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bufio: drop buffer recycling, add Reader.Reset and Writer.Reset

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Fixes #6086

R=golang-dev, pieter, r, rsc
CC=golang-dev
https://golang.org/cl/12603049
This commit is contained in:
Brad Fitzpatrick 2013-08-10 19:22:19 -07:00
parent 7910cd68b5
commit ede9aa9e02
2 changed files with 74 additions and 109 deletions
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151
src/pkg/bufio/bufio.go
View File

@ -29,8 +29,7 @@ var (
// 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 @@ const minReadBufferSize = 16
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 @@ func NewReader(rd io.Reader) *Reader {
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 @@ func (b *Reader) Peek(n int) ([]byte, error) {
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 @@ func (b *Reader) Read(p []byte) (n int, err error) {
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 @@ func (b *Reader) Read(p []byte) (n int, err error) {
b.r += n
b.lastByte = int(b.buf[b.r-1])
b.lastRuneSize = -1
b.putBuf()
return n, nil
}
@ -214,9 +185,6 @@ func (b *Reader) ReadByte() (c byte, err error) {
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) ReadByte() (c byte, err error) {
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 @@ func (b *Reader) Buffered() int { return b.w - b.r }
// 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 @@ func (b *Reader) ReadSlice(delim byte) (line []byte, err error) {
}
// 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) ReadBytes(delim byte) (line []byte, err error) {
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) WriteTo(w io.Writer) (n int64, err error) {
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 @@ func (b *Reader) writeBuf(w io.Writer) (int64, error) {
// 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 @@ func (b *Writer) flush() error {
}
// 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 @@ func (b *Writer) Buffered() int { return b.n }
// 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 @@ func (b *Writer) WriteByte(c byte) error {
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 @@ func (b *Writer) WriteByte(c byte) error {
// 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 @@ 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) {
b.allocBuf()
nn := 0
for len(s) > b.Available() && b.err == nil {
n := copy(b.buf[b.n:], s)
@ -670,7 +604,6 @@ func (b *Writer) WriteString(s string) (int, error) {
// 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)

32
src/pkg/bufio/bufio_test.go
View File

@ -1025,6 +1025,38 @@ func TestWriterReadFromWhileFull(t *testing.T) {
}
}
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