60 lines
1.3 KiB
Go
60 lines
1.3 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package http2
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import (
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"errors"
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)
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// fixedBuffer is an io.ReadWriter backed by a fixed size buffer.
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// It never allocates, but moves old data as new data is written.
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type fixedBuffer struct {
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buf []byte
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r, w int
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}
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var (
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errReadEmpty = errors.New("read from empty fixedBuffer")
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errWriteFull = errors.New("write on full fixedBuffer")
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)
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// Read copies bytes from the buffer into p.
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// It is an error to read when no data is available.
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func (b *fixedBuffer) Read(p []byte) (n int, err error) {
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if b.r == b.w {
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return 0, errReadEmpty
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}
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n = copy(p, b.buf[b.r:b.w])
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b.r += n
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if b.r == b.w {
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b.r = 0
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b.w = 0
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}
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return n, nil
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}
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// Len returns the number of bytes of the unread portion of the buffer.
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func (b *fixedBuffer) Len() int {
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return b.w - b.r
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}
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// Write copies bytes from p into the buffer.
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// It is an error to write more data than the buffer can hold.
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func (b *fixedBuffer) Write(p []byte) (n int, err error) {
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// Slide existing data to beginning.
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if b.r > 0 && len(p) > len(b.buf)-b.w {
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copy(b.buf, b.buf[b.r:b.w])
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b.w -= b.r
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b.r = 0
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}
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// Write new data.
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n = copy(b.buf[b.w:], p)
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b.w += n
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if n < len(p) {
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err = errWriteFull
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}
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return n, err
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}
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