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Maps rely on the keys being comparable. Using an interface type as the map key is dangerous, because some interface types are not comparable. I talked about this in my "Stupid Gopher Tricks" talk: https://talks.golang.org/2015/tricks.slide In this case, if the user-provided writer is backed by a slice (such as io.MultiWriter) then the code will panic at run time. Signed-off-by: Andrew Gerrand <adg@golang.org>
54 lines
1.1 KiB
Go
54 lines
1.1 KiB
Go
package broadcastwriter
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import (
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"io"
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"sync"
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)
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// BroadcastWriter accumulate multiple io.WriteCloser by stream.
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type BroadcastWriter struct {
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mu sync.Mutex
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writers []io.WriteCloser
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}
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// AddWriter adds new io.WriteCloser.
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func (w *BroadcastWriter) AddWriter(writer io.WriteCloser) {
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w.mu.Lock()
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w.writers = append(w.writers, writer)
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w.mu.Unlock()
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}
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// Write writes bytes to all writers. Failed writers will be evicted during
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// this call.
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func (w *BroadcastWriter) Write(p []byte) (n int, err error) {
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w.mu.Lock()
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var evict []int
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for i, sw := range w.writers {
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if n, err := sw.Write(p); err != nil || n != len(p) {
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// On error, evict the writer
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evict = append(evict, i)
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}
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}
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for n, i := range evict {
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w.writers = append(w.writers[:i-n], w.writers[i-n+1:]...)
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}
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w.mu.Unlock()
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return len(p), nil
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}
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// Clean closes and removes all writers. Last non-eol-terminated part of data
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// will be saved.
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func (w *BroadcastWriter) Clean() error {
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w.mu.Lock()
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for _, sw := range w.writers {
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sw.Close()
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}
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w.writers = nil
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w.mu.Unlock()
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return nil
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}
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// New creates a new BroadcastWriter.
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func New() *BroadcastWriter {
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return &BroadcastWriter{}
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}
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