70 lines
1.7 KiB
Go
70 lines
1.7 KiB
Go
package pathway
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import (
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"io"
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)
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type broadcastWriter struct {
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writers []io.Writer
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}
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func (t *broadcastWriter) Close() (err error) {
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for i := 0; i < len(t.writers); i++ {
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if w, ok := t.writers[i].(io.WriteCloser); ok {
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if e := w.Close(); e != nil {
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err = e
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}
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}
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}
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return
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}
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func (t *broadcastWriter) Write(p []byte) (n int, err error) {
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for i := 0; i < len(t.writers); i++ {
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n, err = t.writers[i].Write(p)
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if err == nil && n != len(p) {
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err = io.ErrShortWrite
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}
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if err != nil {
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// if not at the end, move last to here and redo this
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if i < len(t.writers)-1 {
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// close the writer if it implements WriteCloser
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if w, ok := t.writers[i].(io.WriteCloser); ok {
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defer w.Close()
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}
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t.writers[i] = t.writers[len(t.writers)-1]
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i = i - 1
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}
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// always shorten list by one to drop the last one
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t.writers = t.writers[:len(t.writers)-1]
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}
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}
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if len(t.writers) <= 0 {
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return 0, err
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}
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return len(p), nil
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}
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// BroadcastWriter creates a writer that duplicates its writes to all the
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// provided writers, similar to the Unix tee(1) command.
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//
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// Each write is written to each listed writer, one at a time.
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// If a listed writer returns an error, that overall write operation
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// continues and the offending writer is dropped from the list.
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//
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// Only if all writers are dropped, the last error is returned at the end.
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func BroadcastWriter(writers ...io.Writer) io.WriteCloser {
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allWriters := make([]io.Writer, 0, len(writers))
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for _, w := range writers {
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if bw, ok := w.(*broadcastWriter); ok {
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allWriters = append(allWriters, bw.writers...)
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} else {
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allWriters = append(allWriters, w)
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}
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}
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return &broadcastWriter{allWriters}
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}
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