57 lines
1.1 KiB
Go
57 lines
1.1 KiB
Go
package logging
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import (
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"io"
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"sync"
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)
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// GatedWriter is an io.Writer implementation that buffers all of its
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// data into an internal buffer until it is told to let data through.
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type GatedWriter struct {
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Writer io.Writer
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buf [][]byte
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flush bool
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lock sync.RWMutex
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}
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// Flush tells the GatedWriter to flush any buffered data and to stop
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// buffering.
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func (w *GatedWriter) Flush() {
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w.lock.Lock()
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w.flush = true
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w.lock.Unlock()
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for _, p := range w.buf {
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w.Write(p)
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}
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w.buf = nil
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}
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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
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// no use of the internal buffer. This is the happy path.
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w.lock.RLock()
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if w.flush {
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w.lock.RUnlock()
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return w.Writer.Write(p)
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}
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w.lock.RUnlock()
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// Now take the write lock.
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w.lock.Lock()
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defer w.lock.Unlock()
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// Things could have changed between the locking operations, so we
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// have to check one more time.
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if w.flush {
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return w.Writer.Write(p)
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}
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// Buffer up the written data.
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p2 := make([]byte, len(p))
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copy(p2, p)
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w.buf = append(w.buf, p2)
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return len(p), nil
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}
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