// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package io
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type eofReader struct{}
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func (eofReader) Read([]byte) (int, error) {
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return 0, EOF
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}
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type multiReader struct {
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readers []Reader
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}
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func (mr *multiReader) Read(p []byte) (n int, err error) {
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for len(mr.readers) > 0 {
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// Optimization to flatten nested multiReaders (Issue 13558).
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if len(mr.readers) == 1 {
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if r, ok := mr.readers[0].(*multiReader); ok {
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mr.readers = r.readers
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continue
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}
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}
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n, err = mr.readers[0].Read(p)
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if err == EOF {
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// Use eofReader instead of nil to avoid nil panic
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// after performing flatten (Issue 18232).
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mr.readers[0] = eofReader{} // permit earlier GC
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mr.readers = mr.readers[1:]
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}
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if n > 0 || err != EOF {
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if err == EOF && len(mr.readers) > 0 {
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// Don't return EOF yet. More readers remain.
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err = nil
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}
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return
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}
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}
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return 0, EOF
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}
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// MultiReader returns a Reader that's the logical concatenation of
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// the provided input readers. They're read sequentially. Once all
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// inputs have returned EOF, Read will return EOF. If any of the readers
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// return a non-nil, non-EOF error, Read will return that error.
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func MultiReader(readers ...Reader) Reader {
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r := make([]Reader, len(readers))
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copy(r, readers)
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return &multiReader{r}
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}
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type multiWriter struct {
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writers []Writer
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}
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func (t *multiWriter) Write(p []byte) (n int, err error) {
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for _, w := range t.writers {
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n, err = w.Write(p)
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if err != nil {
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return
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}
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if n != len(p) {
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err = ErrShortWrite
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return
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}
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}
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return len(p), nil
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}
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var _ StringWriter = (*multiWriter)(nil)
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func (t *multiWriter) WriteString(s string) (n int, err error) {
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var p []byte // lazily initialized if/when needed
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for _, w := range t.writers {
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if sw, ok := w.(StringWriter); ok {
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n, err = sw.WriteString(s)
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} else {
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if p == nil {
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p = []byte(s)
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}
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n, err = w.Write(p)
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}
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if err != nil {
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return
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}
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if n != len(s) {
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err = ErrShortWrite
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return
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}
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}
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return len(s), nil
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}
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// MultiWriter 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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// stops and returns the error; it does not continue down the list.
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func MultiWriter(writers ...Writer) Writer {
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allWriters := make([]Writer, 0, len(writers))
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for _, w := range writers {
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if mw, ok := w.(*multiWriter); ok {
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allWriters = append(allWriters, mw.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 &multiWriter{allWriters}
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}
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