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729 lines
17 KiB
Go
729 lines
17 KiB
Go
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// 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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"unicode/utf8"
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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 = errors.New("bufio: invalid use of UnreadByte")
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ErrInvalidUnreadRune = errors.New("bufio: invalid use of UnreadRune")
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ErrBufferFull = errors.New("bufio: buffer full")
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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
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r, w int
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err error
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lastByte int
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lastRuneSize int
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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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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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// 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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m := b.w - b.r
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if m > n {
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m = n
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}
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var err error
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if m < n {
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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+m], err
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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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if n > 0 {
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b.lastByte = int(p[n-1])
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b.lastRuneSize = -1
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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.w == b.r {
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return 0, b.readErr()
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}
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}
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if n > b.w-b.r {
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n = b.w - b.r
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}
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copy(p[0:n], b.buf[b.r:])
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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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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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// UnreadByte unreads the last byte. Only the most recently read byte can be unread.
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func (b *Reader) UnreadByte() error {
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if b.lastByte < 0 || b.r == 0 && b.w > 0 {
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return ErrInvalidUnreadByte
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}
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// b.r > 0 || b.w == 0
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if b.r > 0 {
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b.r--
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} else {
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// b.r == 0 && b.w == 0
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b.w = 1
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}
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b.buf[b.r] = byte(b.lastByte)
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b.lastByte = -1
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b.lastRuneSize = -1
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return nil
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}
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// ReadRune reads a single UTF-8 encoded Unicode character and returns the
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// rune and its size in bytes. If the encoded rune is invalid, it consumes one byte
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// and returns unicode.ReplacementChar (U+FFFD) with a size of 1.
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func (b *Reader) ReadRune() (r rune, size int, err error) {
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for b.r+utf8.UTFMax > b.w && !utf8.FullRune(b.buf[b.r:b.w]) && b.err == nil && b.w-b.r < len(b.buf) {
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b.fill() // b.w-b.r < len(buf) => buffer is not full
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}
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b.lastRuneSize = -1
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if b.r == b.w {
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return 0, 0, b.readErr()
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}
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r, size = rune(b.buf[b.r]), 1
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if r >= 0x80 {
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r, size = utf8.DecodeRune(b.buf[b.r:b.w])
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}
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b.r += size
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b.lastByte = int(b.buf[b.r-1])
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b.lastRuneSize = size
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return r, size, nil
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}
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// UnreadRune unreads the last rune. If the most recent read operation on
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// the buffer was not a ReadRune, UnreadRune returns an error. (In this
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// regard it is stricter than UnreadByte, which will unread the last byte
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// from any read operation.)
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func (b *Reader) UnreadRune() error {
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if b.lastRuneSize < 0 || b.r < b.lastRuneSize {
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return ErrInvalidUnreadRune
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}
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b.r -= b.lastRuneSize
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b.lastByte = -1
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b.lastRuneSize = -1
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return nil
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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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// 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 n := b.Buffered(); n >= 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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// Handle last byte, if any.
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if i := len(line) - 1; i >= 0 {
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b.lastByte = int(line[i])
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}
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return
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}
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// ReadN tries to read exactly n bytes.
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// The bytes stop being valid at the next read call.
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// If ReadN encounters an error before reading n bytes,
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// it returns all the data in the buffer and the error itself (often io.EOF).
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// ReadN fails with error ErrBufferFull if the buffer fills
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// without reading N bytes.
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// Because the data returned from ReadN 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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func (b *Reader) ReadN(n int) ([]byte, error) {
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for b.Buffered() < n {
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if b.err != nil {
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buf := b.buf[b.r:b.w]
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b.r = b.w
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return buf, b.readErr()
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}
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// Buffer is full?
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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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b.fill()
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}
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buf := b.buf[b.r : b.r+n]
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b.r += n
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return buf, nil
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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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// ReadBytes reads until the first occurrence of delim in the input,
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// returning a slice containing the data up to and including the delimiter.
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// If ReadBytes encounters an error before finding a delimiter,
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// it returns the data read before the error and the error itself (often io.EOF).
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// ReadBytes returns err != nil if and only if the returned data does not end in
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// delim.
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// For simple uses, a Scanner may be more convenient.
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func (b *Reader) ReadBytes(delim byte) (line []byte, err error) {
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// Use ReadSlice to look for array,
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// accumulating full buffers.
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var frag []byte
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var full [][]byte
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err = nil
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for {
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var e error
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frag, e = b.ReadSlice(delim)
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if e == nil { // got final fragment
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break
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}
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if e != ErrBufferFull { // unexpected error
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err = e
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break
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}
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// Make a copy of the buffer.
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buf := make([]byte, len(frag))
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copy(buf, frag)
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full = append(full, buf)
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}
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// Allocate new buffer to hold the full pieces and the fragment.
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||
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n := 0
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for i := range full {
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n += len(full[i])
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}
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n += len(frag)
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// Copy full pieces and fragment in.
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||
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buf := make([]byte, n)
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n = 0
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for i := range full {
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n += copy(buf[n:], full[i])
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}
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copy(buf[n:], frag)
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return buf, err
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}
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// ReadString reads until the first occurrence of delim in the input,
|
||
|
// returning a string containing the data up to and including the delimiter.
|
||
|
// If ReadString encounters an error before finding a delimiter,
|
||
|
// it returns the data read before the error and the error itself (often io.EOF).
|
||
|
// ReadString returns err != nil if and only if the returned data does not end in
|
||
|
// delim.
|
||
|
// For simple uses, a Scanner may be more convenient.
|
||
|
func (b *Reader) ReadString(delim byte) (line string, err error) {
|
||
|
bytes, err := b.ReadBytes(delim)
|
||
|
line = string(bytes)
|
||
|
return line, err
|
||
|
}
|
||
|
|
||
|
// WriteTo implements io.WriterTo.
|
||
|
func (b *Reader) WriteTo(w io.Writer) (n int64, err error) {
|
||
|
n, err = b.writeBuf(w)
|
||
|
if err != nil {
|
||
|
return
|
||
|
}
|
||
|
|
||
|
if r, ok := b.rd.(io.WriterTo); ok {
|
||
|
m, err := r.WriteTo(w)
|
||
|
n += m
|
||
|
return n, err
|
||
|
}
|
||
|
|
||
|
if w, ok := w.(io.ReaderFrom); ok {
|
||
|
m, err := w.ReadFrom(b.rd)
|
||
|
n += m
|
||
|
return n, err
|
||
|
}
|
||
|
|
||
|
if b.w-b.r < len(b.buf) {
|
||
|
b.fill() // buffer not full
|
||
|
}
|
||
|
|
||
|
for b.r < b.w {
|
||
|
// b.r < b.w => buffer is not empty
|
||
|
m, err := b.writeBuf(w)
|
||
|
n += m
|
||
|
if err != nil {
|
||
|
return n, err
|
||
|
}
|
||
|
b.fill() // buffer is empty
|
||
|
}
|
||
|
|
||
|
if b.err == io.EOF {
|
||
|
b.err = nil
|
||
|
}
|
||
|
|
||
|
return n, b.readErr()
|
||
|
}
|
||
|
|
||
|
// writeBuf writes the Reader's buffer to the writer.
|
||
|
func (b *Reader) writeBuf(w io.Writer) (int64, error) {
|
||
|
n, err := w.Write(b.buf[b.r:b.w])
|
||
|
if n < b.r-b.w {
|
||
|
panic(errors.New("bufio: writer did not write all data"))
|
||
|
}
|
||
|
b.r += n
|
||
|
return int64(n), err
|
||
|
}
|
||
|
|
||
|
// buffered output
|
||
|
|
||
|
// Writer implements buffering for an io.Writer object.
|
||
|
// If an error occurs writing to a Writer, no more data will be
|
||
|
// accepted and all subsequent writes will return the error.
|
||
|
// After all data has been written, the client should call the
|
||
|
// Flush method to guarantee all data has been forwarded to
|
||
|
// the underlying io.Writer.
|
||
|
type Writer struct {
|
||
|
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(w io.Writer, size int) *Writer {
|
||
|
// Is it already a Writer?
|
||
|
b, ok := w.(*Writer)
|
||
|
if ok && len(b.buf) >= size {
|
||
|
return b
|
||
|
}
|
||
|
if size <= 0 {
|
||
|
size = defaultBufSize
|
||
|
}
|
||
|
return &Writer{
|
||
|
buf: make([]byte, size),
|
||
|
wr: w,
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// NewWriter returns a new Writer whose buffer has the default size.
|
||
|
func NewWriter(w io.Writer) *Writer {
|
||
|
return NewWriterSize(w, defaultBufSize)
|
||
|
}
|
||
|
|
||
|
// 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()
|
||
|
return err
|
||
|
}
|
||
|
|
||
|
func (b *Writer) flush() error {
|
||
|
if b.err != nil {
|
||
|
return b.err
|
||
|
}
|
||
|
if b.n == 0 {
|
||
|
return nil
|
||
|
}
|
||
|
n, err := b.wr.Write(b.buf[0:b.n])
|
||
|
if n < b.n && err == nil {
|
||
|
err = io.ErrShortWrite
|
||
|
}
|
||
|
if err != nil {
|
||
|
if n > 0 && n < b.n {
|
||
|
copy(b.buf[0:b.n-n], b.buf[n:b.n])
|
||
|
}
|
||
|
b.n -= n
|
||
|
b.err = err
|
||
|
return err
|
||
|
}
|
||
|
b.n = 0
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
// Available returns how many bytes are unused in the buffer.
|
||
|
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 }
|
||
|
|
||
|
// Write writes the contents of p into the buffer.
|
||
|
// It returns the number of bytes written.
|
||
|
// 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) {
|
||
|
for len(p) > b.Available() && b.err == nil {
|
||
|
var n int
|
||
|
if b.Buffered() == 0 {
|
||
|
// Large write, empty buffer.
|
||
|
// Write directly from p to avoid copy.
|
||
|
n, b.err = b.wr.Write(p)
|
||
|
} else {
|
||
|
n = copy(b.buf[b.n:], p)
|
||
|
b.n += n
|
||
|
b.flush()
|
||
|
}
|
||
|
nn += n
|
||
|
p = p[n:]
|
||
|
}
|
||
|
if b.err != nil {
|
||
|
return nn, b.err
|
||
|
}
|
||
|
n := copy(b.buf[b.n:], p)
|
||
|
b.n += n
|
||
|
nn += n
|
||
|
return nn, nil
|
||
|
}
|
||
|
|
||
|
// WriteByte writes a single byte.
|
||
|
func (b *Writer) WriteByte(c byte) error {
|
||
|
if b.err != nil {
|
||
|
return b.err
|
||
|
}
|
||
|
if b.Available() <= 0 && b.flush() != nil {
|
||
|
return b.err
|
||
|
}
|
||
|
b.buf[b.n] = c
|
||
|
b.n++
|
||
|
return nil
|
||
|
}
|
||
|
|
||
|
// 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 r < utf8.RuneSelf {
|
||
|
err = b.WriteByte(byte(r))
|
||
|
if err != nil {
|
||
|
return 0, err
|
||
|
}
|
||
|
return 1, nil
|
||
|
}
|
||
|
if b.err != nil {
|
||
|
return 0, b.err
|
||
|
}
|
||
|
n := b.Available()
|
||
|
if n < utf8.UTFMax {
|
||
|
if b.flush(); b.err != nil {
|
||
|
return 0, b.err
|
||
|
}
|
||
|
n = b.Available()
|
||
|
if n < utf8.UTFMax {
|
||
|
// Can only happen if buffer is silly small.
|
||
|
return b.WriteString(string(r))
|
||
|
}
|
||
|
}
|
||
|
size = utf8.EncodeRune(b.buf[b.n:], r)
|
||
|
b.n += size
|
||
|
return size, nil
|
||
|
}
|
||
|
|
||
|
// WriteString writes a string.
|
||
|
// It returns the number of bytes written.
|
||
|
// 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) {
|
||
|
nn := 0
|
||
|
for len(s) > b.Available() && b.err == nil {
|
||
|
n := copy(b.buf[b.n:], s)
|
||
|
b.n += n
|
||
|
nn += n
|
||
|
s = s[n:]
|
||
|
b.flush()
|
||
|
}
|
||
|
if b.err != nil {
|
||
|
return nn, b.err
|
||
|
}
|
||
|
n := copy(b.buf[b.n:], s)
|
||
|
b.n += n
|
||
|
nn += n
|
||
|
return nn, nil
|
||
|
}
|
||
|
|
||
|
// ReadFrom implements io.ReaderFrom.
|
||
|
func (b *Writer) ReadFrom(r io.Reader) (n int64, err error) {
|
||
|
if b.Buffered() == 0 {
|
||
|
if w, ok := b.wr.(io.ReaderFrom); ok {
|
||
|
return w.ReadFrom(r)
|
||
|
}
|
||
|
}
|
||
|
var m int
|
||
|
for {
|
||
|
if b.Available() == 0 {
|
||
|
if err1 := b.flush(); err1 != nil {
|
||
|
return n, err1
|
||
|
}
|
||
|
}
|
||
|
nr := 0
|
||
|
for nr < maxConsecutiveEmptyReads {
|
||
|
m, err = r.Read(b.buf[b.n:])
|
||
|
if m != 0 || err != nil {
|
||
|
break
|
||
|
}
|
||
|
nr++
|
||
|
}
|
||
|
if nr == maxConsecutiveEmptyReads {
|
||
|
return n, io.ErrNoProgress
|
||
|
}
|
||
|
b.n += m
|
||
|
n += int64(m)
|
||
|
if err != nil {
|
||
|
break
|
||
|
}
|
||
|
}
|
||
|
if err == io.EOF {
|
||
|
// If we filled the buffer exactly, flush pre-emptively.
|
||
|
if b.Available() == 0 {
|
||
|
err = b.flush()
|
||
|
} else {
|
||
|
err = nil
|
||
|
}
|
||
|
}
|
||
|
return n, err
|
||
|
}
|
||
|
|
||
|
// buffered input and output
|
||
|
|
||
|
// ReadWriter stores pointers to a Reader and a Writer.
|
||
|
// It implements io.ReadWriter.
|
||
|
type ReadWriter struct {
|
||
|
*Reader
|
||
|
*Writer
|
||
|
}
|
||
|
|
||
|
// NewReadWriter allocates a new ReadWriter that dispatches to r and w.
|
||
|
func NewReadWriter(r *Reader, w *Writer) *ReadWriter {
|
||
|
return &ReadWriter{r, w}
|
||
|
}
|