1 /*
2  * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
3  * Copyright (c) 2003 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
24  * Context Adaptive Binary Arithmetic Coder inline functions
25  */
26 
27 #ifndef AVCODEC_CABAC_FUNCTIONS_H
28 #define AVCODEC_CABAC_FUNCTIONS_H
29 
30 #include <stddef.h>
31 #include <stdint.h>
32 
33 #include "libavutil/attributes.h"
34 #include "libavutil/intmath.h"
35 #include "cabac.h"
36 #include "config.h"
37 
38 #ifndef UNCHECKED_BITSTREAM_READER
39 #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
40 #endif
41 
42 #if ARCH_AARCH64
43 #   include "aarch64/cabac.h"
44 #endif
45 #if ARCH_ARM
46 #   include "arm/cabac.h"
47 #endif
48 #if ARCH_X86
49 #   include "x86/cabac.h"
50 #endif
51 #if ARCH_MIPS
52 #   include "mips/cabac.h"
53 #endif
54 #if ARCH_LOONGARCH64
55 #   include "loongarch/cabac.h"
56 #endif
57 
58 static const uint8_t * const ff_h264_norm_shift = ff_h264_cabac_tables + H264_NORM_SHIFT_OFFSET;
59 static const uint8_t * const ff_h264_lps_range = ff_h264_cabac_tables + H264_LPS_RANGE_OFFSET;
60 static const uint8_t * const ff_h264_mlps_state = ff_h264_cabac_tables + H264_MLPS_STATE_OFFSET;
61 static const uint8_t * const ff_h264_last_coeff_flag_offset_8x8 = ff_h264_cabac_tables + H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET;
62 
63 #if !defined(get_cabac_bypass) || !defined(get_cabac_terminate)
refill(CABACContext *c)64 static void refill(CABACContext *c){
65 #if CABAC_BITS == 16
66         c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
67 #else
68         c->low+= c->bytestream[0]<<1;
69 #endif
70     c->low -= CABAC_MASK;
71 #if !UNCHECKED_BITSTREAM_READER
72     if (c->bytestream < c->bytestream_end)
73 #endif
74         c->bytestream += CABAC_BITS / 8;
75 }
76 #endif
77 
78 #ifndef get_cabac_terminate
renorm_cabac_decoder_once(CABACContext *c)79 static inline void renorm_cabac_decoder_once(CABACContext *c){
80     int shift= (uint32_t)(c->range - 0x100)>>31;
81     c->range<<= shift;
82     c->low  <<= shift;
83     if(!(c->low & CABAC_MASK))
84         refill(c);
85 }
86 #endif
87 
88 #ifndef get_cabac_inline
refill2(CABACContext *c)89 static void refill2(CABACContext *c){
90     int i;
91     unsigned x;
92 #if !HAVE_FAST_CLZ
93     x= c->low ^ (c->low-1);
94     i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
95 #else
96     i = ff_ctz(c->low) - CABAC_BITS;
97 #endif
98 
99     x= -CABAC_MASK;
100 
101 #if CABAC_BITS == 16
102         x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
103 #else
104         x+= c->bytestream[0]<<1;
105 #endif
106 
107     c->low += x<<i;
108 #if !UNCHECKED_BITSTREAM_READER
109     if (c->bytestream < c->bytestream_end)
110 #endif
111         c->bytestream += CABAC_BITS/8;
112 }
113 #endif
114 
115 #ifndef get_cabac_inline
get_cabac_inline(CABACContext *c, uint8_t * const state)116 static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
117     int s = *state;
118     int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
119     int bit, lps_mask;
120 
121     c->range -= RangeLPS;
122     lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
123 
124     c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
125     c->range += (RangeLPS - c->range) & lps_mask;
126 
127     s^=lps_mask;
128     *state= (ff_h264_mlps_state+128)[s];
129     bit= s&1;
130 
131     lps_mask= ff_h264_norm_shift[c->range];
132     c->range<<= lps_mask;
133     c->low  <<= lps_mask;
134     if(!(c->low & CABAC_MASK))
135         refill2(c);
136     return bit;
137 }
138 #endif
139 
get_cabac_noinline(CABACContext *c, uint8_t * const state)140 static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
141     return get_cabac_inline(c,state);
142 }
143 
get_cabac(CABACContext *c, uint8_t * const state)144 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
145     return get_cabac_inline(c,state);
146 }
147 
148 #ifndef get_cabac_bypass
get_cabac_bypass(CABACContext *c)149 static int av_unused get_cabac_bypass(CABACContext *c){
150     int range;
151     c->low += c->low;
152 
153     if(!(c->low & CABAC_MASK))
154         refill(c);
155 
156     range= c->range<<(CABAC_BITS+1);
157     if(c->low < range){
158         return 0;
159     }else{
160         c->low -= range;
161         return 1;
162     }
163 }
164 #endif
165 
166 #ifndef get_cabac_bypass_sign
get_cabac_bypass_sign(CABACContext *c, int val)167 static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
168     int range, mask;
169     c->low += c->low;
170 
171     if(!(c->low & CABAC_MASK))
172         refill(c);
173 
174     range= c->range<<(CABAC_BITS+1);
175     c->low -= range;
176     mask= c->low >> 31;
177     range &= mask;
178     c->low += range;
179     return (val^mask)-mask;
180 }
181 #endif
182 
183 /**
184  * @return the number of bytes read or 0 if no end
185  */
186 #ifndef get_cabac_terminate
get_cabac_terminate(CABACContext *c)187 static int av_unused get_cabac_terminate(CABACContext *c){
188     c->range -= 2;
189     if(c->low < c->range<<(CABAC_BITS+1)){
190         renorm_cabac_decoder_once(c);
191         return 0;
192     }else{
193         return c->bytestream - c->bytestream_start;
194     }
195 }
196 #endif
197 
198 /**
199  * Skip @p n bytes and reset the decoder.
200  * @return the address of the first skipped byte or NULL if there's less than @p n bytes left
201  */
202 #ifndef skip_bytes
skip_bytes(CABACContext *c, int n)203 static av_unused const uint8_t* skip_bytes(CABACContext *c, int n) {
204     const uint8_t *ptr = c->bytestream;
205 
206     if (c->low & 0x1)
207         ptr--;
208 #if CABAC_BITS == 16
209     if (c->low & 0x1FF)
210         ptr--;
211 #endif
212     if ((int) (c->bytestream_end - ptr) < n)
213         return NULL;
214     if (ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n) < 0)
215         return NULL;
216 
217     return ptr;
218 }
219 #endif
220 
221 #endif /* AVCODEC_CABAC_FUNCTIONS_H */
222