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Useful for reading png images from a pipe.
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/* | ||
* PNG parser | ||
* Copyright (c) 2009 Peter Holik | ||
* | ||
* This file is part of Libav. | ||
* | ||
* Libav is free software; you can redistribute it and/or | ||
* modify it under the terms of the GNU Lesser General Public | ||
* License as published by the Free Software Foundation; either | ||
* version 2.1 of the License, or (at your option) any later version. | ||
* | ||
* Libav is distributed in the hope that it will be useful, | ||
* but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
* Lesser General Public License for more details. | ||
* | ||
* You should have received a copy of the GNU Lesser General Public | ||
* License along with Libav; if not, write to the Free Software | ||
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
*/ | ||
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/** | ||
* @file | ||
* PNG parser | ||
*/ | ||
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#include "libavutil/intreadwrite.h" | ||
#include "libavutil/common.h" | ||
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#include "parser.h" | ||
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#define PNG_SIGNATURE UINT64_C(0x89504e470d0a1a0a) | ||
#define MNG_SIGNATURE UINT64_C(0x8a4d4e470d0a1a0a) | ||
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typedef struct PNGParseContext { | ||
ParseContext pc; | ||
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int chunk_pos; ///< position inside current chunk | ||
int chunk_length; ///< length of the current chunk | ||
int remaining_size; ///< remaining size of the current chunk | ||
} PNGParseContext; | ||
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static int png_parse(AVCodecParserContext *s, AVCodecContext *avctx, | ||
const uint8_t **poutbuf, int *poutbuf_size, | ||
const uint8_t *buf, int buf_size) | ||
{ | ||
PNGParseContext *ppc = s->priv_data; | ||
int next = END_NOT_FOUND; | ||
int i = 0; | ||
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*poutbuf_size = 0; | ||
if (buf_size == 0) | ||
return 0; | ||
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if (!ppc->pc.frame_start_found) { | ||
uint64_t state64 = ppc->pc.state64; | ||
for (; i < buf_size; i++) { | ||
state64 = (state64 << 8) | buf[i]; | ||
if (state64 == PNG_SIGNATURE || | ||
state64 == MNG_SIGNATURE) { | ||
i++; | ||
ppc->pc.frame_start_found = 1; | ||
break; | ||
} | ||
} | ||
ppc->pc.state64 = state64; | ||
} else if (ppc->remaining_size) { | ||
i = FFMIN(ppc->remaining_size, buf_size); | ||
ppc->remaining_size -= i; | ||
if (ppc->remaining_size) | ||
goto flush; | ||
if (ppc->chunk_pos == -1) { | ||
next = i; | ||
goto flush; | ||
} | ||
} | ||
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for (; ppc->pc.frame_start_found && i < buf_size; i++) { | ||
ppc->pc.state = (ppc->pc.state << 8) | buf[i]; | ||
if (ppc->chunk_pos == 3) { | ||
ppc->chunk_length = AV_RL32(&ppc->pc.state); | ||
if (ppc->chunk_length > 0x7fffffff) { | ||
ppc->chunk_pos = ppc->pc.frame_start_found = 0; | ||
goto flush; | ||
} | ||
ppc->chunk_length += 4; | ||
} else if (ppc->chunk_pos == 7) { | ||
if (ppc->chunk_length >= buf_size - i) | ||
ppc->remaining_size = ppc->chunk_length - buf_size + i + 1; | ||
if (AV_RB32(&ppc->pc.state) == MKTAG('I', 'E', 'N', 'D')) { | ||
if (ppc->remaining_size) | ||
ppc->chunk_pos = -1; | ||
else | ||
next = ppc->chunk_length + i + 1; | ||
break; | ||
} else { | ||
ppc->chunk_pos = 0; | ||
if (ppc->remaining_size) | ||
break; | ||
else | ||
i += ppc->chunk_length; | ||
continue; | ||
} | ||
} | ||
ppc->chunk_pos++; | ||
} | ||
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flush: | ||
if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0) | ||
return buf_size; | ||
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ppc->chunk_pos = ppc->pc.frame_start_found = 0; | ||
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*poutbuf = buf; | ||
*poutbuf_size = buf_size; | ||
return next; | ||
} | ||
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AVCodecParser ff_png_parser = { | ||
.codec_ids = { AV_CODEC_ID_PNG }, | ||
.priv_data_size = sizeof(PNGParseContext), | ||
.parser_parse = png_parse, | ||
.parser_close = ff_parse_close, | ||
}; |
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