522 lines
13 KiB
Go
522 lines
13 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package bufio implements buffered I/O. It wraps an io.Reader or io.Writer
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// object, creating another object (Reader or Writer) that also implements
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// the interface but provides buffering and some help for textual I/O.
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package bufio
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import (
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"bytes"
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"errors"
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"io"
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)
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const (
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defaultBufSize = 4096
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)
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var (
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// ErrInvalidUnreadByte invalid use of UnreadByete
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ErrInvalidUnreadByte = errors.New("bufio: invalid use of UnreadByte")
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// ErrInvalidUnreadRune invalid use of UnreadRune
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ErrInvalidUnreadRune = errors.New("bufio: invalid use of UnreadRune")
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// ErrBufferFull buffer full
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ErrBufferFull = errors.New("bufio: buffer full")
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// ErrNegativeCount negative count
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ErrNegativeCount = errors.New("bufio: negative count")
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)
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// Buffered input.
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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
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rd io.Reader // reader provided by the client
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r, w int // buf read and write positions
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err error
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}
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const minReadBufferSize = 16
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const maxConsecutiveEmptyReads = 100
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// NewReaderSize returns a new Reader whose buffer has at least the specified
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// size. If the argument io.Reader is already a Reader with large enough
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// size, it returns the underlying Reader.
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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 && 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 := 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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// NewReader returns a new Reader whose buffer has the default size.
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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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// ResetBuffer 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) ResetBuffer(r io.Reader, buf []byte) {
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b.reset(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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}
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}
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var errNegativeRead = errors.New("bufio: reader returned negative count from Read")
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// fill reads a new chunk into the buffer.
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func (b *Reader) fill() {
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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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b.w -= b.r
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b.r = 0
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}
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if b.w >= len(b.buf) {
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panic("bufio: tried to fill full buffer")
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}
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// Read new data: try a limited number of times.
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for i := maxConsecutiveEmptyReads; i > 0; i-- {
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n, err := b.rd.Read(b.buf[b.w:])
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if n < 0 {
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panic(errNegativeRead)
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}
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b.w += n
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if err != nil {
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b.err = err
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return
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}
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if n > 0 {
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return
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}
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}
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b.err = io.ErrNoProgress
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}
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func (b *Reader) readErr() error {
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err := b.err
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b.err = nil
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return err
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}
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// Peek returns the next n bytes without advancing the reader. The bytes stop
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// being valid at the next read call. If Peek returns fewer than n bytes, it
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// also returns an error explaining why the read is short. The error is
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// ErrBufferFull if n is larger than b's buffer size.
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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 > len(b.buf) {
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return nil, ErrBufferFull
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}
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// 0 <= n <= len(b.buf)
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for b.w-b.r < n && b.err == nil {
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b.fill() // b.w-b.r < len(b.buf) => buffer is not full
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}
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var err error
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if avail := b.w - b.r; avail < n {
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// not enough data in buffer
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n = avail
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err = b.readErr()
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if err == nil {
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err = ErrBufferFull
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}
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}
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return b.buf[b.r : b.r+n], err
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}
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// Pop returns the next n bytes with advancing the reader. The bytes stop
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// being valid at the next read call. If Pop returns fewer than n bytes, it
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// also returns an error explaining why the read is short. The error is
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// ErrBufferFull if n is larger than b's buffer size.
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func (b *Reader) Pop(n int) ([]byte, error) {
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d, err := b.Peek(n)
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if err == nil {
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b.r += n
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return d, err
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}
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return nil, err
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}
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// Discard skips the next n bytes, returning the number of bytes discarded.
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//
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// If Discard skips fewer than n bytes, it also returns an error.
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// If 0 <= n <= b.Buffered(), Discard is guaranteed to succeed without
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// reading from the underlying io.Reader.
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func (b *Reader) Discard(n int) (discarded int, err error) {
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if n < 0 {
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return 0, ErrNegativeCount
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}
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if n == 0 {
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return
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}
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remain := n
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for {
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skip := b.Buffered()
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if skip == 0 {
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b.fill()
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skip = b.Buffered()
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}
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if skip > remain {
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skip = remain
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}
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b.r += skip
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remain -= skip
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if remain == 0 {
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return n, nil
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}
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if b.err != nil {
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return n - remain, b.readErr()
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}
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}
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}
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// Read reads data into p.
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// It returns the number of bytes read into p.
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// It calls Read at most once on the underlying Reader,
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// hence n may be less than len(p).
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// At EOF, the count will be zero and err will be io.EOF.
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func (b *Reader) Read(p []byte) (n int, err error) {
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n = len(p)
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if n == 0 {
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return 0, b.readErr()
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}
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if b.r == b.w {
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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) >= 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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if n < 0 {
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panic(errNegativeRead)
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}
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return n, b.readErr()
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}
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b.fill() // buffer is empty
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if b.r == b.w {
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return 0, b.readErr()
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}
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}
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// copy as much as we can
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n = copy(p, b.buf[b.r:b.w])
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b.r += n
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return n, nil
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}
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// ReadByte reads and returns a single byte.
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// If no byte is available, returns an error.
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func (b *Reader) ReadByte() (c byte, err error) {
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//b.lastRuneSize = -1
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for b.r == b.w {
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if b.err != nil {
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return 0, b.readErr()
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}
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b.fill() // buffer is empty
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}
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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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return c, nil
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}
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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.
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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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// Because the data returned from ReadSlice will be overwritten
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// by the next I/O operation, most clients should use
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// ReadBytes or ReadString instead.
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// ReadSlice returns err != nil if and only if line does not end in delim.
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func (b *Reader) ReadSlice(delim byte) (line []byte, err error) {
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for {
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// Search buffer.
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if i := bytes.IndexByte(b.buf[b.r:b.w], delim); i >= 0 {
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line = b.buf[b.r : b.r+i+1]
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b.r += i + 1
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break
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}
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// Pending error?
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if b.err != nil {
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line = b.buf[b.r:b.w]
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b.r = b.w
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err = b.readErr()
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break
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}
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// Buffer full?
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if b.Buffered() >= len(b.buf) {
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b.r = b.w
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line = b.buf
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err = ErrBufferFull
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break
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}
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b.fill() // buffer is not full
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}
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return
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}
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// ReadLine is a low-level line-reading primitive. Most callers should use
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// ReadBytes('\n') or ReadString('\n') instead or use a Scanner.
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//
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// ReadLine tries to return a single line, not including the end-of-line bytes.
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// If the line was too long for the buffer then isPrefix is set and the
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// beginning of the line is returned. The rest of the line will be returned
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// from future calls. isPrefix will be false when returning the last fragment
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// of the line. The returned buffer is only valid until the next call to
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// ReadLine. ReadLine either returns a non-nil line or it returns an error,
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// never both.
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//
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// The text returned from ReadLine does not include the line end ("\r\n" or "\n").
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// No indication or error is given if the input ends without a final line end.
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// Calling UnreadByte after ReadLine will always unread the last byte read
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// (possibly a character belonging to the line end) even if that byte is not
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// part of the line returned by ReadLine.
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func (b *Reader) ReadLine() (line []byte, isPrefix bool, err error) {
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line, err = b.ReadSlice('\n')
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if err == ErrBufferFull {
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// Handle the case where "\r\n" straddles the buffer.
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if len(line) > 0 && line[len(line)-1] == '\r' {
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// Put the '\r' back on buf and drop it from line.
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// Let the next call to ReadLine check for "\r\n".
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if b.r == 0 {
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// should be unreachable
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panic("bufio: tried to rewind past start of buffer")
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}
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b.r--
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line = line[:len(line)-1]
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}
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return line, true, nil
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}
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if len(line) == 0 {
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if err != nil {
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line = nil
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}
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return
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}
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err = nil
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if line[len(line)-1] == '\n' {
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drop := 1
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if len(line) > 1 && line[len(line)-2] == '\r' {
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drop = 2
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}
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line = line[:len(line)-drop]
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}
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return
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}
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// Buffered returns the number of bytes that can be read from the current buffer.
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func (b *Reader) Buffered() int { return b.w - b.r }
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// buffered output
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// Writer implements buffering for an io.Writer object.
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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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// After all data has been written, the client should call the
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// Flush method to guarantee all data has been forwarded to
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// the underlying io.Writer.
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type Writer struct {
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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(w io.Writer, size int) *Writer {
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// Is it already a Writer?
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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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return &Writer{
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buf: make([]byte, size),
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wr: w,
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}
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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(w io.Writer) *Writer {
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return NewWriterSize(w, defaultBufSize)
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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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// ResetBuffer 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) ResetBuffer(w io.Writer, buf []byte) {
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b.buf = buf
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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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return err
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}
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func (b *Writer) flush() error {
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if b.err != nil {
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return b.err
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}
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if b.n == 0 {
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return nil
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}
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n, err := b.wr.Write(b.buf[0:b.n])
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if n < b.n && err == nil {
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err = io.ErrShortWrite
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}
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if err != nil {
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if n > 0 && n < b.n {
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copy(b.buf[0:b.n-n], b.buf[n:b.n])
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}
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b.n -= n
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b.err = err
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return err
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}
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b.n = 0
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return nil
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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 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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// Write writes the contents of p into the buffer.
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// It returns the number of bytes written.
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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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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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// Large write, empty buffer.
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// Write directly from p to avoid copy.
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n, b.err = b.wr.Write(p)
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} else {
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n = copy(b.buf[b.n:], p)
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b.n += n
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b.flush()
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}
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nn += n
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p = p[n:]
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}
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if b.err != nil {
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return nn, b.err
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}
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n := copy(b.buf[b.n:], p)
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b.n += n
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nn += n
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return nn, nil
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}
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// WriteRaw writes the contents of p into the raw io.Writer without buffer.
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// It returns the number of bytes written.
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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) WriteRaw(p []byte) (nn int, err error) {
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if b.err != nil {
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return 0, b.err
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}
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if b.Buffered() == 0 {
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// if no buffer data, write raw writer
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nn, err = b.wr.Write(p)
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b.err = err
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} else {
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nn, err = b.Write(p)
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}
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return
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}
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// Peek returns the next n bytes with advancing the writer. The bytes stop
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// being used at the next write call. If Peek returns fewer than n bytes, it
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// also returns an error explaining why the read is short. The error is
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// ErrBufferFull if n is larger than b's buffer size.
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func (b *Writer) 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 > len(b.buf) {
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return nil, ErrBufferFull
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}
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for b.Available() < n && b.err == nil {
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b.flush()
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}
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if b.err != nil {
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return nil, b.err
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}
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d := b.buf[b.n : b.n+n]
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b.n += n
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return d, nil
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}
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// WriteString writes a string.
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// It returns the number of bytes written.
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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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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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b.n += n
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nn += n
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s = s[n:]
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b.flush()
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}
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if b.err != nil {
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return nn, b.err
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}
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n := copy(b.buf[b.n:], s)
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b.n += n
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nn += n
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return nn, nil
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}
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