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 30typedef 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 37static 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 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 103flush: 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 114AVCodecParser ff_png_parser = { 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}; 120