src/pkg/io/multi_reader.go

// 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

import "os"

type multiReader struct {
	readers []Reader
}

func (mr *multiReader) Read(p []byte) (n int, err os.Error) {
	for len(mr.readers) > 0 {
		n, err = mr.readers[0].Read(p)
		if n > 0 || err != os.EOF {
			if err == os.EOF {
				// This shouldn't happen.
				// Well-behaved Readers should never
				// return non-zero bytes read with an
				// EOF.  But if so, we clean it.
				err = nil
			}
			return
		}
		mr.readers = mr.readers[1:]
	}
	return 0, os.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 os.EOF.
func MultiReader(readers ...Reader) Reader {
	return &multiReader{readers}
}