mirror of
https://github.com/golang/go
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105 lines
2.7 KiB
Go
105 lines
2.7 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package io
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// Simple byte buffer for marshaling data.
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import (
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"io";
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"os";
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)
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func bytecopy(dst []byte, doff int, src []byte, soff int, count int) {
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for ; count > 0; count-- {
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dst[doff] = src[soff];
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doff++;
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soff++;
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}
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}
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// A ByteBuffer is a simple implementation of the io.Read and io.Write interfaces
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// connected to a buffer of bytes.
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// The zero value for ByteBuffer is an empty buffer ready to use.
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type ByteBuffer struct {
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buf []byte; // contents are the bytes buf[off : len(buf)]
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off int; // read at &buf[off], write at &buf[len(buf)]
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}
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// Data returns the contents of the unread portion of the buffer;
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// len(b.Data()) == b.Len().
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func (b *ByteBuffer) Data() []byte {
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return b.buf[b.off : len(b.buf)]
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}
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// Len returns the number of bytes of the unread portion of the buffer;
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// b.Len() == len(b.Data()).
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func (b *ByteBuffer) Len() int {
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return len(b.buf) - b.off
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}
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// Truncate discards all but the first n unread bytes from the buffer.
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// It is an error to call b.Truncate(n) with n > b.Len().
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func (b *ByteBuffer) Truncate(n int) {
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b.buf = b.buf[0 : b.off + n];
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}
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// Reset resets the buffer so it has no content.
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// b.Reset() is the same as b.Truncate(0).
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func (b *ByteBuffer) Reset() {
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b.buf = b.buf[0 : b.off];
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}
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// Write appends the contents of p to the buffer. The return
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// value n is the length of p; err is always nil.
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func (b *ByteBuffer) Write(p []byte) (n int, err os.Error) {
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m := b.Len();
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n = len(p);
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if len(b.buf) + n > cap(b.buf) {
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// not enough space at end
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buf := b.buf;
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if m + n > cap(b.buf) {
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// not enough space anywhere
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buf = make([]byte, 2*cap(b.buf) + n)
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}
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bytecopy(buf, 0, b.buf, b.off, m);
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b.buf = buf;
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b.off = 0
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}
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b.buf = b.buf[0 : b.off + m + n];
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bytecopy(b.buf, b.off + m, p, 0, n);
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return n, nil
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}
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// WriteByte appends the byte c to the buffer.
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// Because Write never fails and WriteByte is not part of the
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// io.Writer interface, it does not need to return a value.
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func (b *ByteBuffer) WriteByte(c byte) {
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b.Write([]byte{c});
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}
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// Read reads the next len(p) bytes from the buffer or until the buffer
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// is drained. The return value n is the number of bytes read; err is always nil.
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func (b *ByteBuffer) Read(p []byte) (n int, err os.Error) {
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m := b.Len();
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n = len(p);
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if n > m {
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// more bytes requested than available
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n = m
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}
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bytecopy(p, 0, b.buf, b.off, n);
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b.off += n;
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return n, nil
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}
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// NewByteBufferFromArray creates and initializes a new ByteBuffer
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// with buf as its initial contents.
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func NewByteBufferFromArray(buf []byte) *ByteBuffer {
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return &ByteBuffer{buf, 0};
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}
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