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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.     ParseContext pc;
  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
  35. } PNGParseContext;
  36.  
  37. static int png_parse(AVCodecParserContext *s, AVCodecContext *avctx,
  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.  
  45.     s->pict_type = AV_PICTURE_TYPE_NONE;
  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.  
  112. AVCodecParser ff_png_parser = {
  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. };
  118.