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 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 have returned EOF, Read will return EOF.  If any of the readers
  30 // return a non-nil, non-EOF error, Read will return that error.
  31 func MultiReader(readers ...Reader) Reader {
  32         r := make([]Reader, len(readers))
  33         copy(r, readers)
  34         return &multiReader{r}
  35 }
  36
  37 type multiWriter struct {
  38         writers []Writer
  39 }
  40
  41 func (t *multiWriter) Write(p []byte) (n int, err error) {
  42         for _, w := range t.writers {
  43                 n, err = w.Write(p)
  44                 if err != nil {
  45                         return
  46                 }
  47                 if n != len(p) {
  48                         err = ErrShortWrite
  49                         return
  50                 }
  51         }
  52         return len(p), nil
  53 }
  54
  55 // MultiWriter creates a writer that duplicates its writes to all the
  56 // provided writers, similar to the Unix tee(1) command.
  57 func MultiWriter(writers ...Writer) Writer {
  58         w := make([]Writer, len(writers))
  59         copy(w, writers)
  60         return &multiWriter{w}
  61 }