bufio: drop buffer recycling, add Reader.Reset and Writer.Reset
Fixes #6086
R=golang-dev, pieter, r, rsc
CC=golang-dev
https://golang.org/cl/12603049
diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index 993c22d..a548fd3 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -29,8 +29,7 @@
// Reader implements buffering for an io.Reader object.
type Reader struct {
- buf []byte // either nil or []byte of length bufSize
- bufSize int
+ buf []byte
rd io.Reader
r, w int
err error
@@ -46,22 +45,14 @@
func NewReaderSize(rd io.Reader, size int) *Reader {
// Is it already a Reader?
b, ok := rd.(*Reader)
- if ok && b.bufSize >= size {
+ if ok && len(b.buf) >= size {
return b
}
if size < minReadBufferSize {
size = minReadBufferSize
}
- r := &Reader{
- bufSize: size,
- rd: rd,
- lastByte: -1,
- lastRuneSize: -1,
- }
- if size > defaultBufSize {
- // TODO(bradfitz): make all buffer sizes recycle
- r.buf = make([]byte, r.bufSize)
- }
+ r := new(Reader)
+ r.reset(make([]byte, size), rd)
return r
}
@@ -70,44 +61,25 @@
return NewReaderSize(rd, defaultBufSize)
}
+// Reset discards any buffered data, resets all state, and switches
+// the buffered reader to read from r.
+func (b *Reader) Reset(r io.Reader) {
+ b.reset(b.buf, r)
+}
+
+func (b *Reader) reset(buf []byte, r io.Reader) {
+ *b = Reader{
+ buf: buf,
+ rd: r,
+ lastByte: -1,
+ lastRuneSize: -1,
+ }
+}
+
var errNegativeRead = errors.New("bufio: reader returned negative count from Read")
-// TODO: use a sync.Cache instead of this:
-const arbitrarySize = 8
-
-// bufCache holds only byte slices with capacity defaultBufSize.
-var bufCache = make(chan []byte, arbitrarySize)
-
-// allocBuf makes b.buf non-nil.
-func (b *Reader) allocBuf() {
- if b.buf != nil {
- return
- }
- select {
- case b.buf = <-bufCache:
- b.buf = b.buf[:b.bufSize]
- default:
- b.buf = make([]byte, b.bufSize, defaultBufSize)
- }
-}
-
-// putBuf returns b.buf if it's unused.
-func (b *Reader) putBuf() {
- if b.r == b.w && b.err == io.EOF && cap(b.buf) == defaultBufSize {
- select {
- case bufCache <- b.buf:
- b.buf = nil
- b.r = 0
- b.w = 0
- default:
- }
- }
-}
-
// fill reads a new chunk into the buffer.
func (b *Reader) fill() {
- b.allocBuf()
-
// Slide existing data to beginning.
if b.r > 0 {
copy(b.buf, b.buf[b.r:b.w])
@@ -140,7 +112,7 @@
if n < 0 {
return nil, ErrNegativeCount
}
- if n > b.bufSize {
+ if n > len(b.buf) {
return nil, ErrBufferFull
}
for b.w-b.r < n && b.err == nil {
@@ -174,7 +146,7 @@
if b.err != nil {
return 0, b.readErr()
}
- if len(p) >= b.bufSize {
+ if len(p) >= len(b.buf) {
// Large read, empty buffer.
// Read directly into p to avoid copy.
n, b.err = b.rd.Read(p)
@@ -197,7 +169,6 @@
b.r += n
b.lastByte = int(b.buf[b.r-1])
b.lastRuneSize = -1
- b.putBuf()
return n, nil
}
@@ -214,9 +185,6 @@
c = b.buf[b.r]
b.r++
b.lastByte = int(c)
- if b.err != nil { // avoid putBuf call in the common case
- b.putBuf()
- }
return c, nil
}
@@ -224,7 +192,6 @@
func (b *Reader) UnreadByte() error {
b.lastRuneSize = -1
if b.r == b.w && b.lastByte >= 0 {
- b.allocBuf()
b.w = 1
b.r = 0
b.buf[0] = byte(b.lastByte)
@@ -279,7 +246,7 @@
// ReadSlice reads until the first occurrence of delim in the input,
// returning a slice pointing at the bytes in the buffer.
-// The bytes stop being valid at the next read call.
+// The bytes stop being valid at the next read.
// If ReadSlice encounters an error before finding a delimiter,
// it returns all the data in the buffer and the error itself (often io.EOF).
// ReadSlice fails with error ErrBufferFull if the buffer fills without a delim.
@@ -314,7 +281,7 @@
}
// Buffer is full?
- if b.Buffered() >= b.bufSize {
+ if b.Buffered() >= len(b.buf) {
b.r = b.w
return b.buf, ErrBufferFull
}
@@ -427,7 +394,6 @@
func (b *Reader) ReadString(delim byte) (line string, err error) {
bytes, err := b.ReadBytes(delim)
line = string(bytes)
- b.putBuf()
return line, err
}
@@ -463,7 +429,6 @@
func (b *Reader) writeBuf(w io.Writer) (int64, error) {
n, err := w.Write(b.buf[b.r:b.w])
b.r += n
- b.putBuf()
return int64(n), err
}
@@ -473,69 +438,46 @@
// If an error occurs writing to a Writer, no more data will be
// accepted and all subsequent writes will return the error.
type Writer struct {
- err error
- buf []byte // either nil or []byte of length bufSize
- bufSize int
- n int
- wr io.Writer
+ err error
+ buf []byte
+ n int
+ wr io.Writer
}
// NewWriterSize returns a new Writer whose buffer has at least the specified
// size. If the argument io.Writer is already a Writer with large enough
// size, it returns the underlying Writer.
-func NewWriterSize(wr io.Writer, size int) *Writer {
+func NewWriterSize(w io.Writer, size int) *Writer {
// Is it already a Writer?
- b, ok := wr.(*Writer)
- if ok && b.bufSize >= size {
+ b, ok := w.(*Writer)
+ if ok && len(b.buf) >= size {
return b
}
if size <= 0 {
size = defaultBufSize
}
- b = &Writer{
- wr: wr,
- bufSize: size,
+ return &Writer{
+ buf: make([]byte, size),
+ wr: w,
}
- if size > defaultBufSize {
- // TODO(bradfitz): make all buffer sizes recycle
- b.buf = make([]byte, b.bufSize)
- }
- return b
}
// NewWriter returns a new Writer whose buffer has the default size.
-func NewWriter(wr io.Writer) *Writer {
- return NewWriterSize(wr, defaultBufSize)
+func NewWriter(w io.Writer) *Writer {
+ return NewWriterSize(w, defaultBufSize)
}
-// allocBuf makes b.buf non-nil.
-func (b *Writer) allocBuf() {
- if b.buf != nil {
- return
- }
- select {
- case b.buf = <-bufCache:
- b.buf = b.buf[:b.bufSize]
- default:
- b.buf = make([]byte, b.bufSize, defaultBufSize)
- }
-}
-
-// putBuf returns b.buf if it's unused.
-func (b *Writer) putBuf() {
- if b.n == 0 && cap(b.buf) == defaultBufSize {
- select {
- case bufCache <- b.buf:
- b.buf = nil
- default:
- }
- }
+// Reset discards any unflushed buffered data, clears any error, and
+// resets b to write its output to w.
+func (b *Writer) Reset(w io.Writer) {
+ b.err = nil
+ b.n = 0
+ b.wr = w
}
// Flush writes any buffered data to the underlying io.Writer.
func (b *Writer) Flush() error {
err := b.flush()
- b.putBuf()
return err
}
@@ -563,7 +505,7 @@
}
// Available returns how many bytes are unused in the buffer.
-func (b *Writer) Available() int { return b.bufSize - b.n }
+func (b *Writer) Available() int { return len(b.buf) - b.n }
// Buffered returns the number of bytes that have been written into the current buffer.
func (b *Writer) Buffered() int { return b.n }
@@ -573,7 +515,6 @@
// If nn < len(p), it also returns an error explaining
// why the write is short.
func (b *Writer) Write(p []byte) (nn int, err error) {
- b.allocBuf()
for len(p) > b.Available() && b.err == nil {
var n int
if b.Buffered() == 0 {
@@ -605,9 +546,6 @@
if b.Available() <= 0 && b.flush() != nil {
return b.err
}
- if b.buf == nil {
- b.allocBuf()
- }
b.buf[b.n] = c
b.n++
return nil
@@ -616,9 +554,6 @@
// WriteRune writes a single Unicode code point, returning
// the number of bytes written and any error.
func (b *Writer) WriteRune(r rune) (size int, err error) {
- if b.buf == nil {
- b.allocBuf()
- }
if r < utf8.RuneSelf {
err = b.WriteByte(byte(r))
if err != nil {
@@ -650,7 +585,6 @@
// 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) {
- b.allocBuf()
nn := 0
for len(s) > b.Available() && b.err == nil {
n := copy(b.buf[b.n:], s)
@@ -670,7 +604,6 @@
// ReadFrom implements io.ReaderFrom.
func (b *Writer) ReadFrom(r io.Reader) (n int64, err error) {
- b.allocBuf()
if b.Buffered() == 0 {
if w, ok := b.wr.(io.ReaderFrom); ok {
return w.ReadFrom(r)
diff --git a/src/pkg/bufio/bufio_test.go b/src/pkg/bufio/bufio_test.go
index 68a138e..41bd3d4 100644
--- a/src/pkg/bufio/bufio_test.go
+++ b/src/pkg/bufio/bufio_test.go
@@ -1025,6 +1025,38 @@
}
}
+func TestReaderReset(t *testing.T) {
+ r := NewReader(strings.NewReader("foo foo"))
+ buf := make([]byte, 3)
+ r.Read(buf)
+ if string(buf) != "foo" {
+ t.Errorf("buf = %q; want foo", buf)
+ }
+ r.Reset(strings.NewReader("bar bar"))
+ all, err := ioutil.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
+ w := NewWriter(&buf1)
+ w.WriteString("foo")
+ w.Reset(&buf2) // and not flushed
+ w.WriteString("bar")
+ w.Flush()
+ if buf1.String() != "" {
+ t.Errorf("buf1 = %q; want empty", buf1.String())
+ }
+ if buf2.String() != "bar" {
+ t.Errorf("buf2 = %q; want bar", buf2.String())
+ }
+}
+
// An onlyReader only implements io.Reader, no matter what other methods the underlying implementation may have.
type onlyReader struct {
r io.Reader
