diff options
Diffstat (limited to 'src/bufio/bufio.go')
| -rw-r--r-- | src/bufio/bufio.go | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/src/bufio/bufio.go b/src/bufio/bufio.go index 7483946fc0..bcc273c78b 100644 --- a/src/bufio/bufio.go +++ b/src/bufio/bufio.go @@ -731,13 +731,28 @@ func (b *Writer) WriteRune(r rune) (size int, err error) { // If the count is less than len(s), it also returns an error explaining // why the write is short. func (b *Writer) WriteString(s string) (int, error) { + var sw io.StringWriter + tryStringWriter := true + nn := 0 for len(s) > b.Available() && b.err == nil { - n := copy(b.buf[b.n:], s) - b.n += n + var n int + if b.Buffered() == 0 && sw == nil && tryStringWriter { + // Check at most once whether b.wr is a StringWriter. + sw, tryStringWriter = b.wr.(io.StringWriter) + } + if b.Buffered() == 0 && tryStringWriter { + // Large write, empty buffer, and the underlying writer supports + // WriteString: forward the write to the underlying StringWriter. + // This avoids an extra copy. + n, b.err = sw.WriteString(s) + } else { + n = copy(b.buf[b.n:], s) + b.n += n + b.Flush() + } nn += n s = s[n:] - b.Flush() } if b.err != nil { return nn, b.err |