good good study, day day up!

vendor/gopl.io/ch13/bzip-print/bzip2.c

@@ -0,0 +1,28 @@
+// 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;
+}
+
+//!-

vendor/gopl.io/ch13/bzip-print/bzip2.go

@@ -0,0 +1,96 @@
+// 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

vendor/gopl.io/ch13/bzip-print/bzip2_test.go

@@ -0,0 +1,40 @@
+// 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")
+	}
+}

vendor/gopl.io/ch13/bzip/bzip2.c

@@ -0,0 +1,32 @@
+// 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;
+}
+
+//!-

vendor/gopl.io/ch13/bzip/bzip2.go

@@ -0,0 +1,111 @@
+// 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

vendor/gopl.io/ch13/bzip/bzip2_test.go

@@ -0,0 +1,40 @@
+// 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")
+	}
+}

vendor/gopl.io/ch13/bzipper/main.go

@@ -0,0 +1,29 @@
+// 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)
+	}
+}
+
+//!-

vendor/gopl.io/ch13/equal/equal.go

@@ -0,0 +1,127 @@
+// 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

vendor/gopl.io/ch13/equal/equal_test.go

@@ -0,0 +1,133 @@
+// 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
+}

vendor/gopl.io/ch13/unsafeptr/main.go

@@ -0,0 +1,38 @@
+// 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
+*/