libavcodec/png_parser.c

   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     *poutbuf = NULL;
  49
  50     if (!ppc->pc.frame_start_found) {
  51         uint64_t state64 = ppc->pc.state64;
  52         for (; i < buf_size; i++) {
  53             state64 = (state64 << 8) | buf[i];
  54             if (state64 == PNGSIG || state64 == MNGSIG) {
  55                 i++;
  56                 ppc->pc.frame_start_found = 1;
  57                 break;
  58             }
  59         }
  60         ppc->pc.state64 = state64;
  61     } else if (ppc->remaining_size) {
  62         i = FFMIN(ppc->remaining_size, buf_size);
  63         ppc->remaining_size -= i;
  64         if (ppc->remaining_size)
  65             goto flush;
  66         if (ppc->chunk_pos == -1) {
  67             next = i;
  68             goto flush;
  69         }
  70     }
  71
  72     for (; ppc->pc.frame_start_found && i < buf_size; i++) {
  73         ppc->pc.state = (ppc->pc.state << 8) | buf[i];
  74         if (ppc->chunk_pos == 3) {
  75             ppc->chunk_length = ppc->pc.state;
  76             if (ppc->chunk_length > 0x7fffffff) {
  77                 ppc->chunk_pos = ppc->pc.frame_start_found = 0;
  78                 goto flush;
  79             }
  80             ppc->chunk_length += 4;
  81         } else if (ppc->chunk_pos == 7) {
  82             if (ppc->chunk_length >= buf_size - i)
  83                 ppc->remaining_size = ppc->chunk_length - buf_size + i + 1;
  84             if (ppc->pc.state == MKBETAG('I', 'E', 'N', 'D')) {
  85                 if (ppc->remaining_size)
  86                     ppc->chunk_pos = -1;
  87                 else
  88                     next = ppc->chunk_length + i + 1;
  89                 break;
  90             } else {
  91                 ppc->chunk_pos = 0;
  92                 if (ppc->remaining_size)
  93                     break;
  94                 else
  95                     i += ppc->chunk_length;
  96                 continue;
  97             }
  98         }
  99         ppc->chunk_pos++;
 100     }
 101
 102 flush:
 103     if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0)
 104         return buf_size;
 105
 106     ppc->chunk_pos = ppc->pc.frame_start_found = 0;
 107
 108     *poutbuf      = buf;
 109     *poutbuf_size = buf_size;
 110     return next;
 111 }
 112
 113 const AVCodecParser ff_png_parser = {
 114     .codec_ids      = { AV_CODEC_ID_PNG },
 115     .priv_data_size = sizeof(PNGParseContext),
 116     .parser_parse   = png_parse,
 117     .parser_close   = ff_parse_close,
 118 };