bufio: in Reader.WriteTo, try to use target's ReaderFrom
This is the simple half of https://golang.org/cl/53560043/ with
a new benchmark. pongad is in the C+A files already.
benchmark old ns/op new ns/op delta
BenchmarkReaderWriteToOptimal 2054 825 -59.83%
Update #6373
LGTM=iant, gri
R=golang-codereviews, iant, gri
CC=golang-codereviews
https://golang.org/cl/69220046
diff --git a/src/pkg/bufio/bufio_test.go b/src/pkg/bufio/bufio_test.go
index 3c86857..e48f5f8 100644
--- a/src/pkg/bufio/bufio_test.go
+++ b/src/pkg/bufio/bufio_test.go
@@ -1094,20 +1094,12 @@
// An onlyReader only implements io.Reader, no matter what other methods the underlying implementation may have.
type onlyReader struct {
- r io.Reader
-}
-
-func (r onlyReader) Read(b []byte) (int, error) {
- return r.r.Read(b)
+ io.Reader
}
// An onlyWriter only implements io.Writer, no matter what other methods the underlying implementation may have.
type onlyWriter struct {
- w io.Writer
-}
-
-func (w onlyWriter) Write(b []byte) (int, error) {
- return w.w.Write(b)
+ io.Writer
}
func BenchmarkReaderCopyOptimal(b *testing.B) {
@@ -1152,6 +1144,27 @@
}
}
+func BenchmarkReaderWriteToOptimal(b *testing.B) {
+ const bufSize = 16 << 10
+ buf := make([]byte, bufSize)
+ r := bytes.NewReader(buf)
+ srcReader := NewReaderSize(onlyReader{r}, 1<<10)
+ if _, ok := ioutil.Discard.(io.ReaderFrom); !ok {
+ b.Fatal("ioutil.Discard doesn't support ReaderFrom")
+ }
+ for i := 0; i < b.N; i++ {
+ r.Seek(0, 0)
+ srcReader.Reset(onlyReader{r})
+ n, err := srcReader.WriteTo(ioutil.Discard)
+ if err != nil {
+ b.Fatal(err)
+ }
+ if n != bufSize {
+ b.Fatalf("n = %d; want %d", n, bufSize)
+ }
+ }
+}
+
func BenchmarkWriterCopyOptimal(b *testing.B) {
// Optimal case is where the underlying writer implements io.ReaderFrom
srcBuf := bytes.NewBuffer(make([]byte, 8192))
