moby/pkg/ioutils/buffer.go
Brian Goff 9a25b1d942 Improve performance/reduce allocs of bytespipe
Creates a `fixedBuffer` type that is used to encapsulate functionality
for reading/writing from the underlying byte slices.

Uses lazily-loaded set of sync.Pools for storing buffers that are no
longer needed so they can be re-used.

```
benchmark                     old ns/op     new ns/op     delta
BenchmarkBytesPipeWrite-8     138469        48985         -64.62%
BenchmarkBytesPipeRead-8      130922        56601         -56.77%

benchmark                     old allocs     new allocs     delta
BenchmarkBytesPipeWrite-8     18             8              -55.56%
BenchmarkBytesPipeRead-8      0              0              +0.00%

benchmark                     old bytes     new bytes     delta
BenchmarkBytesPipeWrite-8     66903         1649          -97.54%
BenchmarkBytesPipeRead-8      0             1             +Inf%
```

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
2016-04-05 13:06:04 -04:00

51 lines
808 B
Go

package ioutils
import (
"errors"
"io"
)
var errBufferFull = errors.New("buffer is full")
type fixedBuffer struct {
buf []byte
pos int
lastRead int
}
func (b *fixedBuffer) Write(p []byte) (int, error) {
n := copy(b.buf[b.pos:cap(b.buf)], p)
b.pos += n
if n < len(p) {
if b.pos == cap(b.buf) {
return n, errBufferFull
}
return n, io.ErrShortWrite
}
return n, nil
}
func (b *fixedBuffer) Read(p []byte) (int, error) {
n := copy(p, b.buf[b.lastRead:b.pos])
b.lastRead += n
return n, nil
}
func (b *fixedBuffer) Len() int {
return b.pos - b.lastRead
}
func (b *fixedBuffer) Cap() int {
return cap(b.buf)
}
func (b *fixedBuffer) Reset() {
b.pos = 0
b.lastRead = 0
b.buf = b.buf[:0]
}
func (b *fixedBuffer) String() string {
return string(b.buf[b.lastRead:b.pos])
}