f26b39aa7f10a0d091fb4df3897be55f26993961
[libav.git] / libavcodec / rangecoder.h
1 /*
2 * Range coder
3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file rangecoder.h
24 * Range coder.
25 */
26
27 #ifndef AVCODEC_RANGECODER_H
28 #define AVCODEC_RANGECODER_H
29
30 #include <stdint.h>
31 #include <assert.h>
32 #include "common.h"
33
34 typedef struct RangeCoder{
35 int low;
36 int range;
37 int outstanding_count;
38 int outstanding_byte;
39 uint8_t zero_state[256];
40 uint8_t one_state[256];
41 uint8_t *bytestream_start;
42 uint8_t *bytestream;
43 uint8_t *bytestream_end;
44 }RangeCoder;
45
46 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
47 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
48 int ff_rac_terminate(RangeCoder *c);
49 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
50
51 static inline void renorm_encoder(RangeCoder *c){
52 //FIXME optimize
53 while(c->range < 0x100){
54 if(c->outstanding_byte < 0){
55 c->outstanding_byte= c->low>>8;
56 }else if(c->low <= 0xFF00){
57 *c->bytestream++ = c->outstanding_byte;
58 for(;c->outstanding_count; c->outstanding_count--)
59 *c->bytestream++ = 0xFF;
60 c->outstanding_byte= c->low>>8;
61 }else if(c->low >= 0x10000){
62 *c->bytestream++ = c->outstanding_byte + 1;
63 for(;c->outstanding_count; c->outstanding_count--)
64 *c->bytestream++ = 0x00;
65 c->outstanding_byte= (c->low>>8) & 0xFF;
66 }else{
67 c->outstanding_count++;
68 }
69
70 c->low = (c->low & 0xFF)<<8;
71 c->range <<= 8;
72 }
73 }
74
75 static inline int get_rac_count(RangeCoder *c){
76 int x= c->bytestream - c->bytestream_start + c->outstanding_count;
77 if(c->outstanding_byte >= 0)
78 x++;
79 return 8*x - av_log2(c->range);
80 }
81
82 static inline void put_rac(RangeCoder *c, uint8_t * const state, int bit){
83 int range1= (c->range * (*state)) >> 8;
84
85 assert(*state);
86 assert(range1 < c->range);
87 assert(range1 > 0);
88 if(!bit){
89 c->range -= range1;
90 *state= c->zero_state[*state];
91 }else{
92 c->low += c->range - range1;
93 c->range = range1;
94 *state= c->one_state[*state];
95 }
96
97 renorm_encoder(c);
98 }
99
100 static inline void refill(RangeCoder *c){
101 if(c->range < 0x100){
102 c->range <<= 8;
103 c->low <<= 8;
104 if(c->bytestream < c->bytestream_end)
105 c->low+= c->bytestream[0];
106 c->bytestream++;
107 }
108 }
109
110 static inline int get_rac(RangeCoder *c, uint8_t * const state){
111 int range1= (c->range * (*state)) >> 8;
112 int av_unused one_mask;
113
114 c->range -= range1;
115 #if 1
116 if(c->low < c->range){
117 *state= c->zero_state[*state];
118 refill(c);
119 return 0;
120 }else{
121 c->low -= c->range;
122 *state= c->one_state[*state];
123 c->range = range1;
124 refill(c);
125 return 1;
126 }
127 #else
128 one_mask= (c->range - c->low-1)>>31;
129
130 c->low -= c->range & one_mask;
131 c->range += (range1 - c->range) & one_mask;
132
133 *state= c->zero_state[(*state) + (256&one_mask)];
134
135 refill(c);
136
137 return one_mask&1;
138 #endif
139 }
140
141 #endif // AVCODEC_RANGECODER_H