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bufferedReader is an optimized implementation of io.Reader that behaves like ``` io.MultiReader(bytes.NewReader(buffer.Bytes()), io.TeeReader(source, buffer)) ``` without allocating. This has a measurable effect on benchmarks: ``` name old time/op new time/op delta CMuxConn-4 1.09µs ± 4% 0.99µs ±19% -9.32% (p=0.000 n=17+19) name old alloc/op new alloc/op delta CMuxConn-4 240B ± 0% 260B ± 0% +8.33% (p=0.000 n=20+20) name old allocs/op new allocs/op delta CMuxConn-4 9.00 ± 0% 5.00 ± 0% -44.44% (p=0.000 n=20+20) ``` Note that appropriate test coverage is provided by `TestRead`.
36 lines
722 B
Go
36 lines
722 B
Go
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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