1 /* 2 * Copyright (c) 2010 The WebM project authors. All Rights Reserved. 3 * 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 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef VP9_DECODER_VP9_READER_H_ 12 #define VP9_DECODER_VP9_READER_H_ 13 14 #include <stddef.h> 15 #include <limits.h> 16 17 #include "./vpx_config.h" 18 #include "vpx_ports/mem.h" 19 #include "vpx/vpx_integer.h" 20 21 #include "vp9/common/vp9_prob.h" 22 23 #ifdef __cplusplus 24 extern "C" { 25 #endif 26 27 typedef size_t BD_VALUE; 28 29 #define BD_VALUE_SIZE ((int)sizeof(BD_VALUE) * CHAR_BIT) 30 31 typedef struct { 32 const uint8_t *buffer_end; 33 const uint8_t *buffer; 34 BD_VALUE value; 35 int count; 36 unsigned int range; 37 } vp9_reader; 38 39 int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size); 40 41 void vp9_reader_fill(vp9_reader *r); 42 43 int vp9_reader_has_error(vp9_reader *r); 44 45 const uint8_t *vp9_reader_find_end(vp9_reader *r); 46 47 static int vp9_read(vp9_reader *r, int prob) { 48 unsigned int bit = 0; 49 BD_VALUE value; 50 BD_VALUE bigsplit; 51 int count; 52 unsigned int range; 53 unsigned int split = (r->range * prob + (256 - prob)) >> CHAR_BIT; 54 55 if (r->count < 0) 56 vp9_reader_fill(r); 57 58 value = r->value; 59 count = r->count; 60 61 bigsplit = (BD_VALUE)split << (BD_VALUE_SIZE - CHAR_BIT); 62 63 range = split; 64 65 if (value >= bigsplit) { 66 range = r->range - split; 67 value = value - bigsplit; 68 bit = 1; 69 } 70 71 { 72 register unsigned int shift = vp9_norm[range]; 73 range <<= shift; 74 value <<= shift; 75 count -= shift; 76 } 77 r->value = value; 78 r->count = count; 79 r->range = range; 80 81 return bit; 82 } 83 84 static int vp9_read_bit(vp9_reader *r) { 85 return vp9_read(r, 128); // vp9_prob_half 86 } 87 88 static int vp9_read_literal(vp9_reader *r, int bits) { 89 int literal = 0, bit; 90 91 for (bit = bits - 1; bit >= 0; bit--) 92 literal |= vp9_read_bit(r) << bit; 93 94 return literal; 95 } 96 97 static int vp9_read_tree(vp9_reader *r, const vp9_tree_index *tree, 98 const vp9_prob *probs) { 99 vp9_tree_index i = 0; 100 101 while ((i = tree[i + vp9_read(r, probs[i >> 1])]) > 0) 102 continue; 103 104 return -i; 105 } 106 107 #ifdef __cplusplus 108 } // extern "C" 109 #endif 110 111 #endif // VP9_DECODER_VP9_READER_H_ 112
