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1 /* | 1 /* |
2 * Copyright 2015 The WebRTC Project Authors. All rights reserved. | 2 * Copyright 2015 The WebRTC Project Authors. All rights reserved. |
3 * | 3 * |
4 * Use of this source code is governed by a BSD-style license | 4 * Use of this source code is governed by a BSD-style license |
5 * that can be found in the LICENSE file in the root of the source | 5 * that can be found in the LICENSE file in the root of the source |
6 * tree. An additional intellectual property rights grant can be found | 6 * tree. An additional intellectual property rights grant can be found |
7 * in the file PATENTS. All contributing project authors may | 7 * in the file PATENTS. All contributing project authors may |
8 * be found in the AUTHORS file in the root of the source tree. | 8 * be found in the AUTHORS file in the root of the source tree. |
9 */ | 9 */ |
10 | 10 |
11 #include "webrtc/base/bitbuffer.h" | 11 #include "webrtc/base/bitbuffer.h" |
12 | 12 |
13 #include <algorithm> | 13 #include <algorithm> |
14 #include <limits> | 14 #include <limits> |
15 | 15 |
16 #include "webrtc/base/checks.h" | 16 #include "webrtc/base/checks.h" |
17 | 17 |
18 namespace { | 18 namespace { |
19 | 19 |
20 // Returns the lowest (right-most) |bit_count| bits in |byte|. | 20 // Returns the lowest (right-most) |bit_count| bits in |byte|. |
21 uint8_t LowestBits(uint8_t byte, size_t bit_count) { | 21 uint8_t LowestBits(uint8_t byte, size_t bit_count) { |
22 DCHECK_LE(bit_count, 8u); | 22 RTC_DCHECK_LE(bit_count, 8u); |
23 return byte & ((1 << bit_count) - 1); | 23 return byte & ((1 << bit_count) - 1); |
24 } | 24 } |
25 | 25 |
26 // Returns the highest (left-most) |bit_count| bits in |byte|, shifted to the | 26 // Returns the highest (left-most) |bit_count| bits in |byte|, shifted to the |
27 // lowest bits (to the right). | 27 // lowest bits (to the right). |
28 uint8_t HighestBits(uint8_t byte, size_t bit_count) { | 28 uint8_t HighestBits(uint8_t byte, size_t bit_count) { |
29 DCHECK_LE(bit_count, 8u); | 29 RTC_DCHECK_LE(bit_count, 8u); |
30 uint8_t shift = 8 - static_cast<uint8_t>(bit_count); | 30 uint8_t shift = 8 - static_cast<uint8_t>(bit_count); |
31 uint8_t mask = 0xFF << shift; | 31 uint8_t mask = 0xFF << shift; |
32 return (byte & mask) >> shift; | 32 return (byte & mask) >> shift; |
33 } | 33 } |
34 | 34 |
35 // Returns the highest byte of |val| in a uint8_t. | 35 // Returns the highest byte of |val| in a uint8_t. |
36 uint8_t HighestByte(uint64_t val) { | 36 uint8_t HighestByte(uint64_t val) { |
37 return static_cast<uint8_t>(val >> 56); | 37 return static_cast<uint8_t>(val >> 56); |
38 } | 38 } |
39 | 39 |
40 // Returns the result of writing partial data from |source|, of | 40 // Returns the result of writing partial data from |source|, of |
41 // |source_bit_count| size in the highest bits, to |target| at | 41 // |source_bit_count| size in the highest bits, to |target| at |
42 // |target_bit_offset| from the highest bit. | 42 // |target_bit_offset| from the highest bit. |
43 uint8_t WritePartialByte(uint8_t source, | 43 uint8_t WritePartialByte(uint8_t source, |
44 size_t source_bit_count, | 44 size_t source_bit_count, |
45 uint8_t target, | 45 uint8_t target, |
46 size_t target_bit_offset) { | 46 size_t target_bit_offset) { |
47 DCHECK(target_bit_offset < 8); | 47 RTC_DCHECK(target_bit_offset < 8); |
48 DCHECK(source_bit_count < 9); | 48 RTC_DCHECK(source_bit_count < 9); |
49 DCHECK(source_bit_count <= (8 - target_bit_offset)); | 49 RTC_DCHECK(source_bit_count <= (8 - target_bit_offset)); |
50 // Generate a mask for just the bits we're going to overwrite, so: | 50 // Generate a mask for just the bits we're going to overwrite, so: |
51 uint8_t mask = | 51 uint8_t mask = |
52 // The number of bits we want, in the most significant bits... | 52 // The number of bits we want, in the most significant bits... |
53 static_cast<uint8_t>(0xFF << (8 - source_bit_count)) | 53 static_cast<uint8_t>(0xFF << (8 - source_bit_count)) |
54 // ...shifted over to the target offset from the most signficant bit. | 54 // ...shifted over to the target offset from the most signficant bit. |
55 >> target_bit_offset; | 55 >> target_bit_offset; |
56 | 56 |
57 // We want the target, with the bits we'll overwrite masked off, or'ed with | 57 // We want the target, with the bits we'll overwrite masked off, or'ed with |
58 // the bits from the source we want. | 58 // the bits from the source we want. |
59 return (target & ~mask) | (source >> target_bit_offset); | 59 return (target & ~mask) | (source >> target_bit_offset); |
60 } | 60 } |
61 | 61 |
62 // Counts the number of bits used in the binary representation of val. | 62 // Counts the number of bits used in the binary representation of val. |
63 size_t CountBits(uint64_t val) { | 63 size_t CountBits(uint64_t val) { |
64 size_t bit_count = 0; | 64 size_t bit_count = 0; |
65 while (val != 0) { | 65 while (val != 0) { |
66 bit_count++; | 66 bit_count++; |
67 val >>= 1; | 67 val >>= 1; |
68 } | 68 } |
69 return bit_count; | 69 return bit_count; |
70 } | 70 } |
71 | 71 |
72 } // namespace | 72 } // namespace |
73 | 73 |
74 namespace rtc { | 74 namespace rtc { |
75 | 75 |
76 BitBuffer::BitBuffer(const uint8_t* bytes, size_t byte_count) | 76 BitBuffer::BitBuffer(const uint8_t* bytes, size_t byte_count) |
77 : bytes_(bytes), byte_count_(byte_count), byte_offset_(), bit_offset_() { | 77 : bytes_(bytes), byte_count_(byte_count), byte_offset_(), bit_offset_() { |
78 DCHECK(static_cast<uint64_t>(byte_count_) <= | 78 RTC_DCHECK(static_cast<uint64_t>(byte_count_) <= |
79 std::numeric_limits<uint32_t>::max()); | 79 std::numeric_limits<uint32_t>::max()); |
80 } | 80 } |
81 | 81 |
82 uint64_t BitBuffer::RemainingBitCount() const { | 82 uint64_t BitBuffer::RemainingBitCount() const { |
83 return (static_cast<uint64_t>(byte_count_) - byte_offset_) * 8 - bit_offset_; | 83 return (static_cast<uint64_t>(byte_count_) - byte_offset_) * 8 - bit_offset_; |
84 } | 84 } |
85 | 85 |
86 bool BitBuffer::ReadUInt8(uint8_t* val) { | 86 bool BitBuffer::ReadUInt8(uint8_t* val) { |
87 uint32_t bit_val; | 87 uint32_t bit_val; |
88 if (!ReadBits(&bit_val, sizeof(uint8_t) * 8)) { | 88 if (!ReadBits(&bit_val, sizeof(uint8_t) * 8)) { |
89 return false; | 89 return false; |
90 } | 90 } |
91 DCHECK(bit_val <= std::numeric_limits<uint8_t>::max()); | 91 RTC_DCHECK(bit_val <= std::numeric_limits<uint8_t>::max()); |
92 *val = static_cast<uint8_t>(bit_val); | 92 *val = static_cast<uint8_t>(bit_val); |
93 return true; | 93 return true; |
94 } | 94 } |
95 | 95 |
96 bool BitBuffer::ReadUInt16(uint16_t* val) { | 96 bool BitBuffer::ReadUInt16(uint16_t* val) { |
97 uint32_t bit_val; | 97 uint32_t bit_val; |
98 if (!ReadBits(&bit_val, sizeof(uint16_t) * 8)) { | 98 if (!ReadBits(&bit_val, sizeof(uint16_t) * 8)) { |
99 return false; | 99 return false; |
100 } | 100 } |
101 DCHECK(bit_val <= std::numeric_limits<uint16_t>::max()); | 101 RTC_DCHECK(bit_val <= std::numeric_limits<uint16_t>::max()); |
102 *val = static_cast<uint16_t>(bit_val); | 102 *val = static_cast<uint16_t>(bit_val); |
103 return true; | 103 return true; |
104 } | 104 } |
105 | 105 |
106 bool BitBuffer::ReadUInt32(uint32_t* val) { | 106 bool BitBuffer::ReadUInt32(uint32_t* val) { |
107 return ReadBits(val, sizeof(uint32_t) * 8); | 107 return ReadBits(val, sizeof(uint32_t) * 8); |
108 } | 108 } |
109 | 109 |
110 bool BitBuffer::PeekBits(uint32_t* val, size_t bit_count) { | 110 bool BitBuffer::PeekBits(uint32_t* val, size_t bit_count) { |
111 if (!val || bit_count > RemainingBitCount() || bit_count > 32) { | 111 if (!val || bit_count > RemainingBitCount() || bit_count > 32) { |
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166 | 166 |
167 // Count the number of leading 0 bits by peeking/consuming them one at a time. | 167 // Count the number of leading 0 bits by peeking/consuming them one at a time. |
168 size_t zero_bit_count = 0; | 168 size_t zero_bit_count = 0; |
169 uint32_t peeked_bit; | 169 uint32_t peeked_bit; |
170 while (PeekBits(&peeked_bit, 1) && peeked_bit == 0) { | 170 while (PeekBits(&peeked_bit, 1) && peeked_bit == 0) { |
171 zero_bit_count++; | 171 zero_bit_count++; |
172 ConsumeBits(1); | 172 ConsumeBits(1); |
173 } | 173 } |
174 | 174 |
175 // We should either be at the end of the stream, or the next bit should be 1. | 175 // We should either be at the end of the stream, or the next bit should be 1. |
176 DCHECK(!PeekBits(&peeked_bit, 1) || peeked_bit == 1); | 176 RTC_DCHECK(!PeekBits(&peeked_bit, 1) || peeked_bit == 1); |
177 | 177 |
178 // The bit count of the value is the number of zeros + 1. Make sure that many | 178 // The bit count of the value is the number of zeros + 1. Make sure that many |
179 // bits fits in a uint32_t and that we have enough bits left for it, and then | 179 // bits fits in a uint32_t and that we have enough bits left for it, and then |
180 // read the value. | 180 // read the value. |
181 size_t value_bit_count = zero_bit_count + 1; | 181 size_t value_bit_count = zero_bit_count + 1; |
182 if (value_bit_count > 32 || !ReadBits(val, value_bit_count)) { | 182 if (value_bit_count > 32 || !ReadBits(val, value_bit_count)) { |
183 CHECK(Seek(original_byte_offset, original_bit_offset)); | 183 RTC_CHECK(Seek(original_byte_offset, original_bit_offset)); |
184 return false; | 184 return false; |
185 } | 185 } |
186 *val -= 1; | 186 *val -= 1; |
187 return true; | 187 return true; |
188 } | 188 } |
189 | 189 |
190 void BitBuffer::GetCurrentOffset( | 190 void BitBuffer::GetCurrentOffset( |
191 size_t* out_byte_offset, size_t* out_bit_offset) { | 191 size_t* out_byte_offset, size_t* out_bit_offset) { |
192 CHECK(out_byte_offset != NULL); | 192 RTC_CHECK(out_byte_offset != NULL); |
193 CHECK(out_bit_offset != NULL); | 193 RTC_CHECK(out_bit_offset != NULL); |
194 *out_byte_offset = byte_offset_; | 194 *out_byte_offset = byte_offset_; |
195 *out_bit_offset = bit_offset_; | 195 *out_bit_offset = bit_offset_; |
196 } | 196 } |
197 | 197 |
198 bool BitBuffer::Seek(size_t byte_offset, size_t bit_offset) { | 198 bool BitBuffer::Seek(size_t byte_offset, size_t bit_offset) { |
199 if (byte_offset > byte_count_ || bit_offset > 7 || | 199 if (byte_offset > byte_count_ || bit_offset > 7 || |
200 (byte_offset == byte_count_ && bit_offset > 0)) { | 200 (byte_offset == byte_count_ && bit_offset > 0)) { |
201 return false; | 201 return false; |
202 } | 202 } |
203 byte_offset_ = byte_offset; | 203 byte_offset_ = byte_offset; |
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274 } | 274 } |
275 uint64_t val_to_encode = static_cast<uint64_t>(val) + 1; | 275 uint64_t val_to_encode = static_cast<uint64_t>(val) + 1; |
276 | 276 |
277 // We need to write CountBits(val+1) 0s and then val+1. Since val (as a | 277 // We need to write CountBits(val+1) 0s and then val+1. Since val (as a |
278 // uint64_t) has leading zeros, we can just write the total golomb encoded | 278 // uint64_t) has leading zeros, we can just write the total golomb encoded |
279 // size worth of bits, knowing the value will appear last. | 279 // size worth of bits, knowing the value will appear last. |
280 return WriteBits(val_to_encode, CountBits(val_to_encode) * 2 - 1); | 280 return WriteBits(val_to_encode, CountBits(val_to_encode) * 2 - 1); |
281 } | 281 } |
282 | 282 |
283 } // namespace rtc | 283 } // namespace rtc |
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