1 // Copyright 2010 Google Inc. 2 // 3 // This code is licensed under the same terms as WebM: 4 // Software License Agreement: http://www.webmproject.org/license/software/ 5 // Additional IP Rights Grant: http://www.webmproject.org/license/additional/ 6 // ----------------------------------------------------------------------------- 7 // 8 // Boolean decoder 9 // 10 // Author: Skal (pascal.massimino (at) gmail.com) 11 12 #include "bits.h" 13 14 #if defined(__cplusplus) || defined(c_plusplus) 15 extern "C" { 16 #endif 17 18 //----------------------------------------------------------------------------- 19 // VP8BitReader 20 21 void VP8InitBitReader(VP8BitReader* const br, 22 const uint8_t* const start, const uint8_t* const end) { 23 assert(br); 24 assert(start); 25 assert(start <= end); 26 br->range_ = 255 - 1; 27 br->buf_ = start; 28 br->buf_end_ = end; 29 br->value_ = 0; 30 br->missing_ = 8; 31 br->eof_ = 0; 32 } 33 34 const uint8_t kVP8Log2Range[128] = { 35 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 36 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 37 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 38 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 39 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 40 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 41 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 42 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 43 0 44 }; 45 46 // range = ((range + 1) << kVP8Log2Range[range]) - 1 47 const uint8_t kVP8NewRange[128] = { 48 127, 127, 191, 127, 159, 191, 223, 127, 143, 159, 175, 191, 207, 223, 239, 49 127, 135, 143, 151, 159, 167, 175, 183, 191, 199, 207, 215, 223, 231, 239, 50 247, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179, 51 183, 187, 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239, 52 243, 247, 251, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 53 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179, 54 181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201, 203, 205, 207, 209, 55 211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239, 56 241, 243, 245, 247, 249, 251, 253, 127 57 }; 58 59 //----------------------------------------------------------------------------- 60 // Higher-level calls 61 62 uint32_t VP8GetValue(VP8BitReader* const br, int bits) { 63 uint32_t v = 0; 64 while (bits-- > 0) { 65 v |= VP8GetBit(br, 0x80) << bits; 66 } 67 return v; 68 } 69 70 int32_t VP8GetSignedValue(VP8BitReader* const br, int bits) { 71 const int value = VP8GetValue(br, bits); 72 return VP8Get(br) ? -value : value; 73 } 74 75 //----------------------------------------------------------------------------- 76 77 #if defined(__cplusplus) || defined(c_plusplus) 78 } // extern "C" 79 #endif 80
