File size: 3,419 Bytes
e36aeda | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 | // 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
type eofReader struct{}
func (eofReader) Read([]byte) (int, error) {
return 0, EOF
}
type multiReader struct {
readers []Reader
}
func (mr *multiReader) Read(p []byte) (n int, err error) {
for len(mr.readers) > 0 {
// Optimization to flatten nested multiReaders (Issue 13558).
if len(mr.readers) == 1 {
if r, ok := mr.readers[0].(*multiReader); ok {
mr.readers = r.readers
continue
}
}
n, err = mr.readers[0].Read(p)
if err == EOF {
// Use eofReader instead of nil to avoid nil panic
// after performing flatten (Issue 18232).
mr.readers[0] = eofReader{} // permit earlier GC
mr.readers = mr.readers[1:]
}
if n > 0 || err != EOF {
if err == EOF && len(mr.readers) > 0 {
// Don't return EOF yet. More readers remain.
err = nil
}
return
}
}
return 0, EOF
}
func (mr *multiReader) WriteTo(w Writer) (sum int64, err error) {
return mr.writeToWithBuffer(w, make([]byte, 1024*32))
}
func (mr *multiReader) writeToWithBuffer(w Writer, buf []byte) (sum int64, err error) {
for i, r := range mr.readers {
var n int64
if subMr, ok := r.(*multiReader); ok { // reuse buffer with nested multiReaders
n, err = subMr.writeToWithBuffer(w, buf)
} else {
n, err = copyBuffer(w, r, buf)
}
sum += n
if err != nil {
mr.readers = mr.readers[i:] // permit resume / retry after error
return sum, err
}
mr.readers[i] = nil // permit early GC
}
mr.readers = nil
return sum, nil
}
var _ WriterTo = (*multiReader)(nil)
// MultiReader returns a Reader that's the logical concatenation of
// the provided input readers. They're read sequentially. Once all
// inputs have returned EOF, Read will return EOF. If any of the readers
// return a non-nil, non-EOF error, Read will return that error.
func MultiReader(readers ...Reader) Reader {
r := make([]Reader, len(readers))
copy(r, readers)
return &multiReader{r}
}
type multiWriter struct {
writers []Writer
}
func (t *multiWriter) Write(p []byte) (n int, err error) {
for _, w := range t.writers {
n, err = w.Write(p)
if err != nil {
return
}
if n != len(p) {
err = ErrShortWrite
return
}
}
return len(p), nil
}
var _ StringWriter = (*multiWriter)(nil)
func (t *multiWriter) WriteString(s string) (n int, err error) {
var p []byte // lazily initialized if/when needed
for _, w := range t.writers {
if sw, ok := w.(StringWriter); ok {
n, err = sw.WriteString(s)
} else {
if p == nil {
p = []byte(s)
}
n, err = w.Write(p)
}
if err != nil {
return
}
if n != len(s) {
err = ErrShortWrite
return
}
}
return len(s), nil
}
// MultiWriter creates a writer that duplicates its writes to all the
// provided writers, similar to the Unix tee(1) command.
//
// Each write is written to each listed writer, one at a time.
// If a listed writer returns an error, that overall write operation
// stops and returns the error; it does not continue down the list.
func MultiWriter(writers ...Writer) Writer {
allWriters := make([]Writer, 0, len(writers))
for _, w := range writers {
if mw, ok := w.(*multiWriter); ok {
allWriters = append(allWriters, mw.writers...)
} else {
allWriters = append(allWriters, w)
}
}
return &multiWriter{allWriters}
}
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