93 lines
2 KiB
Go
93 lines
2 KiB
Go
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package ioutils
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import (
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"io"
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"sync"
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)
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// WriteFlusher wraps the Write and Flush operation ensuring that every write
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// is a flush. In addition, the Close method can be called to intercept
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// Read/Write calls if the targets lifecycle has already ended.
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type WriteFlusher struct {
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w io.Writer
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flusher flusher
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flushed chan struct{}
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flushedOnce sync.Once
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closed chan struct{}
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closeLock sync.Mutex
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}
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type flusher interface {
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Flush()
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}
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var errWriteFlusherClosed = io.EOF
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func (wf *WriteFlusher) Write(b []byte) (n int, err error) {
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select {
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case <-wf.closed:
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return 0, errWriteFlusherClosed
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default:
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}
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n, err = wf.w.Write(b)
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wf.Flush() // every write is a flush.
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return n, err
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}
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// Flush the stream immediately.
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func (wf *WriteFlusher) Flush() {
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select {
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case <-wf.closed:
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return
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default:
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}
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wf.flushedOnce.Do(func() {
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close(wf.flushed)
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})
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wf.flusher.Flush()
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}
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// Flushed returns the state of flushed.
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// If it's flushed, return true, or else it return false.
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func (wf *WriteFlusher) Flushed() bool {
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// BUG(stevvooe): Remove this method. Its use is inherently racy. Seems to
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// be used to detect whether or a response code has been issued or not.
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// Another hook should be used instead.
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var flushed bool
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select {
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case <-wf.flushed:
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flushed = true
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default:
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}
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return flushed
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}
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// Close closes the write flusher, disallowing any further writes to the
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// target. After the flusher is closed, all calls to write or flush will
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// result in an error.
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func (wf *WriteFlusher) Close() error {
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wf.closeLock.Lock()
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defer wf.closeLock.Unlock()
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select {
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case <-wf.closed:
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return errWriteFlusherClosed
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default:
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close(wf.closed)
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}
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return nil
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}
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// NewWriteFlusher returns a new WriteFlusher.
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func NewWriteFlusher(w io.Writer) *WriteFlusher {
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var fl flusher
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if f, ok := w.(flusher); ok {
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fl = f
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} else {
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fl = &NopFlusher{}
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}
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return &WriteFlusher{w: w, flusher: fl, closed: make(chan struct{}), flushed: make(chan struct{})}
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}
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