1 | // Copyright 2014 Google Inc. All Rights Reserved. |
2 | // |
3 | // Use of this source code is governed by a BSD-style license |
4 | // that can be found in the COPYING file in the root of the source |
5 | // tree. An additional intellectual property rights grant can be found |
6 | // in the file PATENTS. All contributing project authors may |
7 | // be found in the AUTHORS file in the root of the source tree. |
8 | // ----------------------------------------------------------------------------- |
9 | // |
10 | // Specific inlined methods for boolean decoder [VP8GetBit() ...] |
11 | // This file should be included by the .c sources that actually need to call |
12 | // these methods. |
13 | // |
14 | // Author: Skal (pascal.massimino@gmail.com) |
15 | |
16 | #ifndef WEBP_UTILS_BIT_READER_INL_UTILS_H_ |
17 | #define WEBP_UTILS_BIT_READER_INL_UTILS_H_ |
18 | |
19 | #ifdef HAVE_CONFIG_H |
20 | #include "src/webp/config.h" |
21 | #endif |
22 | |
23 | #include <string.h> // for memcpy |
24 | |
25 | #include "src/dsp/dsp.h" |
26 | #include "src/utils/bit_reader_utils.h" |
27 | #include "src/utils/endian_inl_utils.h" |
28 | #include "src/utils/utils.h" |
29 | |
30 | #ifdef __cplusplus |
31 | extern "C" { |
32 | #endif |
33 | |
34 | //------------------------------------------------------------------------------ |
35 | // Derived type lbit_t = natural type for memory I/O |
36 | |
37 | #if (BITS > 32) |
38 | typedef uint64_t lbit_t; |
39 | #elif (BITS > 16) |
40 | typedef uint32_t lbit_t; |
41 | #elif (BITS > 8) |
42 | typedef uint16_t lbit_t; |
43 | #else |
44 | typedef uint8_t lbit_t; |
45 | #endif |
46 | |
47 | extern const uint8_t kVP8Log2Range[128]; |
48 | extern const uint8_t kVP8NewRange[128]; |
49 | |
50 | // special case for the tail byte-reading |
51 | void VP8LoadFinalBytes(VP8BitReader* const br); |
52 | |
53 | //------------------------------------------------------------------------------ |
54 | // Inlined critical functions |
55 | |
56 | // makes sure br->value_ has at least BITS bits worth of data |
57 | static WEBP_UBSAN_IGNORE_UNDEF WEBP_INLINE |
58 | void VP8LoadNewBytes(VP8BitReader* const br) { |
59 | assert(br != NULL && br->buf_ != NULL); |
60 | // Read 'BITS' bits at a time if possible. |
61 | if (br->buf_ < br->buf_max_) { |
62 | // convert memory type to register type (with some zero'ing!) |
63 | bit_t bits; |
64 | #if defined(WEBP_USE_MIPS32) |
65 | // This is needed because of un-aligned read. |
66 | lbit_t in_bits; |
67 | lbit_t* p_buf_ = (lbit_t*)br->buf_; |
68 | __asm__ volatile( |
69 | ".set push \n\t" |
70 | ".set at \n\t" |
71 | ".set macro \n\t" |
72 | "ulw %[in_bits], 0(%[p_buf_]) \n\t" |
73 | ".set pop \n\t" |
74 | : [in_bits]"=r" (in_bits) |
75 | : [p_buf_]"r" (p_buf_) |
76 | : "memory" , "at" |
77 | ); |
78 | #else |
79 | lbit_t in_bits; |
80 | memcpy(&in_bits, br->buf_, sizeof(in_bits)); |
81 | #endif |
82 | br->buf_ += BITS >> 3; |
83 | #if !defined(WORDS_BIGENDIAN) |
84 | #if (BITS > 32) |
85 | bits = BSwap64(in_bits); |
86 | bits >>= 64 - BITS; |
87 | #elif (BITS >= 24) |
88 | bits = BSwap32(in_bits); |
89 | bits >>= (32 - BITS); |
90 | #elif (BITS == 16) |
91 | bits = BSwap16(in_bits); |
92 | #else // BITS == 8 |
93 | bits = (bit_t)in_bits; |
94 | #endif // BITS > 32 |
95 | #else // WORDS_BIGENDIAN |
96 | bits = (bit_t)in_bits; |
97 | if (BITS != 8 * sizeof(bit_t)) bits >>= (8 * sizeof(bit_t) - BITS); |
98 | #endif |
99 | br->value_ = bits | (br->value_ << BITS); |
100 | br->bits_ += BITS; |
101 | } else { |
102 | VP8LoadFinalBytes(br); // no need to be inlined |
103 | } |
104 | } |
105 | |
106 | // Read a bit with proba 'prob'. Speed-critical function! |
107 | static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, |
108 | int prob, const char label[]) { |
109 | // Don't move this declaration! It makes a big speed difference to store |
110 | // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't |
111 | // alter br->range_ value. |
112 | range_t range = br->range_; |
113 | if (br->bits_ < 0) { |
114 | VP8LoadNewBytes(br); |
115 | } |
116 | { |
117 | const int pos = br->bits_; |
118 | const range_t split = (range * prob) >> 8; |
119 | const range_t value = (range_t)(br->value_ >> pos); |
120 | const int bit = (value > split); |
121 | if (bit) { |
122 | range -= split; |
123 | br->value_ -= (bit_t)(split + 1) << pos; |
124 | } else { |
125 | range = split + 1; |
126 | } |
127 | { |
128 | const int shift = 7 ^ BitsLog2Floor(range); |
129 | range <<= shift; |
130 | br->bits_ -= shift; |
131 | } |
132 | br->range_ = range - 1; |
133 | BT_TRACK(br); |
134 | return bit; |
135 | } |
136 | } |
137 | |
138 | // simplified version of VP8GetBit() for prob=0x80 (note shift is always 1 here) |
139 | static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE |
140 | int VP8GetSigned(VP8BitReader* const br, int v, const char label[]) { |
141 | if (br->bits_ < 0) { |
142 | VP8LoadNewBytes(br); |
143 | } |
144 | { |
145 | const int pos = br->bits_; |
146 | const range_t split = br->range_ >> 1; |
147 | const range_t value = (range_t)(br->value_ >> pos); |
148 | const int32_t mask = (int32_t)(split - value) >> 31; // -1 or 0 |
149 | br->bits_ -= 1; |
150 | br->range_ += mask; |
151 | br->range_ |= 1; |
152 | br->value_ -= (bit_t)((split + 1) & mask) << pos; |
153 | BT_TRACK(br); |
154 | return (v ^ mask) - mask; |
155 | } |
156 | } |
157 | |
158 | static WEBP_INLINE int VP8GetBitAlt(VP8BitReader* const br, |
159 | int prob, const char label[]) { |
160 | // Don't move this declaration! It makes a big speed difference to store |
161 | // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't |
162 | // alter br->range_ value. |
163 | range_t range = br->range_; |
164 | if (br->bits_ < 0) { |
165 | VP8LoadNewBytes(br); |
166 | } |
167 | { |
168 | const int pos = br->bits_; |
169 | const range_t split = (range * prob) >> 8; |
170 | const range_t value = (range_t)(br->value_ >> pos); |
171 | int bit; // Don't use 'const int bit = (value > split);", it's slower. |
172 | if (value > split) { |
173 | range -= split + 1; |
174 | br->value_ -= (bit_t)(split + 1) << pos; |
175 | bit = 1; |
176 | } else { |
177 | range = split; |
178 | bit = 0; |
179 | } |
180 | if (range <= (range_t)0x7e) { |
181 | const int shift = kVP8Log2Range[range]; |
182 | range = kVP8NewRange[range]; |
183 | br->bits_ -= shift; |
184 | } |
185 | br->range_ = range; |
186 | BT_TRACK(br); |
187 | return bit; |
188 | } |
189 | } |
190 | |
191 | #ifdef __cplusplus |
192 | } // extern "C" |
193 | #endif |
194 | |
195 | #endif // WEBP_UTILS_BIT_READER_INL_UTILS_H_ |
196 | |