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