3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26 typedef struct RangeCoder{
29 int outstanding_count;
31 uint8_t zero_state[256];
32 uint8_t one_state[256];
33 uint8_t *bytestream_start;
35 uint8_t *bytestream_end;
38 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
39 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
40 int ff_rac_terminate(RangeCoder *c);
41 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
43 static inline void renorm_encoder(RangeCoder *c){
45 while(c->range < 0x100){
46 if(c->outstanding_byte < 0){
47 c->outstanding_byte= c->low>>8;
48 }else if(c->low <= 0xFF00){
49 *c->bytestream++ = c->outstanding_byte;
50 for(;c->outstanding_count; c->outstanding_count--)
51 *c->bytestream++ = 0xFF;
52 c->outstanding_byte= c->low>>8;
53 }else if(c->low >= 0x10000){
54 *c->bytestream++ = c->outstanding_byte + 1;
55 for(;c->outstanding_count; c->outstanding_count--)
56 *c->bytestream++ = 0x00;
57 c->outstanding_byte= (c->low>>8) & 0xFF;
59 c->outstanding_count++;
62 c->low = (c->low & 0xFF)<<8;
67 static inline void put_rac(RangeCoder *c, uint8_t * const state, int bit){
68 int range1= (c->range * (*state)) >> 8;
71 assert(range1 < c->range);
75 *state= c->zero_state[*state];
77 c->low += c->range - range1;
79 *state= c->one_state[*state];
85 static inline void refill(RangeCoder *c){
89 if(c->bytestream < c->bytestream_end)
90 c->low+= c->bytestream[0];
95 static inline int get_rac(RangeCoder *c, uint8_t * const state){
96 int range1= (c->range * (*state)) >> 8;
97 int attribute_unused one_mask;
101 if(c->low < c->range){
102 *state= c->zero_state[*state];
107 *state= c->one_state[*state];
113 one_mask= (c->range - c->low-1)>>31;
115 c->low -= c->range & one_mask;
116 c->range += (range1 - c->range) & one_mask;
118 *state= c->zero_state[(*state) + (256&one_mask)];