FFmpeg
pnm_parser.c
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1 /*
2  * PNM image parser
3  * Copyright (c) 2002, 2003 Fabrice Bellard
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 #include "libavutil/avassert.h"
23 #include "libavutil/imgutils.h"
24 
25 #include "parser.h" //for ParseContext
26 #include "pnm.h"
27 
28 typedef struct PNMParseContext {
33 
35  const uint8_t **poutbuf, int *poutbuf_size,
36  const uint8_t *buf, int buf_size)
37 {
38  PNMParseContext *pnmpc = s->priv_data;
39  ParseContext *pc = &pnmpc->pc;
40  PNMContext pnmctx;
41  int next = END_NOT_FOUND;
42  int skip = 0;
43 
44  if (pc->overread > 0) {
45  memmove(pc->buffer + pc->index, pc->buffer + pc->overread_index, pc->overread);
46  pc->index += pc->overread;
47  pc->overread_index += pc->overread;
48  pc->overread = 0;
49  }
50 
51  if (pnmpc->remaining_bytes) {
52  int inc = FFMIN(pnmpc->remaining_bytes, buf_size);
53  skip += inc;
54  pnmpc->remaining_bytes -= inc;
55 
56  if (!pnmpc->remaining_bytes)
57  next = skip;
58  goto end;
59  }
60 
61 retry:
62  if (pc->index) {
63  pnmctx.bytestream_start =
64  pnmctx.bytestream = pc->buffer;
65  pnmctx.bytestream_end = pc->buffer + pc->index;
66  } else {
67  pnmctx.bytestream_start =
68  pnmctx.bytestream = buf + skip;
69  pnmctx.bytestream_end = buf + buf_size - skip;
70  }
71  if (ff_pnm_decode_header(avctx, &pnmctx) < 0) {
72  if (pnmctx.bytestream < pnmctx.bytestream_end) {
73  if (pc->index) {
74  pc->index = 0;
75  pnmpc->ascii_scan = 0;
76  } else {
77  unsigned step = FFMAX(1, pnmctx.bytestream - pnmctx.bytestream_start);
78 
79  skip += step;
80  }
81  goto retry;
82  }
83  } else if (pnmctx.type < 4) {
84  const uint8_t *bs = pnmctx.bytestream;
85  const uint8_t *end = pnmctx.bytestream_end;
86  const uint8_t *sync = bs;
87 
88  if (pc->index) {
89  av_assert0(pnmpc->ascii_scan <= end - bs);
90  bs += pnmpc->ascii_scan;
91  }
92 
93  while (bs < end) {
94  int c;
95  sync = bs;
96  c = *bs++;
97  if (c == '#') {
98  uint8_t *match = memchr(bs, '\n', end-bs);
99  if (match)
100  bs = match + 1;
101  else
102  break;
103  } else if (c == 'P') {
104  next = bs - pnmctx.bytestream_start + skip - 1;
105  pnmpc->ascii_scan = 0;
106  break;
107  }
108  }
109  if (next == END_NOT_FOUND)
110  pnmpc->ascii_scan = sync - pnmctx.bytestream + skip;
111  } else {
112  int ret = av_image_get_buffer_size(avctx->pix_fmt, avctx->width, avctx->height, 1);
113  next = pnmctx.bytestream - pnmctx.bytestream_start + skip;
114  if (ret > 0 && pnmctx.half)
115  ret >>= 1;
116  if (ret >= 0 && next + (uint64_t)ret <= INT_MAX)
117  next += ret;
118  }
119  if (next != END_NOT_FOUND && pnmctx.bytestream_start != buf + skip)
120  next -= pc->index;
121  if (next > buf_size) {
122  pnmpc->remaining_bytes = next - buf_size;
123  next = END_NOT_FOUND;
124  }
125 end:
126  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
127  *poutbuf = NULL;
128  *poutbuf_size = 0;
129  return buf_size;
130  }
131  *poutbuf = buf;
132  *poutbuf_size = buf_size;
133  return next;
134 }
135 
139  AV_CODEC_ID_PHM },
140  .priv_data_size = sizeof(PNMParseContext),
141  .parser_parse = pnm_parse,
142  .parser_close = ff_parse_close,
143 };
AV_CODEC_ID_PBM
@ AV_CODEC_ID_PBM
Definition: codec_id.h:115
AV_CODEC_ID_PFM
@ AV_CODEC_ID_PFM
Definition: codec_id.h:303
ParseContext::overread_index
int overread_index
the index into ParseContext.buffer of the overread bytes
Definition: parser.h:36
PNMParseContext::ascii_scan
int ascii_scan
Definition: pnm_parser.c:31
step
trying all byte sequences megabyte in length and selecting the best looking sequence will yield cases to try But a word about which is also called distortion Distortion can be quantified by almost any quality measurement one chooses the sum of squared differences is used but more complex methods that consider psychovisual effects can be used as well It makes no difference in this discussion First step
Definition: rate_distortion.txt:58
ff_parse_close
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:289
AV_CODEC_ID_PPM
@ AV_CODEC_ID_PPM
Definition: codec_id.h:114
AV_CODEC_ID_PGM
@ AV_CODEC_ID_PGM
Definition: codec_id.h:116
PNMContext::bytestream_end
const uint8_t * bytestream_end
Definition: pnm.h:31
FFMAX
#define FFMAX(a, b)
Definition: macros.h:47
AV_CODEC_ID_PHM
@ AV_CODEC_ID_PHM
Definition: codec_id.h:315
ParseContext
Definition: parser.h:28
PNMContext::bytestream_start
const uint8_t * bytestream_start
Definition: pnm.h:30
ParseContext::buffer
uint8_t * buffer
Definition: parser.h:29
avassert.h
ParseContext::index
int index
Definition: parser.h:30
s
#define s(width, name)
Definition: cbs_vp9.c:198
pnm_parse
static int pnm_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: pnm_parser.c:34
PNMParseContext::pc
ParseContext pc
Definition: pnm_parser.c:29
ParseContext::overread
int overread
the number of bytes which where irreversibly read from the next frame
Definition: parser.h:35
av_assert0
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:40
NULL
#define NULL
Definition: coverity.c:32
AV_CODEC_ID_PGMYUV
@ AV_CODEC_ID_PGMYUV
Definition: codec_id.h:117
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
pnm.h
AV_CODEC_ID_PAM
@ AV_CODEC_ID_PAM
Definition: codec_id.h:118
AVCodecParser::codec_ids
int codec_ids[7]
Definition: avcodec.h:2867
PNMContext
Definition: pnm.h:28
av_image_get_buffer_size
int av_image_get_buffer_size(enum AVPixelFormat pix_fmt, int width, int height, int align)
Return the size in bytes of the amount of data required to store an image with the given parameters.
Definition: imgutils.c:466
ff_combine_frame
int ff_combine_frame(ParseContext *pc, int next, const uint8_t **buf, int *buf_size)
Combine the (truncated) bitstream to a complete frame.
Definition: parser.c:203
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
parser.h
AVCodecContext::height
int height
Definition: avcodec.h:618
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:657
AVCodecParserContext
Definition: avcodec.h:2707
ff_pnm_parser
const AVCodecParser ff_pnm_parser
Definition: pnm_parser.c:136
ret
ret
Definition: filter_design.txt:187
PNMParseContext
Definition: pnm_parser.c:28
PNMContext::type
int type
Definition: pnm.h:33
AVCodecContext
main external API structure.
Definition: avcodec.h:445
PNMContext::bytestream
const uint8_t * bytestream
Definition: pnm.h:29
ff_pnm_decode_header
int ff_pnm_decode_header(AVCodecContext *avctx, PNMContext *const s)
Definition: pnm.c:65
END_NOT_FOUND
#define END_NOT_FOUND
Definition: parser.h:40
AVCodecParser
Definition: avcodec.h:2866
AVCodecContext::width
int width
picture width / height.
Definition: avcodec.h:618
imgutils.h
PNMContext::half
int half
Definition: pnm.h:35
skip
static void BS_FUNC() skip(BSCTX *bc, unsigned int n)
Skip n bits in the buffer.
Definition: bitstream_template.h:375
PNMParseContext::remaining_bytes
int remaining_bytes
Definition: pnm_parser.c:30