mirror of
https://github.com/prometheus/prometheus.git
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50 lines
1.3 KiB
Go
50 lines
1.3 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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}
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func (s *bufferedReader) Read(p []byte) (int, error) {
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// Functionality of bytes.Reader.
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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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p = p[bn:]
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// Funtionality of io.TeeReader.
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sn, sErr := s.source.Read(p)
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if sn > 0 {
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if wn, wErr := s.buffer.Write(p[:sn]); wErr != nil {
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return bn + wn, wErr
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}
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}
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return bn + sn, sErr
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}
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