1 files changed, 61 insertions, 0 deletions
diff --git a/src/io/multi.go b/src/io/multi.go
new file mode 100644
index 000000000..e26cc53e9
--- /dev/null
+++ b/src/io/multi.go
@@ -0,0 +1,61 @@
+// 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 multiReader struct {
+	readers []Reader
+}
+
+func (mr *multiReader) Read(p []byte) (n int, err error) {
+	for len(mr.readers) > 0 {
+		n, err = mr.readers[0].Read(p)
+		if n > 0 || err != EOF {
+			if err == EOF {
+				// Don't return EOF yet. There may be more bytes
+				// in the remaining readers.
+				err = nil
+			}
+			return
+		}
+		mr.readers = mr.readers[1:]
+	}
+	return 0, EOF
+}
+
+// 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
+}
+
+// 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 {
+	w := make([]Writer, len(writers))
+	copy(w, writers)
+	return &multiWriter{w}
+}