dviextractor.c

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/*
     This file is part of libextractor.
     (C) 2002, 2003, 2004 Vidyut Samanta and Christian Grothoff

     libextractor is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 2, or (at your
     option) any later version.

     libextractor 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
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with libextractor; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
 */

#include "platform.h"
#include "extractor.h"

static EXTRACTOR_KeywordList *
addKeyword (EXTRACTOR_KeywordType type,
            char *keyword, EXTRACTOR_KeywordList * next)
{
  EXTRACTOR_KeywordList *result;

  if (keyword == NULL)
    return next;
  result = malloc (sizeof (EXTRACTOR_KeywordList));
  result->next = next;
  result->keyword = keyword;
  result->keywordType = type;
  return result;
}

typedef struct
{
  char *text;
  EXTRACTOR_KeywordType type;
} Matches;

static Matches tmap[] = {
  {"/Title (", EXTRACTOR_TITLE},
  {"/Subject (", EXTRACTOR_SUBJECT},
  {"/Author (", EXTRACTOR_AUTHOR},
  {"/Keywords (", EXTRACTOR_KEYWORDS},
  {"/Creator (", EXTRACTOR_CREATOR},
  {"/Producer (", EXTRACTOR_PRODUCER},
  {NULL, 0},
};

static struct EXTRACTOR_Keywords *
parseZZZ (const char *data,
          size_t pos, size_t len, struct EXTRACTOR_Keywords *prev)
{
  size_t slen;
  size_t end;
  int i;
  char *value;

  end = pos + len;
  slen = strlen ("ps:SDict begin [");
  if (len <= slen)
    return prev;
  if (0 != strncmp ("ps:SDict begin [ ", &data[pos], slen))
    return prev;
  pos += slen;
  while (pos < end)
    {
      i = 0;
      while (tmap[i].text != NULL)
        {
          slen = strlen (tmap[i].text);
          if (pos + slen < end)
            {
              if (0 == strncmp (&data[pos], tmap[i].text, slen))
                {
                  pos += slen;
                  slen = pos;
                  while ((slen < end) && (data[slen] != ')'))
                    slen++;
                  slen = slen - pos;
                  value = malloc (slen + 1);
                  value[slen] = '\0';
                  memcpy (value, &data[pos], slen);
                  prev = addKeyword (tmap[i].type, value, prev);
                  pos += slen + 1;
                }
            }
          i++;
        }
      pos++;
    }
  return prev;
}

static unsigned int
getIntAt (const void *data)
{
  char p[4];

  memcpy (p, data, 4);          /* ensure alignment! */
  return *(unsigned int *) &p[0];
}

static unsigned int
getShortAt (const void *data)
{
  char p[2];

  memcpy (p, data, 2);          /* ensure alignment! */
  return *(unsigned short *) &p[0];
}

struct EXTRACTOR_Keywords *
libextractor_dvi_extract (const char *filename,
                          const unsigned char *data,
                          size_t size, struct EXTRACTOR_Keywords *prev)
{
  unsigned int klen;
  char *comment;
  unsigned int pos;
  unsigned int opos;
  unsigned int len;
  unsigned int pageCount;
  char *pages;

  if (size < 40)
    return prev;
  if ((data[0] != 247) || (data[1] != 2))
    return prev;                /* cannot be dvi or unsupported version */
  klen = data[14];

  pos = size - 1;
  while ((data[pos] == 223) && (pos > 0))
    pos--;
  if ((data[pos] != 2) || (pos < 40))
    return prev;
  pos--;
  pos -= 4;
  /* assert pos at 'post_post tag' */
  if (data[pos] != 249)
    return prev;
  opos = pos;
  pos = ntohl (getIntAt (&data[opos + 1]));
  if (pos + 25 > size)
    return prev;
  /* assert pos at 'post' command */
  if (data[pos] != 248)
    return prev;
  pageCount = 0;
  opos = pos;
  pos = ntohl (getIntAt (&data[opos + 1]));
  while (1)
    {
      if (pos == (unsigned int) -1)
        break;
      if (pos + 45 > size)
        return prev;
      if (data[pos] != 139)     /* expect 'bop' */
        return prev;
      pageCount++;
      opos = pos;
      pos = ntohl (getIntAt (&data[opos + 41]));
      if (pos == (unsigned int) -1)
        break;
      if (pos >= opos)
        return prev;            /* invalid! */
    }
  /* ok, now we believe it's a dvi... */
  pages = malloc (16);
  snprintf (pages, 16, "%u", pageCount);
  comment = malloc (klen + 1);
  comment[klen] = '\0';
  memcpy (comment, &data[15], klen);
  prev = addKeyword (EXTRACTOR_MIMETYPE, strdup ("application/x-dvi"), prev);
  prev = addKeyword (EXTRACTOR_COMMENT, comment, prev);
  prev = addKeyword (EXTRACTOR_PAGE_COUNT, pages, prev);
  /* try to find PDF/ps special */
  pos = opos;
  while (pos < size - 100)
    {
      switch (data[pos])
        {
        case 139:              /* begin page 'bop', we typically have to skip that one to
                                   find the zzz's */
          pos += 45;            /* skip bop */
          break;
        case 239:              /* zzz1 */
          len = data[pos + 1];
          if (pos + 2 + len < size)
            prev = parseZZZ ((const char *) data, pos + 2, len, prev);
          pos += len + 2;
          break;
        case 240:              /* zzz2 */
          len = ntohs (getShortAt (&data[pos + 1]));
          if (pos + 3 + len < size)
            prev = parseZZZ ((const char *) data, pos + 3, len, prev);
          pos += len + 3;
          break;
        case 241:              /* zzz3, who uses that? */
          len = (ntohs (getShortAt (&data[pos + 1]))) + 65536 * data[pos + 3];
          if (pos + 4 + len < size)
            prev = parseZZZ ((const char *) data, pos + 4, len, prev);
          pos += len + 4;
          break;
        case 242:              /* zzz4, hurray! */
          len = ntohl (getIntAt (&data[pos + 1]));
          if (pos + 1 + len < size)
            prev = parseZZZ ((const char *) data, pos + 5, len, prev);
          pos += len + 5;
          break;
        default:               /* unsupported opcode, abort scan */
          return prev;
        }
    }
  return prev;
}

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