Update to gobook@0a3e8d997823052c6a8575feca6e515ac6f8299d
This commit is contained in:
parent
84af1e6bd3
commit
34cd1719c0
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 362.
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// This is the version that appears in print,
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// but it does not comply with the proposed
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// rules for passing pointers between Go and C.
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// (https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md)
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// See gopl.io/ch13/bzip for an updated version.
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//!+
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/* This file is gopl.io/ch13/bzip/bzip2.c, */
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/* a simple wrapper for libbzip2 suitable for cgo. */
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#include <bzlib.h>
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int bz2compress(bz_stream *s, int action,
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char *in, unsigned *inlen, char *out, unsigned *outlen) {
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s->next_in = in;
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s->avail_in = *inlen;
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s->next_out = out;
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s->avail_out = *outlen;
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int r = BZ2_bzCompress(s, action);
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*inlen -= s->avail_in;
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*outlen -= s->avail_out;
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return r;
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}
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//!-
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@ -0,0 +1,96 @@
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 362.
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// This is the version that appears in print,
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// but it does not comply with the proposed
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// rules for passing pointers between Go and C.
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// (https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md)
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// See gopl.io/ch13/bzip for an updated version.
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//!+
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// Package bzip provides a writer that uses bzip2 compression (bzip.org).
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package bzip
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/*
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#cgo CFLAGS: -I/usr/include
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#cgo LDFLAGS: -L/usr/lib -lbz2
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#include <bzlib.h>
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int bz2compress(bz_stream *s, int action,
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char *in, unsigned *inlen, char *out, unsigned *outlen);
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*/
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import "C"
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import (
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"io"
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"unsafe"
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)
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type writer struct {
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w io.Writer // underlying output stream
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stream *C.bz_stream
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outbuf [64 * 1024]byte
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}
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// NewWriter returns a writer for bzip2-compressed streams.
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func NewWriter(out io.Writer) io.WriteCloser {
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const (
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blockSize = 9
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verbosity = 0
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workFactor = 30
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)
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w := &writer{w: out, stream: new(C.bz_stream)}
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C.BZ2_bzCompressInit(w.stream, blockSize, verbosity, workFactor)
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return w
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}
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//!-
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//!+write
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func (w *writer) Write(data []byte) (int, error) {
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if w.stream == nil {
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panic("closed")
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}
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var total int // uncompressed bytes written
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for len(data) > 0 {
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inlen, outlen := C.uint(len(data)), C.uint(cap(w.outbuf))
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C.bz2compress(w.stream, C.BZ_RUN,
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(*C.char)(unsafe.Pointer(&data[0])), &inlen,
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(*C.char)(unsafe.Pointer(&w.outbuf)), &outlen)
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total += int(inlen)
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data = data[inlen:]
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if _, err := w.w.Write(w.outbuf[:outlen]); err != nil {
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return total, err
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}
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}
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return total, nil
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}
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//!-write
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//!+close
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// Close flushes the compressed data and closes the stream.
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// It does not close the underlying io.Writer.
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func (w *writer) Close() error {
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if w.stream == nil {
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panic("closed")
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}
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defer func() {
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C.BZ2_bzCompressEnd(w.stream)
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w.stream = nil
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}()
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for {
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inlen, outlen := C.uint(0), C.uint(cap(w.outbuf))
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r := C.bz2compress(w.stream, C.BZ_FINISH, nil, &inlen,
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(*C.char)(unsafe.Pointer(&w.outbuf)), &outlen)
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if _, err := w.w.Write(w.outbuf[:outlen]); err != nil {
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return err
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}
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if r == C.BZ_STREAM_END {
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return nil
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}
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}
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}
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//!-close
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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package bzip_test
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import (
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"bytes"
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"compress/bzip2" // reader
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"io"
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"testing"
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"gopl.io/ch13/bzip" // writer
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)
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func TestBzip2(t *testing.T) {
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var compressed, uncompressed bytes.Buffer
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w := bzip.NewWriter(&compressed)
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// Write a repetitive message in a million pieces,
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// compressing one copy but not the other.
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tee := io.MultiWriter(w, &uncompressed)
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for i := 0; i < 1000000; i++ {
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io.WriteString(tee, "hello")
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}
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if err := w.Close(); err != nil {
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t.Fatal(err)
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}
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// Check the size of the compressed stream.
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if got, want := compressed.Len(), 255; got != want {
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t.Errorf("1 million hellos compressed to %d bytes, want %d", got, want)
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}
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// Decompress and compare with original.
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var decompressed bytes.Buffer
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io.Copy(&decompressed, bzip2.NewReader(&compressed))
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if !bytes.Equal(uncompressed.Bytes(), decompressed.Bytes()) {
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t.Error("decompression yielded a different message")
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}
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}
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int r = BZ2_bzCompress(s, action);
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int r = BZ2_bzCompress(s, action);
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*inlen -= s->avail_in;
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*inlen -= s->avail_in;
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*outlen -= s->avail_out;
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*outlen -= s->avail_out;
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/* "C code may store a Go pointer in C memory subject to rule 2:
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* it must stop storing the pointer before it returns to Go." */
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s->next_in = NULL;
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s->next_out = NULL;
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return r;
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return r;
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}
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}
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@ -2,6 +2,20 @@
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 362.
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// See page 362.
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// The version of this file that appears in the book does not comply
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// with the proposed rules for passing pointers between Go and C.
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// (https://github.com/golang/proposal/blob/master/design/12416-cgo-pointers.md)
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// The rules forbid a C function like bz2compress from storing 'in' and
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// 'out' (pointers to variables allocated by Go) into the Go variable 's',
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// even temporarily.
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//
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// To comply with the rules, the bz_stream variable must be allocated
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// by C code. We have introduced two C functions, bz2alloc and
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// bz2free, to allocate and free instances of the bz_stream type.
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// Also, we have changed bz2compress so that before it returns, it
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// clears the fields of the bz_stream that contain point to Go
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// variables.
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//!+
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//!+
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// Package bzip provides a writer that uses bzip2 compression (bzip.org).
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// Package bzip provides a writer that uses bzip2 compression (bzip.org).
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@ -11,8 +25,12 @@ package bzip
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#cgo CFLAGS: -I/usr/include
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#cgo CFLAGS: -I/usr/include
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#cgo LDFLAGS: -L/usr/lib -lbz2
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#cgo LDFLAGS: -L/usr/lib -lbz2
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#include <bzlib.h>
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#include <bzlib.h>
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#include <stdlib.h>
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bz_stream* bz2alloc() { return calloc(1, sizeof(bz_stream)); }
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int bz2compress(bz_stream *s, int action,
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int bz2compress(bz_stream *s, int action,
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char *in, unsigned *inlen, char *out, unsigned *outlen);
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char *in, unsigned *inlen, char *out, unsigned *outlen);
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void bz2free(bz_stream* s) { return free(s); }
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*/
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*/
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import "C"
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import "C"
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@ -34,9 +52,7 @@ func NewWriter(out io.Writer) io.WriteCloser {
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verbosity = 0
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verbosity = 0
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workFactor = 30
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workFactor = 30
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)
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)
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// NOTE: This code may not work in future Go releases.
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w := &writer{w: out, stream: C.bz2alloc()}
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// See http://www.gopl.io/errata.html for explanation.
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w := &writer{w: out, stream: new(C.bz_stream)}
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C.BZ2_bzCompressInit(w.stream, blockSize, verbosity, workFactor)
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C.BZ2_bzCompressInit(w.stream, blockSize, verbosity, workFactor)
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return w
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return w
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}
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}
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@ -75,6 +91,7 @@ func (w *writer) Close() error {
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}
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}
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defer func() {
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defer func() {
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C.BZ2_bzCompressEnd(w.stream)
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C.BZ2_bzCompressEnd(w.stream)
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C.bz2free(w.stream)
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w.stream = nil
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w.stream = nil
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}()
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}()
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for {
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for {
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@ -0,0 +1,64 @@
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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// Package tempconv performs Celsius and Fahrenheit temperature computations.
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package tempconv
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import (
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"flag"
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"fmt"
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)
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type Celsius float64
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type Fahrenheit float64
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func CToF(c Celsius) Fahrenheit { return Fahrenheit(c*9.0/5.0 + 32.0) }
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func FToC(f Fahrenheit) Celsius { return Celsius((f - 32.0) * 5.0 / 9.0) }
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func (c Celsius) String() string { return fmt.Sprintf("%g°C", c) }
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/*
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//!+flagvalue
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package flag
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// Value is the interface to the value stored in a flag.
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type Value interface {
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String() string
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||||||
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Set(string) error
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||||||
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}
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//!-flagvalue
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||||||
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*/
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//!+celsiusflag
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// *celsiusFlag satisfies the flag.Value interface.
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type celsiusFlag struct{ Celsius }
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||||||
|
func (f *celsiusFlag) Set(s string) error {
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|
var unit string
|
||||||
|
var value float64
|
||||||
|
fmt.Sscanf(s, "%f%s", &value, &unit) // no error check needed
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||||||
|
switch unit {
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||||||
|
case "C", "°C":
|
||||||
|
f.Celsius = Celsius(value)
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||||||
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return nil
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||||||
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case "F", "°F":
|
||||||
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f.Celsius = FToC(Fahrenheit(value))
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||||||
|
return nil
|
||||||
|
}
|
||||||
|
return fmt.Errorf("invalid temperature %q", s)
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||||||
|
}
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||||||
|
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||||||
|
//!-celsiusflag
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||||||
|
|
||||||
|
//!+Celsiusflag
|
||||||
|
// CelsiusFlag defines a Celsius flag with the specified name,
|
||||||
|
// default value, and usage, and returns the address of the flag variable.
|
||||||
|
// The flag argument must have a quantity and a unit, e.g., "100C".
|
||||||
|
func CelsiusFlag(name string, value Celsius, usage string) *Celsius {
|
||||||
|
f := celsiusFlag{value}
|
||||||
|
flag.CommandLine.Var(&f, name, usage)
|
||||||
|
return &f.Celsius
|
||||||
|
}
|
||||||
|
|
||||||
|
//!-Celsiusflag
|
|
@ -0,0 +1,89 @@
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||||||
|
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
|
||||||
|
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
|
||||||
|
|
||||||
|
//!+
|
||||||
|
|
||||||
|
// Chat is a server that lets clients chat with each other.
|
||||||
|
package main
|
||||||
|
|
||||||
|
import (
|
||||||
|
"bufio"
|
||||||
|
"fmt"
|
||||||
|
"log"
|
||||||
|
"net"
|
||||||
|
)
|
||||||
|
|
||||||
|
//!+broadcaster
|
||||||
|
type client chan<- string // an outgoing message channel
|
||||||
|
|
||||||
|
var (
|
||||||
|
entering = make(chan client)
|
||||||
|
leaving = make(chan client)
|
||||||
|
messages = make(chan string) // all incoming client messages
|
||||||
|
)
|
||||||
|
|
||||||
|
func broadcaster() {
|
||||||
|
clients := make(map[client]bool) // all connected clients
|
||||||
|
for {
|
||||||
|
select {
|
||||||
|
case msg := <-messages:
|
||||||
|
// Broadcast incoming message to all
|
||||||
|
// clients' outgoing message channels.
|
||||||
|
for cli := range clients {
|
||||||
|
cli <- msg
|
||||||
|
}
|
||||||
|
case cli := <-entering:
|
||||||
|
clients[cli] = true
|
||||||
|
case cli := <-leaving:
|
||||||
|
delete(clients, cli)
|
||||||
|
close(cli)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
//!-broadcaster
|
||||||
|
|
||||||
|
//!+handleConn
|
||||||
|
func handleConn(conn net.Conn) {
|
||||||
|
ch := make(chan string) // outgoing client messages
|
||||||
|
go clientWriter(conn, ch)
|
||||||
|
|
||||||
|
who := conn.RemoteAddr().String()
|
||||||
|
entering <- ch
|
||||||
|
messages <- who + " has arrived"
|
||||||
|
input := bufio.NewScanner(conn)
|
||||||
|
for input.Scan() {
|
||||||
|
messages <- who + ": " + input.Text()
|
||||||
|
}
|
||||||
|
messages <- who + " has left"
|
||||||
|
leaving <- ch
|
||||||
|
conn.Close()
|
||||||
|
}
|
||||||
|
|
||||||
|
func clientWriter(conn net.Conn, ch <-chan string) {
|
||||||
|
for msg := range ch {
|
||||||
|
fmt.Fprintln(conn, msg)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
//!-handleConn
|
||||||
|
|
||||||
|
//!+main
|
||||||
|
func main() {
|
||||||
|
listener, err := net.Listen("tcp", "localhost:8000")
|
||||||
|
if err != nil {
|
||||||
|
log.Fatal(err)
|
||||||
|
}
|
||||||
|
|
||||||
|
go broadcaster()
|
||||||
|
for {
|
||||||
|
conn, err := listener.Accept()
|
||||||
|
if err != nil {
|
||||||
|
log.Print(err)
|
||||||
|
continue
|
||||||
|
}
|
||||||
|
go handleConn(conn)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
//!-main
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