buffer.go: minor optimization, expanded comment
R=r
CC=golang-dev
https://golang.org/cl/4169043
diff --git a/src/pkg/bytes/buffer.go b/src/pkg/bytes/buffer.go
index 4aa7437..3da8008 100644
--- a/src/pkg/bytes/buffer.go
+++ b/src/pkg/bytes/buffer.go
@@ -154,17 +154,20 @@
}
// WriteTo writes data to w until the buffer is drained or an error
-// occurs. The return value n is the number of bytes written.
+// occurs. The return value n is the number of bytes written; it always
+// fits into an int, but it is int64 to match the io.WriterTo interface.
// Any error encountered during the write is also returned.
func (b *Buffer) WriteTo(w io.Writer) (n int64, err os.Error) {
b.lastRead = opInvalid
- for b.off < len(b.buf) {
+ if b.off < len(b.buf) {
m, e := w.Write(b.buf[b.off:])
- n += int64(m)
b.off += m
+ n = int64(m)
if e != nil {
return n, e
}
+ // otherwise all bytes were written, by definition of
+ // Write method in io.Writer
}
// Buffer is now empty; reset.
b.Truncate(0)
