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package byteutil
import (
"errors"
"io"
"unicode/utf8"
)
var (
// ensure we conform to interfaces.
_ interface {
io.Writer
io.ByteWriter
WriteRune(rune) (int, error)
io.StringWriter
io.WriterAt
WriteStringAt(string, int64) (int, error)
} = (*Buffer)(nil)
// ErrBeyondBufferLen is returned if .WriteAt() is attempted beyond buffer length.
ErrBeyondBufferLen = errors.New("start beyond buffer length")
)
// Buffer is a simple wrapper around a byte slice.
type Buffer struct{ B []byte }
// WriteByte will append given byte to buffer, fulfilling io.ByteWriter.
func (buf *Buffer) WriteByte(c byte) error {
buf.B = append(buf.B, c)
return nil
}
// WriteRune will append given rune to buffer.
func (buf *Buffer) WriteRune(r rune) (int, error) {
// Check for single-byte rune
if r < utf8.RuneSelf {
buf.B = append(buf.B, byte(r))
return 1, nil
}
// Before-len
l := len(buf.B)
// Grow to max size rune
buf.Grow(utf8.UTFMax)
// Write encoded rune to buffer
n := utf8.EncodeRune(buf.B[l:len(buf.B)], r)
buf.B = buf.B[:l+n]
return n, nil
}
// Write will append given byte slice to buffer, fulfilling io.Writer.
func (buf *Buffer) Write(b []byte) (int, error) {
buf.B = append(buf.B, b...)
return len(b), nil
}
// WriteString will append given string to buffer, fulfilling io.StringWriter.
func (buf *Buffer) WriteString(s string) (int, error) {
buf.B = append(buf.B, s...)
return len(s), nil
}
// WriteAt will append given byte slice to buffer at index 'start', fulfilling io.WriterAt.
func (buf *Buffer) WriteAt(b []byte, start int64) (int, error) {
if start > int64(len(buf.B)) {
return 0, ErrBeyondBufferLen
}
buf.Grow(len(b) - int(int64(len(buf.B))-start))
return copy(buf.B[start:], b), nil
}
// WriteStringAt will append given string to buffer at index 'start'.
func (buf *Buffer) WriteStringAt(s string, start int64) (int, error) {
if start > int64(len(buf.B)) {
return 0, ErrBeyondBufferLen
}
buf.Grow(len(s) - int(int64(len(buf.B))-start))
return copy(buf.B[start:], s), nil
}
// Len returns the length of the buffer's underlying byte slice.
func (buf *Buffer) Len() int {
return len(buf.B)
}
// Cap returns the capacity of the buffer's underlying byte slice.
func (buf *Buffer) Cap() int {
return cap(buf.B)
}
// Grow will increase the buffers length by 'sz', and the capacity by at least this.
func (buf *Buffer) Grow(sz int) {
buf.Guarantee(sz)
buf.B = buf.B[:len(buf.B)+sz]
}
// Guarantee will guarantee buffer containers at least 'sz' remaining capacity.
func (buf *Buffer) Guarantee(sz int) {
if sz > cap(buf.B)-len(buf.B) {
nb := make([]byte, 2*cap(buf.B)+sz)
copy(nb, buf.B)
buf.B = nb[:len(buf.B)]
}
}
// Truncate will reduce the length of the buffer by 'n'.
func (buf *Buffer) Truncate(n int) {
if n > len(buf.B) {
n = len(buf.B)
}
buf.B = buf.B[:len(buf.B)-n]
}
// Reset will reset the buffer length to 0 (retains capacity).
func (buf *Buffer) Reset() {
buf.B = buf.B[:0]
}
// String returns the underlying byte slice as a string. Please note
// this value is tied directly to the underlying byte slice, if you
// write to the buffer then returned string values will also change.
//
// To get an immutable string from buffered data, use string(buf.B).
func (buf *Buffer) String() string {
return B2S(buf.B)
}
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