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gitea/vendor/github.com/dsnet/compress/internal/prefix/wrap.go

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// Copyright 2015, Joe Tsai. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE.md file.
package prefix
import (
"bytes"
"io"
"strings"
)
// For some of the common Readers, we wrap and extend them to satisfy the
// compress.BufferedReader interface to improve performance.
type buffer struct {
*bytes.Buffer
}
type bytesReader struct {
*bytes.Reader
pos int64
buf []byte
arr [512]byte
}
type stringReader struct {
*strings.Reader
pos int64
buf []byte
arr [512]byte
}
func (r *buffer) Buffered() int {
return r.Len()
}
func (r *buffer) Peek(n int) ([]byte, error) {
b := r.Bytes()
if len(b) < n {
return b, io.EOF
}
return b[:n], nil
}
func (r *buffer) Discard(n int) (int, error) {
b := r.Next(n)
if len(b) < n {
return len(b), io.EOF
}
return n, nil
}
func (r *bytesReader) Buffered() int {
r.update()
if r.Len() > len(r.buf) {
return len(r.buf)
}
return r.Len()
}
func (r *bytesReader) Peek(n int) ([]byte, error) {
if n > len(r.arr) {
return nil, io.ErrShortBuffer
}
// Return sub-slice of local buffer if possible.
r.update()
if len(r.buf) >= n {
return r.buf[:n], nil
}
// Fill entire local buffer, and return appropriate sub-slice.
cnt, err := r.ReadAt(r.arr[:], r.pos)
r.buf = r.arr[:cnt]
if cnt < n {
return r.arr[:cnt], err
}
return r.arr[:n], nil
}
func (r *bytesReader) Discard(n int) (int, error) {
var err error
if n > r.Len() {
n, err = r.Len(), io.EOF
}
r.Seek(int64(n), io.SeekCurrent)
return n, err
}
// update reslices the internal buffer to be consistent with the read offset.
func (r *bytesReader) update() {
pos, _ := r.Seek(0, io.SeekCurrent)
if off := pos - r.pos; off >= 0 && off < int64(len(r.buf)) {
r.buf, r.pos = r.buf[off:], pos
} else {
r.buf, r.pos = nil, pos
}
}
func (r *stringReader) Buffered() int {
r.update()
if r.Len() > len(r.buf) {
return len(r.buf)
}
return r.Len()
}
func (r *stringReader) Peek(n int) ([]byte, error) {
if n > len(r.arr) {
return nil, io.ErrShortBuffer
}
// Return sub-slice of local buffer if possible.
r.update()
if len(r.buf) >= n {
return r.buf[:n], nil
}
// Fill entire local buffer, and return appropriate sub-slice.
cnt, err := r.ReadAt(r.arr[:], r.pos)
r.buf = r.arr[:cnt]
if cnt < n {
return r.arr[:cnt], err
}
return r.arr[:n], nil
}
func (r *stringReader) Discard(n int) (int, error) {
var err error
if n > r.Len() {
n, err = r.Len(), io.EOF
}
r.Seek(int64(n), io.SeekCurrent)
return n, err
}
// update reslices the internal buffer to be consistent with the read offset.
func (r *stringReader) update() {
pos, _ := r.Seek(0, io.SeekCurrent)
if off := pos - r.pos; off >= 0 && off < int64(len(r.buf)) {
r.buf, r.pos = r.buf[off:], pos
} else {
r.buf, r.pos = nil, pos
}
}