1// Copyright 2014-2022 Ulrich Kunitz. All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5package lzma
 6
 7import (
 8	"errors"
 9	"io"
10)
11
12// breader provides the ReadByte function for a Reader. It doesn't read
13// more data from the reader than absolutely necessary.
14type breader struct {
15	io.Reader
16	// helper slice to save allocations
17	p []byte
18}
19
20// ByteReader converts an io.Reader into an io.ByteReader.
21func ByteReader(r io.Reader) io.ByteReader {
22	br, ok := r.(io.ByteReader)
23	if !ok {
24		return &breader{r, make([]byte, 1)}
25	}
26	return br
27}
28
29// ReadByte read byte function.
30func (r *breader) ReadByte() (c byte, err error) {
31	n, err := r.Reader.Read(r.p)
32	if n < 1 {
33		if err == nil {
34			err = errors.New("breader.ReadByte: no data")
35		}
36		return 0, err
37	}
38	return r.p[0], nil
39}