open-consul/logging/gated_writer.go

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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package logging
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import (
"io"
"sync"
)
// GatedWriter is an io.Writer implementation that buffers all of its
// data into an internal buffer until it is told to let data through.
type GatedWriter struct {
Writer io.Writer
buf [][]byte
flush bool
lock sync.RWMutex
}
// Flush tells the GatedWriter to flush any buffered data and to stop
// buffering.
func (w *GatedWriter) Flush() {
w.lock.Lock()
w.flush = true
w.lock.Unlock()
for _, p := range w.buf {
w.Write(p)
}
w.buf = nil
}
func (w *GatedWriter) Write(p []byte) (n int, err error) {
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// Once we flush we no longer synchronize writers since there's
// no use of the internal buffer. This is the happy path.
w.lock.RLock()
if w.flush {
w.lock.RUnlock()
return w.Writer.Write(p)
}
w.lock.RUnlock()
// Now take the write lock.
w.lock.Lock()
defer w.lock.Unlock()
// Things could have changed between the locking operations, so we
// have to check one more time.
if w.flush {
return w.Writer.Write(p)
}
// Buffer up the written data.
p2 := make([]byte, len(p))
copy(p2, p)
w.buf = append(w.buf, p2)
return len(p), nil
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}