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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package io

type multiReader struct {
        readers []Reader
}

func (mr *multiReader) Read(p []byte) (n int, err error) {
        for len(mr.readers) > 0 {
                n, err = mr.readers[0].Read(p)
                if n > 0 || err != EOF {
                        if err == EOF {
                                // Don't return EOF yet. There may be more bytes
                                // in the remaining readers.
                                err = nil
                        }
                        return
                }
                mr.readers = mr.readers[1:]
        }
        return 0, EOF
}

// MultiReader returns a Reader that's the logical concatenation of
// the provided input readers.  They're read sequentially.  Once all
// inputs are drained, Read will return EOF.
func MultiReader(readers ...Reader) Reader {
        return &multiReader{readers}
}

type multiWriter struct {
        writers []Writer
}

func (t *multiWriter) Write(p []byte) (n int, err error) {
        for _, w := range t.writers {
                n, err = w.Write(p)
                if err != nil {
                        return
                }
                if n != len(p) {
                        err = ErrShortWrite
                        return
                }
        }
        return len(p), nil
}

// MultiWriter creates a writer that duplicates its writes to all the
// provided writers, similar to the Unix tee(1) command.
func MultiWriter(writers ...Writer) Writer {
        return &multiWriter{writers}
}