xref: /aosp_15_r20/external/pdfium/core/fxcodec/jbig2/JBig2_BitStream.cpp (revision 3ac0a46f773bac49fa9476ec2b1cf3f8da5ec3a4) 
1 // Copyright 2015 The PDFium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
6 
7 #include "core/fxcodec/jbig2/JBig2_BitStream.h"
8 
9 #include <algorithm>
10 
11 #include "third_party/base/numerics/safe_conversions.h"
12 
13 namespace {
14 
ValidatedSpan(pdfium::span<const uint8_t> sp)15 pdfium::span<const uint8_t> ValidatedSpan(pdfium::span<const uint8_t> sp) {
16   if (sp.size() > 256 * 1024 * 1024)
17     return {};
18   return sp;
19 }
20 
21 }  // namespace
22 
CJBig2_BitStream(pdfium::span<const uint8_t> pSrcStream,uint64_t key)23 CJBig2_BitStream::CJBig2_BitStream(pdfium::span<const uint8_t> pSrcStream,
24                                    uint64_t key)
25     : m_Span(ValidatedSpan(pSrcStream)), m_Key(key) {}
26 
27 CJBig2_BitStream::~CJBig2_BitStream() = default;
28 
readNBits(uint32_t dwBits,uint32_t * dwResult)29 int32_t CJBig2_BitStream::readNBits(uint32_t dwBits, uint32_t* dwResult) {
30   if (!IsInBounds())
31     return -1;
32 
33   uint32_t dwBitPos = getBitPos();
34   if (dwBitPos > LengthInBits())
35     return -1;
36 
37   *dwResult = 0;
38   if (dwBitPos + dwBits <= LengthInBits())
39     dwBitPos = dwBits;
40   else
41     dwBitPos = LengthInBits() - dwBitPos;
42 
43   for (; dwBitPos > 0; --dwBitPos) {
44     *dwResult =
45         (*dwResult << 1) | ((m_Span[m_dwByteIdx] >> (7 - m_dwBitIdx)) & 0x01);
46     AdvanceBit();
47   }
48   return 0;
49 }
50 
readNBits(uint32_t dwBits,int32_t * nResult)51 int32_t CJBig2_BitStream::readNBits(uint32_t dwBits, int32_t* nResult) {
52   if (!IsInBounds())
53     return -1;
54 
55   uint32_t dwBitPos = getBitPos();
56   if (dwBitPos > LengthInBits())
57     return -1;
58 
59   *nResult = 0;
60   if (dwBitPos + dwBits <= LengthInBits())
61     dwBitPos = dwBits;
62   else
63     dwBitPos = LengthInBits() - dwBitPos;
64 
65   for (; dwBitPos > 0; --dwBitPos) {
66     *nResult =
67         (*nResult << 1) | ((m_Span[m_dwByteIdx] >> (7 - m_dwBitIdx)) & 0x01);
68     AdvanceBit();
69   }
70   return 0;
71 }
72 
read1Bit(uint32_t * dwResult)73 int32_t CJBig2_BitStream::read1Bit(uint32_t* dwResult) {
74   if (!IsInBounds())
75     return -1;
76 
77   *dwResult = (m_Span[m_dwByteIdx] >> (7 - m_dwBitIdx)) & 0x01;
78   AdvanceBit();
79   return 0;
80 }
81 
read1Bit(bool * bResult)82 int32_t CJBig2_BitStream::read1Bit(bool* bResult) {
83   if (!IsInBounds())
84     return -1;
85 
86   *bResult = (m_Span[m_dwByteIdx] >> (7 - m_dwBitIdx)) & 0x01;
87   AdvanceBit();
88   return 0;
89 }
90 
read1Byte(uint8_t * cResult)91 int32_t CJBig2_BitStream::read1Byte(uint8_t* cResult) {
92   if (!IsInBounds())
93     return -1;
94 
95   *cResult = m_Span[m_dwByteIdx];
96   ++m_dwByteIdx;
97   return 0;
98 }
99 
readInteger(uint32_t * dwResult)100 int32_t CJBig2_BitStream::readInteger(uint32_t* dwResult) {
101   if (m_dwByteIdx + 3 >= m_Span.size())
102     return -1;
103 
104   *dwResult = (m_Span[m_dwByteIdx] << 24) | (m_Span[m_dwByteIdx + 1] << 16) |
105               (m_Span[m_dwByteIdx + 2] << 8) | m_Span[m_dwByteIdx + 3];
106   m_dwByteIdx += 4;
107   return 0;
108 }
109 
readShortInteger(uint16_t * dwResult)110 int32_t CJBig2_BitStream::readShortInteger(uint16_t* dwResult) {
111   if (m_dwByteIdx + 1 >= m_Span.size())
112     return -1;
113 
114   *dwResult = (m_Span[m_dwByteIdx] << 8) | m_Span[m_dwByteIdx + 1];
115   m_dwByteIdx += 2;
116   return 0;
117 }
118 
alignByte()119 void CJBig2_BitStream::alignByte() {
120   if (m_dwBitIdx != 0) {
121     ++m_dwByteIdx;
122     m_dwBitIdx = 0;
123   }
124 }
125 
getCurByte() const126 uint8_t CJBig2_BitStream::getCurByte() const {
127   return IsInBounds() ? m_Span[m_dwByteIdx] : 0;
128 }
129 
incByteIdx()130 void CJBig2_BitStream::incByteIdx() {
131   if (IsInBounds())
132     ++m_dwByteIdx;
133 }
134 
getCurByte_arith() const135 uint8_t CJBig2_BitStream::getCurByte_arith() const {
136   return IsInBounds() ? m_Span[m_dwByteIdx] : 0xFF;
137 }
138 
getNextByte_arith() const139 uint8_t CJBig2_BitStream::getNextByte_arith() const {
140   return m_dwByteIdx + 1 < m_Span.size() ? m_Span[m_dwByteIdx + 1] : 0xFF;
141 }
142 
getOffset() const143 uint32_t CJBig2_BitStream::getOffset() const {
144   return m_dwByteIdx;
145 }
146 
setOffset(uint32_t dwOffset)147 void CJBig2_BitStream::setOffset(uint32_t dwOffset) {
148   m_dwByteIdx = std::min(dwOffset, getLength());
149 }
150 
getBitPos() const151 uint32_t CJBig2_BitStream::getBitPos() const {
152   return (m_dwByteIdx << 3) + m_dwBitIdx;
153 }
154 
setBitPos(uint32_t dwBitPos)155 void CJBig2_BitStream::setBitPos(uint32_t dwBitPos) {
156   m_dwByteIdx = dwBitPos >> 3;
157   m_dwBitIdx = dwBitPos & 7;
158 }
159 
getBuf() const160 const uint8_t* CJBig2_BitStream::getBuf() const {
161   return m_Span.data();
162 }
163 
getLength() const164 uint32_t CJBig2_BitStream::getLength() const {
165   return pdfium::base::checked_cast<uint32_t>(m_Span.size());
166 }
167 
getPointer() const168 const uint8_t* CJBig2_BitStream::getPointer() const {
169   return m_Span.subspan(m_dwByteIdx).data();
170 }
171 
offset(uint32_t dwOffset)172 void CJBig2_BitStream::offset(uint32_t dwOffset) {
173   m_dwByteIdx += dwOffset;
174 }
175 
getByteLeft() const176 uint32_t CJBig2_BitStream::getByteLeft() const {
177   return getLength() - m_dwByteIdx;
178 }
179 
AdvanceBit()180 void CJBig2_BitStream::AdvanceBit() {
181   if (m_dwBitIdx == 7) {
182     ++m_dwByteIdx;
183     m_dwBitIdx = 0;
184   } else {
185     ++m_dwBitIdx;
186   }
187 }
188 
IsInBounds() const189 bool CJBig2_BitStream::IsInBounds() const {
190   return m_dwByteIdx < getLength();
191 }
192 
LengthInBits() const193 uint32_t CJBig2_BitStream::LengthInBits() const {
194   return getLength() << 3;
195 }
196