forked from TrueCloudLab/distribution
76 lines
1.7 KiB
Go
76 lines
1.7 KiB
Go
// Copyright 2014 The Go Authors.
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// See https://code.google.com/p/go/source/browse/CONTRIBUTORS
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// Licensed under the same terms as Go itself:
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// https://code.google.com/p/go/source/browse/LICENSE
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package http2
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import (
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"errors"
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)
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// buffer is an io.ReadWriteCloser 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 buffer struct {
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buf []byte
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r, w int
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closed bool
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err error // err to return to reader
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}
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var (
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errReadEmpty = errors.New("read from empty buffer")
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errWriteClosed = errors.New("write on closed buffer")
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errWriteFull = errors.New("write on full buffer")
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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 *buffer) Read(p []byte) (n int, err error) {
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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.closed && b.r == b.w {
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err = b.err
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} else if b.r == b.w && n == 0 {
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err = errReadEmpty
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}
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return n, err
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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 *buffer) 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 *buffer) Write(p []byte) (n int, err error) {
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if b.closed {
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return 0, errWriteClosed
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}
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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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// Close marks the buffer as closed. Future calls to Write will
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// return an error. Future calls to Read, once the buffer is
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// empty, will return err.
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func (b *buffer) Close(err error) {
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if !b.closed {
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b.closed = true
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b.err = err
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}
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}
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