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 (at) gmail.com) 15 16 #ifndef WEBP_UTILS_BIT_READER_INL_H_ 17 #define WEBP_UTILS_BIT_READER_INL_H_ 18 19 #ifdef HAVE_CONFIG_H 20 #include "../webp/config.h" 21 #endif 22 23 #include <string.h> // for memcpy 24 25 #include "../dsp/dsp.h" 26 #include "./bit_reader_utils.h" 27 #include "./endian_inl_utils.h" 28 #include "./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, int prob) { 108 // Don't move this declaration! It makes a big speed difference to store 109 // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't 110 // alter br->range_ value. 111 range_t range = br->range_; 112 if (br->bits_ < 0) { 113 VP8LoadNewBytes(br); 114 } 115 { 116 const int pos = br->bits_; 117 const range_t split = (range * prob) >> 8; 118 const range_t value = (range_t)(br->value_ >> pos); 119 const int bit = (value > split); 120 if (bit) { 121 range -= split; 122 br->value_ -= (bit_t)(split + 1) << pos; 123 } else { 124 range = split + 1; 125 } 126 { 127 const int shift = 7 ^ BitsLog2Floor(range); 128 range <<= shift; 129 br->bits_ -= shift; 130 } 131 br->range_ = range - 1; 132 return bit; 133 } 134 } 135 136 // simplified version of VP8GetBit() for prob=0x80 (note shift is always 1 here) 137 static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE 138 int VP8GetSigned(VP8BitReader* const br, int v) { 139 if (br->bits_ < 0) { 140 VP8LoadNewBytes(br); 141 } 142 { 143 const int pos = br->bits_; 144 const range_t split = br->range_ >> 1; 145 const range_t value = (range_t)(br->value_ >> pos); 146 const int32_t mask = (int32_t)(split - value) >> 31; // -1 or 0 147 br->bits_ -= 1; 148 br->range_ += mask; 149 br->range_ |= 1; 150 br->value_ -= (bit_t)((split + 1) & mask) << pos; 151 return (v ^ mask) - mask; 152 } 153 } 154 155 static WEBP_INLINE int VP8GetBitAlt(VP8BitReader* const br, int prob) { 156 // Don't move this declaration! It makes a big speed difference to store 157 // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't 158 // alter br->range_ value. 159 range_t range = br->range_; 160 if (br->bits_ < 0) { 161 VP8LoadNewBytes(br); 162 } 163 { 164 const int pos = br->bits_; 165 const range_t split = (range * prob) >> 8; 166 const range_t value = (range_t)(br->value_ >> pos); 167 int bit; // Don't use 'const int bit = (value > split);", it's slower. 168 if (value > split) { 169 range -= split + 1; 170 br->value_ -= (bit_t)(split + 1) << pos; 171 bit = 1; 172 } else { 173 range = split; 174 bit = 0; 175 } 176 if (range <= (range_t)0x7e) { 177 const int shift = kVP8Log2Range[range]; 178 range = kVP8NewRange[range]; 179 br->bits_ -= shift; 180 } 181 br->range_ = range; 182 return bit; 183 } 184 } 185 186 #ifdef __cplusplus 187 } // extern "C" 188 #endif 189 190 #endif // WEBP_UTILS_BIT_READER_INL_H_ 191
