libgo/go/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 import "os"
   8
   9 type multiReader struct {
  10         readers []Reader
  11 }
  12
  13 func (mr *multiReader) Read(p []byte) (n int, err os.Error) {
  14         for len(mr.readers) > 0 {
  15                 n, err = mr.readers[0].Read(p)
  16                 if n > 0 || err != os.EOF {
  17                         if err == os.EOF {
  18                                 // This shouldn't happen.
  19                                 // Well-behaved Readers should never
  20                                 // return non-zero bytes read with an
  21                                 // EOF.  But if so, we clean it.
  22                                 err = nil
  23                         }
  24                         return
  25                 }
  26                 mr.readers = mr.readers[1:]
  27         }
  28         return 0, os.EOF
  29 }
  30
  31 // MultiReader returns a Reader that's the logical concatenation of
  32 // the provided input readers.  They're read sequentially.  Once all
  33 // inputs are drained, Read will return os.EOF.
  34 func MultiReader(readers ...Reader) Reader {
  35         return &multiReader{readers}
  36 }
  37
  38 type multiWriter struct {
  39         writers []Writer
  40 }
  41
  42 func (t *multiWriter) Write(p []byte) (n int, err os.Error) {
  43         for _, w := range t.writers {
  44                 n, err = w.Write(p)
  45                 if err != nil {
  46                         return
  47                 }
  48                 if n != len(p) {
  49                         err = ErrShortWrite
  50                         return
  51                 }
  52         }
  53         return len(p), nil
  54 }
  55
  56 // MultiWriter creates a writer that duplicates its writes to all the
  57 // provided writers, similar to the Unix tee(1) command.
  58 func MultiWriter(writers ...Writer) Writer {
  59         return &multiWriter{writers}
  60 }