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