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// Copyright 2009 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 io
// Simple byte buffer for marshaling data.
import (
"io";
"os";
)
// TODO(r): Do better memory management.
func bytecopy(dst []byte, doff int, src []byte, soff int, count int) {
for i := 0; i < count; i++ {
dst[doff] = src[soff];
doff++;
soff++;
}
}
// A ByteBuffer is a simple implementation of the io.Read and io.Write interfaces
// connected to a buffer of bytes.
// The zero value for ByteBuffer is an empty buffer ready to use.
type ByteBuffer struct {
buf []byte;
off int; // Read from here
len int; // Write to here
cap int;
}
// Reset resets the buffer so it has no content.
func (b *ByteBuffer) Reset() {
b.off = 0;
b.len = 0;
}
// Write appends the contents of p to the buffer. The return
// value is the length of p; err is always nil.
func (b *ByteBuffer) Write(p []byte) (n int, err os.Error) {
plen := len(p);
if len(b.buf) == 0 {
b.cap = plen + 1024;
b.buf = make([]byte, b.cap);
b.len = 0;
}
if b.len + plen > b.cap {
b.cap = 2*(b.cap + plen);
nb := make([]byte, b.cap);
bytecopy(nb, 0, b.buf, 0, b.len);
b.buf = nb;
}
bytecopy(b.buf, b.len, p, 0, plen);
b.len += plen;
return plen, nil;
}
// Read reads the next len(p) bytes from the buffer or until the buffer
// is drained. The return value is the number of bytes read; err is always nil.
func (b *ByteBuffer) Read(p []byte) (n int, err os.Error) {
plen := len(p);
if len(b.buf) == 0 {
return 0, nil
}
if b.off == b.len { // empty buffer
b.Reset();
return 0, nil
}
if plen > b.len - b.off {
plen = b.len - b.off
}
bytecopy(p, 0, b.buf, b.off, plen);
b.off += plen;
return plen, nil;
}
// Len returns the length of the underlying buffer.
func (b *ByteBuffer) Len() int {
return b.len
}
// Off returns the location within the buffer of the next byte to be read.
func (b *ByteBuffer) Off() int {
return b.off
}
// Data returns the contents of the unread portion of the buffer.
func (b *ByteBuffer) Data() []byte {
return b.buf[b.off:b.len]
}
// NewByteBufferFromArray creates and initializes a new ByteBuffer
// with buf as its initial contents.
func NewByteBufferFromArray(buf []byte) *ByteBuffer {
b := new(ByteBuffer);
b.buf = buf;
b.off = 0;
b.len = len(buf);
b.cap = len(buf);
return b;
}
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