io: consolidate multi_reader and multi_writer into a single file, multi.go
R=rsc
CC=golang-dev
https://golang.org/cl/1860046
diff --git a/src/pkg/io/multi.go b/src/pkg/io/multi.go
new file mode 100644
index 0000000..88e4f1b
--- /dev/null
+++ b/src/pkg/io/multi.go
@@ -0,0 +1,60 @@
+// 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
+
+import "os"
+
+type multiReader struct {
+ readers []Reader
+}
+
+func (mr *multiReader) Read(p []byte) (n int, err os.Error) {
+ for len(mr.readers) > 0 {
+ n, err = mr.readers[0].Read(p)
+ if n > 0 || err != os.EOF {
+ if err == os.EOF {
+ // This shouldn't happen.
+ // Well-behaved Readers should never
+ // return non-zero bytes read with an
+ // EOF. But if so, we clean it.
+ err = nil
+ }
+ return
+ }
+ mr.readers = mr.readers[1:]
+ }
+ return 0, os.EOF
+}
+
+// MultiReader returns a Reader that's the logical concatenation of
+// the provided input readers. They're read sequentially. Once all
+// inputs are drained, Read will return os.EOF.
+func MultiReader(readers ...Reader) Reader {
+ return &multiReader{readers}
+}
+
+type multiWriter struct {
+ writers []Writer
+}
+
+func (t *multiWriter) Write(p []byte) (n int, err os.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
+}
+
+// MultiWriter creates a writer that duplicates its writes to all the
+// provided writers, similar to the Unix tee(1) command.
+func MultiWriter(writers ...Writer) Writer {
+ return &multiWriter{writers}
+}
