text: /*
   * XBM image format
   *
   * Copyright (c) 2012 Paul B Mahol
   *
   * 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/avstring.h"
  
  #include "avcodec.h"
  #include "internal.h"
  #include "mathops.h"
  
  static int convert(uint8_t x)
  {
      if (x >= 'a')
          x -= 87;
      else if (x >= 'A')
          x -= 55;
      else
          x -= '0';
      return x;
  }
  
  static int parse_str_int(const uint8_t *p, int len, const uint8_t *key)
  {
      const uint8_t *end = p + len;
  
      for(; p<end - strlen(key); p++) {
          if (!memcmp(p, key, strlen(key)))
              break;
      }
      p += strlen(key);
      if (p >= end)
          return INT_MIN;
  
      for(; p<end; p++) {
          char *eptr;
          int64_t ret = strtol(p, &eptr, 10);
          if ((const uint8_t *)eptr != p)
              return ret;
      }
      return INT_MIN;
  }
  
  static int xbm_decode_frame(AVCodecContext *avctx, void *data,
                              int *got_frame, AVPacket *avpkt)
  {
      AVFrame *p = data;
      int ret, linesize, i, j;
      int width  = 0;
      int height = 0;
      const uint8_t *end, *ptr = avpkt->data;
      const uint8_t *next;
      uint8_t *dst;
  
      avctx->pix_fmt = AV_PIX_FMT_MONOWHITE;
      end = avpkt->data + avpkt->size;
  
      width  = parse_str_int(avpkt->data, avpkt->size, "_width");
      height = parse_str_int(avpkt->data, avpkt->size, "_height");
  
      if ((ret = ff_set_dimensions(avctx, width, height)) < 0)
          return ret;
  
      if ((ret = ff_get_buffer(avctx, p, 0)) < 0)
          return ret;
  
      // goto start of image data
      next = memchr(ptr, '{', avpkt->size);
      if (!next)
          next = memchr(ptr, '(', avpkt->size);
      if (!next)
          return AVERROR_INVALIDDATA;
      ptr = next + 1;
  
      linesize = (avctx->width + 7) / 8;
      for (i = 0; i < avctx->height; i++) {
          dst = p->data[0] + i * p->linesize[0];
          for (j = 0; j < linesize; j++) {
              uint8_t val;
  
              while (ptr < end && *ptr != 'x' && *ptr != '$')
                  ptr++;
  
              ptr ++;
              if (ptr < end && av_isxdigit(*ptr)) {
                  val = convert(*ptr++);
                  if (av_isxdigit(*ptr))
                      val = (val << 4) + convert(*ptr++);
                  *dst++ = ff_reverse[val];
                  if (av_isxdigit(*ptr) && j+1 < linesize) {
                      j++;
                      val = convert(*ptr++);
                      if (av_isxdigit(*ptr))
                          val = (val << 4) + convert(*ptr++);
                      *dst++ = ff_reverse[val];
                  }
              } else {
                  av_log(avctx, AV_LOG_ERROR,
                         "Unexpected data at %.8s.\n", ptr);
                  return AVERROR_INVALIDDATA;
              }
          }
      }
  
      p->key_frame = 1;
      p->pict_type = AV_PICTURE_TYPE_I;
  
      *got_frame       = 1;
  
      return avpkt->size;
  }
  
  AVCodec ff_xbm_decoder = {
      .name         = "xbm",
      .long_name    = NULL_IF_CONFIG_SMALL("XBM (X BitMap) image"),
      .type         = AVMEDIA_TYPE_VIDEO,
      .id           = AV_CODEC_ID_XBM,
      .decode       = xbm_decode_frame,
      .capabilities = AV_CODEC_CAP_DR1,
  };
  