io: add WriteString support to MultiWriter
Fixes #11805
Change-Id: I081e16b869dc706bd847ee645bb902bc671c123f
Reviewed-on: https://go-review.googlesource.com/12485
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/io/multi.go b/src/io/multi.go
index e26cc53..16860aa 100644
--- a/src/io/multi.go
+++ b/src/io/multi.go
@@ -52,6 +52,30 @@
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.
func MultiWriter(writers ...Writer) Writer {
