text: /*
   * PNM image parser
   * Copyright (c) 2002, 2003 Fabrice Bellard
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg 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.
   *
   * FFmpeg 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 FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "libavutil/avassert.h"
  #include "libavutil/imgutils.h"
  
  #include "parser.h" //for ParseContext
  #include "pnm.h"
  
  typedef struct PNMParseContext {
      ParseContext pc;
      int remaining_bytes;
      int ascii_scan;
  }PNMParseContext;
  
  static int pnm_parse(AVCodecParserContext *s, AVCodecContext *avctx,
                       const uint8_t **poutbuf, int *poutbuf_size,
                       const uint8_t *buf, int buf_size)
  {
      PNMParseContext *pnmpc = s->priv_data;
      ParseContext *pc = &pnmpc->pc;
      PNMContext pnmctx;
      int next = END_NOT_FOUND;
      int skip = 0;
  
      if (pc->overread > 0) {
          memmove(pc->buffer + pc->index, pc->buffer + pc->overread_index, pc->overread);
          pc->index          += pc->overread;
          pc->overread_index += pc->overread;
          pc->overread = 0;
      }
  
      if (pnmpc->remaining_bytes) {
          int inc = FFMIN(pnmpc->remaining_bytes, buf_size);
          skip += inc;
          pnmpc->remaining_bytes -= inc;
  
          if (!pnmpc->remaining_bytes)
              next = skip;
          goto end;
      }
  
  retry:
      if (pc->index) {
          pnmctx.bytestream_start =
          pnmctx.bytestream       = pc->buffer;
          pnmctx.bytestream_end   = pc->buffer + pc->index;
      } else {
          pnmctx.bytestream_start =
          pnmctx.bytestream       = (uint8_t *) buf + skip; /* casts avoid warnings */
          pnmctx.bytestream_end   = (uint8_t *) buf + buf_size - skip;
      }
      if (ff_pnm_decode_header(avctx, &pnmctx) < 0) {
          if (pnmctx.bytestream < pnmctx.bytestream_end) {
              if (pc->index) {
                  pc->index = 0;
                  pnmpc->ascii_scan = 0;
              } else {
                  unsigned step = FFMAX(1, pnmctx.bytestream - pnmctx.bytestream_start);
  
                  skip += step;
              }
              goto retry;
          }
      } else if (pnmctx.type < 4) {
                uint8_t *bs  = pnmctx.bytestream;
          const uint8_t *end = pnmctx.bytestream_end;
          uint8_t *sync      = bs;
  
          if (pc->index) {
              av_assert0(pnmpc->ascii_scan <= end - bs);
              bs += pnmpc->ascii_scan;
          }
  
          while (bs < end) {
              int c;
              sync = bs;
              c = *bs++;
              if (c == '#')  {
                  uint8_t *match = memchr(bs, '\n', end-bs);
                  if (match)
                      bs = match + 1;
                  else
                      break;
              } else if (c == 'P') {
                  next = bs - pnmctx.bytestream_start + skip - 1;
                  pnmpc->ascii_scan = 0;
                  break;
              }
          }
          if (next == END_NOT_FOUND)
              pnmpc->ascii_scan = sync - pnmctx.bytestream + skip;
      } else {
          int ret = av_image_get_buffer_size(avctx->pix_fmt, avctx->width, avctx->height, 1);
          next = pnmctx.bytestream - pnmctx.bytestream_start + skip;
          if (ret >= 0 && next + (uint64_t)ret <= INT_MAX)
              next += ret;
      }
      if (next != END_NOT_FOUND && pnmctx.bytestream_start != buf + skip)
          next -= pc->index;
      if (next > buf_size) {
          pnmpc->remaining_bytes = next - buf_size;
          next = END_NOT_FOUND;
      }
  end:
      if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
          *poutbuf      = NULL;
          *poutbuf_size = 0;
          return buf_size;
      }
      *poutbuf      = buf;
      *poutbuf_size = buf_size;
      return next;
  }
  
  AVCodecParser ff_pnm_parser = {
      .codec_ids      = { AV_CODEC_ID_PGM, AV_CODEC_ID_PGMYUV, AV_CODEC_ID_PPM,
                          AV_CODEC_ID_PBM, AV_CODEC_ID_PAM },
      .priv_data_size = sizeof(PNMParseContext),
      .parser_parse   = pnm_parse,
      .parser_close   = ff_parse_close,
  };
  