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When the buffer is empty, reset b.off to the beginning of the buffer

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to avoid growing unnecessarily.

R=rsc
CC=golang-dev
https://golang.org/cl/176071
This commit is contained in:
Rob Pike 2009-12-14 13:13:01 +11:00
parent 58578905ba
commit d14c813377
1 changed files with 20 additions and 2 deletions
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22
src/pkg/bytes/buffer.go
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@ -84,6 +84,10 @@ func (b *Buffer) resize(n int) {
// value n is the length of p; err is always nil.
func (b *Buffer) Write(p []byte) (n int, err os.Error) {
m := b.Len();
// If buffer is empty, reset to recover space.
if m == 0 && b.off != 0 {
b.Truncate(0)
}
n = len(p);
if len(b.buf)+n > cap(b.buf) {
b.resize(n)
@ -97,6 +101,10 @@ func (b *Buffer) Write(p []byte) (n int, err os.Error) {
// value n is the length of s; err is always nil.
func (b *Buffer) WriteString(s string) (n int, err os.Error) {
m := b.Len();
// If buffer is empty, reset to recover space.
if m == 0 && b.off != 0 {
b.Truncate(0)
}
n = len(s);
if len(b.buf)+n > cap(b.buf) {
b.resize(n)
@ -117,6 +125,10 @@ const MinRead = 512
// Any error except os.EOF encountered during the read
// is also returned.
func (b *Buffer) ReadFrom(r io.Reader) (n int64, err os.Error) {
// If buffer is empty, reset to recover space.
if b.off >= len(b.buf) {
b.Truncate(0)
}
for {
if cap(b.buf)-len(b.buf) < MinRead {
var newBuf []byte;
@ -157,6 +169,8 @@ func (b *Buffer) WriteTo(w io.Writer) (n int64, err os.Error) {
return n, e
}
}
// Buffer is now empty; reset.
b.Truncate(0);
return;
}
@ -175,7 +189,9 @@ func (b *Buffer) WriteByte(c byte) os.Error {
// otherwise it is nil.
func (b *Buffer) Read(p []byte) (n int, err os.Error) {
if b.off >= len(b.buf) {
return 0, os.EOF
// Buffer is empty, reset to recover space.
b.Truncate(0);
return 0, os.EOF;
}
m := b.Len();
n = len(p);
@ -194,7 +210,9 @@ func (b *Buffer) Read(p []byte) (n int, err os.Error) {
// If no byte is available, it returns error os.EOF.
func (b *Buffer) ReadByte() (c byte, err os.Error) {
if b.off >= len(b.buf) {
return 0, os.EOF
// Buffer is empty, reset to recover space.
b.Truncate(0);
return 0, os.EOF;
}
c = b.buf[b.off];
b.off++;