z |= 1
}
if nz++; nz == 8 {
row[j] = z
j++
nz = 0
}
}
}
if j < len(row) {
row[j] = z
}
for _, z := range row {
b.byte(z)
}
// Scale-1 copies.
b.repeat((scale-1)*(1+n), 1+n)
b.adler32.WriteN(row, scale)
}
// White border.
// First row.
b.byte(ftNone)
b.byte(255)
b.repeat(n-1, 1)
// 4*scale rows total.
b.repeat((4*scale-1)*(1+n), 1+n)
for i := 0; i < 4*scale; i++ {
b.adler32.WriteNByte(ftNone, 1)
b.adler32.WriteNByte(255, n)
}
// End of block.
b.hcode(256)
b.flushBits()
// adler32
binary.BigEndian.PutUint32(b.tmp[0:], b.adler32.Sum32())
b.bytes.Write(b.tmp[0:4])
}
// A bitWriter is a write buffer for bit-oriented data like deflate.
type bitWriter struct {
bytes bytes.Buffer
bit uint32
nbit uint
tmp [4]byte
adler32 adigest
}
func (b *bitWriter) writeBits(bit uint32, nbit uint, rev bool) {
// reverse, for huffman codes
if rev {
br := uint32(0)
for i := uint(0); i < nbit; i++ {
br |= ((bit >> i) & 1) << (nbit - 1 - i)
}
bit = br
}
b.bit |= bit << b.nbit
b.nbit += nbit
for b.nbit >= 8 {
b.bytes.WriteByte(byte(b.bit))
b.bit >>= 8
b.nbit -= 8
}
}
func (b *bitWriter) flushBits() {
if b.nbit > 0 {
b.bytes.WriteByte(byte(b.bit))
b.nbit = 0
b.bit = 0
}
}
func (b *bitWriter) hcode(v int) {
/*
Lit Value Bits Codes
--------- ---- -----
0 - 143 8 00110000 through
10111111
144 - 255 9 110010000 through
111111111
256 - 279 7 0000000 through
0010111
280 - 287 8 11000000 through
11000111
*/
switch {
case v <= 143:
b.writeBits(uint32(v)+0x30, 8, true)
case v <= 255:
b.writeBits(uint32(v-144)+0x190, 9, true)
case v <= 279:
b.writeBits(uint32(v-256)+0, 7, true)
case v <= 287:
b.writeBits(uint32(v-280)+0xc0, 8, true)
default:
panic("invalid hcode")
}
}
func (b *bitWriter) byte(x byte) {
b.hcode(int(x))
}
func (b *bitWriter) codex(c int, val int, nx uint) {
b.hcode(c + val>>nx)
b.writeBits(uint32(val)&(1<<nx-1), nx, false)
}
func (b *bitWriter) repeat(n, d int) {
for ; n >= 258+3; n -= 258 {
b.repeat1(258, d)
}
if n > 258 {
// 258 < n < 258+3
b.repeat1(10, d)
b.repeat1(n-10, d)
return
}
if n < 3 {
panic("invalid flate repeat")
}
b.repeat1(n, d)
}
func (b *bitWriter) repeat1(n, d int) {
/*
Extra Extra Extra
Code Bits Length(s) Code Bits Lengths Code Bits Length(s)
---- ---- ------ ---- ---- ------- ---- ---- -------
257 0 3 267 1 15,16 277 4 67-82
258 0 4 268 1 17,18 278 4 83-98
259 0 5 269 2 19-22 279 4 99-114
260 0 6 270 2 23-26 280 4 115-130
261 0 7 271 2 27-30 281 5 131-162
262 0 8 272 2 31-34 282 5 163-194
263 0 9 273 3 35-42 283 5 195-226
264 0 10 274 3 43-50 284 5 227-257
265 1 11,12 275 3 51-58 285 0 258
266 1 13,14 276 3 59-66
*/
switch {
case n <= 10:
b.codex(257, n-3, 0)
case n <= 18:
b.codex(265, n-11, 1)
case n <= 34:
b.codex(269, n-19, 2)
case n <= 66:
b.codex(273, n-35, 3)
case n <= 130:
b.codex(277, n-67, 4)
case n <= 257:
b.codex(281, n-131, 5)
case n == 258:
b.hcode(285)
default:
panic("invalid repeat length")
}
/*
Extra Extra Extra
Code Bits Dist Code Bits Dist Code Bits Distance
---- ---- ---- ---- ---- ------ ---- ---- --------
0 0 1 10 4 33-48 20 9 1025-1536
1 0 2 11 4 49-64 21 9 1537-2048
2 0 3 12 5 65-96 22 10 2049-3072
3 0 4 13 5 97-128 23 10 3073-4096
4 1 5,6 14 6 129-192 24 11 4097-6144
5 1 7,8 15 6 193-256 25 11 6145-8192
6 2 9-12 16 7 257-384 26 12 8193-12288
7 2 13-16 17 7 385-512 27 12 12289-16384
8 3 17-24 18 8 513-768 28 13 16385-24576
9 3 25-32 19 8 769-1024 29 13 24577-32768
*/
if d <= 4 {
b.writeBits(uint32(d-1), 5, true)
} else if d <= 32768 {
nbit := uint(16)
for d <= 1<<(nbit-1) {
nbit--
}
v := uint32(d - 1)
v &^= 1 << (nbit - 1) // top bit is implicit
code := uint32(2*nbit - 2) // second bit is low bit of code
code |= v >> (nbit - 2)
v &^= 1 << (nbit - 2)
b.writeBits(code, 5, true)
// rest of bits follow
b.writeBits(uint32(v), nbit-2, false)
} else {
panic("invalid repeat distance")
}
}
func (b *bitWriter) run(v byte, n int) {
if n == 0 {
return
}
b.byte(v)
if n-1 < 3 {
for i := 0; i < n-1; i++ {
b.byte(v)
}
} else {
b.repeat(n-1, 1)
}
}
type adigest struct {
a, b uint32
}
func (d *adigest) Reset() { d.a, d.b = 1, 0 }
const amod = 65521
func aupdate(a, b uint32, pi byte, n int) (aa, bb uint32) {
// TODO(rsc): 6g doesn't do magic multiplies for b %= amod,
// only for b = b%amod.
// invariant: a, b < amod
if pi == 0 {
b += uint32(n%amod) * a
b = b % amod
return a, b
}
// n times:
// a += pi
// b += a
// is same as
// b += n*a + n*(n+1)/2*pi
// a += n*pi
m := uint32(n)
b += (m % amod) * a
b = b % amod
b += (m * (m + 1) / 2) % amod * uint32(pi)
b = b % amod
a += (m % amod) * uint32(pi)
a = a % amod
return a, b
}
func afinish(a, b uint32) uint32 {
return b<<16 | a
}
func (d *adigest) WriteN(p []byte, n int) {
for i := 0; i < n; i++ {
for _, pi := range p {
d.a, d.b = aupdate(d.a, d.b, pi, 1)
}
}
}
func (d *adigest) WriteNByte(pi byte, n int) {
d.a, d.b = aupdate(d.a, d.b, pi, n)
}
func (d *adigest) Sum32() uint32 { return afinish(d.a, d.b) }

69
vendor/github.com/chai2010/image/qrencoder/png_test.go generated vendored Normal file
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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package qrcode
import (
"bytes"
"image"
"image/color"
"image/png"
"testing"
)
func TestPNG(t *testing.T) {
c, err := Encode("hello, world", L)
if err != nil {
t.Fatal(err)
}
pngdat := c.PNG()
m, err := png.Decode(bytes.NewBuffer(pngdat))
if err != nil {
t.Fatal(err)
}
gm := m.(*image.Gray)
scale := c.Scale
siz := c.Size
nbad := 0
for y := 0; y < scale*(8+siz); y++ {
for x := 0; x < scale*(8+siz); x++ {
v := byte(255)
if c.Black(x/scale-4, y/scale-4) {
v = 0
}
if gv := gm.At(x, y).(color.Gray).Y; gv != v {
t.Errorf("%d,%d = %d, want %d", x, y, gv, v)
if nbad++; nbad >= 20 {
t.Fatalf("too many bad pixels")
}
}
}
}
}
func BenchmarkPNG(b *testing.B) {
c, err := Encode("0123456789012345678901234567890123456789", L)
if err != nil {
panic(err)
}
var bytes []byte
for i := 0; i < b.N; i++ {
bytes = c.PNG()
}
b.SetBytes(int64(len(bytes)))
}
func BenchmarkImagePNG(b *testing.B) {
c, err := Encode("0123456789012345678901234567890123456789", L)
if err != nil {
panic(err)
}
var buf bytes.Buffer
for i := 0; i < b.N; i++ {
buf.Reset()
png.Encode(&buf, c.Image())
}
b.SetBytes(int64(buf.Len()))
}

114
vendor/github.com/chai2010/image/qrencoder/qr.go generated vendored Normal file
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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package qrencoder implements a encoder for QR code.
package qrcode
import (
"errors"
"image"
"image/color"
"github.com/chai2010/image/qrencoder/internal/coding"
)
// A Level denotes a QR error correction level.
// From least to most tolerant of errors, they are L, M, Q, H.
type Level int
const (
L Level = iota // 20% redundant
M // 38% redundant
Q // 55% redundant
H // 65% redundant
)
// Encode returns an encoding of text at the given error correction level.
func Encode(text string, level Level) (*Code, error) {
// Pick data encoding, smallest first.
// We could split the string and use different encodings
// but that seems like overkill for now.
var enc coding.Encoding
switch {
case coding.Num(text).Check() == nil:
enc = coding.Num(text)
case coding.Alpha(text).Check() == nil:
enc = coding.Alpha(text)
default:
enc = coding.String(text)
}
// Pick size.
l := coding.Level(level)
var v coding.Version
for v = coding.MinVersion; ; v++ {
if v > coding.MaxVersion {
return nil, errors.New("text too long to encode as QR")
}
if enc.Bits(v) <= v.DataBytes(l)*8 {
break
}
}
// Build and execute plan.
p, err := coding.NewPlan(v, l, 0)
if err != nil {
return nil, err
}
cc, err := p.Encode(enc)
if err != nil {
return nil, err
}
// TODO: Pick appropriate mask.
return &Code{cc.Bitmap, cc.Size, cc.Stride, 8}, nil
}
// A Code is a square pixel grid.
// It implements image.Image and direct PNG encoding.
type Code struct {
Bitmap []byte // 1 is black, 0 is white
Size int // number of pixels on a side
Stride int // number of bytes per row
Scale int // number of image pixels per QR pixel
}
// Black returns true if the pixel at (x,y) is black.
func (c *Code) Black(x, y int) bool {
return 0 <= x && x < c.Size && 0 <= y && y < c.Size &&
c.Bitmap[y*c.Stride+x/8]&(1<<uint(7-x&7)) != 0
}
// Image returns an Image displaying the code.
func (c *Code) Image() image.Image {
return &codeImage{c}
}
// codeImage implements image.Image
type codeImage struct {
*Code
}
var (
whiteColor color.Color = color.Gray{0xFF}
blackColor color.Color = color.Gray{0x00}
)
func (c *codeImage) Bounds() image.Rectangle {
d := (c.Size + 8) * c.Scale
return image.Rect(0, 0, d, d)
}
func (c *codeImage) At(x, y int) color.Color {
if c.Black(x, y) {
return blackColor
}
return whiteColor
}
func (c *codeImage) ColorModel() color.Model {
return color.GrayModel
}

31
vendor/gopl.io/ch1/dup1/main.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 8.
//!+
// Dup1 prints the text of each line that appears more than
// once in the standard input, preceded by its count.
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
counts := make(map[string]int)
input := bufio.NewScanner(os.Stdin)
for input.Scan() {
counts[input.Text()]++
}
// NOTE: ignoring potential errors from input.Err()
for line, n := range counts {
if n > 1 {
fmt.Printf("%d\t%s\n", n, line)
}
}
}
//!-

48
vendor/gopl.io/ch1/dup2/main.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 10.
//!+
// Dup2 prints the count and text of lines that appear more than once
// in the input. It reads from stdin or from a list of named files.
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
counts := make(map[string]int)
files := os.Args[1:]
if len(files) == 0 {
countLines(os.Stdin, counts)
} else {
for _, arg := range files {
f, err := os.Open(arg)
if err != nil {
fmt.Fprintf(os.Stderr, "dup2: %v\n", err)
continue
}
countLines(f, counts)
f.Close()
}
}
for line, n := range counts {
if n > 1 {
fmt.Printf("%d\t%s\n", n, line)
}
}
}
func countLines(f *os.File, counts map[string]int) {
input := bufio.NewScanner(f)
for input.Scan() {
counts[input.Text()]++
}
// NOTE: ignoring potential errors from input.Err()
}
//!-

38
vendor/gopl.io/ch1/dup3/main.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 12.
//!+
// Dup3 prints the count and text of lines that
// appear more than once in the named input files.
package main
import (
"fmt"
"io/ioutil"
"os"
"strings"
)
func main() {
counts := make(map[string]int)
for _, filename := range os.Args[1:] {
data, err := ioutil.ReadFile(filename)
if err != nil {
fmt.Fprintf(os.Stderr, "dup3: %v\n", err)
continue
}
for _, line := range strings.Split(string(data), "\n") {
counts[line]++
}
}
for line, n := range counts {
if n > 1 {
fmt.Printf("%d\t%s\n", n, line)
}
}
}
//!-

24
vendor/gopl.io/ch1/echo1/main.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 4.
//!+
// Echo1 prints its command-line arguments.
package main
import (
"fmt"
"os"
)
func main() {
var s, sep string
for i := 1; i < len(os.Args); i++ {
s += sep + os.Args[i]
sep = " "
}
fmt.Println(s)
}
//!-

24
vendor/gopl.io/ch1/echo2/main.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 6.
//!+
// Echo2 prints its command-line arguments.
package main
import (
"fmt"
"os"
)
func main() {
s, sep := "", ""
for _, arg := range os.Args[1:] {
s += sep + arg
sep = " "
}
fmt.Println(s)
}
//!-

20
vendor/gopl.io/ch1/echo3/main.go generated vendored Normal file
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@@ -0,0 +1,20 @@
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 8.
// Echo3 prints its command-line arguments.
package main
import (
"fmt"
"os"
"strings"
)
//!+
func main() {
fmt.Println(strings.Join(os.Args[1:], " "))
}
//!-

34
vendor/gopl.io/ch1/fetch/main.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 16.
//!+
// Fetch prints the content found at each specified URL.
package main
import (
"fmt"
"io/ioutil"
"net/http"
"os"
)
func main() {
for _, url := range os.Args[1:] {
resp, err := http.Get(url)
if err != nil {
fmt.Fprintf(os.Stderr, "fetch: %v\n", err)
os.Exit(1)
}
b, err := ioutil.ReadAll(resp.Body)
resp.Body.Close()
if err != nil {
fmt.Fprintf(os.Stderr, "fetch: reading %s: %v\n", url, err)
os.Exit(1)
}
fmt.Printf("%s", b)
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 17.
//!+
// Fetchall fetches URLs in parallel and reports their times and sizes.
package main
import (
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"time"
)
func main() {
start := time.Now()
ch := make(chan string)
for _, url := range os.Args[1:] {
go fetch(url, ch) // start a goroutine
}
for range os.Args[1:] {
fmt.Println(<-ch) // receive from channel ch
}
fmt.Printf("%.2fs elapsed\n", time.Since(start).Seconds())
}
func fetch(url string, ch chan<- string) {
start := time.Now()
resp, err := http.Get(url)
if err != nil {
ch <- fmt.Sprint(err) // send to channel ch
return
}
nbytes, err := io.Copy(ioutil.Discard, resp.Body)
resp.Body.Close() // don't leak resources
if err != nil {
ch <- fmt.Sprintf("while reading %s: %v", url, err)
return
}
secs := time.Since(start).Seconds()
ch <- fmt.Sprintf("%.2fs %7d %s", secs, nbytes, url)
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 1.
// Helloworld is our first Go program.
//!+
package main
import "fmt"
func main() {
fmt.Println("Hello, 世界")
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// Run with "web" command-line argument for web server.
// See page 13.
//!+main
// Lissajous generates GIF animations of random Lissajous figures.
package main
import (
"image"
"image/color"
"image/gif"
"io"
"math"
"math/rand"
"os"
)
//!-main
// Packages not needed by version in book.
import (
"log"
"net/http"
"time"
)
//!+main
var palette = []color.Color{color.White, color.Black}
const (
whiteIndex = 0 // first color in palette
blackIndex = 1 // next color in palette
)
func main() {
//!-main
// The sequence of images is deterministic unless we seed
// the pseudo-random number generator using the current time.
// Thanks to Randall McPherson for pointing out the omission.
rand.Seed(time.Now().UTC().UnixNano())
if len(os.Args) > 1 && os.Args[1] == "web" {
//!+http
handler := func(w http.ResponseWriter, r *http.Request) {
lissajous(w)
}
http.HandleFunc("/", handler)
//!-http
log.Fatal(http.ListenAndServe("localhost:8000", nil))
return
}
//!+main
lissajous(os.Stdout)
}
func lissajous(out io.Writer) {
const (
cycles = 5 // number of complete x oscillator revolutions
res = 0.001 // angular resolution
size = 100 // image canvas covers [-size..+size]
nframes = 64 // number of animation frames
delay = 8 // delay between frames in 10ms units
)
freq := rand.Float64() * 3.0 // relative frequency of y oscillator
anim := gif.GIF{LoopCount: nframes}
phase := 0.0 // phase difference
for i := 0; i < nframes; i++ {
rect := image.Rect(0, 0, 2*size+1, 2*size+1)
img := image.NewPaletted(rect, palette)
for t := 0.0; t < cycles*2*math.Pi; t += res {
x := math.Sin(t)
y := math.Sin(t*freq + phase)
img.SetColorIndex(size+int(x*size+0.5), size+int(y*size+0.5),
blackIndex)
}
phase += 0.1
anim.Delay = append(anim.Delay, delay)
anim.Image = append(anim.Image, img)
}
gif.EncodeAll(out, &anim) // NOTE: ignoring encoding errors
}
//!-main

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 19.
//!+
// Server1 is a minimal "echo" server.
package main
import (
"fmt"
"log"
"net/http"
)
func main() {
http.HandleFunc("/", handler) // each request calls handler
log.Fatal(http.ListenAndServe("localhost:8000", nil))
}
// handler echoes the Path component of the requested URL.
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "URL.Path = %q\n", r.URL.Path)
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 20.
//!+
// Server2 is a minimal "echo" and counter server.
package main
import (
"fmt"
"log"
"net/http"
"sync"
)
var mu sync.Mutex
var count int
func main() {
http.HandleFunc("/", handler)
http.HandleFunc("/count", counter)
log.Fatal(http.ListenAndServe("localhost:8000", nil))
}
// handler echoes the Path component of the requested URL.
func handler(w http.ResponseWriter, r *http.Request) {
mu.Lock()
count++
mu.Unlock()
fmt.Fprintf(w, "URL.Path = %q\n", r.URL.Path)
}
// counter echoes the number of calls so far.
func counter(w http.ResponseWriter, r *http.Request) {
mu.Lock()
fmt.Fprintf(w, "Count %d\n", count)
mu.Unlock()
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 21.
// Server3 is an "echo" server that displays request parameters.
package main
import (
"fmt"
"log"
"net/http"
)
func main() {
http.HandleFunc("/", handler)
log.Fatal(http.ListenAndServe("localhost:8000", nil))
}
//!+handler
// handler echoes the HTTP request.
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "%s %s %s\n", r.Method, r.URL, r.Proto)
for k, v := range r.Header {
fmt.Fprintf(w, "Header[%q] = %q\n", k, v)
}
fmt.Fprintf(w, "Host = %q\n", r.Host)
fmt.Fprintf(w, "RemoteAddr = %q\n", r.RemoteAddr)
if err := r.ParseForm(); err != nil {
log.Print(err)
}
for k, v := range r.Form {
fmt.Fprintf(w, "Form[%q] = %q\n", k, v)
}
}
//!-handler

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 295.
// The cross command prints the values of GOOS and GOARCH for this target.
package main
import (
"fmt"
"runtime"
)
//!+
func main() {
fmt.Println(runtime.GOOS, runtime.GOARCH)
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 287.
//!+main
// The jpeg command reads a PNG image from the standard input
// and writes it as a JPEG image to the standard output.
package main
import (
"fmt"
"image"
"image/jpeg"
_ "image/png" // register PNG decoder
"io"
"os"
)
func main() {
if err := toJPEG(os.Stdin, os.Stdout); err != nil {
fmt.Fprintf(os.Stderr, "jpeg: %v\n", err)
os.Exit(1)
}
}
func toJPEG(in io.Reader, out io.Writer) error {
img, kind, err := image.Decode(in)
if err != nil {
return err
}
fmt.Fprintln(os.Stderr, "Input format =", kind)
return jpeg.Encode(out, img, &jpeg.Options{Quality: 95})
}
//!-main
/*
//!+with
$ go build gopl.io/ch3/mandelbrot
$ go build gopl.io/ch10/jpeg
$ ./mandelbrot | ./jpeg >mandelbrot.jpg
Input format = png
//!-with
//!+without
$ go build gopl.io/ch10/jpeg
$ ./mandelbrot | ./jpeg >mandelbrot.jpg
jpeg: image: unknown format
//!-without
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 308.
//!+
// Echo prints its command-line arguments.
package main
import (
"flag"
"fmt"
"io"
"os"
"strings"
)
var (
n = flag.Bool("n", false, "omit trailing newline")
s = flag.String("s", " ", "separator")
)
var out io.Writer = os.Stdout // modified during testing
func main() {
flag.Parse()
if err := echo(!*n, *s, flag.Args()); err != nil {
fmt.Fprintf(os.Stderr, "echo: %v\n", err)
os.Exit(1)
}
}
func echo(newline bool, sep string, args []string) error {
fmt.Fprint(out, strings.Join(args, sep))
if newline {
fmt.Fprintln(out)
}
return nil
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// Test of echo command. Run with: go test gopl.io/ch11/echo
//!+
package main
import (
"bytes"
"fmt"
"testing"
)
func TestEcho(t *testing.T) {
var tests = []struct {
newline bool
sep string
args []string
want string
}{
{true, "", []string{}, "\n"},
{false, "", []string{}, ""},
{true, "\t", []string{"one", "two", "three"}, "one\ttwo\tthree\n"},
{true, ",", []string{"a", "b", "c"}, "a,b,c\n"},
{false, ":", []string{"1", "2", "3"}, "1:2:3"},
}
for _, test := range tests {
descr := fmt.Sprintf("echo(%v, %q, %q)",
test.newline, test.sep, test.args)
out = new(bytes.Buffer) // captured output
if err := echo(test.newline, test.sep, test.args); err != nil {
t.Errorf("%s failed: %v", descr, err)
continue
}
got := out.(*bytes.Buffer).String()
if got != test.want {
t.Errorf("%s = %q, want %q", descr, got, test.want)
}
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 311.
// Package storage is part of a hypothetical cloud storage server.
//!+main
package storage
import (
"fmt"
"log"
"net/smtp"
)
var usage = make(map[string]int64)
func bytesInUse(username string) int64 { return usage[username] }
// Email sender configuration.
// NOTE: never put passwords in source code!
const sender = "notifications@example.com"
const password = "correcthorsebatterystaple"
const hostname = "smtp.example.com"
const template = `Warning: you are using %d bytes of storage,
%d%% of your quota.`
func CheckQuota(username string) {
used := bytesInUse(username)
const quota = 1000000000 // 1GB
percent := 100 * used / quota
if percent < 90 {
return // OK
}
msg := fmt.Sprintf(template, used, percent)
auth := smtp.PlainAuth("", sender, password, hostname)
err := smtp.SendMail(hostname+":587", auth, sender,
[]string{username}, []byte(msg))
if err != nil {
log.Printf("smtp.SendMail(%s) failed: %s", username, err)
}
}
//!-main

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//!+test
package storage
import (
"strings"
"testing"
)
func TestCheckQuotaNotifiesUser(t *testing.T) {
var notifiedUser, notifiedMsg string
notifyUser = func(user, msg string) {
notifiedUser, notifiedMsg = user, msg
}
const user = "joe@example.org"
usage[user] = 980000000 // simulate a 980MB-used condition
CheckQuota(user)
if notifiedUser == "" && notifiedMsg == "" {
t.Fatalf("notifyUser not called")
}
if notifiedUser != user {
t.Errorf("wrong user (%s) notified, want %s",
notifiedUser, user)
}
const wantSubstring = "98% of your quota"
if !strings.Contains(notifiedMsg, wantSubstring) {
t.Errorf("unexpected notification message <<%s>>, "+
"want substring %q", notifiedMsg, wantSubstring)
}
}
//!-test
/*
//!+defer
func TestCheckQuotaNotifiesUser(t *testing.T) {
// Save and restore original notifyUser.
saved := notifyUser
defer func() { notifyUser = saved }()
// Install the test's fake notifyUser.
var notifiedUser, notifiedMsg string
notifyUser = func(user, msg string) {
notifiedUser, notifiedMsg = user, msg
}
// ...rest of test...
}
//!-defer
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 312.
// Package storage is part of a hypothetical cloud storage server.
package storage
import (
"fmt"
"log"
"net/smtp"
)
var usage = make(map[string]int64)
func bytesInUse(username string) int64 { return usage[username] }
// E-mail sender configuration.
// NOTE: never put passwords in source code!
const sender = "notifications@example.com"
const password = "correcthorsebatterystaple"
const hostname = "smtp.example.com"
const template = `Warning: you are using %d bytes of storage,
%d%% of your quota.`
//!+factored
var notifyUser = func(username, msg string) {
auth := smtp.PlainAuth("", sender, password, hostname)
err := smtp.SendMail(hostname+":587", auth, sender,
[]string{username}, []byte(msg))
if err != nil {
log.Printf("smtp.SendEmail(%s) failed: %s", username, err)
}
}
func CheckQuota(username string) {
used := bytesInUse(username)
const quota = 1000000000 // 1GB
percent := 100 * used / quota
if percent < 90 {
return // OK
}
msg := fmt.Sprintf(template, used, percent)
notifyUser(username, msg)
}
//!-factored

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 303.
//!+
// Package word provides utilities for word games.
package word
// IsPalindrome reports whether s reads the same forward and backward.
// (Our first attempt.)
func IsPalindrome(s string) bool {
for i := range s {
if s[i] != s[len(s)-1-i] {
return false
}
}
return true
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//!+test
package word
import "testing"
func TestPalindrome(t *testing.T) {
if !IsPalindrome("detartrated") {
t.Error(`IsPalindrome("detartrated") = false`)
}
if !IsPalindrome("kayak") {
t.Error(`IsPalindrome("kayak") = false`)
}
}
func TestNonPalindrome(t *testing.T) {
if IsPalindrome("palindrome") {
t.Error(`IsPalindrome("palindrome") = true`)
}
}
//!-test
// The tests below are expected to fail.
// See package gopl.io/ch11/word2 for the fix.
//!+more
func TestFrenchPalindrome(t *testing.T) {
if !IsPalindrome("été") {
t.Error(`IsPalindrome("été") = false`)
}
}
func TestCanalPalindrome(t *testing.T) {
input := "A man, a plan, a canal: Panama"
if !IsPalindrome(input) {
t.Errorf(`IsPalindrome(%q) = false`, input)
}
}
//!-more

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 305.
//!+
// Package word provides utilities for word games.
package word
import "unicode"
// IsPalindrome reports whether s reads the same forward and backward.
// Letter case is ignored, as are non-letters.
func IsPalindrome(s string) bool {
var letters []rune
for _, r := range s {
if unicode.IsLetter(r) {
letters = append(letters, unicode.ToLower(r))
}
}
for i := range letters {
if letters[i] != letters[len(letters)-1-i] {
return false
}
}
return true
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package word
import (
"fmt"
"math/rand"
"time"
)
//!+bench
import "testing"
//!-bench
//!+test
func TestIsPalindrome(t *testing.T) {
var tests = []struct {
input string
want bool
}{
{"", true},
{"a", true},
{"aa", true},
{"ab", false},
{"kayak", true},
{"detartrated", true},
{"A man, a plan, a canal: Panama", true},
{"Evil I did dwell; lewd did I live.", true},
{"Able was I ere I saw Elba", true},
{"été", true},
{"Et se resservir, ivresse reste.", true},
{"palindrome", false}, // non-palindrome
{"desserts", false}, // semi-palindrome
}
for _, test := range tests {
if got := IsPalindrome(test.input); got != test.want {
t.Errorf("IsPalindrome(%q) = %v", test.input, got)
}
}
}
//!-test
//!+bench
func BenchmarkIsPalindrome(b *testing.B) {
for i := 0; i < b.N; i++ {
IsPalindrome("A man, a plan, a canal: Panama")
}
}
//!-bench
//!+example
func ExampleIsPalindrome() {
fmt.Println(IsPalindrome("A man, a plan, a canal: Panama"))
fmt.Println(IsPalindrome("palindrome"))
// Output:
// true
// false
}
//!-example
/*
//!+random
import "math/rand"
//!-random
*/
//!+random
// randomPalindrome returns a palindrome whose length and contents
// are derived from the pseudo-random number generator rng.
func randomPalindrome(rng *rand.Rand) string {
n := rng.Intn(25) // random length up to 24
runes := make([]rune, n)
for i := 0; i < (n+1)/2; i++ {
r := rune(rng.Intn(0x1000)) // random rune up to '\u0999'
runes[i] = r
runes[n-1-i] = r
}
return string(runes)
}
func TestRandomPalindromes(t *testing.T) {
// Initialize a pseudo-random number generator.
seed := time.Now().UTC().UnixNano()
t.Logf("Random seed: %d", seed)
rng := rand.New(rand.NewSource(seed))
for i := 0; i < 1000; i++ {
p := randomPalindrome(rng)
if !IsPalindrome(p) {
t.Errorf("IsPalindrome(%q) = false", p)
}
}
}
//!-random
/*
// Answer for Exercicse 11.1: Modify randomPalindrome to exercise
// IsPalindrome's handling of punctuation and spaces.
// WARNING: the conversion r -> upper -> lower doesn't preserve
// the value of r in some cases, e.g., µ Μ, ſ S, ı I
// randomPalindrome returns a palindrome whose length and contents
// are derived from the pseudo-random number generator rng.
func randomNoisyPalindrome(rng *rand.Rand) string {
n := rng.Intn(25) // random length up to 24
runes := make([]rune, n)
for i := 0; i < (n+1)/2; i++ {
r := rune(rng.Intn(0x200)) // random rune up to \u99
runes[i] = r
r1 := r
if unicode.IsLetter(r) && unicode.IsLower(r) {
r = unicode.ToUpper(r)
if unicode.ToLower(r) != r1 {
fmt.Printf("cap? %c %c\n", r1, r)
}
}
runes[n-1-i] = r
}
return "?" + string(runes) + "!"
}
func TestRandomNoisyPalindromes(t *testing.T) {
// Initialize a pseudo-random number generator.
seed := time.Now().UTC().UnixNano()
t.Logf("Random seed: %d", seed)
rng := rand.New(rand.NewSource(seed))
n := 0
for i := 0; i < 1000; i++ {
p := randomNoisyPalindrome(rng)
if !IsPalindrome(p) {
t.Errorf("IsNoisyPalindrome(%q) = false", p)
n++
}
}
fmt.Fprintf(os.Stderr, "fail = %d\n", n)
}
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 333.
// Package display provides a means to display structured data.
package display
import (
"fmt"
"reflect"
"strconv"
)
//!+Display
func Display(name string, x interface{}) {
fmt.Printf("Display %s (%T):\n", name, x)
display(name, reflect.ValueOf(x))
}
//!-Display
// formatAtom formats a value without inspecting its internal structure.
// It is a copy of the the function in gopl.io/ch11/format.
func formatAtom(v reflect.Value) string {
switch v.Kind() {
case reflect.Invalid:
return "invalid"
case reflect.Int, reflect.Int8, reflect.Int16,
reflect.Int32, reflect.Int64:
return strconv.FormatInt(v.Int(), 10)
case reflect.Uint, reflect.Uint8, reflect.Uint16,
reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return strconv.FormatUint(v.Uint(), 10)
// ...floating-point and complex cases omitted for brevity...
case reflect.Bool:
if v.Bool() {
return "true"
}
return "false"
case reflect.String:
return strconv.Quote(v.String())
case reflect.Chan, reflect.Func, reflect.Ptr,
reflect.Slice, reflect.Map:
return v.Type().String() + " 0x" +
strconv.FormatUint(uint64(v.Pointer()), 16)
default: // reflect.Array, reflect.Struct, reflect.Interface
return v.Type().String() + " value"
}
}
//!+display
func display(path string, v reflect.Value) {
switch v.Kind() {
case reflect.Invalid:
fmt.Printf("%s = invalid\n", path)
case reflect.Slice, reflect.Array:
for i := 0; i < v.Len(); i++ {
display(fmt.Sprintf("%s[%d]", path, i), v.Index(i))
}
case reflect.Struct:
for i := 0; i < v.NumField(); i++ {
fieldPath := fmt.Sprintf("%s.%s", path, v.Type().Field(i).Name)
display(fieldPath, v.Field(i))
}
case reflect.Map:
for _, key := range v.MapKeys() {
display(fmt.Sprintf("%s[%s]", path,
formatAtom(key)), v.MapIndex(key))
}
case reflect.Ptr:
if v.IsNil() {
fmt.Printf("%s = nil\n", path)
} else {
display(fmt.Sprintf("(*%s)", path), v.Elem())
}
case reflect.Interface:
if v.IsNil() {
fmt.Printf("%s = nil\n", path)
} else {
fmt.Printf("%s.type = %s\n", path, v.Elem().Type())
display(path+".value", v.Elem())
}
default: // basic types, channels, funcs
fmt.Printf("%s = %s\n", path, formatAtom(v))
}
}
//!-display

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package display
import (
"io"
"net"
"os"
"reflect"
"sync"
"testing"
"gopl.io/ch7/eval"
)
// NOTE: we can't use !+..!- comments to excerpt these tests
// into the book because it defeats the Example mechanism,
// which requires the // Output comment to be at the end
// of the function.
func Example_expr() {
e, _ := eval.Parse("sqrt(A / pi)")
Display("e", e)
// Output:
// Display e (eval.call):
// e.fn = "sqrt"
// e.args[0].type = eval.binary
// e.args[0].value.op = 47
// e.args[0].value.x.type = eval.Var
// e.args[0].value.x.value = "A"
// e.args[0].value.y.type = eval.Var
// e.args[0].value.y.value = "pi"
}
func Example_slice() {
Display("slice", []*int{new(int), nil})
// Output:
// Display slice ([]*int):
// (*slice[0]) = 0
// slice[1] = nil
}
func Example_nilInterface() {
var w io.Writer
Display("w", w)
// Output:
// Display w (<nil>):
// w = invalid
}
func Example_ptrToInterface() {
var w io.Writer
Display("&w", &w)
// Output:
// Display &w (*io.Writer):
// (*&w) = nil
}
func Example_struct() {
Display("x", struct{ x interface{} }{3})
// Output:
// Display x (struct { x interface {} }):
// x.x.type = int
// x.x.value = 3
}
func Example_interface() {
var i interface{} = 3
Display("i", i)
// Output:
// Display i (int):
// i = 3
}
func Example_ptrToInterface2() {
var i interface{} = 3
Display("&i", &i)
// Output:
// Display &i (*interface {}):
// (*&i).type = int
// (*&i).value = 3
}
func Example_array() {
Display("x", [1]interface{}{3})
// Output:
// Display x ([1]interface {}):
// x[0].type = int
// x[0].value = 3
}
func Example_movie() {
//!+movie
type Movie struct {
Title, Subtitle string
Year int
Color bool
Actor map[string]string
Oscars []string
Sequel *string
}
//!-movie
//!+strangelove
strangelove := Movie{
Title: "Dr. Strangelove",
Subtitle: "How I Learned to Stop Worrying and Love the Bomb",
Year: 1964,
Color: false,
Actor: map[string]string{
"Dr. Strangelove": "Peter Sellers",
"Grp. Capt. Lionel Mandrake": "Peter Sellers",
"Pres. Merkin Muffley": "Peter Sellers",
"Gen. Buck Turgidson": "George C. Scott",
"Brig. Gen. Jack D. Ripper": "Sterling Hayden",
`Maj. T.J. "King" Kong`: "Slim Pickens",
},
Oscars: []string{
"Best Actor (Nomin.)",
"Best Adapted Screenplay (Nomin.)",
"Best Director (Nomin.)",
"Best Picture (Nomin.)",
},
}
//!-strangelove
Display("strangelove", strangelove)
// We don't use an Output: comment since displaying
// a map is nondeterministic.
/*
//!+output
Display strangelove (display.Movie):
strangelove.Title = "Dr. Strangelove"
strangelove.Subtitle = "How I Learned to Stop Worrying and Love the Bomb"
strangelove.Year = 1964
strangelove.Color = false
strangelove.Actor["Gen. Buck Turgidson"] = "George C. Scott"
strangelove.Actor["Brig. Gen. Jack D. Ripper"] = "Sterling Hayden"
strangelove.Actor["Maj. T.J. \"King\" Kong"] = "Slim Pickens"
strangelove.Actor["Dr. Strangelove"] = "Peter Sellers"
strangelove.Actor["Grp. Capt. Lionel Mandrake"] = "Peter Sellers"
strangelove.Actor["Pres. Merkin Muffley"] = "Peter Sellers"
strangelove.Oscars[0] = "Best Actor (Nomin.)"
strangelove.Oscars[1] = "Best Adapted Screenplay (Nomin.)"
strangelove.Oscars[2] = "Best Director (Nomin.)"
strangelove.Oscars[3] = "Best Picture (Nomin.)"
strangelove.Sequel = nil
//!-output
*/
}
// This test ensures that the program terminates without crashing.
func Test(t *testing.T) {
// Some other values (YMMV)
Display("os.Stderr", os.Stderr)
// Output:
// Display os.Stderr (*os.File):
// (*(*os.Stderr).file).fd = 2
// (*(*os.Stderr).file).name = "/dev/stderr"
// (*(*os.Stderr).file).nepipe = 0
var w io.Writer = os.Stderr
Display("&w", &w)
// Output:
// Display &w (*io.Writer):
// (*&w).type = *os.File
// (*(*(*&w).value).file).fd = 2
// (*(*(*&w).value).file).name = "/dev/stderr"
// (*(*(*&w).value).file).nepipe = 0
var locker sync.Locker = new(sync.Mutex)
Display("(&locker)", &locker)
// Output:
// Display (&locker) (*sync.Locker):
// (*(&locker)).type = *sync.Mutex
// (*(*(&locker)).value).state = 0
// (*(*(&locker)).value).sema = 0
Display("locker", locker)
// Output:
// Display locker (*sync.Mutex):
// (*locker).state = 0
// (*locker).sema = 0
// (*(&locker)) = nil
locker = nil
Display("(&locker)", &locker)
// Output:
// Display (&locker) (*sync.Locker):
// (*(&locker)) = nil
ips, _ := net.LookupHost("golang.org")
Display("ips", ips)
// Output:
// Display ips ([]string):
// ips[0] = "173.194.68.141"
// ips[1] = "2607:f8b0:400d:c06::8d"
// Even metarecursion! (YMMV)
Display("rV", reflect.ValueOf(os.Stderr))
// Output:
// Display rV (reflect.Value):
// (*rV.typ).size = 8
// (*rV.typ).ptrdata = 8
// (*rV.typ).hash = 871609668
// (*rV.typ)._ = 0
// ...
// a pointer that points to itself
type P *P
var p P
p = &p
if false {
Display("p", p)
// Output:
// Display p (display.P):
// ...stuck, no output...
}
// a map that contains itself
type M map[string]M
m := make(M)
m[""] = m
if false {
Display("m", m)
// Output:
// Display m (display.M):
// ...stuck, no output...
}
// a slice that contains itself
type S []S
s := make(S, 1)
s[0] = s
if false {
Display("s", s)
// Output:
// Display s (display.S):
// ...stuck, no output...
}
// a linked list that eats its own tail
type Cycle struct {
Value int
Tail *Cycle
}
var c Cycle
c = Cycle{42, &c}
if false {
Display("c", c)
// Output:
// Display c (display.Cycle):
// c.Value = 42
// (*c.Tail).Value = 42
// (*(*c.Tail).Tail).Value = 42
// ...ad infinitum...
}
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 332.
// Package format provides an Any function that can format any value.
//!+
package format
import (
"reflect"
"strconv"
)
// Any formats any value as a string.
func Any(value interface{}) string {
return formatAtom(reflect.ValueOf(value))
}
// formatAtom formats a value without inspecting its internal structure.
func formatAtom(v reflect.Value) string {
switch v.Kind() {
case reflect.Invalid:
return "invalid"
case reflect.Int, reflect.Int8, reflect.Int16,
reflect.Int32, reflect.Int64:
return strconv.FormatInt(v.Int(), 10)
case reflect.Uint, reflect.Uint8, reflect.Uint16,
reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return strconv.FormatUint(v.Uint(), 10)
// ...floating-point and complex cases omitted for brevity...
case reflect.Bool:
return strconv.FormatBool(v.Bool())
case reflect.String:
return strconv.Quote(v.String())
case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Slice, reflect.Map:
return v.Type().String() + " 0x" +
strconv.FormatUint(uint64(v.Pointer()), 16)
default: // reflect.Array, reflect.Struct, reflect.Interface
return v.Type().String() + " value"
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package format_test
import (
"fmt"
"testing"
"time"
"gopl.io/ch12/format"
)
func Test(t *testing.T) {
// The pointer values are just examples, and may vary from run to run.
//!+time
var x int64 = 1
var d time.Duration = 1 * time.Nanosecond
fmt.Println(format.Any(x)) // "1"
fmt.Println(format.Any(d)) // "1"
fmt.Println(format.Any([]int64{x})) // "[]int64 0x8202b87b0"
fmt.Println(format.Any([]time.Duration{d})) // "[]time.Duration 0x8202b87e0"
//!-time
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 351.
// Package methods provides a function to print the methods of any value.
package methods
import (
"fmt"
"reflect"
"strings"
)
//!+print
// Print prints the method set of the value x.
func Print(x interface{}) {
v := reflect.ValueOf(x)
t := v.Type()
fmt.Printf("type %s\n", t)
for i := 0; i < v.NumMethod(); i++ {
methType := v.Method(i).Type()
fmt.Printf("func (%s) %s%s\n", t, t.Method(i).Name,
strings.TrimPrefix(methType.String(), "func"))
}
}
//!-print

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package methods_test
import (
"strings"
"time"
"gopl.io/ch12/methods"
)
func ExamplePrintDuration() {
methods.Print(time.Hour)
// Output:
// type time.Duration
// func (time.Duration) Hours() float64
// func (time.Duration) Minutes() float64
// func (time.Duration) Nanoseconds() int64
// func (time.Duration) Seconds() float64
// func (time.Duration) String() string
}
func ExamplePrintReplacer() {
methods.Print(new(strings.Replacer))
// Output:
// type *strings.Replacer
// func (*strings.Replacer) Replace(string) string
// func (*strings.Replacer) WriteString(io.Writer, string) (int, error)
}
/*
//!+output
methods.Print(time.Hour)
// Output:
// type time.Duration
// func (time.Duration) Hours() float64
// func (time.Duration) Minutes() float64
// func (time.Duration) Nanoseconds() int64
// func (time.Duration) Seconds() float64
// func (time.Duration) String() string
methods.Print(new(strings.Replacer))
// Output:
// type *strings.Replacer
// func (*strings.Replacer) Replace(string) string
// func (*strings.Replacer) WriteString(io.Writer, string) (int, error)
//!-output
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 349.
// Package params provides a reflection-based parser for URL parameters.
package params
import (
"fmt"
"net/http"
"reflect"
"strconv"
"strings"
)
//!+Unpack
// Unpack populates the fields of the struct pointed to by ptr
// from the HTTP request parameters in req.
func Unpack(req *http.Request, ptr interface{}) error {
if err := req.ParseForm(); err != nil {
return err
}
// Build map of fields keyed by effective name.
fields := make(map[string]reflect.Value)
v := reflect.ValueOf(ptr).Elem() // the struct variable
for i := 0; i < v.NumField(); i++ {
fieldInfo := v.Type().Field(i) // a reflect.StructField
tag := fieldInfo.Tag // a reflect.StructTag
name := tag.Get("http")
if name == "" {
name = strings.ToLower(fieldInfo.Name)
}
fields[name] = v.Field(i)
}
// Update struct field for each parameter in the request.
for name, values := range req.Form {
f := fields[name]
if !f.IsValid() {
continue // ignore unrecognized HTTP parameters
}
for _, value := range values {
if f.Kind() == reflect.Slice {
elem := reflect.New(f.Type().Elem()).Elem()
if err := populate(elem, value); err != nil {
return fmt.Errorf("%s: %v", name, err)
}
f.Set(reflect.Append(f, elem))
} else {
if err := populate(f, value); err != nil {
return fmt.Errorf("%s: %v", name, err)
}
}
}
}
return nil
}
//!-Unpack
//!+populate
func populate(v reflect.Value, value string) error {
switch v.Kind() {
case reflect.String:
v.SetString(value)
case reflect.Int:
i, err := strconv.ParseInt(value, 10, 64)
if err != nil {
return err
}
v.SetInt(i)
case reflect.Bool:
b, err := strconv.ParseBool(value)
if err != nil {
return err
}
v.SetBool(b)
default:
return fmt.Errorf("unsupported kind %s", v.Type())
}
return nil
}
//!-populate

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 348.
// Search is a demo of the params.Unpack function.
package main
import (
"fmt"
"log"
"net/http"
)
//!+
import "gopl.io/ch12/params"
// search implements the /search URL endpoint.
func search(resp http.ResponseWriter, req *http.Request) {
var data struct {
Labels []string `http:"l"`
MaxResults int `http:"max"`
Exact bool `http:"x"`
}
data.MaxResults = 10 // set default
if err := params.Unpack(req, &data); err != nil {
http.Error(resp, err.Error(), http.StatusBadRequest) // 400
return
}
// ...rest of handler...
fmt.Fprintf(resp, "Search: %+v\n", data)
}
//!-
func main() {
http.HandleFunc("/search", search)
log.Fatal(http.ListenAndServe(":12345", nil))
}
/*
//!+output
$ go build gopl.io/ch12/search
$ ./search &
$ ./fetch 'http://localhost:12345/search'
Search: {Labels:[] MaxResults:10 Exact:false}
$ ./fetch 'http://localhost:12345/search?l=golang&l=programming'
Search: {Labels:[golang programming] MaxResults:10 Exact:false}
$ ./fetch 'http://localhost:12345/search?l=golang&l=programming&max=100'
Search: {Labels:[golang programming] MaxResults:100 Exact:false}
$ ./fetch 'http://localhost:12345/search?x=true&l=golang&l=programming'
Search: {Labels:[golang programming] MaxResults:10 Exact:true}
$ ./fetch 'http://localhost:12345/search?q=hello&x=123'
x: strconv.ParseBool: parsing "123": invalid syntax
$ ./fetch 'http://localhost:12345/search?q=hello&max=lots'
max: strconv.ParseInt: parsing "lots": invalid syntax
//!-output
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 344.
// Package sexpr provides a means for converting Go objects to and
// from S-expressions.
package sexpr
import (
"bytes"
"fmt"
"reflect"
"strconv"
"text/scanner"
)
//!+Unmarshal
// Unmarshal parses S-expression data and populates the variable
// whose address is in the non-nil pointer out.
func Unmarshal(data []byte, out interface{}) (err error) {
lex := &lexer{scan: scanner.Scanner{Mode: scanner.GoTokens}}
lex.scan.Init(bytes.NewReader(data))
lex.next() // get the first token
defer func() {
// NOTE: this is not an example of ideal error handling.
if x := recover(); x != nil {
err = fmt.Errorf("error at %s: %v", lex.scan.Position, x)
}
}()
read(lex, reflect.ValueOf(out).Elem())
return nil
}
//!-Unmarshal
//!+lexer
type lexer struct {
scan scanner.Scanner
token rune // the current token
}
func (lex *lexer) next() { lex.token = lex.scan.Scan() }
func (lex *lexer) text() string { return lex.scan.TokenText() }
func (lex *lexer) consume(want rune) {
if lex.token != want { // NOTE: Not an example of good error handling.
panic(fmt.Sprintf("got %q, want %q", lex.text(), want))
}
lex.next()
}
//!-lexer
// The read function is a decoder for a small subset of well-formed
// S-expressions. For brevity of our example, it takes many dubious
// shortcuts.
//
// The parser assumes
// - that the S-expression input is well-formed; it does no error checking.
// - that the S-expression input corresponds to the type of the variable.
// - that all numbers in the input are non-negative decimal integers.
// - that all keys in ((key value) ...) struct syntax are unquoted symbols.
// - that the input does not contain dotted lists such as (1 2 . 3).
// - that the input does not contain Lisp reader macros such 'x and #'x.
//
// The reflection logic assumes
// - that v is always a variable of the appropriate type for the
// S-expression value. For example, v must not be a boolean,
// interface, channel, or function, and if v is an array, the input
// must have the correct number of elements.
// - that v in the top-level call to read has the zero value of its
// type and doesn't need clearing.
// - that if v is a numeric variable, it is a signed integer.
//!+read
func read(lex *lexer, v reflect.Value) {
switch lex.token {
case scanner.Ident:
// The only valid identifiers are
// "nil" and struct field names.
if lex.text() == "nil" {
v.Set(reflect.Zero(v.Type()))
lex.next()
return
}
case scanner.String:
s, _ := strconv.Unquote(lex.text()) // NOTE: ignoring errors
v.SetString(s)
lex.next()
return
case scanner.Int:
i, _ := strconv.Atoi(lex.text()) // NOTE: ignoring errors
v.SetInt(int64(i))
lex.next()
return
case '(':
lex.next()
readList(lex, v)
lex.next() // consume ')'
return
}
panic(fmt.Sprintf("unexpected token %q", lex.text()))
}
//!-read
//!+readlist
func readList(lex *lexer, v reflect.Value) {
switch v.Kind() {
case reflect.Array: // (item ...)
for i := 0; !endList(lex); i++ {
read(lex, v.Index(i))
}
case reflect.Slice: // (item ...)
for !endList(lex) {
item := reflect.New(v.Type().Elem()).Elem()
read(lex, item)
v.Set(reflect.Append(v, item))
}
case reflect.Struct: // ((name value) ...)
for !endList(lex) {
lex.consume('(')
if lex.token != scanner.Ident {
panic(fmt.Sprintf("got token %q, want field name", lex.text()))
}
name := lex.text()
lex.next()
read(lex, v.FieldByName(name))
lex.consume(')')
}
case reflect.Map: // ((key value) ...)
v.Set(reflect.MakeMap(v.Type()))
for !endList(lex) {
lex.consume('(')
key := reflect.New(v.Type().Key()).Elem()
read(lex, key)
value := reflect.New(v.Type().Elem()).Elem()
read(lex, value)
v.SetMapIndex(key, value)
lex.consume(')')
}
default:
panic(fmt.Sprintf("cannot decode list into %v", v.Type()))
}
}
func endList(lex *lexer) bool {
switch lex.token {
case scanner.EOF:
panic("end of file")
case ')':
return true
}
return false
}
//!-readlist

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 339.
package sexpr
import (
"bytes"
"fmt"
"reflect"
)
//!+Marshal
// Marshal encodes a Go value in S-expression form.
func Marshal(v interface{}) ([]byte, error) {
var buf bytes.Buffer
if err := encode(&buf, reflect.ValueOf(v)); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
//!-Marshal
// encode writes to buf an S-expression representation of v.
//!+encode
func encode(buf *bytes.Buffer, v reflect.Value) error {
switch v.Kind() {
case reflect.Invalid:
buf.WriteString("nil")
case reflect.Int, reflect.Int8, reflect.Int16,
reflect.Int32, reflect.Int64:
fmt.Fprintf(buf, "%d", v.Int())
case reflect.Uint, reflect.Uint8, reflect.Uint16,
reflect.Uint32, reflect.Uint64, reflect.Uintptr:
fmt.Fprintf(buf, "%d", v.Uint())
case reflect.String:
fmt.Fprintf(buf, "%q", v.String())
case reflect.Ptr:
return encode(buf, v.Elem())
case reflect.Array, reflect.Slice: // (value ...)
buf.WriteByte('(')
for i := 0; i < v.Len(); i++ {
if i > 0 {
buf.WriteByte(' ')
}
if err := encode(buf, v.Index(i)); err != nil {
return err
}
}
buf.WriteByte(')')
case reflect.Struct: // ((name value) ...)
buf.WriteByte('(')
for i := 0; i < v.NumField(); i++ {
if i > 0 {
buf.WriteByte(' ')
}
fmt.Fprintf(buf, "(%s ", v.Type().Field(i).Name)
if err := encode(buf, v.Field(i)); err != nil {
return err
}
buf.WriteByte(')')
}
buf.WriteByte(')')
case reflect.Map: // ((key value) ...)
buf.WriteByte('(')
for i, key := range v.MapKeys() {
if i > 0 {
buf.WriteByte(' ')
}
buf.WriteByte('(')
if err := encode(buf, key); err != nil {
return err
}
buf.WriteByte(' ')
if err := encode(buf, v.MapIndex(key)); err != nil {
return err
}
buf.WriteByte(')')
}
buf.WriteByte(')')
default: // float, complex, bool, chan, func, interface
return fmt.Errorf("unsupported type: %s", v.Type())
}
return nil
}
//!-encode

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package sexpr
// This file implements the algorithm described in Derek C. Oppen's
// 1979 Stanford technical report, "Pretty Printing".
import (
"bytes"
"fmt"
"reflect"
)
func MarshalIndent(v interface{}) ([]byte, error) {
p := printer{width: margin}
if err := pretty(&p, reflect.ValueOf(v)); err != nil {
return nil, err
}
return p.Bytes(), nil
}
const margin = 80
type token struct {
kind rune // one of "s ()" (string, blank, start, end)
str string
size int
}
type printer struct {
tokens []*token // FIFO buffer
stack []*token // stack of open ' ' and '(' tokens
rtotal int // total number of spaces needed to print stream
bytes.Buffer
indents []int
width int // remaining space
}
func (p *printer) string(str string) {
tok := &token{kind: 's', str: str, size: len(str)}
if len(p.stack) == 0 {
p.print(tok)
} else {
p.tokens = append(p.tokens, tok)
p.rtotal += len(str)
}
}
func (p *printer) pop() (top *token) {
last := len(p.stack) - 1
top, p.stack = p.stack[last], p.stack[:last]
return
}
func (p *printer) begin() {
if len(p.stack) == 0 {
p.rtotal = 1
}
t := &token{kind: '(', size: -p.rtotal}
p.tokens = append(p.tokens, t)
p.stack = append(p.stack, t) // push
p.string("(")
}
func (p *printer) end() {
p.string(")")
p.tokens = append(p.tokens, &token{kind: ')'})
x := p.pop()
x.size += p.rtotal
if x.kind == ' ' {
p.pop().size += p.rtotal
}
if len(p.stack) == 0 {
for _, tok := range p.tokens {
p.print(tok)
}
p.tokens = nil
}
}
func (p *printer) space() {
last := len(p.stack) - 1
x := p.stack[last]
if x.kind == ' ' {
x.size += p.rtotal
p.stack = p.stack[:last] // pop
}
t := &token{kind: ' ', size: -p.rtotal}
p.tokens = append(p.tokens, t)
p.stack = append(p.stack, t)
p.rtotal++
}
func (p *printer) print(t *token) {
switch t.kind {
case 's':
p.WriteString(t.str)
p.width -= len(t.str)
case '(':
p.indents = append(p.indents, p.width)
case ')':
p.indents = p.indents[:len(p.indents)-1] // pop
case ' ':
if t.size > p.width {
p.width = p.indents[len(p.indents)-1] - 1
fmt.Fprintf(&p.Buffer, "\n%*s", margin-p.width, "")
} else {
p.WriteByte(' ')
p.width--
}
}
}
func (p *printer) stringf(format string, args ...interface{}) {
p.string(fmt.Sprintf(format, args...))
}
func pretty(p *printer, v reflect.Value) error {
switch v.Kind() {
case reflect.Invalid:
p.string("nil")
case reflect.Int, reflect.Int8, reflect.Int16,
reflect.Int32, reflect.Int64:
p.stringf("%d", v.Int())
case reflect.Uint, reflect.Uint8, reflect.Uint16,
reflect.Uint32, reflect.Uint64, reflect.Uintptr:
p.stringf("%d", v.Uint())
case reflect.String:
p.stringf("%q", v.String())
case reflect.Array, reflect.Slice: // (value ...)
p.begin()
for i := 0; i < v.Len(); i++ {
if i > 0 {
p.space()
}
if err := pretty(p, v.Index(i)); err != nil {
return err
}
}
p.end()
case reflect.Struct: // ((name value ...)
p.begin()
for i := 0; i < v.NumField(); i++ {
if i > 0 {
p.space()
}
p.begin()
p.string(v.Type().Field(i).Name)
p.space()
if err := pretty(p, v.Field(i)); err != nil {
return err
}
p.end()
}
p.end()
case reflect.Map: // ((key value ...)
p.begin()
for i, key := range v.MapKeys() {
if i > 0 {
p.space()
}
p.begin()
if err := pretty(p, key); err != nil {
return err
}
p.space()
if err := pretty(p, v.MapIndex(key)); err != nil {
return err
}
p.end()
}
p.end()
case reflect.Ptr:
return pretty(p, v.Elem())
default: // float, complex, bool, chan, func, interface
return fmt.Errorf("unsupported type: %s", v.Type())
}
return nil
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package sexpr
import (
"reflect"
"testing"
)
// Test verifies that encoding and decoding a complex data value
// produces an equal result.
//
// The test does not make direct assertions about the encoded output
// because the output depends on map iteration order, which is
// nondeterministic. The output of the t.Log statements can be
// inspected by running the test with the -v flag:
//
// $ go test -v gopl.io/ch12/sexpr
//
func Test(t *testing.T) {
type Movie struct {
Title, Subtitle string
Year int
Actor map[string]string
Oscars []string
Sequel *string
}
strangelove := Movie{
Title: "Dr. Strangelove",
Subtitle: "How I Learned to Stop Worrying and Love the Bomb",
Year: 1964,
Actor: map[string]string{
"Dr. Strangelove": "Peter Sellers",
"Grp. Capt. Lionel Mandrake": "Peter Sellers",
"Pres. Merkin Muffley": "Peter Sellers",
"Gen. Buck Turgidson": "George C. Scott",
"Brig. Gen. Jack D. Ripper": "Sterling Hayden",
`Maj. T.J. "King" Kong`: "Slim Pickens",
},
Oscars: []string{
"Best Actor (Nomin.)",
"Best Adapted Screenplay (Nomin.)",
"Best Director (Nomin.)",
"Best Picture (Nomin.)",
},
}
// Encode it
data, err := Marshal(strangelove)
if err != nil {
t.Fatalf("Marshal failed: %v", err)
}
t.Logf("Marshal() = %s\n", data)
// Decode it
var movie Movie
if err := Unmarshal(data, &movie); err != nil {
t.Fatalf("Unmarshal failed: %v", err)
}
t.Logf("Unmarshal() = %+v\n", movie)
// Check equality.
if !reflect.DeepEqual(movie, strangelove) {
t.Fatal("not equal")
}
// Pretty-print it:
data, err = MarshalIndent(strangelove)
if err != nil {
t.Fatal(err)
}
t.Logf("MarshalIdent() = %s\n", data)
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 362.
// This is the version that appears in print,
// but it does not comply with the proposed
// rules for passing pointers between Go and C.
// (https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md)
// See gopl.io/ch13/bzip for an updated version.
//!+
/* This file is gopl.io/ch13/bzip/bzip2.c, */
/* a simple wrapper for libbzip2 suitable for cgo. */
#include <bzlib.h>
int bz2compress(bz_stream *s, int action,
char *in, unsigned *inlen, char *out, unsigned *outlen) {
s->next_in = in;
s->avail_in = *inlen;
s->next_out = out;
s->avail_out = *outlen;
int r = BZ2_bzCompress(s, action);
*inlen -= s->avail_in;
*outlen -= s->avail_out;
return r;
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 362.
// This is the version that appears in print,
// but it does not comply with the proposed
// rules for passing pointers between Go and C.
// (https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md)
// See gopl.io/ch13/bzip for an updated version.
//!+
// Package bzip provides a writer that uses bzip2 compression (bzip.org).
package bzip
/*
#cgo CFLAGS: -I/usr/include
#cgo LDFLAGS: -L/usr/lib -lbz2
#include <bzlib.h>
int bz2compress(bz_stream *s, int action,
char *in, unsigned *inlen, char *out, unsigned *outlen);
*/
import "C"
import (
"io"
"unsafe"
)
type writer struct {
w io.Writer // underlying output stream
stream *C.bz_stream
outbuf [64 * 1024]byte
}
// NewWriter returns a writer for bzip2-compressed streams.
func NewWriter(out io.Writer) io.WriteCloser {
const (
blockSize = 9
verbosity = 0
workFactor = 30
)
w := &writer{w: out, stream: new(C.bz_stream)}
C.BZ2_bzCompressInit(w.stream, blockSize, verbosity, workFactor)
return w
}
//!-
//!+write
func (w *writer) Write(data []byte) (int, error) {
if w.stream == nil {
panic("closed")
}
var total int // uncompressed bytes written
for len(data) > 0 {
inlen, outlen := C.uint(len(data)), C.uint(cap(w.outbuf))
C.bz2compress(w.stream, C.BZ_RUN,
(*C.char)(unsafe.Pointer(&data[0])), &inlen,
(*C.char)(unsafe.Pointer(&w.outbuf)), &outlen)
total += int(inlen)
data = data[inlen:]
if _, err := w.w.Write(w.outbuf[:outlen]); err != nil {
return total, err
}
}
return total, nil
}
//!-write
//!+close
// Close flushes the compressed data and closes the stream.
// It does not close the underlying io.Writer.
func (w *writer) Close() error {
if w.stream == nil {
panic("closed")
}
defer func() {
C.BZ2_bzCompressEnd(w.stream)
w.stream = nil
}()
for {
inlen, outlen := C.uint(0), C.uint(cap(w.outbuf))
r := C.bz2compress(w.stream, C.BZ_FINISH, nil, &inlen,
(*C.char)(unsafe.Pointer(&w.outbuf)), &outlen)
if _, err := w.w.Write(w.outbuf[:outlen]); err != nil {
return err
}
if r == C.BZ_STREAM_END {
return nil
}
}
}
//!-close

40
vendor/gopl.io/ch13/bzip-print/bzip2_test.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package bzip_test
import (
"bytes"
"compress/bzip2" // reader
"io"
"testing"
"gopl.io/ch13/bzip" // writer
)
func TestBzip2(t *testing.T) {
var compressed, uncompressed bytes.Buffer
w := bzip.NewWriter(&compressed)
// Write a repetitive message in a million pieces,
// compressing one copy but not the other.
tee := io.MultiWriter(w, &uncompressed)
for i := 0; i < 1000000; i++ {
io.WriteString(tee, "hello")
}
if err := w.Close(); err != nil {
t.Fatal(err)
}
// Check the size of the compressed stream.
if got, want := compressed.Len(), 255; got != want {
t.Errorf("1 million hellos compressed to %d bytes, want %d", got, want)
}
// Decompress and compare with original.
var decompressed bytes.Buffer
io.Copy(&decompressed, bzip2.NewReader(&compressed))
if !bytes.Equal(uncompressed.Bytes(), decompressed.Bytes()) {
t.Error("decompression yielded a different message")
}
}

32
vendor/gopl.io/ch13/bzip/bzip2.c generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 362.
//
// The version of this program that appeared in the first and second
// printings did not comply with the proposed rules for passing
// pointers between Go and C, described here:
// https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md
//
// The version below, which appears in the third printing,
// has been corrected. See bzip2.go for explanation.
//!+
/* This file is gopl.io/ch13/bzip/bzip2.c, */
/* a simple wrapper for libbzip2 suitable for cgo. */
#include <bzlib.h>
int bz2compress(bz_stream *s, int action,
char *in, unsigned *inlen, char *out, unsigned *outlen) {
s->next_in = in;
s->avail_in = *inlen;
s->next_out = out;
s->avail_out = *outlen;
int r = BZ2_bzCompress(s, action);
*inlen -= s->avail_in;
*outlen -= s->avail_out;
s->next_in = s->next_out = NULL;
return r;
}
//!-

111
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 362.
//
// The version of this program that appeared in the first and second
// printings did not comply with the proposed rules for passing
// pointers between Go and C, described here:
// https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md
//
// The rules forbid a C function like bz2compress from storing 'in'
// and 'out' (pointers to variables allocated by Go) into the Go
// variable 's', even temporarily.
//
// The version below, which appears in the third printing, has been
// corrected. To comply with the rules, the bz_stream variable must
// be allocated by C code. We have introduced two C functions,
// bz2alloc and bz2free, to allocate and free instances of the
// bz_stream type. Also, we have changed bz2compress so that before
// it returns, it clears the fields of the bz_stream that contain
// pointers to Go variables.
//!+
// Package bzip provides a writer that uses bzip2 compression (bzip.org).
package bzip
/*
#cgo CFLAGS: -I/usr/include
#cgo LDFLAGS: -L/usr/lib -lbz2
#include <bzlib.h>
#include <stdlib.h>
bz_stream* bz2alloc() { return calloc(1, sizeof(bz_stream)); }
int bz2compress(bz_stream *s, int action,
char *in, unsigned *inlen, char *out, unsigned *outlen);
void bz2free(bz_stream* s) { free(s); }
*/
import "C"
import (
"io"
"unsafe"
)
type writer struct {
w io.Writer // underlying output stream
stream *C.bz_stream
outbuf [64 * 1024]byte
}
// NewWriter returns a writer for bzip2-compressed streams.
func NewWriter(out io.Writer) io.WriteCloser {
const blockSize = 9
const verbosity = 0
const workFactor = 30
w := &writer{w: out, stream: C.bz2alloc()}
C.BZ2_bzCompressInit(w.stream, blockSize, verbosity, workFactor)
return w
}
//!-
//!+write
func (w *writer) Write(data []byte) (int, error) {
if w.stream == nil {
panic("closed")
}
var total int // uncompressed bytes written
for len(data) > 0 {
inlen, outlen := C.uint(len(data)), C.uint(cap(w.outbuf))
C.bz2compress(w.stream, C.BZ_RUN,
(*C.char)(unsafe.Pointer(&data[0])), &inlen,
(*C.char)(unsafe.Pointer(&w.outbuf)), &outlen)
total += int(inlen)
data = data[inlen:]
if _, err := w.w.Write(w.outbuf[:outlen]); err != nil {
return total, err
}
}
return total, nil
}
//!-write
//!+close
// Close flushes the compressed data and closes the stream.
// It does not close the underlying io.Writer.
func (w *writer) Close() error {
if w.stream == nil {
panic("closed")
}
defer func() {
C.BZ2_bzCompressEnd(w.stream)
C.bz2free(w.stream)
w.stream = nil
}()
for {
inlen, outlen := C.uint(0), C.uint(cap(w.outbuf))
r := C.bz2compress(w.stream, C.BZ_FINISH, nil, &inlen,
(*C.char)(unsafe.Pointer(&w.outbuf)), &outlen)
if _, err := w.w.Write(w.outbuf[:outlen]); err != nil {
return err
}
if r == C.BZ_STREAM_END {
return nil
}
}
}
//!-close

40
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package bzip_test
import (
"bytes"
"compress/bzip2" // reader
"io"
"testing"
"gopl.io/ch13/bzip" // writer
)
func TestBzip2(t *testing.T) {
var compressed, uncompressed bytes.Buffer
w := bzip.NewWriter(&compressed)
// Write a repetitive message in a million pieces,
// compressing one copy but not the other.
tee := io.MultiWriter(w, &uncompressed)
for i := 0; i < 1000000; i++ {
io.WriteString(tee, "hello")
}
if err := w.Close(); err != nil {
t.Fatal(err)
}
// Check the size of the compressed stream.
if got, want := compressed.Len(), 255; got != want {
t.Errorf("1 million hellos compressed to %d bytes, want %d", got, want)
}
// Decompress and compare with original.
var decompressed bytes.Buffer
io.Copy(&decompressed, bzip2.NewReader(&compressed))
if !bytes.Equal(uncompressed.Bytes(), decompressed.Bytes()) {
t.Error("decompression yielded a different message")
}
}

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vendor/gopl.io/ch13/bzipper/main.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 365.
//!+
// Bzipper reads input, bzip2-compresses it, and writes it out.
package main
import (
"io"
"log"
"os"
"gopl.io/ch13/bzip"
)
func main() {
w := bzip.NewWriter(os.Stdout)
if _, err := io.Copy(w, os.Stdin); err != nil {
log.Fatalf("bzipper: %v\n", err)
}
if err := w.Close(); err != nil {
log.Fatalf("bzipper: close: %v\n", err)
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 359.
// Package equal provides a deep equivalence relation for arbitrary values.
package equal
import (
"reflect"
"unsafe"
)
//!+
func equal(x, y reflect.Value, seen map[comparison]bool) bool {
if !x.IsValid() || !y.IsValid() {
return x.IsValid() == y.IsValid()
}
if x.Type() != y.Type() {
return false
}
// ...cycle check omitted (shown later)...
//!-
//!+cyclecheck
// cycle check
if x.CanAddr() && y.CanAddr() {
xptr := unsafe.Pointer(x.UnsafeAddr())
yptr := unsafe.Pointer(y.UnsafeAddr())
if xptr == yptr {
return true // identical references
}
c := comparison{xptr, yptr, x.Type()}
if seen[c] {
return true // already seen
}
seen[c] = true
}
//!-cyclecheck
//!+
switch x.Kind() {
case reflect.Bool:
return x.Bool() == y.Bool()
case reflect.String:
return x.String() == y.String()
// ...numeric cases omitted for brevity...
//!-
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
reflect.Int64:
return x.Int() == y.Int()
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32,
reflect.Uint64, reflect.Uintptr:
return x.Uint() == y.Uint()
case reflect.Float32, reflect.Float64:
return x.Float() == y.Float()
case reflect.Complex64, reflect.Complex128:
return x.Complex() == y.Complex()
//!+
case reflect.Chan, reflect.UnsafePointer, reflect.Func:
return x.Pointer() == y.Pointer()
case reflect.Ptr, reflect.Interface:
return equal(x.Elem(), y.Elem(), seen)
case reflect.Array, reflect.Slice:
if x.Len() != y.Len() {
return false
}
for i := 0; i < x.Len(); i++ {
if !equal(x.Index(i), y.Index(i), seen) {
return false
}
}
return true
// ...struct and map cases omitted for brevity...
//!-
case reflect.Struct:
for i, n := 0, x.NumField(); i < n; i++ {
if !equal(x.Field(i), y.Field(i), seen) {
return false
}
}
return true
case reflect.Map:
if x.Len() != y.Len() {
return false
}
for _, k := range x.MapKeys() {
if !equal(x.MapIndex(k), y.MapIndex(k), seen) {
return false
}
}
return true
//!+
}
panic("unreachable")
}
//!-
//!+comparison
// Equal reports whether x and y are deeply equal.
//!-comparison
//
// Map keys are always compared with ==, not deeply.
// (This matters for keys containing pointers or interfaces.)
//!+comparison
func Equal(x, y interface{}) bool {
seen := make(map[comparison]bool)
return equal(reflect.ValueOf(x), reflect.ValueOf(y), seen)
}
type comparison struct {
x, y unsafe.Pointer
t reflect.Type
}
//!-comparison

133
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package equal
import (
"bytes"
"fmt"
"testing"
)
func TestEqual(t *testing.T) {
one, oneAgain, two := 1, 1, 2
type CyclePtr *CyclePtr
var cyclePtr1, cyclePtr2 CyclePtr
cyclePtr1 = &cyclePtr1
cyclePtr2 = &cyclePtr2
type CycleSlice []CycleSlice
var cycleSlice CycleSlice
cycleSlice = append(cycleSlice, cycleSlice)
ch1, ch2 := make(chan int), make(chan int)
var ch1ro <-chan int = ch1
type mystring string
var iface1, iface1Again, iface2 interface{} = &one, &oneAgain, &two
for _, test := range []struct {
x, y interface{}
want bool
}{
// basic types
{1, 1, true},
{1, 2, false}, // different values
{1, 1.0, false}, // different types
{"foo", "foo", true},
{"foo", "bar", false},
{mystring("foo"), "foo", false}, // different types
// slices
{[]string{"foo"}, []string{"foo"}, true},
{[]string{"foo"}, []string{"bar"}, false},
{[]string{}, []string(nil), true},
// slice cycles
{cycleSlice, cycleSlice, true},
// maps
{
map[string][]int{"foo": {1, 2, 3}},
map[string][]int{"foo": {1, 2, 3}},
true,
},
{
map[string][]int{"foo": {1, 2, 3}},
map[string][]int{"foo": {1, 2, 3, 4}},
false,
},
{
map[string][]int{},
map[string][]int(nil),
true,
},
// pointers
{&one, &one, true},
{&one, &two, false},
{&one, &oneAgain, true},
{new(bytes.Buffer), new(bytes.Buffer), true},
// pointer cycles
{cyclePtr1, cyclePtr1, true},
{cyclePtr2, cyclePtr2, true},
{cyclePtr1, cyclePtr2, true}, // they're deeply equal
// functions
{(func())(nil), (func())(nil), true},
{(func())(nil), func() {}, false},
{func() {}, func() {}, false},
// arrays
{[...]int{1, 2, 3}, [...]int{1, 2, 3}, true},
{[...]int{1, 2, 3}, [...]int{1, 2, 4}, false},
// channels
{ch1, ch1, true},
{ch1, ch2, false},
{ch1ro, ch1, false}, // NOTE: not equal
// interfaces
{&iface1, &iface1, true},
{&iface1, &iface2, false},
{&iface1Again, &iface1, true},
} {
if Equal(test.x, test.y) != test.want {
t.Errorf("Equal(%v, %v) = %t",
test.x, test.y, !test.want)
}
}
}
func Example_equal() {
//!+
fmt.Println(Equal([]int{1, 2, 3}, []int{1, 2, 3})) // "true"
fmt.Println(Equal([]string{"foo"}, []string{"bar"})) // "false"
fmt.Println(Equal([]string(nil), []string{})) // "true"
fmt.Println(Equal(map[string]int(nil), map[string]int{})) // "true"
//!-
// Output:
// true
// false
// true
// true
}
func Example_equalCycle() {
//!+cycle
// Circular linked lists a -> b -> a and c -> c.
type link struct {
value string
tail *link
}
a, b, c := &link{value: "a"}, &link{value: "b"}, &link{value: "c"}
a.tail, b.tail, c.tail = b, a, c
fmt.Println(Equal(a, a)) // "true"
fmt.Println(Equal(b, b)) // "true"
fmt.Println(Equal(c, c)) // "true"
fmt.Println(Equal(a, b)) // "false"
fmt.Println(Equal(a, c)) // "false"
//!-cycle
// Output:
// true
// true
// true
// false
// false
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 357.
// Package unsafeptr demonstrates basic use of unsafe.Pointer.
package main
import (
"fmt"
"unsafe"
)
func main() {
//!+main
var x struct {
a bool
b int16
c []int
}
// equivalent to pb := &x.b
pb := (*int16)(unsafe.Pointer(
uintptr(unsafe.Pointer(&x)) + unsafe.Offsetof(x.b)))
*pb = 42
fmt.Println(x.b) // "42"
//!-main
}
/*
//!+wrong
// NOTE: subtly incorrect!
tmp := uintptr(unsafe.Pointer(&x)) + unsafe.Offsetof(x.b)
pb := (*int16)(unsafe.Pointer(tmp))
*pb = 42
//!-wrong
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 29.
//!+
// Boiling prints the boiling point of water.
package main
import "fmt"
const boilingF = 212.0
func main() {
var f = boilingF
var c = (f - 32) * 5 / 9
fmt.Printf("boiling point = %g°F or %g°C\n", f, c)
// Output:
// boiling point = 212°F or 100°C
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 43.
//!+
// Cf converts its numeric argument to Celsius and Fahrenheit.
package main
import (
"fmt"
"os"
"strconv"
"gopl.io/ch2/tempconv"
)
func main() {
for _, arg := range os.Args[1:] {
t, err := strconv.ParseFloat(arg, 64)
if err != nil {
fmt.Fprintf(os.Stderr, "cf: %v\n", err)
os.Exit(1)
}
f := tempconv.Fahrenheit(t)
c := tempconv.Celsius(t)
fmt.Printf("%s = %s, %s = %s\n",
f, tempconv.FToC(f), c, tempconv.CToF(c))
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 33.
//!+
// Echo4 prints its command-line arguments.
package main
import (
"flag"
"fmt"
"strings"
)
var n = flag.Bool("n", false, "omit trailing newline")
var sep = flag.String("s", " ", "separator")
func main() {
flag.Parse()
fmt.Print(strings.Join(flag.Args(), *sep))
if !*n {
fmt.Println()
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 29.
//!+
// Ftoc prints two Fahrenheit-to-Celsius conversions.
package main
import "fmt"
func main() {
const freezingF, boilingF = 32.0, 212.0
fmt.Printf("%g°F = %g°C\n", freezingF, fToC(freezingF)) // "32°F = 0°C"
fmt.Printf("%g°F = %g°C\n", boilingF, fToC(boilingF)) // "212°F = 100°C"
}
func fToC(f float64) float64 {
return (f - 32) * 5 / 9
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 45.
// (Package doc comment intentionally malformed to demonstrate golint.)
//!+
package popcount
// pc[i] is the population count of i.
var pc [256]byte
func init() {
for i := range pc {
pc[i] = pc[i/2] + byte(i&1)
}
}
// PopCount returns the population count (number of set bits) of x.
func PopCount(x uint64) int {
return int(pc[byte(x>>(0*8))] +
pc[byte(x>>(1*8))] +
pc[byte(x>>(2*8))] +
pc[byte(x>>(3*8))] +
pc[byte(x>>(4*8))] +
pc[byte(x>>(5*8))] +
pc[byte(x>>(6*8))] +
pc[byte(x>>(7*8))])
}
//!-

83
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package popcount_test
import (
"testing"
"gopl.io/ch2/popcount"
)
// -- Alternative implementations --
func BitCount(x uint64) int {
// Hacker's Delight, Figure 5-2.
x = x - ((x >> 1) & 0x5555555555555555)
x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333)
x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f
x = x + (x >> 8)
x = x + (x >> 16)
x = x + (x >> 32)
return int(x & 0x7f)
}
func PopCountByClearing(x uint64) int {
n := 0
for x != 0 {
x = x & (x - 1) // clear rightmost non-zero bit
n++
}
return n
}
func PopCountByShifting(x uint64) int {
n := 0
for i := uint(0); i < 64; i++ {
if x&(1<<i) != 0 {
n++
}
}
return n
}
// -- Benchmarks --
func BenchmarkPopCount(b *testing.B) {
for i := 0; i < b.N; i++ {
popcount.PopCount(0x1234567890ABCDEF)
}
}
func BenchmarkBitCount(b *testing.B) {
for i := 0; i < b.N; i++ {
BitCount(0x1234567890ABCDEF)
}
}
func BenchmarkPopCountByClearing(b *testing.B) {
for i := 0; i < b.N; i++ {
PopCountByClearing(0x1234567890ABCDEF)
}
}
func BenchmarkPopCountByShifting(b *testing.B) {
for i := 0; i < b.N; i++ {
PopCountByShifting(0x1234567890ABCDEF)
}
}
// 2.67GHz Xeon
// $ go test -cpu=4 -bench=. gopl.io/ch2/popcount
// BenchmarkPopCount-4 200000000 6.30 ns/op
// BenchmarkBitCount-4 300000000 4.15 ns/op
// BenchmarkPopCountByClearing-4 30000000 45.2 ns/op
// BenchmarkPopCountByShifting-4 10000000 153 ns/op
//
// 2.5GHz Intel Core i5
// $ go test -cpu=4 -bench=. gopl.io/ch2/popcount
// testing: warning: no tests to run
// BenchmarkPopCount-4 200000000 7.52 ns/op
// BenchmarkBitCount-4 500000000 3.36 ns/op
// BenchmarkPopCountByClearing-4 50000000 34.3 ns/op
// BenchmarkPopCountByShifting-4 20000000 108 ns/op

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 41.
//!+
package tempconv
// CToF converts a Celsius temperature to Fahrenheit.
func CToF(c Celsius) Fahrenheit { return Fahrenheit(c*9/5 + 32) }
// FToC converts a Fahrenheit temperature to Celsius.
func FToC(f Fahrenheit) Celsius { return Celsius((f - 32) * 5 / 9) }
//!-

23
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//!+
// Package tempconv performs Celsius and Fahrenheit conversions.
package tempconv
import "fmt"
type Celsius float64
type Fahrenheit float64
const (
AbsoluteZeroC Celsius = -273.15
FreezingC Celsius = 0
BoilingC Celsius = 100
)
func (c Celsius) String() string { return fmt.Sprintf("%g°C", c) }
func (f Fahrenheit) String() string { return fmt.Sprintf("%g°F", f) }
//!-

27
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 39.
//!+
// Package tempconv performs Celsius and Fahrenheit temperature computations.
package tempconv
import "fmt"
type Celsius float64
type Fahrenheit float64
const (
AbsoluteZeroC Celsius = -273.15
FreezingC Celsius = 0
BoilingC Celsius = 100
)
func CToF(c Celsius) Fahrenheit { return Fahrenheit(c*9/5 + 32) }
func FToC(f Fahrenheit) Celsius { return Celsius((f - 32) * 5 / 9) }
//!-
func (c Celsius) String() string { return fmt.Sprintf("%g°C", c) }

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package tempconv
import "fmt"
func Example_one() {
{
//!+arith
fmt.Printf("%g\n", BoilingC-FreezingC) // "100" °C
boilingF := CToF(BoilingC)
fmt.Printf("%g\n", boilingF-CToF(FreezingC)) // "180" °F
//!-arith
}
/*
//!+arith
fmt.Printf("%g\n", boilingF-FreezingC) // compile error: type mismatch
//!-arith
*/
// Output:
// 100
// 180
}
func Example_two() {
//!+printf
c := FToC(212.0)
fmt.Println(c.String()) // "100°C"
fmt.Printf("%v\n", c) // "100°C"; no need to call String explicitly
fmt.Printf("%s\n", c) // "100°C"
fmt.Println(c) // "100°C"
fmt.Printf("%g\n", c) // "100"; does not call String
fmt.Println(float64(c)) // "100"; does not call String
//!-printf
// Output:
// 100°C
// 100°C
// 100°C
// 100°C
// 100
// 100
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 72.
// Basename1 reads file names from stdin and prints the base name of each one.
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
input := bufio.NewScanner(os.Stdin)
for input.Scan() {
fmt.Println(basename(input.Text()))
}
// NOTE: ignoring potential errors from input.Err()
}
//!+
// basename removes directory components and a .suffix.
// e.g., a => a, a.go => a, a/b/c.go => c, a/b.c.go => b.c
func basename(s string) string {
// Discard last '/' and everything before.
for i := len(s) - 1; i >= 0; i-- {
if s[i] == '/' {
s = s[i+1:]
break
}
}
// Preserve everything before last '.'.
for i := len(s) - 1; i >= 0; i-- {
if s[i] == '.' {
s = s[:i]
break
}
}
return s
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 72.
// Basename2 reads file names from stdin and prints the base name of each one.
package main
import (
"bufio"
"fmt"
"os"
"strings"
)
func main() {
input := bufio.NewScanner(os.Stdin)
for input.Scan() {
fmt.Println(basename(input.Text()))
}
// NOTE: ignoring potential errors from input.Err()
}
// basename removes directory components and a trailing .suffix.
// e.g., a => a, a.go => a, a/b/c.go => c, a/b.c.go => b.c
//!+
func basename(s string) string {
slash := strings.LastIndex(s, "/") // -1 if "/" not found
s = s[slash+1:]
if dot := strings.LastIndex(s, "."); dot >= 0 {
s = s[:dot]
}
return s
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 73.
// Comma prints its argument numbers with a comma at each power of 1000.
//
// Example:
// $ go build gopl.io/ch3/comma
// $ ./comma 1 12 123 1234 1234567890
// 1
// 12
// 123
// 1,234
// 1,234,567,890
//
package main
import (
"fmt"
"os"
)
func main() {
for i := 1; i < len(os.Args); i++ {
fmt.Printf(" %s\n", comma(os.Args[i]))
}
}
//!+
// comma inserts commas in a non-negative decimal integer string.
func comma(s string) string {
n := len(s)
if n <= 3 {
return s
}
return comma(s[:n-3]) + "," + s[n-3:]
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 61.
//!+
// Mandelbrot emits a PNG image of the Mandelbrot fractal.
package main
import (
"image"
"image/color"
"image/png"
"math/cmplx"
"os"
)
func main() {
const (
xmin, ymin, xmax, ymax = -2, -2, +2, +2
width, height = 1024, 1024
)
img := image.NewRGBA(image.Rect(0, 0, width, height))
for py := 0; py < height; py++ {
y := float64(py)/height*(ymax-ymin) + ymin
for px := 0; px < width; px++ {
x := float64(px)/width*(xmax-xmin) + xmin
z := complex(x, y)
// Image point (px, py) represents complex value z.
img.Set(px, py, mandelbrot(z))
}
}
png.Encode(os.Stdout, img) // NOTE: ignoring errors
}
func mandelbrot(z complex128) color.Color {
const iterations = 200
const contrast = 15
var v complex128
for n := uint8(0); n < iterations; n++ {
v = v*v + z
if cmplx.Abs(v) > 2 {
return color.Gray{255 - contrast*n}
}
}
return color.Black
}
//!-
// Some other interesting functions:
func acos(z complex128) color.Color {
v := cmplx.Acos(z)
blue := uint8(real(v)*128) + 127
red := uint8(imag(v)*128) + 127
return color.YCbCr{192, blue, red}
}
func sqrt(z complex128) color.Color {
v := cmplx.Sqrt(z)
blue := uint8(real(v)*128) + 127
red := uint8(imag(v)*128) + 127
return color.YCbCr{128, blue, red}
}
// f(x) = x^4 - 1
//
// z' = z - f(z)/f'(z)
// = z - (z^4 - 1) / (4 * z^3)
// = z - (z - 1/z^3) / 4
func newton(z complex128) color.Color {
const iterations = 37
const contrast = 7
for i := uint8(0); i < iterations; i++ {
z -= (z - 1/(z*z*z)) / 4
if cmplx.Abs(z*z*z*z-1) < 1e-6 {
return color.Gray{255 - contrast*i}
}
}
return color.Black
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 77.
// Netflag demonstrates an integer type used as a bit field.
package main
import (
"fmt"
. "net"
)
//!+
func IsUp(v Flags) bool { return v&FlagUp == FlagUp }
func TurnDown(v *Flags) { *v &^= FlagUp }
func SetBroadcast(v *Flags) { *v |= FlagBroadcast }
func IsCast(v Flags) bool { return v&(FlagBroadcast|FlagMulticast) != 0 }
func main() {
var v Flags = FlagMulticast | FlagUp
fmt.Printf("%b %t\n", v, IsUp(v)) // "10001 true"
TurnDown(&v)
fmt.Printf("%b %t\n", v, IsUp(v)) // "10000 false"
SetBroadcast(&v)
fmt.Printf("%b %t\n", v, IsUp(v)) // "10010 false"
fmt.Printf("%b %t\n", v, IsCast(v)) // "10010 true"
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 74.
// Printints demonstrates the use of bytes.Buffer to format a string.
package main
import (
"bytes"
"fmt"
)
//!+
// intsToString is like fmt.Sprint(values) but adds commas.
func intsToString(values []int) string {
var buf bytes.Buffer
buf.WriteByte('[')
for i, v := range values {
if i > 0 {
buf.WriteString(", ")
}
fmt.Fprintf(&buf, "%d", v)
}
buf.WriteByte(']')
return buf.String()
}
func main() {
fmt.Println(intsToString([]int{1, 2, 3})) // "[1, 2, 3]"
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 58.
//!+
// Surface computes an SVG rendering of a 3-D surface function.
package main
import (
"fmt"
"math"
)
const (
width, height = 600, 320 // canvas size in pixels
cells = 100 // number of grid cells
xyrange = 30.0 // axis ranges (-xyrange..+xyrange)
xyscale = width / 2 / xyrange // pixels per x or y unit
zscale = height * 0.4 // pixels per z unit
angle = math.Pi / 6 // angle of x, y axes (=30°)
)
var sin30, cos30 = math.Sin(angle), math.Cos(angle) // sin(30°), cos(30°)
func main() {
fmt.Printf("<svg xmlns='http://www.w3.org/2000/svg' "+
"style='stroke: grey; fill: white; stroke-width: 0.7' "+
"width='%d' height='%d'>", width, height)
for i := 0; i < cells; i++ {
for j := 0; j < cells; j++ {
ax, ay := corner(i+1, j)
bx, by := corner(i, j)
cx, cy := corner(i, j+1)
dx, dy := corner(i+1, j+1)
fmt.Printf("<polygon points='%g,%g %g,%g %g,%g %g,%g'/>\n",
ax, ay, bx, by, cx, cy, dx, dy)
}
}
fmt.Println("</svg>")
}
func corner(i, j int) (float64, float64) {
// Find point (x,y) at corner of cell (i,j).
x := xyrange * (float64(i)/cells - 0.5)
y := xyrange * (float64(j)/cells - 0.5)
// Compute surface height z.
z := f(x, y)
// Project (x,y,z) isometrically onto 2-D SVG canvas (sx,sy).
sx := width/2 + (x-y)*cos30*xyscale
sy := height/2 + (x+y)*sin30*xyscale - z*zscale
return sx, sy
}
func f(x, y float64) float64 {
r := math.Hypot(x, y) // distance from (0,0)
return math.Sin(r) / r
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 88.
// Append illustrates the behavior of the built-in append function.
package main
import "fmt"
func appendslice(x []int, y ...int) []int {
var z []int
zlen := len(x) + len(y)
if zlen <= cap(x) {
// There is room to expand the slice.
z = x[:zlen]
} else {
// There is insufficient space.
// Grow by doubling, for amortized linear complexity.
zcap := zlen
if zcap < 2*len(x) {
zcap = 2 * len(x)
}
z = make([]int, zlen, zcap)
copy(z, x)
}
copy(z[len(x):], y)
return z
}
//!+append
func appendInt(x []int, y int) []int {
var z []int
zlen := len(x) + 1
if zlen <= cap(x) {
// There is room to grow. Extend the slice.
z = x[:zlen]
} else {
// There is insufficient space. Allocate a new array.
// Grow by doubling, for amortized linear complexity.
zcap := zlen
if zcap < 2*len(x) {
zcap = 2 * len(x)
}
z = make([]int, zlen, zcap)
copy(z, x) // a built-in function; see text
}
z[len(x)] = y
return z
}
//!-append
//!+growth
func main() {
var x, y []int
for i := 0; i < 10; i++ {
y = appendInt(x, i)
fmt.Printf("%d cap=%d\t%v\n", i, cap(y), y)
x = y
}
}
//!-growth
/*
//!+output
0 cap=1 [0]
1 cap=2 [0 1]
2 cap=4 [0 1 2]
3 cap=4 [0 1 2 3]
4 cap=8 [0 1 2 3 4]
5 cap=8 [0 1 2 3 4 5]
6 cap=8 [0 1 2 3 4 5 6]
7 cap=8 [0 1 2 3 4 5 6 7]
8 cap=16 [0 1 2 3 4 5 6 7 8]
9 cap=16 [0 1 2 3 4 5 6 7 8 9]
//!-output
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 117.
// Autoescape demonstrates automatic HTML escaping in html/template.
package main
import (
"html/template"
"log"
"os"
)
//!+
func main() {
const templ = `<p>A: {{.A}}</p><p>B: {{.B}}</p>`
t := template.Must(template.New("escape").Parse(templ))
var data struct {
A string // untrusted plain text
B template.HTML // trusted HTML
}
data.A = "<b>Hello!</b>"
data.B = "<b>Hello!</b>"
if err := t.Execute(os.Stdout, data); err != nil {
log.Fatal(err)
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 97.
//!+
// Charcount computes counts of Unicode characters.
package main
import (
"bufio"
"fmt"
"io"
"os"
"unicode"
"unicode/utf8"
)
func main() {
counts := make(map[rune]int) // counts of Unicode characters
var utflen [utf8.UTFMax + 1]int // count of lengths of UTF-8 encodings
invalid := 0 // count of invalid UTF-8 characters
in := bufio.NewReader(os.Stdin)
for {
r, n, err := in.ReadRune() // returns rune, nbytes, error
if err == io.EOF {
break
}
if err != nil {
fmt.Fprintf(os.Stderr, "charcount: %v\n", err)
os.Exit(1)
}
if r == unicode.ReplacementChar && n == 1 {
invalid++
continue
}
counts[r]++
utflen[n]++
}
fmt.Printf("rune\tcount\n")
for c, n := range counts {
fmt.Printf("%q\t%d\n", c, n)
}
fmt.Print("\nlen\tcount\n")
for i, n := range utflen {
if i > 0 {
fmt.Printf("%d\t%d\n", i, n)
}
}
if invalid > 0 {
fmt.Printf("\n%d invalid UTF-8 characters\n", invalid)
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 96.
// Dedup prints only one instance of each line; duplicates are removed.
package main
import (
"bufio"
"fmt"
"os"
)
//!+
func main() {
seen := make(map[string]bool) // a set of strings
input := bufio.NewScanner(os.Stdin)
for input.Scan() {
line := input.Text()
if !seen[line] {
seen[line] = true
fmt.Println(line)
}
}
if err := input.Err(); err != nil {
fmt.Fprintf(os.Stderr, "dedup: %v\n", err)
os.Exit(1)
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 106.
// Embed demonstrates basic struct embedding.
package main
import "fmt"
type Point struct{ X, Y int }
type Circle struct {
Point
Radius int
}
type Wheel struct {
Circle
Spokes int
}
func main() {
var w Wheel
//!+
w = Wheel{Circle{Point{8, 8}, 5}, 20}
w = Wheel{
Circle: Circle{
Point: Point{X: 8, Y: 8},
Radius: 5,
},
Spokes: 20, // NOTE: trailing comma necessary here (and at Radius)
}
fmt.Printf("%#v\n", w)
// Output:
// Wheel{Circle:Circle{Point:Point{X:8, Y:8}, Radius:5}, Spokes:20}
w.X = 42
fmt.Printf("%#v\n", w)
// Output:
// Wheel{Circle:Circle{Point:Point{X:42, Y:8}, Radius:5}, Spokes:20}
//!-
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 110.
//!+
// Package github provides a Go API for the GitHub issue tracker.
// See https://developer.github.com/v3/search/#search-issues.
package github
import "time"
const IssuesURL = "https://api.github.com/search/issues"
type IssuesSearchResult struct {
TotalCount int `json:"total_count"`
Items []*Issue
}
type Issue struct {
Number int
HTMLURL string `json:"html_url"`
Title string
State string
User *User
CreatedAt time.Time `json:"created_at"`
Body string // in Markdown format
}
type User struct {
Login string
HTMLURL string `json:"html_url"`
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//!+
package github
import (
"encoding/json"
"fmt"
"net/http"
"net/url"
"strings"
)
// SearchIssues queries the GitHub issue tracker.
func SearchIssues(terms []string) (*IssuesSearchResult, error) {
q := url.QueryEscape(strings.Join(terms, " "))
resp, err := http.Get(IssuesURL + "?q=" + q)
if err != nil {
return nil, err
}
//!-
// For long-term stability, instead of http.Get, use the
// variant below which adds an HTTP request header indicating
// that only version 3 of the GitHub API is acceptable.
//
// req, err := http.NewRequest("GET", IssuesURL+"?q="+q, nil)
// if err != nil {
// return nil, err
// }
// req.Header.Set(
// "Accept", "application/vnd.github.v3.text-match+json")
// resp, err := http.DefaultClient.Do(req)
//!+
// We must close resp.Body on all execution paths.
// (Chapter 5 presents 'defer', which makes this simpler.)
if resp.StatusCode != http.StatusOK {
resp.Body.Close()
return nil, fmt.Errorf("search query failed: %s", resp.Status)
}
var result IssuesSearchResult
if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
resp.Body.Close()
return nil, err
}
resp.Body.Close()
return &result, nil
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 99.
// Graph shows how to use a map of maps to represent a directed graph.
package main
import "fmt"
//!+
var graph = make(map[string]map[string]bool)
func addEdge(from, to string) {
edges := graph[from]
if edges == nil {
edges = make(map[string]bool)
graph[from] = edges
}
edges[to] = true
}
func hasEdge(from, to string) bool {
return graph[from][to]
}
//!-
func main() {
addEdge("a", "b")
addEdge("c", "d")
addEdge("a", "d")
addEdge("d", "a")
fmt.Println(hasEdge("a", "b"))
fmt.Println(hasEdge("c", "d"))
fmt.Println(hasEdge("a", "d"))
fmt.Println(hasEdge("d", "a"))
fmt.Println(hasEdge("x", "b"))
fmt.Println(hasEdge("c", "d"))
fmt.Println(hasEdge("x", "d"))
fmt.Println(hasEdge("d", "x"))
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 112.
//!+
// Issues prints a table of GitHub issues matching the search terms.
package main
import (
"fmt"
"log"
"os"
"gopl.io/ch4/github"
)
//!+
func main() {
result, err := github.SearchIssues(os.Args[1:])
if err != nil {
log.Fatal(err)
}
fmt.Printf("%d issues:\n", result.TotalCount)
for _, item := range result.Items {
fmt.Printf("#%-5d %9.9s %.55s\n",
item.Number, item.User.Login, item.Title)
}
}
//!-
/*
//!+textoutput
$ go build gopl.io/ch4/issues
$ ./issues repo:golang/go is:open json decoder
13 issues:
#5680 eaigner encoding/json: set key converter on en/decoder
#6050 gopherbot encoding/json: provide tokenizer
#8658 gopherbot encoding/json: use bufio
#8462 kortschak encoding/json: UnmarshalText confuses json.Unmarshal
#5901 rsc encoding/json: allow override type marshaling
#9812 klauspost encoding/json: string tag not symmetric
#7872 extempora encoding/json: Encoder internally buffers full output
#9650 cespare encoding/json: Decoding gives errPhase when unmarshalin
#6716 gopherbot encoding/json: include field name in unmarshal error me
#6901 lukescott encoding/json, encoding/xml: option to treat unknown fi
#6384 joeshaw encoding/json: encode precise floating point integers u
#6647 btracey x/tools/cmd/godoc: display type kind of each named type
#4237 gjemiller encoding/base64: URLEncoding padding is optional
//!-textoutput
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 115.
// Issueshtml prints an HTML table of issues matching the search terms.
package main
import (
"log"
"os"
"gopl.io/ch4/github"
)
//!+template
import "html/template"
var issueList = template.Must(template.New("issuelist").Parse(`
<h1>{{.TotalCount}} issues</h1>
<table>
<tr style='text-align: left'>
<th>#</th>
<th>State</th>
<th>User</th>
<th>Title</th>
</tr>
{{range .Items}}
<tr>
<td><a href='{{.HTMLURL}}'>{{.Number}}</a></td>
<td>{{.State}}</td>
<td><a href='{{.User.HTMLURL}}'>{{.User.Login}}</a></td>
<td><a href='{{.HTMLURL}}'>{{.Title}}</a></td>
</tr>
{{end}}
</table>
`))
//!-template
//!+
func main() {
result, err := github.SearchIssues(os.Args[1:])
if err != nil {
log.Fatal(err)
}
if err := issueList.Execute(os.Stdout, result); err != nil {
log.Fatal(err)
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 113.
// Issuesreport prints a report of issues matching the search terms.
package main
import (
"log"
"os"
"text/template"
"time"
"gopl.io/ch4/github"
)
//!+template
const templ = `{{.TotalCount}} issues:
{{range .Items}}----------------------------------------
Number: {{.Number}}
User: {{.User.Login}}
Title: {{.Title | printf "%.64s"}}
Age: {{.CreatedAt | daysAgo}} days
{{end}}`
//!-template
//!+daysAgo
func daysAgo(t time.Time) int {
return int(time.Since(t).Hours() / 24)
}
//!-daysAgo
//!+exec
var report = template.Must(template.New("issuelist").
Funcs(template.FuncMap{"daysAgo": daysAgo}).
Parse(templ))
func main() {
result, err := github.SearchIssues(os.Args[1:])
if err != nil {
log.Fatal(err)
}
if err := report.Execute(os.Stdout, result); err != nil {
log.Fatal(err)
}
}
//!-exec
func noMust() {
//!+parse
report, err := template.New("report").
Funcs(template.FuncMap{"daysAgo": daysAgo}).
Parse(templ)
if err != nil {
log.Fatal(err)
}
//!-parse
result, err := github.SearchIssues(os.Args[1:])
if err != nil {
log.Fatal(err)
}
if err := report.Execute(os.Stdout, result); err != nil {
log.Fatal(err)
}
}
/*
//!+output
$ go build gopl.io/ch4/issuesreport
$ ./issuesreport repo:golang/go is:open json decoder
13 issues:
----------------------------------------
Number: 5680
User: eaigner
Title: encoding/json: set key converter on en/decoder
Age: 750 days
----------------------------------------
Number: 6050
User: gopherbot
Title: encoding/json: provide tokenizer
Age: 695 days
----------------------------------------
...
//!-output
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 108.
// Movie prints Movies as JSON.
package main
import (
"encoding/json"
"fmt"
"log"
)
//!+
type Movie struct {
Title string
Year int `json:"released"`
Color bool `json:"color,omitempty"`
Actors []string
}
var movies = []Movie{
{Title: "Casablanca", Year: 1942, Color: false,
Actors: []string{"Humphrey Bogart", "Ingrid Bergman"}},
{Title: "Cool Hand Luke", Year: 1967, Color: true,
Actors: []string{"Paul Newman"}},
{Title: "Bullitt", Year: 1968, Color: true,
Actors: []string{"Steve McQueen", "Jacqueline Bisset"}},
// ...
}
//!-
func main() {
{
//!+Marshal
data, err := json.Marshal(movies)
if err != nil {
log.Fatalf("JSON marshaling failed: %s", err)
}
fmt.Printf("%s\n", data)
//!-Marshal
}
{
//!+MarshalIndent
data, err := json.MarshalIndent(movies, "", " ")
if err != nil {
log.Fatalf("JSON marshaling failed: %s", err)
}
fmt.Printf("%s\n", data)
//!-MarshalIndent
//!+Unmarshal
var titles []struct{ Title string }
if err := json.Unmarshal(data, &titles); err != nil {
log.Fatalf("JSON unmarshaling failed: %s", err)
}
fmt.Println(titles) // "[{Casablanca} {Cool Hand Luke} {Bullitt}]"
//!-Unmarshal
}
}
/*
//!+output
[{"Title":"Casablanca","released":1942,"Actors":["Humphrey Bogart","Ingr
id Bergman"]},{"Title":"Cool Hand Luke","released":1967,"color":true,"Ac
tors":["Paul Newman"]},{"Title":"Bullitt","released":1968,"color":true,"
Actors":["Steve McQueen","Jacqueline Bisset"]}]
//!-output
*/
/*
//!+indented
[
{
"Title": "Casablanca",
"released": 1942,
"Actors": [
"Humphrey Bogart",
"Ingrid Bergman"
]
},
{
"Title": "Cool Hand Luke",
"released": 1967,
"color": true,
"Actors": [
"Paul Newman"
]
},
{
"Title": "Bullitt",
"released": 1968,
"color": true,
"Actors": [
"Steve McQueen",
"Jacqueline Bisset"
]
}
]
//!-indented
*/

47
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 91.
//!+nonempty
// Nonempty is an example of an in-place slice algorithm.
package main
import "fmt"
// nonempty returns a slice holding only the non-empty strings.
// The underlying array is modified during the call.
func nonempty(strings []string) []string {
i := 0
for _, s := range strings {
if s != "" {
strings[i] = s
i++
}
}
return strings[:i]
}
//!-nonempty
func main() {
//!+main
data := []string{"one", "", "three"}
fmt.Printf("%q\n", nonempty(data)) // `["one" "three"]`
fmt.Printf("%q\n", data) // `["one" "three" "three"]`
//!-main
}
//!+alt
func nonempty2(strings []string) []string {
out := strings[:0] // zero-length slice of original
for _, s := range strings {
if s != "" {
out = append(out, s)
}
}
return out
}
//!-alt

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 86.
// Rev reverses a slice.
package main
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
func main() {
//!+array
a := [...]int{0, 1, 2, 3, 4, 5}
reverse(a[:])
fmt.Println(a) // "[5 4 3 2 1 0]"
//!-array
//!+slice
s := []int{0, 1, 2, 3, 4, 5}
// Rotate s left by two positions.
reverse(s[:2])
reverse(s[2:])
reverse(s)
fmt.Println(s) // "[2 3 4 5 0 1]"
//!-slice
// Interactive test of reverse.
input := bufio.NewScanner(os.Stdin)
outer:
for input.Scan() {
var ints []int
for _, s := range strings.Fields(input.Text()) {
x, err := strconv.ParseInt(s, 10, 64)
if err != nil {
fmt.Fprintln(os.Stderr, err)
continue outer
}
ints = append(ints, int(x))
}
reverse(ints)
fmt.Printf("%v\n", ints)
}
// NOTE: ignoring potential errors from input.Err()
}
//!+rev
// reverse reverses a slice of ints in place.
func reverse(s []int) {
for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
s[i], s[j] = s[j], s[i]
}
}
//!-rev

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 83.
// The sha256 command computes the SHA256 hash (an array) of a string.
package main
import "fmt"
//!+
import "crypto/sha256"
func main() {
c1 := sha256.Sum256([]byte("x"))
c2 := sha256.Sum256([]byte("X"))
fmt.Printf("%x\n%x\n%t\n%T\n", c1, c2, c1 == c2, c1)
// Output:
// 2d711642b726b04401627ca9fbac32f5c8530fb1903cc4db02258717921a4881
// 4b68ab3847feda7d6c62c1fbcbeebfa35eab7351ed5e78f4ddadea5df64b8015
// false
// [32]uint8
}
//!-

50
vendor/gopl.io/ch4/treesort/sort.go generated vendored Normal file
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 101.
// Package treesort provides insertion sort using an unbalanced binary tree.
package treesort
//!+
type tree struct {
value int
left, right *tree
}
// Sort sorts values in place.
func Sort(values []int) {
var root *tree
for _, v := range values {
root = add(root, v)
}
appendValues(values[:0], root)
}
// appendValues appends the elements of t to values in order
// and returns the resulting slice.
func appendValues(values []int, t *tree) []int {
if t != nil {
values = appendValues(values, t.left)
values = append(values, t.value)
values = appendValues(values, t.right)
}
return values
}
func add(t *tree, value int) *tree {
if t == nil {
// Equivalent to return &tree{value: value}.
t = new(tree)
t.value = value
return t
}
if value < t.value {
t.left = add(t.left, value)
} else {
t.right = add(t.right, value)
}
return t
}
//!-

23
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package treesort_test
import (
"math/rand"
"sort"
"testing"
"gopl.io/ch4/treesort"
)
func TestSort(t *testing.T) {
data := make([]int, 50)
for i := range data {
data[i] = rand.Int() % 50
}
treesort.Sort(data)
if !sort.IntsAreSorted(data) {
t.Errorf("not sorted: %v", data)
}
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 150.
// Defer1 demonstrates a deferred call being invoked during a panic.
package main
import "fmt"
//!+f
func main() {
f(3)
}
func f(x int) {
fmt.Printf("f(%d)\n", x+0/x) // panics if x == 0
defer fmt.Printf("defer %d\n", x)
f(x - 1)
}
//!-f
/*
//!+stdout
f(3)
f(2)
f(1)
defer 1
defer 2
defer 3
//!-stdout
//!+stderr
panic: runtime error: integer divide by zero
main.f(0)
src/gopl.io/ch5/defer1/defer.go:14
main.f(1)
src/gopl.io/ch5/defer1/defer.go:16
main.f(2)
src/gopl.io/ch5/defer1/defer.go:16
main.f(3)
src/gopl.io/ch5/defer1/defer.go:16
main.main()
src/gopl.io/ch5/defer1/defer.go:10
//!-stderr
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 151.
// Defer2 demonstrates a deferred call to runtime.Stack during a panic.
package main
import (
"fmt"
"os"
"runtime"
)
//!+
func main() {
defer printStack()
f(3)
}
func printStack() {
var buf [4096]byte
n := runtime.Stack(buf[:], false)
os.Stdout.Write(buf[:n])
}
//!-
func f(x int) {
fmt.Printf("f(%d)\n", x+0/x) // panics if x == 0
defer fmt.Printf("defer %d\n", x)
f(x - 1)
}
/*
//!+printstack
goroutine 1 [running]:
main.printStack()
src/gopl.io/ch5/defer2/defer.go:20
main.f(0)
src/gopl.io/ch5/defer2/defer.go:27
main.f(1)
src/gopl.io/ch5/defer2/defer.go:29
main.f(2)
src/gopl.io/ch5/defer2/defer.go:29
main.f(3)
src/gopl.io/ch5/defer2/defer.go:29
main.main()
src/gopl.io/ch5/defer2/defer.go:15
//!-printstack
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 148.
// Fetch saves the contents of a URL into a local file.
package main
import (
"fmt"
"io"
"net/http"
"os"
"path"
)
//!+
// Fetch downloads the URL and returns the
// name and length of the local file.
func fetch(url string) (filename string, n int64, err error) {
resp, err := http.Get(url)
if err != nil {
return "", 0, err
}
defer resp.Body.Close()
local := path.Base(resp.Request.URL.Path)
if local == "/" {
local = "index.html"
}
f, err := os.Create(local)
if err != nil {
return "", 0, err
}
n, err = io.Copy(f, resp.Body)
// Close file, but prefer error from Copy, if any.
if closeErr := f.Close(); err == nil {
err = closeErr
}
return local, n, err
}
//!-
func main() {
for _, url := range os.Args[1:] {
local, n, err := fetch(url)
if err != nil {
fmt.Fprintf(os.Stderr, "fetch %s: %v\n", url, err)
continue
}
fmt.Fprintf(os.Stderr, "%s => %s (%d bytes).\n", url, local, n)
}
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 122.
//!+main
// Findlinks1 prints the links in an HTML document read from standard input.
package main
import (
"fmt"
"os"
"golang.org/x/net/html"
)
func main() {
doc, err := html.Parse(os.Stdin)
if err != nil {
fmt.Fprintf(os.Stderr, "findlinks1: %v\n", err)
os.Exit(1)
}
for _, link := range visit(nil, doc) {
fmt.Println(link)
}
}
//!-main
//!+visit
// visit appends to links each link found in n and returns the result.
func visit(links []string, n *html.Node) []string {
if n.Type == html.ElementNode && n.Data == "a" {
for _, a := range n.Attr {
if a.Key == "href" {
links = append(links, a.Val)
}
}
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
links = visit(links, c)
}
return links
}
//!-visit
/*
//!+html
package html
type Node struct {
Type NodeType
Data string
Attr []Attribute
FirstChild, NextSibling *Node
}
type NodeType int32
const (
ErrorNode NodeType = iota
TextNode
DocumentNode
ElementNode
CommentNode
DoctypeNode
)
type Attribute struct {
Key, Val string
}
func Parse(r io.Reader) (*Node, error)
//!-html
*/

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 125.
// Findlinks2 does an HTTP GET on each URL, parses the
// result as HTML, and prints the links within it.
//
// Usage:
// findlinks url ...
package main
import (
"fmt"
"net/http"
"os"
"golang.org/x/net/html"
)
// visit appends to links each link found in n, and returns the result.
func visit(links []string, n *html.Node) []string {
if n.Type == html.ElementNode && n.Data == "a" {
for _, a := range n.Attr {
if a.Key == "href" {
links = append(links, a.Val)
}
}
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
links = visit(links, c)
}
return links
}
//!+
func main() {
for _, url := range os.Args[1:] {
links, err := findLinks(url)
if err != nil {
fmt.Fprintf(os.Stderr, "findlinks2: %v\n", err)
continue
}
for _, link := range links {
fmt.Println(link)
}
}
}
// findLinks performs an HTTP GET request for url, parses the
// response as HTML, and extracts and returns the links.
func findLinks(url string) ([]string, error) {
resp, err := http.Get(url)
if err != nil {
return nil, err
}
if resp.StatusCode != http.StatusOK {
resp.Body.Close()
return nil, fmt.Errorf("getting %s: %s", url, resp.Status)
}
doc, err := html.Parse(resp.Body)
resp.Body.Close()
if err != nil {
return nil, fmt.Errorf("parsing %s as HTML: %v", url, err)
}
return visit(nil, doc), nil
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 139.
// Findlinks3 crawls the web, starting with the URLs on the command line.
package main
import (
"fmt"
"log"
"os"
"gopl.io/ch5/links"
)
//!+breadthFirst
// breadthFirst calls f for each item in the worklist.
// Any items returned by f are added to the worklist.
// f is called at most once for each item.
func breadthFirst(f func(item string) []string, worklist []string) {
seen := make(map[string]bool)
for len(worklist) > 0 {
items := worklist
worklist = nil
for _, item := range items {
if !seen[item] {
seen[item] = true
worklist = append(worklist, f(item)...)
}
}
}
}
//!-breadthFirst
//!+crawl
func crawl(url string) []string {
fmt.Println(url)
list, err := links.Extract(url)
if err != nil {
log.Print(err)
}
return list
}
//!-crawl
//!+main
func main() {
// Crawl the web breadth-first,
// starting from the command-line arguments.
breadthFirst(crawl, os.Args[1:])
}
//!-main

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 138.
//!+Extract
// Package links provides a link-extraction function.
package links
import (
"fmt"
"net/http"
"golang.org/x/net/html"
)
// Extract makes an HTTP GET request to the specified URL, parses
// the response as HTML, and returns the links in the HTML document.
func Extract(url string) ([]string, error) {
resp, err := http.Get(url)
if err != nil {
return nil, err
}
if resp.StatusCode != http.StatusOK {
resp.Body.Close()
return nil, fmt.Errorf("getting %s: %s", url, resp.Status)
}
doc, err := html.Parse(resp.Body)
resp.Body.Close()
if err != nil {
return nil, fmt.Errorf("parsing %s as HTML: %v", url, err)
}
var links []string
visitNode := func(n *html.Node) {
if n.Type == html.ElementNode && n.Data == "a" {
for _, a := range n.Attr {
if a.Key != "href" {
continue
}
link, err := resp.Request.URL.Parse(a.Val)
if err != nil {
continue // ignore bad URLs
}
links = append(links, link.String())
}
}
}
forEachNode(doc, visitNode, nil)
return links, nil
}
//!-Extract
// Copied from gopl.io/ch5/outline2.
func forEachNode(n *html.Node, pre, post func(n *html.Node)) {
if pre != nil {
pre(n)
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
forEachNode(c, pre, post)
}
if post != nil {
post(n)
}
}

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 123.
// Outline prints the outline of an HTML document tree.
package main
import (
"fmt"
"os"
"golang.org/x/net/html"
)
//!+
func main() {
doc, err := html.Parse(os.Stdin)
if err != nil {
fmt.Fprintf(os.Stderr, "outline: %v\n", err)
os.Exit(1)
}
outline(nil, doc)
}
func outline(stack []string, n *html.Node) {
if n.Type == html.ElementNode {
stack = append(stack, n.Data) // push tag
fmt.Println(stack)
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
outline(stack, c)
}
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 133.
// Outline prints the outline of an HTML document tree.
package main
import (
"fmt"
"net/http"
"os"
"golang.org/x/net/html"
)
func main() {
for _, url := range os.Args[1:] {
outline(url)
}
}
func outline(url string) error {
resp, err := http.Get(url)
if err != nil {
return err
}
defer resp.Body.Close()
doc, err := html.Parse(resp.Body)
if err != nil {
return err
}
//!+call
forEachNode(doc, startElement, endElement)
//!-call
return nil
}
//!+forEachNode
// forEachNode calls the functions pre(x) and post(x) for each node
// x in the tree rooted at n. Both functions are optional.
// pre is called before the children are visited (preorder) and
// post is called after (postorder).
func forEachNode(n *html.Node, pre, post func(n *html.Node)) {
if pre != nil {
pre(n)
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
forEachNode(c, pre, post)
}
if post != nil {
post(n)
}
}
//!-forEachNode
//!+startend
var depth int
func startElement(n *html.Node) {
if n.Type == html.ElementNode {
fmt.Printf("%*s<%s>\n", depth*2, "", n.Data)
depth++
}
}
func endElement(n *html.Node) {
if n.Type == html.ElementNode {
depth--
fmt.Printf("%*s</%s>\n", depth*2, "", n.Data)
}
}
//!-startend

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 135.
// The squares program demonstrates a function value with state.
package main
import "fmt"
//!+
// squares returns a function that returns
// the next square number each time it is called.
func squares() func() int {
var x int
return func() int {
x++
return x * x
}
}
func main() {
f := squares()
fmt.Println(f()) // "1"
fmt.Println(f()) // "4"
fmt.Println(f()) // "9"
fmt.Println(f()) // "16"
}
//!-

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 142.
// The sum program demonstrates a variadic function.
package main
import "fmt"
//!+
func sum(vals ...int) int {
total := 0
for _, val := range vals {
total += val
}
return total
}
//!-
func main() {
//!+main
fmt.Println(sum()) // "0"
fmt.Println(sum(3)) // "3"
fmt.Println(sum(1, 2, 3, 4)) // "10"
//!-main
//!+slice
values := []int{1, 2, 3, 4}
fmt.Println(sum(values...)) // "10"
//!-slice
}

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