68 lines
2 KiB
Go
68 lines
2 KiB
Go
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// Copyright 2016 The CMux Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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// implied. See the License for the specific language governing
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// permissions and limitations under the License.
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package cmux
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import (
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"bytes"
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"io"
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)
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// bufferedReader is an optimized implementation of io.Reader that behaves like
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// ```
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// io.MultiReader(bytes.NewReader(buffer.Bytes()), io.TeeReader(source, buffer))
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// ```
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// without allocating.
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type bufferedReader struct {
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source io.Reader
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buffer bytes.Buffer
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bufferRead int
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bufferSize int
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sniffing bool
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lastErr error
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}
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func (s *bufferedReader) Read(p []byte) (int, error) {
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if s.bufferSize > s.bufferRead {
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// If we have already read something from the buffer before, we return the
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// same data and the last error if any. We need to immediately return,
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// otherwise we may block for ever, if we try to be smart and call
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// source.Read() seeking a little bit of more data.
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bn := copy(p, s.buffer.Bytes()[s.bufferRead:s.bufferSize])
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s.bufferRead += bn
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return bn, s.lastErr
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} else if !s.sniffing && s.buffer.Cap() != 0 {
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// We don't need the buffer anymore.
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// Reset it to release the internal slice.
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s.buffer = bytes.Buffer{}
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}
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// If there is nothing more to return in the sniffed buffer, read from the
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// source.
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sn, sErr := s.source.Read(p)
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if sn > 0 && s.sniffing {
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s.lastErr = sErr
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if wn, wErr := s.buffer.Write(p[:sn]); wErr != nil {
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return wn, wErr
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}
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}
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return sn, sErr
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}
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func (s *bufferedReader) reset(snif bool) {
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s.sniffing = snif
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s.bufferRead = 0
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s.bufferSize = s.buffer.Len()
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}
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