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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 
49  if (!ppc->pc.frame_start_found) {
50  uint64_t state64 = ppc->pc.state64;
51  for (; i < buf_size; i++) {
52  state64 = (state64 << 8) | buf[i];
53  if (state64 == PNGSIG || state64 == MNGSIG) {
54  i++;
55  ppc->pc.frame_start_found = 1;
56  break;
57  }
58  }
59  ppc->pc.state64 = state64;
60  } else if (ppc->remaining_size) {
61  i = FFMIN(ppc->remaining_size, buf_size);
62  ppc->remaining_size -= i;
63  if (ppc->remaining_size)
64  goto flush;
65  if (ppc->chunk_pos == -1) {
66  next = i;
67  goto flush;
68  }
69  }
70 
71  for (; ppc->pc.frame_start_found && i < buf_size; i++) {
72  ppc->pc.state = (ppc->pc.state << 8) | buf[i];
73  if (ppc->chunk_pos == 3) {
74  ppc->chunk_length = ppc->pc.state;
75  if (ppc->chunk_length > 0x7fffffff) {
76  ppc->chunk_pos = ppc->pc.frame_start_found = 0;
77  goto flush;
78  }
79  ppc->chunk_length += 4;
80  } else if (ppc->chunk_pos == 7) {
81  if (ppc->chunk_length >= buf_size - i)
82  ppc->remaining_size = ppc->chunk_length - buf_size + i + 1;
83  if (ppc->pc.state == MKBETAG('I', 'E', 'N', 'D')) {
84  if (ppc->remaining_size)
85  ppc->chunk_pos = -1;
86  else
87  next = ppc->chunk_length + i + 1;
88  break;
89  } else {
90  ppc->chunk_pos = 0;
91  if (ppc->remaining_size)
92  break;
93  else
94  i += ppc->chunk_length;
95  continue;
96  }
97  }
98  ppc->chunk_pos++;
99  }
100 
101 flush:
102  if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0)
103  return buf_size;
104 
105  ppc->chunk_pos = ppc->pc.frame_start_found = 0;
106 
107  *poutbuf = buf;
108  *poutbuf_size = buf_size;
109  return next;
110 }
111 
113  .codec_ids = { AV_CODEC_ID_PNG },
114  .priv_data_size = sizeof(PNGParseContext),
115  .parser_parse = png_parse,
116  .parser_close = ff_parse_close,
117 };
const char * s
Definition: avisynth_c.h:631
static void flush(AVCodecContext *avctx)
int codec_ids[5]
Definition: avcodec.h:5108
int frame_start_found
Definition: parser.h:34
Undefined.
Definition: avutil.h:265
uint8_t
static int png_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: png_parser.c:37
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:245
#define PNGSIG
Definition: png.h:52
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:321
#define FFMIN(a, b)
Definition: common.h:96
ParseContext pc
Definition: png_parser.c:31
AVCodecParser ff_png_parser
Definition: png_parser.c:112
main external API structure.
Definition: avcodec.h:1657
void * buf
Definition: avisynth_c.h:553
uint32_t state
contains the last few bytes in MSB order
Definition: parser.h:33
uint32_t chunk_pos
position inside current chunk
Definition: png_parser.c:32
uint64_t state64
contains the last 8 bytes in MSB order
Definition: parser.h:37
#define END_NOT_FOUND
Definition: parser.h:40
uint32_t chunk_length
length of the current chunk
Definition: png_parser.c:33
#define MKBETAG(a, b, c, d)
Definition: common.h:343
uint32_t remaining_size
remaining size of the current chunk
Definition: png_parser.c:34
#define MNGSIG
Definition: png.h:53