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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [bytes/] [buffer.go] - Blame information for rev 801

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Line No. Rev Author Line
1 747 jeremybenn
// 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 bytes
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// Simple byte buffer for marshaling data.
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import (
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        "errors"
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        "io"
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        "unicode/utf8"
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)
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// A Buffer is a variable-sized buffer of bytes with Read and Write methods.
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// The zero value for Buffer is an empty buffer ready to use.
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type Buffer struct {
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        buf       []byte            // contents are the bytes buf[off : len(buf)]
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        off       int               // read at &buf[off], write at &buf[len(buf)]
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        runeBytes [utf8.UTFMax]byte // avoid allocation of slice on each WriteByte or Rune
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        bootstrap [64]byte          // memory to hold first slice; helps small buffers (Printf) avoid allocation.
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        lastRead  readOp            // last read operation, so that Unread* can work correctly.
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}
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// The readOp constants describe the last action performed on
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// the buffer, so that UnreadRune and UnreadByte can
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// check for invalid usage.
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type readOp int
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const (
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        opInvalid  readOp = iota // Non-read operation.
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        opReadRune               // Read rune.
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        opRead                   // Any other read operation.
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)
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// ErrTooLarge is passed to panic if memory cannot be allocated to store data in a buffer.
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var ErrTooLarge = errors.New("bytes.Buffer: too large")
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// Bytes returns a slice of the contents of the unread portion of the buffer;
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// len(b.Bytes()) == b.Len().  If the caller changes the contents of the
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// returned slice, the contents of the buffer will change provided there
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// are no intervening method calls on the Buffer.
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func (b *Buffer) Bytes() []byte { return b.buf[b.off:] }
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// String returns the contents of the unread portion of the buffer
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// as a string.  If the Buffer is a nil pointer, it returns "".
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func (b *Buffer) String() string {
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        if b == nil {
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                // Special case, useful in debugging.
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                return ""
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        }
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        return string(b.buf[b.off:])
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}
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// Len returns the number of bytes of the unread portion of the buffer;
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// b.Len() == len(b.Bytes()).
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func (b *Buffer) Len() int { return len(b.buf) - b.off }
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// Truncate discards all but the first n unread bytes from the buffer.
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// It panics if n is negative or greater than the length of the buffer.
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func (b *Buffer) Truncate(n int) {
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        b.lastRead = opInvalid
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        switch {
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        case n < 0 || n > b.Len():
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                panic("bytes.Buffer: truncation out of range")
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        case n == 0:
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                // Reuse buffer space.
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                b.off = 0
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        }
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        b.buf = b.buf[0 : b.off+n]
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}
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// Reset resets the buffer so it has no content.
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// b.Reset() is the same as b.Truncate(0).
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func (b *Buffer) Reset() { b.Truncate(0) }
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// grow grows the buffer to guarantee space for n more bytes.
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// It returns the index where bytes should be written.
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// If the buffer can't grow it will panic with ErrTooLarge.
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func (b *Buffer) grow(n int) int {
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        m := b.Len()
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        // If buffer is empty, reset to recover space.
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        if m == 0 && b.off != 0 {
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                b.Truncate(0)
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        }
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        if len(b.buf)+n > cap(b.buf) {
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                var buf []byte
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                if b.buf == nil && n <= len(b.bootstrap) {
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                        buf = b.bootstrap[0:]
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                } else {
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                        // not enough space anywhere
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                        buf = makeSlice(2*cap(b.buf) + n)
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                        copy(buf, b.buf[b.off:])
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                }
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                b.buf = buf
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                b.off = 0
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        }
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        b.buf = b.buf[0 : b.off+m+n]
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        return b.off + m
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}
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// Write appends the contents of p to the buffer.  The return
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// value n is the length of p; err is always nil.
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// If the buffer becomes too large, Write will panic with
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// ErrTooLarge.
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func (b *Buffer) Write(p []byte) (n int, err error) {
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        b.lastRead = opInvalid
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        m := b.grow(len(p))
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        return copy(b.buf[m:], p), nil
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}
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// WriteString appends the contents of s to the buffer.  The return
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// value n is the length of s; err is always nil.
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// If the buffer becomes too large, WriteString will panic with
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// ErrTooLarge.
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func (b *Buffer) WriteString(s string) (n int, err error) {
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        b.lastRead = opInvalid
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        m := b.grow(len(s))
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        return copy(b.buf[m:], s), nil
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}
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// MinRead is the minimum slice size passed to a Read call by
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// Buffer.ReadFrom.  As long as the Buffer has at least MinRead bytes beyond
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// what is required to hold the contents of r, ReadFrom will not grow the
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// underlying buffer.
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const MinRead = 512
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// ReadFrom reads data from r until EOF and appends it to the buffer.
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// The return value n is the number of bytes read.
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// Any error except io.EOF encountered during the read
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// is also returned.
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// If the buffer becomes too large, ReadFrom will panic with
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// ErrTooLarge.
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func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {
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        b.lastRead = opInvalid
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        // If buffer is empty, reset to recover space.
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        if b.off >= len(b.buf) {
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                b.Truncate(0)
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        }
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        for {
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                if free := cap(b.buf) - len(b.buf); free < MinRead {
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                        // not enough space at end
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                        newBuf := b.buf
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                        if b.off+free < MinRead {
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                                // not enough space using beginning of buffer;
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                                // double buffer capacity
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                                newBuf = makeSlice(2*cap(b.buf) + MinRead)
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                        }
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                        copy(newBuf, b.buf[b.off:])
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                        b.buf = newBuf[:len(b.buf)-b.off]
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                        b.off = 0
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                }
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                m, e := r.Read(b.buf[len(b.buf):cap(b.buf)])
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                b.buf = b.buf[0 : len(b.buf)+m]
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                n += int64(m)
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                if e == io.EOF {
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                        break
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                }
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                if e != nil {
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                        return n, e
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                }
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        }
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        return n, nil // err is EOF, so return nil explicitly
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}
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// makeSlice allocates a slice of size n. If the allocation fails, it panics
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// with ErrTooLarge.
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func makeSlice(n int) []byte {
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        // If the make fails, give a known error.
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        defer func() {
171
                if recover() != nil {
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                        panic(ErrTooLarge)
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                }
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        }()
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        return make([]byte, n)
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}
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178
// WriteTo writes data to w until the buffer is drained or an error
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// occurs. The return value n is the number of bytes written; it always
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// fits into an int, but it is int64 to match the io.WriterTo interface.
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// Any error encountered during the write is also returned.
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func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
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        b.lastRead = opInvalid
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        if b.off < len(b.buf) {
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                m, e := w.Write(b.buf[b.off:])
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                b.off += m
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                n = int64(m)
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                if e != nil {
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                        return n, e
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                }
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                // otherwise all bytes were written, by definition of
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                // Write method in io.Writer
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        }
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        // Buffer is now empty; reset.
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        b.Truncate(0)
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        return
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}
198
 
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// WriteByte appends the byte c to the buffer.
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// The returned error is always nil, but is included
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// to match bufio.Writer's WriteByte.
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// If the buffer becomes too large, WriteByte will panic with
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// ErrTooLarge.
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func (b *Buffer) WriteByte(c byte) error {
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        b.lastRead = opInvalid
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        m := b.grow(1)
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        b.buf[m] = c
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        return nil
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}
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// WriteRune appends the UTF-8 encoding of Unicode
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// code point r to the buffer, returning its length and
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// an error, which is always nil but is included
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// to match bufio.Writer's WriteRune.
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// If the buffer becomes too large, WriteRune will panic with
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// ErrTooLarge.
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func (b *Buffer) WriteRune(r rune) (n int, err error) {
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        if r < utf8.RuneSelf {
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                b.WriteByte(byte(r))
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                return 1, nil
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        }
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        n = utf8.EncodeRune(b.runeBytes[0:], r)
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        b.Write(b.runeBytes[0:n])
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        return n, nil
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}
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227
// Read reads the next len(p) bytes from the buffer or until the buffer
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// is drained.  The return value n is the number of bytes read.  If the
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// buffer has no data to return, err is io.EOF (unless len(p) is zero);
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// otherwise it is nil.
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func (b *Buffer) Read(p []byte) (n int, err error) {
232
        b.lastRead = opInvalid
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        if b.off >= len(b.buf) {
234
                // Buffer is empty, reset to recover space.
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                b.Truncate(0)
236
                if len(p) == 0 {
237
                        return
238
                }
239
                return 0, io.EOF
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        }
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        n = copy(p, b.buf[b.off:])
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        b.off += n
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        if n > 0 {
244
                b.lastRead = opRead
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        }
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        return
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}
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249
// Next returns a slice containing the next n bytes from the buffer,
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// advancing the buffer as if the bytes had been returned by Read.
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// If there are fewer than n bytes in the buffer, Next returns the entire buffer.
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// The slice is only valid until the next call to a read or write method.
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func (b *Buffer) Next(n int) []byte {
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        b.lastRead = opInvalid
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        m := b.Len()
256
        if n > m {
257
                n = m
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        }
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        data := b.buf[b.off : b.off+n]
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        b.off += n
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        if n > 0 {
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                b.lastRead = opRead
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        }
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        return data
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}
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// ReadByte reads and returns the next byte from the buffer.
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// If no byte is available, it returns error io.EOF.
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func (b *Buffer) ReadByte() (c byte, err error) {
270
        b.lastRead = opInvalid
271
        if b.off >= len(b.buf) {
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                // Buffer is empty, reset to recover space.
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                b.Truncate(0)
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                return 0, io.EOF
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        }
276
        c = b.buf[b.off]
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        b.off++
278
        b.lastRead = opRead
279
        return c, nil
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}
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282
// ReadRune reads and returns the next UTF-8-encoded
283
// Unicode code point from the buffer.
284
// If no bytes are available, the error returned is io.EOF.
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// If the bytes are an erroneous UTF-8 encoding, it
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// consumes one byte and returns U+FFFD, 1.
287
func (b *Buffer) ReadRune() (r rune, size int, err error) {
288
        b.lastRead = opInvalid
289
        if b.off >= len(b.buf) {
290
                // Buffer is empty, reset to recover space.
291
                b.Truncate(0)
292
                return 0, 0, io.EOF
293
        }
294
        b.lastRead = opReadRune
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        c := b.buf[b.off]
296
        if c < utf8.RuneSelf {
297
                b.off++
298
                return rune(c), 1, nil
299
        }
300
        r, n := utf8.DecodeRune(b.buf[b.off:])
301
        b.off += n
302
        return r, n, nil
303
}
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305
// UnreadRune unreads the last rune returned by ReadRune.
306
// If the most recent read or write operation on the buffer was
307
// not a ReadRune, UnreadRune returns an error.  (In this regard
308
// it is stricter than UnreadByte, which will unread the last byte
309
// from any read operation.)
310
func (b *Buffer) UnreadRune() error {
311
        if b.lastRead != opReadRune {
312
                return errors.New("bytes.Buffer: UnreadRune: previous operation was not ReadRune")
313
        }
314
        b.lastRead = opInvalid
315
        if b.off > 0 {
316
                _, n := utf8.DecodeLastRune(b.buf[0:b.off])
317
                b.off -= n
318
        }
319
        return nil
320
}
321
 
322
// UnreadByte unreads the last byte returned by the most recent
323
// read operation.  If write has happened since the last read, UnreadByte
324
// returns an error.
325
func (b *Buffer) UnreadByte() error {
326
        if b.lastRead != opReadRune && b.lastRead != opRead {
327
                return errors.New("bytes.Buffer: UnreadByte: previous operation was not a read")
328
        }
329
        b.lastRead = opInvalid
330
        if b.off > 0 {
331
                b.off--
332
        }
333
        return nil
334
}
335
 
336
// ReadBytes reads until the first occurrence of delim in the input,
337
// returning a slice containing the data up to and including the delimiter.
338
// If ReadBytes encounters an error before finding a delimiter,
339
// it returns the data read before the error and the error itself (often io.EOF).
340
// ReadBytes returns err != nil if and only if the returned data does not end in
341
// delim.
342
func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
343
        i := IndexByte(b.buf[b.off:], delim)
344
        size := i + 1
345
        if i < 0 {
346
                size = len(b.buf) - b.off
347
                err = io.EOF
348
        }
349
        line = make([]byte, size)
350
        copy(line, b.buf[b.off:])
351
        b.off += size
352
        return
353
}
354
 
355
// ReadString reads until the first occurrence of delim in the input,
356
// returning a string containing the data up to and including the delimiter.
357
// If ReadString encounters an error before finding a delimiter,
358
// it returns the data read before the error and the error itself (often io.EOF).
359
// ReadString returns err != nil if and only if the returned data does not end
360
// in delim.
361
func (b *Buffer) ReadString(delim byte) (line string, err error) {
362
        bytes, err := b.ReadBytes(delim)
363
        return string(bytes), err
364
}
365
 
366
// NewBuffer creates and initializes a new Buffer using buf as its initial
367
// contents.  It is intended to prepare a Buffer to read existing data.  It
368
// can also be used to size the internal buffer for writing. To do that,
369
// buf should have the desired capacity but a length of zero.
370
//
371
// In most cases, new(Buffer) (or just declaring a Buffer variable) is
372
// sufficient to initialize a Buffer.
373
func NewBuffer(buf []byte) *Buffer { return &Buffer{buf: buf} }
374
 
375
// NewBufferString creates and initializes a new Buffer using string s as its
376
// initial contents. It is intended to prepare a buffer to read an existing
377
// string.
378
//
379
// In most cases, new(Buffer) (or just declaring a Buffer variable) is
380
// sufficient to initialize a Buffer.
381
func NewBufferString(s string) *Buffer {
382
        return &Buffer{buf: []byte(s)}
383
}

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