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// 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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