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https://github.com/golang/go
synced 2024-11-12 03:00:22 -07:00
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
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7910cd68b5
commit
ede9aa9e02
@ -29,8 +29,7 @@ var (
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// Reader implements buffering for an io.Reader object.
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type Reader struct {
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buf []byte // either nil or []byte of length bufSize
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bufSize int
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buf []byte
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rd io.Reader
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r, w int
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err error
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@ -46,22 +45,14 @@ const minReadBufferSize = 16
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func NewReaderSize(rd io.Reader, size int) *Reader {
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// Is it already a Reader?
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b, ok := rd.(*Reader)
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if ok && b.bufSize >= size {
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if ok && len(b.buf) >= size {
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return b
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}
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if size < minReadBufferSize {
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size = minReadBufferSize
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}
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r := &Reader{
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bufSize: size,
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rd: rd,
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lastByte: -1,
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lastRuneSize: -1,
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}
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if size > defaultBufSize {
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// TODO(bradfitz): make all buffer sizes recycle
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r.buf = make([]byte, r.bufSize)
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}
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r := new(Reader)
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r.reset(make([]byte, size), rd)
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return r
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}
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@ -70,44 +61,25 @@ func NewReader(rd io.Reader) *Reader {
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return NewReaderSize(rd, defaultBufSize)
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}
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// Reset discards any buffered data, resets all state, and switches
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// the buffered reader to read from r.
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func (b *Reader) Reset(r io.Reader) {
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b.reset(b.buf, r)
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}
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func (b *Reader) reset(buf []byte, r io.Reader) {
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*b = Reader{
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buf: buf,
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rd: r,
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lastByte: -1,
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lastRuneSize: -1,
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}
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}
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var errNegativeRead = errors.New("bufio: reader returned negative count from Read")
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// TODO: use a sync.Cache instead of this:
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const arbitrarySize = 8
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// bufCache holds only byte slices with capacity defaultBufSize.
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var bufCache = make(chan []byte, arbitrarySize)
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// allocBuf makes b.buf non-nil.
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func (b *Reader) allocBuf() {
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if b.buf != nil {
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return
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}
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select {
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case b.buf = <-bufCache:
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b.buf = b.buf[:b.bufSize]
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default:
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b.buf = make([]byte, b.bufSize, defaultBufSize)
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}
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}
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// putBuf returns b.buf if it's unused.
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func (b *Reader) putBuf() {
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if b.r == b.w && b.err == io.EOF && cap(b.buf) == defaultBufSize {
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select {
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case bufCache <- b.buf:
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b.buf = nil
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b.r = 0
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b.w = 0
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default:
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}
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}
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}
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// fill reads a new chunk into the buffer.
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func (b *Reader) fill() {
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b.allocBuf()
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// Slide existing data to beginning.
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if b.r > 0 {
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copy(b.buf, b.buf[b.r:b.w])
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@ -140,7 +112,7 @@ func (b *Reader) Peek(n int) ([]byte, error) {
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if n < 0 {
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return nil, ErrNegativeCount
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}
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if n > b.bufSize {
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if n > len(b.buf) {
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return nil, ErrBufferFull
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}
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for b.w-b.r < n && b.err == nil {
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@ -174,7 +146,7 @@ func (b *Reader) Read(p []byte) (n int, err error) {
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if b.err != nil {
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return 0, b.readErr()
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}
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if len(p) >= b.bufSize {
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if len(p) >= len(b.buf) {
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// Large read, empty buffer.
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// Read directly into p to avoid copy.
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n, b.err = b.rd.Read(p)
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@ -197,7 +169,6 @@ func (b *Reader) Read(p []byte) (n int, err error) {
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b.r += n
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b.lastByte = int(b.buf[b.r-1])
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b.lastRuneSize = -1
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b.putBuf()
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return n, nil
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}
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@ -214,9 +185,6 @@ func (b *Reader) ReadByte() (c byte, err error) {
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c = b.buf[b.r]
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b.r++
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b.lastByte = int(c)
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if b.err != nil { // avoid putBuf call in the common case
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b.putBuf()
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}
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return c, nil
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}
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@ -224,7 +192,6 @@ func (b *Reader) ReadByte() (c byte, err error) {
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func (b *Reader) UnreadByte() error {
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b.lastRuneSize = -1
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if b.r == b.w && b.lastByte >= 0 {
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b.allocBuf()
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b.w = 1
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b.r = 0
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b.buf[0] = byte(b.lastByte)
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@ -279,7 +246,7 @@ func (b *Reader) Buffered() int { return b.w - b.r }
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// ReadSlice reads until the first occurrence of delim in the input,
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// returning a slice pointing at the bytes in the buffer.
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// The bytes stop being valid at the next read call.
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// The bytes stop being valid at the next read.
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// If ReadSlice encounters an error before finding a delimiter,
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// it returns all the data in the buffer and the error itself (often io.EOF).
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// ReadSlice fails with error ErrBufferFull if the buffer fills without a delim.
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@ -314,7 +281,7 @@ func (b *Reader) ReadSlice(delim byte) (line []byte, err error) {
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}
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// Buffer is full?
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if b.Buffered() >= b.bufSize {
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if b.Buffered() >= len(b.buf) {
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b.r = b.w
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return b.buf, ErrBufferFull
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}
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@ -427,7 +394,6 @@ func (b *Reader) ReadBytes(delim byte) (line []byte, err error) {
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func (b *Reader) ReadString(delim byte) (line string, err error) {
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bytes, err := b.ReadBytes(delim)
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line = string(bytes)
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b.putBuf()
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return line, err
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}
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@ -463,7 +429,6 @@ func (b *Reader) WriteTo(w io.Writer) (n int64, err error) {
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func (b *Reader) writeBuf(w io.Writer) (int64, error) {
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n, err := w.Write(b.buf[b.r:b.w])
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b.r += n
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b.putBuf()
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return int64(n), err
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}
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@ -473,69 +438,46 @@ func (b *Reader) writeBuf(w io.Writer) (int64, error) {
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// If an error occurs writing to a Writer, no more data will be
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// accepted and all subsequent writes will return the error.
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type Writer struct {
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err error
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buf []byte // either nil or []byte of length bufSize
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bufSize int
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n int
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wr io.Writer
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err error
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buf []byte
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n int
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wr io.Writer
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}
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// NewWriterSize returns a new Writer whose buffer has at least the specified
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// size. If the argument io.Writer is already a Writer with large enough
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// size, it returns the underlying Writer.
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func NewWriterSize(wr io.Writer, size int) *Writer {
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func NewWriterSize(w io.Writer, size int) *Writer {
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// Is it already a Writer?
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b, ok := wr.(*Writer)
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if ok && b.bufSize >= size {
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b, ok := w.(*Writer)
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if ok && len(b.buf) >= size {
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return b
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}
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if size <= 0 {
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size = defaultBufSize
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}
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b = &Writer{
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wr: wr,
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bufSize: size,
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return &Writer{
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buf: make([]byte, size),
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wr: w,
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}
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if size > defaultBufSize {
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// TODO(bradfitz): make all buffer sizes recycle
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b.buf = make([]byte, b.bufSize)
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}
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return b
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}
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// NewWriter returns a new Writer whose buffer has the default size.
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func NewWriter(wr io.Writer) *Writer {
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return NewWriterSize(wr, defaultBufSize)
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func NewWriter(w io.Writer) *Writer {
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return NewWriterSize(w, defaultBufSize)
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}
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// allocBuf makes b.buf non-nil.
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func (b *Writer) allocBuf() {
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if b.buf != nil {
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return
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}
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select {
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case b.buf = <-bufCache:
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b.buf = b.buf[:b.bufSize]
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default:
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b.buf = make([]byte, b.bufSize, defaultBufSize)
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}
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}
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// putBuf returns b.buf if it's unused.
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func (b *Writer) putBuf() {
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if b.n == 0 && cap(b.buf) == defaultBufSize {
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select {
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case bufCache <- b.buf:
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b.buf = nil
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default:
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}
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}
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// Reset discards any unflushed buffered data, clears any error, and
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// resets b to write its output to w.
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func (b *Writer) Reset(w io.Writer) {
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b.err = nil
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b.n = 0
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b.wr = w
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}
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// Flush writes any buffered data to the underlying io.Writer.
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func (b *Writer) Flush() error {
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err := b.flush()
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b.putBuf()
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return err
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}
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@ -563,7 +505,7 @@ func (b *Writer) flush() error {
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}
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// Available returns how many bytes are unused in the buffer.
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func (b *Writer) Available() int { return b.bufSize - b.n }
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func (b *Writer) Available() int { return len(b.buf) - b.n }
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// Buffered returns the number of bytes that have been written into the current buffer.
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func (b *Writer) Buffered() int { return b.n }
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@ -573,7 +515,6 @@ func (b *Writer) Buffered() int { return b.n }
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// If nn < len(p), it also returns an error explaining
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// why the write is short.
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func (b *Writer) Write(p []byte) (nn int, err error) {
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b.allocBuf()
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for len(p) > b.Available() && b.err == nil {
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var n int
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if b.Buffered() == 0 {
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@ -605,9 +546,6 @@ func (b *Writer) WriteByte(c byte) error {
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if b.Available() <= 0 && b.flush() != nil {
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return b.err
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}
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if b.buf == nil {
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b.allocBuf()
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}
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b.buf[b.n] = c
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b.n++
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return nil
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@ -616,9 +554,6 @@ func (b *Writer) WriteByte(c byte) error {
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// WriteRune writes a single Unicode code point, returning
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// the number of bytes written and any error.
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func (b *Writer) WriteRune(r rune) (size int, err error) {
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if b.buf == nil {
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b.allocBuf()
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}
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if r < utf8.RuneSelf {
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err = b.WriteByte(byte(r))
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if err != nil {
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@ -650,7 +585,6 @@ func (b *Writer) WriteRune(r rune) (size int, err error) {
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// If the count is less than len(s), it also returns an error explaining
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// why the write is short.
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func (b *Writer) WriteString(s string) (int, error) {
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b.allocBuf()
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nn := 0
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for len(s) > b.Available() && b.err == nil {
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n := copy(b.buf[b.n:], s)
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@ -670,7 +604,6 @@ func (b *Writer) WriteString(s string) (int, error) {
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// ReadFrom implements io.ReaderFrom.
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func (b *Writer) ReadFrom(r io.Reader) (n int64, err error) {
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b.allocBuf()
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if b.Buffered() == 0 {
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if w, ok := b.wr.(io.ReaderFrom); ok {
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return w.ReadFrom(r)
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@ -1025,6 +1025,38 @@ func TestWriterReadFromWhileFull(t *testing.T) {
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}
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}
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func TestReaderReset(t *testing.T) {
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r := NewReader(strings.NewReader("foo foo"))
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buf := make([]byte, 3)
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r.Read(buf)
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if string(buf) != "foo" {
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t.Errorf("buf = %q; want foo", buf)
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}
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r.Reset(strings.NewReader("bar bar"))
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all, err := ioutil.ReadAll(r)
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if err != nil {
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t.Fatal(err)
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}
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if string(all) != "bar bar" {
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t.Errorf("ReadAll = %q; want bar bar", all)
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}
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}
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func TestWriterReset(t *testing.T) {
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var buf1, buf2 bytes.Buffer
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w := NewWriter(&buf1)
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w.WriteString("foo")
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w.Reset(&buf2) // and not flushed
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w.WriteString("bar")
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w.Flush()
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if buf1.String() != "" {
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t.Errorf("buf1 = %q; want empty", buf1.String())
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}
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if buf2.String() != "bar" {
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t.Errorf("buf2 = %q; want bar", buf2.String())
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}
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}
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// An onlyReader only implements io.Reader, no matter what other methods the underlying implementation may have.
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type onlyReader struct {
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r io.Reader
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