| // Copyright 2014 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 http2 |
| |
| import ( |
| "errors" |
| ) |
| |
| // fixedBuffer is an io.ReadWriter backed by a fixed size buffer. |
| // It never allocates, but moves old data as new data is written. |
| type fixedBuffer struct { |
| buf []byte |
| r, w int |
| } |
| |
| var ( |
| errReadEmpty = errors.New("read from empty fixedBuffer") |
| errWriteFull = errors.New("write on full fixedBuffer") |
| ) |
| |
| // Read copies bytes from the buffer into p. |
| // It is an error to read when no data is available. |
| func (b *fixedBuffer) Read(p []byte) (n int, err error) { |
| if b.r == b.w { |
| return 0, errReadEmpty |
| } |
| n = copy(p, b.buf[b.r:b.w]) |
| b.r += n |
| if b.r == b.w { |
| b.r = 0 |
| b.w = 0 |
| } |
| return n, nil |
| } |
| |
| // Len returns the number of bytes of the unread portion of the buffer. |
| func (b *fixedBuffer) Len() int { |
| return b.w - b.r |
| } |
| |
| // Write copies bytes from p into the buffer. |
| // It is an error to write more data than the buffer can hold. |
| func (b *fixedBuffer) Write(p []byte) (n int, err error) { |
| // Slide existing data to beginning. |
| if b.r > 0 && len(p) > len(b.buf)-b.w { |
| copy(b.buf, b.buf[b.r:b.w]) |
| b.w -= b.r |
| b.r = 0 |
| } |
| |
| // Write new data. |
| n = copy(b.buf[b.w:], p) |
| b.w += n |
| if n < len(p) { |
| err = errWriteFull |
| } |
| return n, err |
| } |