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.
7 type eofReader struct{}
9 func (eofReader) Read([]byte) (int, error) {
13 type multiReader struct {
17 func (mr *multiReader) Read(p []byte) (n int, err error) {
18 for len(mr.readers) > 0 {
19 // Optimization to flatten nested multiReaders (Issue 13558).
20 if len(mr.readers) == 1 {
21 if r, ok := mr.readers[0].(*multiReader); ok {
22 mr.readers = r.readers
26 n, err = mr.readers[0].Read(p)
28 // Use eofReader instead of nil to avoid nil panic
29 // after performing flatten (Issue 18232).
30 mr.readers[0] = eofReader{} // permit earlier GC
31 mr.readers = mr.readers[1:]
33 if n > 0 || err != EOF {
34 if err == EOF && len(mr.readers) > 0 {
35 // Don't return EOF yet. More readers remain.
44 func (mr *multiReader) WriteTo(w Writer) (sum int64, err error) {
45 return mr.writeToWithBuffer(w, make([]byte, 1024*32))
48 func (mr *multiReader) writeToWithBuffer(w Writer, buf []byte) (sum int64, err error) {
49 for i, r := range mr.readers {
51 if subMr, ok := r.(*multiReader); ok { // reuse buffer with nested multiReaders
52 n, err = subMr.writeToWithBuffer(w, buf)
54 n, err = copyBuffer(w, r, buf)
58 mr.readers = mr.readers[i:] // permit resume / retry after error
61 mr.readers[i] = nil // permit early GC
67 var _ WriterTo = (*multiReader)(nil)
69 // MultiReader returns a Reader that's the logical concatenation of
70 // the provided input readers. They're read sequentially. Once all
71 // inputs have returned EOF, Read will return EOF. If any of the readers
72 // return a non-nil, non-EOF error, Read will return that error.
73 func MultiReader(readers ...Reader) Reader {
74 r := make([]Reader, len(readers))
76 return &multiReader{r}
79 type multiWriter struct {
83 func (t *multiWriter) Write(p []byte) (n int, err error) {
84 for _, w := range t.writers {
97 var _ StringWriter = (*multiWriter)(nil)
99 func (t *multiWriter) WriteString(s string) (n int, err error) {
100 var p []byte // lazily initialized if/when needed
101 for _, w := range t.writers {
102 if sw, ok := w.(StringWriter); ok {
103 n, err = sw.WriteString(s)
121 // MultiWriter creates a writer that duplicates its writes to all the
122 // provided writers, similar to the Unix tee(1) command.
124 // Each write is written to each listed writer, one at a time.
125 // If a listed writer returns an error, that overall write operation
126 // stops and returns the error; it does not continue down the list.
127 func MultiWriter(writers ...Writer) Writer {
128 allWriters := make([]Writer, 0, len(writers))
129 for _, w := range writers {
130 if mw, ok := w.(*multiWriter); ok {
131 allWriters = append(allWriters, mw.writers...)
133 allWriters = append(allWriters, w)
136 return &multiWriter{allWriters}