Source file src/pkg/io/multi.go

     1	// Copyright 2010 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package io
     6	
     7	type multiReader struct {
     8		readers []Reader
     9	}
    10	
    11	func (mr *multiReader) Read(p []byte) (n int, err error) {
    12		for len(mr.readers) > 0 {
    13			n, err = mr.readers[0].Read(p)
    14			if n > 0 || err != EOF {
    15				if err == EOF {
    16					// Don't return EOF yet. There may be more bytes
    17					// in the remaining readers.
    18					err = nil
    19				}
    20				return
    21			}
    22			mr.readers = mr.readers[1:]
    23		}
    24		return 0, EOF
    25	}
    26	
    27	// MultiReader returns a Reader that's the logical concatenation of
    28	// the provided input readers.  They're read sequentially.  Once all
    29	// inputs are drained, Read will return EOF.
    30	func MultiReader(readers ...Reader) Reader {
    31		return &multiReader{readers}
    32	}
    33	
    34	type multiWriter struct {
    35		writers []Writer
    36	}
    37	
    38	func (t *multiWriter) Write(p []byte) (n int, err error) {
    39		for _, w := range t.writers {
    40			n, err = w.Write(p)
    41			if err != nil {
    42				return
    43			}
    44			if n != len(p) {
    45				err = ErrShortWrite
    46				return
    47			}
    48		}
    49		return len(p), nil
    50	}
    51	
    52	// MultiWriter creates a writer that duplicates its writes to all the
    53	// provided writers, similar to the Unix tee(1) command.
    54	func MultiWriter(writers ...Writer) Writer {
    55		return &multiWriter{writers}
    56	}