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1 // Copyright 2010 The Go Authors. All rights reserved.
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2 // Use of this source code is governed by a BSD-style
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3 // license that can be found in the LICENSE file.
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4
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5 package io
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6
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7 type eofReader struct{}
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8
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9 func (eofReader) Read([]byte) (int, error) {
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10 return 0, EOF
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11 }
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12
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13 type multiReader struct {
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14 readers []Reader
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15 }
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16
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17 func (mr *multiReader) Read(p []byte) (n int, err error) {
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18 for len(mr.readers) > 0 {
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19 // Optimization to flatten nested multiReaders (Issue 13558).
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20 if len(mr.readers) == 1 {
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21 if r, ok := mr.readers[0].(*multiReader); ok {
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22 mr.readers = r.readers
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23 continue
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24 }
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25 }
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26 n, err = mr.readers[0].Read(p)
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27 if err == EOF {
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28 // Use eofReader instead of nil to avoid nil panic
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29 // after performing flatten (Issue 18232).
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30 mr.readers[0] = eofReader{} // permit earlier GC
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31 mr.readers = mr.readers[1:]
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32 }
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33 if n > 0 || err != EOF {
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34 if err == EOF && len(mr.readers) > 0 {
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35 // Don't return EOF yet. More readers remain.
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36 err = nil
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37 }
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38 return
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39 }
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40 }
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41 return 0, EOF
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42 }
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43
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44 // MultiReader returns a Reader that's the logical concatenation of
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45 // the provided input readers. They're read sequentially. Once all
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46 // inputs have returned EOF, Read will return EOF. If any of the readers
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47 // return a non-nil, non-EOF error, Read will return that error.
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48 func MultiReader(readers ...Reader) Reader {
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49 r := make([]Reader, len(readers))
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50 copy(r, readers)
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51 return &multiReader{r}
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52 }
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53
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54 type multiWriter struct {
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55 writers []Writer
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56 }
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57
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58 func (t *multiWriter) Write(p []byte) (n int, err error) {
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59 for _, w := range t.writers {
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60 n, err = w.Write(p)
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61 if err != nil {
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62 return
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63 }
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64 if n != len(p) {
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65 err = ErrShortWrite
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66 return
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67 }
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68 }
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69 return len(p), nil
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70 }
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71
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145
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72 var _ StringWriter = (*multiWriter)(nil)
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111
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73
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74 func (t *multiWriter) WriteString(s string) (n int, err error) {
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75 var p []byte // lazily initialized if/when needed
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76 for _, w := range t.writers {
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145
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77 if sw, ok := w.(StringWriter); ok {
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111
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78 n, err = sw.WriteString(s)
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79 } else {
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80 if p == nil {
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81 p = []byte(s)
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82 }
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83 n, err = w.Write(p)
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84 }
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85 if err != nil {
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86 return
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87 }
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88 if n != len(s) {
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89 err = ErrShortWrite
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90 return
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91 }
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92 }
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93 return len(s), nil
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94 }
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95
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96 // MultiWriter creates a writer that duplicates its writes to all the
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97 // provided writers, similar to the Unix tee(1) command.
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131
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98 //
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99 // Each write is written to each listed writer, one at a time.
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100 // If a listed writer returns an error, that overall write operation
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101 // stops and returns the error; it does not continue down the list.
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111
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102 func MultiWriter(writers ...Writer) Writer {
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131
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103 allWriters := make([]Writer, 0, len(writers))
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104 for _, w := range writers {
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105 if mw, ok := w.(*multiWriter); ok {
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106 allWriters = append(allWriters, mw.writers...)
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107 } else {
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108 allWriters = append(allWriters, w)
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109 }
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110 }
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111 return &multiWriter{allWriters}
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111
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112 }
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