FFmpeg
rangecoder.c
Go to the documentation of this file.
1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include <stdint.h>
20 #include <string.h>
21 
22 #include "libavutil/error.h"
23 #include "libavutil/lfg.h"
24 #include "libavutil/log.h"
25 
26 #include "libavcodec/rangecoder.h"
27 
28 #define SIZE 1240
29 
30 /**
31  * Check if at the current position there is a valid looking termination
32  * @param version version 0 requires the decoder to know the data size in bytes
33  * version 1 needs about 1 bit more space but does not need to
34  * carry the size from encoder to decoder
35  * @returns negative AVERROR code on error or non negative.
36  */
38 {
39  if (version == 1) {
40  RangeCoder tmp = *c;
41  get_rac(c, (uint8_t[]) { 129 });
42 
43  if (c->bytestream == tmp.bytestream && c->bytestream > c->bytestream_start)
44  tmp.low -= *--tmp.bytestream;
45  tmp.bytestream_end = tmp.bytestream;
46 
47  if (get_rac(&tmp, (uint8_t[]) { 129 }))
48  return AVERROR_INVALIDDATA;
49  } else {
50  if (c->bytestream_end != c->bytestream)
51  return AVERROR_INVALIDDATA;
52  }
53  return 0;
54 }
55 
56 int main(void)
57 {
58  RangeCoder c;
59  uint8_t b[9 * SIZE] = {0};
60  uint8_t r[9 * SIZE];
61  int i, p, actual_length, version;
62  uint8_t state[10];
63  AVLFG prng;
64 
65  av_lfg_init(&prng, 1);
66  for (version = 0; version < 2; version++) {
67  for (p = 0; p< 1024; p++) {
69  ff_build_rac_states(&c, (1LL << 32) / 20, 128 + 64 + 32 + 16);
70 
71  memset(state, 128, sizeof(state));
72 
73  for (i = 0; i < SIZE; i++)
74  r[i] = av_lfg_get(&prng) % 7;
75 
76  for (i = 0; i < SIZE; i++)
77  put_rac(&c, state, r[i] & 1);
78 
79  actual_length = ff_rac_terminate(&c, version);
80 
81  ff_init_range_decoder(&c, b, version ? SIZE : actual_length);
82 
83  memset(state, 128, sizeof(state));
84 
85  for (i = 0; i < SIZE; i++)
86  if ((r[i] & 1) != get_rac(&c, state)) {
87  av_log(NULL, AV_LOG_ERROR, "rac failure at %d pass %d version %d\n", i, p, version);
88  return 1;
89  }
90 
91  if (rac_check_termination(&c, version) < 0) {
92  av_log(NULL, AV_LOG_ERROR, "rac failure at termination pass %d version %d\n", p, version);
93  return 1;
94  }
95  if (c.bytestream - c.bytestream_start - actual_length != version) {
96  av_log(NULL, AV_LOG_ERROR, "rac failure at pass %d version %d\n", p, version);
97  return 1;
98  }
99  }
100  }
101 
102  return 0;
103 }
r
const char * r
Definition: vf_curves.c:126
av_lfg_init
av_cold void av_lfg_init(AVLFG *c, unsigned int seed)
Definition: lfg.c:32
tmp
static uint8_t tmp[11]
Definition: aes_ctr.c:28
rac_check_termination
static int rac_check_termination(RangeCoder *c, int version)
Check if at the current position there is a valid looking termination.
Definition: rangecoder.c:37
b
#define b
Definition: input.c:41
rangecoder.h
ff_init_range_encoder
av_cold void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size)
Definition: rangecoder.c:42
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
av_lfg_get
static unsigned int av_lfg_get(AVLFG *c)
Get the next random unsigned 32-bit number using an ALFG.
Definition: lfg.h:53
lfg.h
NULL
#define NULL
Definition: coverity.c:32
ff_rac_terminate
int ff_rac_terminate(RangeCoder *c, int version)
Terminates the range coder.
Definition: rangecoder.c:109
main
int main(void)
Definition: rangecoder.c:56
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
error.h
ff_init_range_decoder
av_cold void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size)
Definition: rangecoder.c:53
AVLFG
Context structure for the Lagged Fibonacci PRNG.
Definition: lfg.h:33
state
static struct @384 state
ff_build_rac_states
void ff_build_rac_states(RangeCoder *c, int factor, int max_p)
Definition: rangecoder.c:68
version
version
Definition: libkvazaar.c:321
log.h
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:255
get_rac
static int get_rac(RangeCoder *c, uint8_t *const state)
Definition: rangecoder.h:127
put_rac
#define put_rac(C, S, B)
SIZE
#define SIZE
Definition: rangecoder.c:28
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
RangeCoder
Definition: mss3.c:62