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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package bufio implements buffered I/O. It wraps an io.Reader or io.Writer
// object, creating another object (Reader or Writer) that also implements
// the interface but provides buffering and some help for textual I/O.
package bufio
import (
"bytes"
"io"
"strconv"
"unicode/utf8"
)
const (
defaultBufSize = 4096
)
// Errors introduced by this package.
type Error struct {
ErrorString string
}
func (err *Error) Error() string { return err.ErrorString }
var (
ErrInvalidUnreadByte error = &Error{"bufio: invalid use of UnreadByte"}
ErrInvalidUnreadRune error = &Error{"bufio: invalid use of UnreadRune"}
ErrBufferFull error = &Error{"bufio: buffer full"}
ErrNegativeCount error = &Error{"bufio: negative count"}
errInternal error = &Error{"bufio: internal error"}
)
// BufSizeError is the error representing an invalid buffer size.
type BufSizeError int
func (b BufSizeError) Error() string {
return "bufio: bad buffer size " + strconv.Itoa(int(b))
}
// Buffered input.
// Reader implements buffering for an io.Reader object.
type Reader struct {
buf []byte
rd io.Reader
r, w int
err error
lastByte int
lastRuneSize int
}
// NewReaderSize creates a new Reader whose buffer has the specified size,
// which must be greater than one. If the argument io.Reader is already a
// Reader with large enough size, it returns the underlying Reader.
// It returns the Reader and any error.
func NewReaderSize(rd io.Reader, size int) (*Reader, error) {
if size <= 1 {
return nil, BufSizeError(size)
}
// Is it already a Reader?
b, ok := rd.(*Reader)
if ok && len(b.buf) >= size {
return b, nil
}
b = new(Reader)
b.buf = make([]byte, size)
b.rd = rd
b.lastByte = -1
b.lastRuneSize = -1
return b, nil
}
// NewReader returns a new Reader whose buffer has the default size.
func NewReader(rd io.Reader) *Reader {
b, err := NewReaderSize(rd, defaultBufSize)
if err != nil {
// cannot happen - defaultBufSize is a valid size
panic(err)
}
return b
}
// fill reads a new chunk into the buffer.
func (b *Reader) fill() {
// Slide existing data to beginning.
if b.r > 0 {
copy(b.buf, b.buf[b.r:b.w])
b.w -= b.r
b.r = 0
}
// Read new data.
n, e := b.rd.Read(b.buf[b.w:])
b.w += n
if e != nil {
b.err = e
}
}
func (b *Reader) readErr() error {
err := b.err
b.err = nil
return err
}
// Peek returns the next n bytes without advancing the reader. The bytes stop
// being valid at the next read call. If Peek returns fewer than n bytes, it
// also returns an error explaining why the read is short. The error is
// ErrBufferFull if n is larger than b's buffer size.
func (b *Reader) Peek(n int) ([]byte, error) {
if n < 0 {
return nil, ErrNegativeCount
}
if n > len(b.buf) {
return nil, ErrBufferFull
}
for b.w-b.r < n && b.err == nil {
b.fill()
}
m := b.w - b.r
if m > n {
m = n
}
err := b.readErr()
if m < n && err == nil {
err = ErrBufferFull
}
return b.buf[b.r : b.r+m], err
}
// Read reads data into p.
// It returns the number of bytes read into p.
// It calls Read at most once on the underlying Reader,
// hence n may be less than len(p).
// At EOF, the count will be zero and err will be io.EOF.
func (b *Reader) Read(p []byte) (n int, err error) {
n = len(p)
if n == 0 {
return 0, b.readErr()
}
if b.w == b.r {
if b.err != nil {
return 0, b.readErr()
}
if len(p) >= len(b.buf) {
// Large read, empty buffer.
// Read directly into p to avoid copy.
n, b.err = b.rd.Read(p)
if n > 0 {
b.lastByte = int(p[n-1])
b.lastRuneSize = -1
}
return n, b.readErr()
}
b.fill()
if b.w == b.r {
return 0, b.readErr()
}
}
if n > b.w-b.r {
n = b.w - b.r
}
copy(p[0:n], b.buf[b.r:])
b.r += n
b.lastByte = int(b.buf[b.r-1])
b.lastRuneSize = -1
return n, nil
}
// ReadByte reads and returns a single byte.
// If no byte is available, returns an error.
func (b *Reader) ReadByte() (c byte, err error) {
b.lastRuneSize = -1
for b.w == b.r {
if b.err != nil {
return 0, b.readErr()
}
b.fill()
}
c = b.buf[b.r]
b.r++
b.lastByte = int(c)
return c, nil
}
// UnreadByte unreads the last byte. Only the most recently read byte can be unread.
func (b *Reader) UnreadByte() error {
b.lastRuneSize = -1
if b.r == b.w && b.lastByte >= 0 {
b.w = 1
b.r = 0
b.buf[0] = byte(b.lastByte)
b.lastByte = -1
return nil
}
if b.r <= 0 {
return ErrInvalidUnreadByte
}
b.r--
b.lastByte = -1
return nil
}
// ReadRune reads a single UTF-8 encoded Unicode character and returns the
// rune and its size in bytes.
func (b *Reader) ReadRune() (r rune, size int, err error) {
for b.r+utf8.UTFMax > b.w && !utf8.FullRune(b.buf[b.r:b.w]) && b.err == nil {
b.fill()
}
b.lastRuneSize = -1
if b.r == b.w {
return 0, 0, b.readErr()
}
r, size = rune(b.buf[b.r]), 1
if r >= 0x80 {
r, size = utf8.DecodeRune(b.buf[b.r:b.w])
}
b.r += size
b.lastByte = int(b.buf[b.r-1])
b.lastRuneSize = size
return r, size, nil
}
// UnreadRune unreads the last rune. If the most recent read operation on
// the buffer was not a ReadRune, UnreadRune returns an error. (In this
// regard it is stricter than UnreadByte, which will unread the last byte
// from any read operation.)
func (b *Reader) UnreadRune() error {
if b.lastRuneSize < 0 || b.r == 0 {
return ErrInvalidUnreadRune
}
b.r -= b.lastRuneSize
b.lastByte = -1
b.lastRuneSize = -1
return nil
}
// Buffered returns the number of bytes that can be read from the current buffer.
func (b *Reader) Buffered() int { return b.w - b.r }
// ReadSlice reads until the first occurrence of delim in the input,
// returning a slice pointing at the bytes in the buffer.
// The bytes stop being valid at the next read call.
// If ReadSlice encounters an error before finding a delimiter,
// it returns all the data in the buffer and the error itself (often io.EOF).
// ReadSlice fails with error ErrBufferFull if the buffer fills without a delim.
// Because the data returned from ReadSlice will be overwritten
// by the next I/O operation, most clients should use
// ReadBytes or ReadString instead.
// ReadSlice returns err != nil if and only if line does not end in delim.
func (b *Reader) ReadSlice(delim byte) (line []byte, err error) {
// Look in buffer.
if i := bytes.IndexByte(b.buf[b.r:b.w], delim); i >= 0 {
line1 := b.buf[b.r : b.r+i+1]
b.r += i + 1
return line1, nil
}
// Read more into buffer, until buffer fills or we find delim.
for {
if b.err != nil {
line := b.buf[b.r:b.w]
b.r = b.w
return line, b.readErr()
}
n := b.Buffered()
b.fill()
// Search new part of buffer
if i := bytes.IndexByte(b.buf[n:b.w], delim); i >= 0 {
line := b.buf[0 : n+i+1]
b.r = n + i + 1
return line, nil
}
// Buffer is full?
if b.Buffered() >= len(b.buf) {
b.r = b.w
return b.buf, ErrBufferFull
}
}
panic("not reached")
}
// ReadLine tries to return a single line, not including the end-of-line bytes.
// If the line was too long for the buffer then isPrefix is set and the
// beginning of the line is returned. The rest of the line will be returned
// from future calls. isPrefix will be false when returning the last fragment
// of the line. The returned buffer is only valid until the next call to
// ReadLine. ReadLine either returns a non-nil line or it returns an error,
// never both.
func (b *Reader) ReadLine() (line []byte, isPrefix bool, err error) {
line, err = b.ReadSlice('\n')
if err == ErrBufferFull {
// Handle the case where "\r\n" straddles the buffer.
if len(line) > 0 && line[len(line)-1] == '\r' {
// Put the '\r' back on buf and drop it from line.
// Let the next call to ReadLine check for "\r\n".
if b.r == 0 {
// should be unreachable
panic("bufio: tried to rewind past start of buffer")
}
b.r--
line = line[:len(line)-1]
}
return line, true, nil
}
if len(line) == 0 {
if err != nil {
line = nil
}
return
}
err = nil
if line[len(line)-1] == '\n' {
drop := 1
if len(line) > 1 && line[len(line)-2] == '\r' {
drop = 2
}
line = line[:len(line)-drop]
}
return
}
// ReadBytes reads until the first occurrence of delim in the input,
// returning a slice containing the data up to and including the delimiter.
// If ReadBytes encounters an error before finding a delimiter,
// it returns the data read before the error and the error itself (often io.EOF).
// ReadBytes returns err != nil if and only if the returned data does not end in
// delim.
func (b *Reader) ReadBytes(delim byte) (line []byte, err error) {
// Use ReadSlice to look for array,
// accumulating full buffers.
var frag []byte
var full [][]byte
err = nil
for {
var e error
frag, e = b.ReadSlice(delim)
if e == nil { // got final fragment
break
}
if e != ErrBufferFull { // unexpected error
err = e
break
}
// Make a copy of the buffer.
buf := make([]byte, len(frag))
copy(buf, frag)
full = append(full, buf)
}
// Allocate new buffer to hold the full pieces and the fragment.
n := 0
for i := range full {
n += len(full[i])
}
n += len(frag)
// Copy full pieces and fragment in.
buf := make([]byte, n)
n = 0
for i := range full {
n += copy(buf[n:], full[i])
}
copy(buf[n:], frag)
return buf, err
}
// 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.
func (b *Reader) ReadString(delim byte) (line string, err error) {
bytes, e := b.ReadBytes(delim)
return string(bytes), e
}
// buffered output
// Writer implements buffering for an io.Writer object.
type Writer struct {
err error
buf []byte
n int
wr io.Writer
}
// NewWriterSize creates a new Writer whose buffer has the specified size,
// which must be greater than zero. If the argument io.Writer is already a
// Writer with large enough size, it returns the underlying Writer.
// It returns the Writer and any error.
func NewWriterSize(wr io.Writer, size int) (*Writer, error) {
if size <= 0 {
return nil, BufSizeError(size)
}
// Is it already a Writer?
b, ok := wr.(*Writer)
if ok && len(b.buf) >= size {
return b, nil
}
b = new(Writer)
b.buf = make([]byte, size)
b.wr = wr
return b, nil
}
// NewWriter returns a new Writer whose buffer has the default size.
func NewWriter(wr io.Writer) *Writer {
b, err := NewWriterSize(wr, defaultBufSize)
if err != nil {
// cannot happen - defaultBufSize is valid size
panic(err)
}
return b
}
// Flush writes any buffered data to the underlying io.Writer.
func (b *Writer) Flush() error {
if b.err != nil {
return b.err
}
if b.n == 0 {
return nil
}
n, e := b.wr.Write(b.buf[0:b.n])
if n < b.n && e == nil {
e = io.ErrShortWrite
}
if e != nil {
if n > 0 && n < b.n {
copy(b.buf[0:b.n-n], b.buf[n:b.n])
}
b.n -= n
b.err = e
return e
}
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
}
// 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}
}
|