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 #ifdef WEBP_FORCE_ALIGNED 24 #include <string.h> // memcpy 25 #endif 26 27 #include "../dsp/dsp.h" 28 #include "./bit_reader.h" 29 #include "./endian_inl.h" 30 31 #ifdef __cplusplus 32 extern "C" { 33 #endif 34 35 //------------------------------------------------------------------------------ 36 // Derived type lbit_t = natural type for memory I/O 37 38 #if (BITS > 32) 39 typedef uint64_t lbit_t; 40 #elif (BITS > 16) 41 typedef uint32_t lbit_t; 42 #elif (BITS > 8) 43 typedef uint16_t lbit_t; 44 #else 45 typedef uint8_t lbit_t; 46 #endif 47 48 extern const uint8_t kVP8Log2Range[128]; 49 extern const range_t kVP8NewRange[128]; 50 51 // special case for the tail byte-reading 52 void VP8LoadFinalBytes(VP8BitReader* const br); 53 54 //------------------------------------------------------------------------------ 55 // Inlined critical functions 56 57 // makes sure br->value_ has at least BITS bits worth of data 58 static WEBP_INLINE 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_ + sizeof(lbit_t) <= br->buf_end_) { 62 // convert memory type to register type (with some zero'ing!) 63 bit_t bits; 64 #if defined(WEBP_FORCE_ALIGNED) 65 lbit_t in_bits; 66 memcpy(&in_bits, br->buf_, sizeof(in_bits)); 67 #elif defined(WEBP_USE_MIPS32) 68 // This is needed because of un-aligned read. 69 lbit_t in_bits; 70 lbit_t* p_buf_ = (lbit_t*)br->buf_; 71 __asm__ volatile( 72 ".set push \n\t" 73 ".set at \n\t" 74 ".set macro \n\t" 75 "ulw %[in_bits], 0(%[p_buf_]) \n\t" 76 ".set pop \n\t" 77 : [in_bits]"=r"(in_bits) 78 : [p_buf_]"r"(p_buf_) 79 : "memory", "at" 80 ); 81 #else 82 const lbit_t in_bits = *(const lbit_t*)br->buf_; 83 #endif 84 br->buf_ += BITS >> 3; 85 #if !defined(WORDS_BIGENDIAN) 86 #if (BITS > 32) 87 bits = BSwap64(in_bits); 88 bits >>= 64 - BITS; 89 #elif (BITS >= 24) 90 bits = BSwap32(in_bits); 91 bits >>= (32 - BITS); 92 #elif (BITS == 16) 93 bits = BSwap16(in_bits); 94 #else // BITS == 8 95 bits = (bit_t)in_bits; 96 #endif // BITS > 32 97 #else // WORDS_BIGENDIAN 98 bits = (bit_t)in_bits; 99 if (BITS != 8 * sizeof(bit_t)) bits >>= (8 * sizeof(bit_t) - BITS); 100 #endif 101 br->value_ = bits | (br->value_ << BITS); 102 br->bits_ += BITS; 103 } else { 104 VP8LoadFinalBytes(br); // no need to be inlined 105 } 106 } 107 108 // Read a bit with proba 'prob'. Speed-critical function! 109 static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) { 110 // Don't move this declaration! It makes a big speed difference to store 111 // 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't 112 // alter br->range_ value. 113 range_t range = br->range_; 114 if (br->bits_ < 0) { 115 VP8LoadNewBytes(br); 116 } 117 { 118 const int pos = br->bits_; 119 const range_t split = (range * prob) >> 8; 120 const range_t value = (range_t)(br->value_ >> pos); 121 #if defined(__arm__) || defined(_M_ARM) // ARM-specific 122 const int bit = ((int)(split - value) >> 31) & 1; 123 if (value > split) { 124 range -= split + 1; 125 br->value_ -= (bit_t)(split + 1) << pos; 126 } else { 127 range = split; 128 } 129 #else // faster version on x86 130 int bit; // Don't use 'const int bit = (value > split);", it's slower. 131 if (value > split) { 132 range -= split + 1; 133 br->value_ -= (bit_t)(split + 1) << pos; 134 bit = 1; 135 } else { 136 range = split; 137 bit = 0; 138 } 139 #endif 140 if (range <= (range_t)0x7e) { 141 const int shift = kVP8Log2Range[range]; 142 range = kVP8NewRange[range]; 143 br->bits_ -= shift; 144 } 145 br->range_ = range; 146 return bit; 147 } 148 } 149 150 // simplified version of VP8GetBit() for prob=0x80 (note shift is always 1 here) 151 static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) { 152 if (br->bits_ < 0) { 153 VP8LoadNewBytes(br); 154 } 155 { 156 const int pos = br->bits_; 157 const range_t split = br->range_ >> 1; 158 const range_t value = (range_t)(br->value_ >> pos); 159 const int32_t mask = (int32_t)(split - value) >> 31; // -1 or 0 160 br->bits_ -= 1; 161 br->range_ += mask; 162 br->range_ |= 1; 163 br->value_ -= (bit_t)((split + 1) & mask) << pos; 164 return (v ^ mask) - mask; 165 } 166 } 167 168 #ifdef __cplusplus 169 } // extern "C" 170 #endif 171 172 #endif // WEBP_UTILS_BIT_READER_INL_H_ 173
