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bufio: make Reader.Reset and Writer.Reset work on the zero value

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For batch allocation reasons, it would be useful to nest a
bufio.Reader or bufio.Writer in a struct as a value,
rather than a pointer. When the Reset method is called,
have it use the default buffer size if the buffer is nil.

Fixes #45374

Change-Id: I80df18a13575431428a42ed150a1579de1282637
Reviewed-on: https://go-review.googlesource.com/c/go/+/345570
Trust: Joe Tsai <joetsai@digital-static.net>
Run-TryBot: Joe Tsai <joetsai@digital-static.net>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Joe Tsai 2021-08-04 00:57:07 -07:00
parent cf2fe5d6f1
commit a50225a0dc
2 changed files with 34 additions and 1 deletions
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10
src/bufio/bufio.go
View File

@ -68,7 +68,12 @@ func (b *Reader) Size() int { return len(b.buf) }
// Reset discards any buffered data, resets all state, and switches
// the buffered reader to read from r.
// Calling Reset on the zero value of Reader initializes the internal buffer
// to the default size.
func (b *Reader) Reset(r io.Reader) {
if b.buf == nil {
b.buf = make([]byte, defaultBufSize)
}
b.reset(b.buf, r)
}
@ -590,7 +595,12 @@ func (b *Writer) Size() int { return len(b.buf) }
// Reset discards any unflushed buffered data, clears any error, and
// resets b to write its output to w.
// Calling Reset on the zero value of Writer initializes the internal buffer
// to the default size.
func (b *Writer) Reset(w io.Writer) {
if b.buf == nil {
b.buf = make([]byte, defaultBufSize)
}
b.err = nil
b.n = 0
b.wr = w

25
src/bufio/bufio_test.go
View File

@ -1312,6 +1312,7 @@ func TestReaderReset(t *testing.T) {
if string(buf) != "foo" {
t.Errorf("buf = %q; want foo", buf)
}
r.Reset(strings.NewReader("bar bar"))
all, err := io.ReadAll(r)
if err != nil {
@ -1320,12 +1321,23 @@ func TestReaderReset(t *testing.T) {
if string(all) != "bar bar" {
t.Errorf("ReadAll = %q; want bar bar", all)
}
*r = Reader{} // zero out the Reader
r.Reset(strings.NewReader("bar bar"))
all, err = io.ReadAll(r)
if err != nil {
t.Fatal(err)
}
if string(all) != "bar bar" {
t.Errorf("ReadAll = %q; want bar bar", all)
}
}
func TestWriterReset(t *testing.T) {
var buf1, buf2 bytes.Buffer
var buf1, buf2, buf3 bytes.Buffer
w := NewWriter(&buf1)
w.WriteString("foo")
w.Reset(&buf2) // and not flushed
w.WriteString("bar")
w.Flush()
@ -1335,6 +1347,17 @@ func TestWriterReset(t *testing.T) {
if buf2.String() != "bar" {
t.Errorf("buf2 = %q; want bar", buf2.String())
}
*w = Writer{} // zero out the Writer
w.Reset(&buf3) // and not flushed
w.WriteString("bar")
w.Flush()
if buf1.String() != "" {
t.Errorf("buf1 = %q; want empty", buf1.String())
}
if buf3.String() != "bar" {
t.Errorf("buf3 = %q; want bar", buf3.String())
}
}
func TestReaderDiscard(t *testing.T) {