1 files changed, 109 insertions, 0 deletions
diff --git a/src/pkg/io/bytebuffer.go b/src/pkg/io/bytebuffer.go
new file mode 100644
index 000000000..921ddb17a
--- /dev/null
+++ b/src/pkg/io/bytebuffer.go
@@ -0,0 +1,109 @@
+// 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";
+)
+
+func bytecopy(dst []byte, doff int, src []byte, soff int, count int) {
+	for ; count > 0; count-- {
+		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;	// contents are the bytes buf[off : len(buf)]
+	off	int;	// read at &buf[off], write at &buf[len(buf)]
+}
+
+// Data returns the contents of the unread portion of the buffer;
+// len(b.Data()) == b.Len().
+func (b *ByteBuffer) Data() []byte {
+	return b.buf[b.off : len(b.buf)]
+}
+
+// Len returns the number of bytes of the unread portion of the buffer;
+// b.Len() == len(b.Data()).
+func (b *ByteBuffer) Len() int {
+	return len(b.buf) - b.off
+}
+
+// Truncate discards all but the first n unread bytes from the buffer.
+// It is an error to call b.Truncate(n) with n > b.Len().
+func (b *ByteBuffer) Truncate(n int) {
+	if n == 0 {
+		// Reuse buffer space.
+		b.off = 0;
+	}
+	b.buf = b.buf[0 : b.off + n];
+}
+
+// Reset resets the buffer so it has no content.
+// b.Reset() is the same as b.Truncate(0).
+func (b *ByteBuffer) Reset() {
+	b.Truncate(0);
+}
+
+// Write appends the contents of p to the buffer.  The return
+// value n is the length of p; err is always nil.
+func (b *ByteBuffer) Write(p []byte) (n int, err os.Error) {
+	m := b.Len();
+	n = len(p);
+
+	if len(b.buf) + n > cap(b.buf) {
+		// not enough space at end
+		buf := b.buf;
+		if m + n > cap(b.buf) {
+			// not enough space anywhere
+			buf = make([]byte, 2*cap(b.buf) + n)
+		}
+		bytecopy(buf, 0, b.buf, b.off, m);
+		b.buf = buf;
+		b.off = 0
+	}
+
+	b.buf = b.buf[0 : b.off + m + n];
+	bytecopy(b.buf, b.off + m, p, 0, n);
+	return n, nil
+}
+
+// WriteByte appends the byte c to the buffer.
+// The returned error is always nil, but is included
+// to match bufio.Writer's WriteByte.
+func (b *ByteBuffer) WriteByte(c byte) os.Error {
+	b.Write([]byte{c});
+	return nil;
+}
+
+// Read reads the next len(p) bytes from the buffer or until the buffer
+// is drained.  The return value n is the number of bytes read; err is always nil.
+func (b *ByteBuffer) Read(p []byte) (n int, err os.Error) {
+	m := b.Len();
+	n = len(p);
+
+	if n > m {
+		// more bytes requested than available
+		n = m
+	}
+
+	bytecopy(p, 0, b.buf, b.off, n);
+	b.off += n;
+	return n, nil
+}
+
+// NewByteBufferFromArray creates and initializes a new ByteBuffer
+// with buf as its initial contents.
+func NewByteBufferFromArray(buf []byte) *ByteBuffer {
+	return &ByteBuffer{buf, 0};
+}