1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
/*
* Copyright (C) 2022 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include "config.h"
#include "BitReader.h"
namespace WebCore {
std::optional<uint64_t> BitReader::read(size_t bits)
{
ASSERT(bits <= 64);
// FIXME: We should optimize this routine.
size_t value = 0;
do {
auto bit = readBit();
if (!bit)
return { };
value = (value << 1) | (*bit ? 1 : 0);
--bits;
} while (bits);
return value;
}
std::optional<bool> BitReader::readBit()
{
if (!m_remainingBits) {
if (m_index >= m_data.size())
return { };
m_currentByte = m_data[m_index++];
m_remainingBits = 8;
}
bool value = m_currentByte & 0x80;
--m_remainingBits;
m_currentByte = m_currentByte << 1;
return value;
}
bool BitReader::skipBytes(size_t bytes)
{
m_index += bytes;
if (m_index >= m_data.size()) {
bool over = m_index > m_data.size() || m_remainingBits;
m_index = m_data.size();
m_remainingBits = 0;
return !over;
}
m_currentByte = m_data[m_index];
return true;
}
size_t BitReader::bitOffset() const
{
ASSERT(m_index <= m_data.size());
return (m_remainingBits ? 8 - m_remainingBits : 0) + m_index * 8;
}
} // namespace WebCore
|
