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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
  31. {
  32.     ParseContext pc;
  33.     uint32_t index;
  34.     uint32_t chunk_length;
  35.     uint32_t remaining_size;
  36. } PNGParseContext;
  37.  
  38. static int png_parse(AVCodecParserContext *s, AVCodecContext *avctx,
  39.                      const uint8_t **poutbuf, int *poutbuf_size,
  40.                      const uint8_t *buf, int buf_size)
  41. {
  42.     PNGParseContext *ppc = s->priv_data;
  43.     int next = END_NOT_FOUND;
  44.     int i = 0;
  45.  
  46.     s->pict_type = AV_PICTURE_TYPE_NONE;
  47.  
  48.     *poutbuf_size = 0;
  49.     if (buf_size == 0)
  50.         return 0;
  51.  
  52.     if (!ppc->pc.frame_start_found) {
  53.         uint64_t state64 = ppc->pc.state64;
  54.         for (; i < buf_size; i++) {
  55.             state64 = (state64 << 8) | buf[i];
  56.             if (state64 == PNGSIG || state64 == MNGSIG) {
  57.                 i++;
  58.                 ppc->pc.frame_start_found = 1;
  59.                 break;
  60.             }
  61.         }
  62.         ppc->pc.state64 = state64;
  63.     } else
  64.         if (ppc->remaining_size) {
  65.             i = FFMIN(ppc->remaining_size, buf_size);
  66.             ppc->remaining_size -= i;
  67.             if (ppc->remaining_size)
  68.                 goto flush;
  69.             if (ppc->index == -1) {
  70.                 next = i;
  71.                 goto flush;
  72.             }
  73.         }
  74.  
  75.     for (;ppc->pc.frame_start_found && i < buf_size; i++) {
  76.         ppc->pc.state = (ppc->pc.state<<8) | buf[i];
  77.         if (ppc->index == 3) {
  78.             ppc->chunk_length = ppc->pc.state;
  79.             if (ppc->chunk_length > 0x7fffffff) {
  80.                 ppc->index = ppc->pc.frame_start_found = 0;
  81.                 goto flush;
  82.             }
  83.             ppc->chunk_length += 4;
  84.         } else if (ppc->index == 7) {
  85.             if (ppc->chunk_length >= buf_size - i)
  86.                     ppc->remaining_size = ppc->chunk_length - buf_size + i + 1;
  87.             if (ppc->pc.state == MKBETAG('I', 'E', 'N', 'D')) {
  88.                 if (ppc->remaining_size)
  89.                     ppc->index = -1;
  90.                 else
  91.                     next = ppc->chunk_length + i + 1;
  92.                 break;
  93.             } else {
  94.                 ppc->index = 0;
  95.                 if (ppc->remaining_size)
  96.                     break;
  97.                 else
  98.                     i += ppc->chunk_length;
  99.                 continue;
  100.             }
  101.         }
  102.         ppc->index++;
  103.     }
  104. flush:
  105.     if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0)
  106.         return buf_size;
  107.  
  108.     ppc->index = ppc->pc.frame_start_found = 0;
  109.  
  110.     *poutbuf      = buf;
  111.     *poutbuf_size = buf_size;
  112.     return next;
  113. }
  114.  
  115. AVCodecParser ff_png_parser = {
  116.     .codec_ids      = { AV_CODEC_ID_PNG },
  117.     .priv_data_size = sizeof(PNGParseContext),
  118.     .parser_parse   = png_parse,
  119.     .parser_close   = ff_parse_close,
  120. };
  121.