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
58static const uint8_t * const ff_h264_norm_shift = ff_h264_cabac_tables + H264_NORM_SHIFT_OFFSET;
59static const uint8_t * const ff_h264_lps_range = ff_h264_cabac_tables + H264_LPS_RANGE_OFFSET;
60static const uint8_t * const ff_h264_mlps_state = ff_h264_cabac_tables + H264_MLPS_STATE_OFFSET;
61static 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)
64static 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
79static 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
89static 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
116static 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
140static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
141    return get_cabac_inline(c,state);
142}
143
144static 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
149static 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
167static 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
187static 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
203static 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