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png_parser.c
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1 /*
2  * PNG parser
3  * Copyright (c) 2009 Peter Holik
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  * PNG parser
25  */
26 
27 #include "parser.h"
28 #include "png.h"
29 
30 typedef struct PNGParseContext {
32  uint32_t chunk_pos; ///< position inside current chunk
33  uint32_t chunk_length; ///< length of the current chunk
34  uint32_t remaining_size; ///< remaining size of the current chunk
36 
38  const uint8_t **poutbuf, int *poutbuf_size,
39  const uint8_t *buf, int buf_size)
40 {
41  PNGParseContext *ppc = s->priv_data;
42  int next = END_NOT_FOUND;
43  int i = 0;
44 
46 
47  *poutbuf_size = 0;
48  if (buf_size == 0)
49  return 0;
50 
51  if (!ppc->pc.frame_start_found) {
52  uint64_t state64 = ppc->pc.state64;
53  for (; i < buf_size; i++) {
54  state64 = (state64 << 8) | buf[i];
55  if (state64 == PNGSIG || state64 == MNGSIG) {
56  i++;
57  ppc->pc.frame_start_found = 1;
58  break;
59  }
60  }
61  ppc->pc.state64 = state64;
62  } else if (ppc->remaining_size) {
63  i = FFMIN(ppc->remaining_size, buf_size);
64  ppc->remaining_size -= i;
65  if (ppc->remaining_size)
66  goto flush;
67  if (ppc->chunk_pos == -1) {
68  next = i;
69  goto flush;
70  }
71  }
72 
73  for (; ppc->pc.frame_start_found && i < buf_size; i++) {
74  ppc->pc.state = (ppc->pc.state << 8) | buf[i];
75  if (ppc->chunk_pos == 3) {
76  ppc->chunk_length = ppc->pc.state;
77  if (ppc->chunk_length > 0x7fffffff) {
78  ppc->chunk_pos = ppc->pc.frame_start_found = 0;
79  goto flush;
80  }
81  ppc->chunk_length += 4;
82  } else if (ppc->chunk_pos == 7) {
83  if (ppc->chunk_length >= buf_size - i)
84  ppc->remaining_size = ppc->chunk_length - buf_size + i + 1;
85  if (ppc->pc.state == MKBETAG('I', 'E', 'N', 'D')) {
86  if (ppc->remaining_size)
87  ppc->chunk_pos = -1;
88  else
89  next = ppc->chunk_length + i + 1;
90  break;
91  } else {
92  ppc->chunk_pos = 0;
93  if (ppc->remaining_size)
94  break;
95  else
96  i += ppc->chunk_length;
97  continue;
98  }
99  }
100  ppc->chunk_pos++;
101  }
102 
103 flush:
104  if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0)
105  return buf_size;
106 
107  ppc->chunk_pos = ppc->pc.frame_start_found = 0;
108 
109  *poutbuf = buf;
110  *poutbuf_size = buf_size;
111  return next;
112 }
113 
115  .codec_ids = { AV_CODEC_ID_PNG },
116  .priv_data_size = sizeof(PNGParseContext),
117  .parser_parse = png_parse,
118  .parser_close = ff_parse_close,
119 };