libextractor

pdf_extractor.c (5530B)

---

 /*
      This file is part of libextractor.
      Copyright (C) 2016 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 3, 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., 51 Franklin Street, Fifth Floor,
      Boston, MA 02110-1301, USA.
  */
 /**
  * @file plugins/pdf_extractor.c
  * @brief plugin to support PDF files
  * @author Christian Grothoff
  *
  * PDF libraries today are a nightmare (TM).  So instead of doing the
  * fast thing and calling some library functions to parse the PDF,
  * we execute 'pdfinfo' and parse the output. Because that's 21st
  * century plumbing: nobody writes reasonable code anymore.
  */
 #include "platform.h"
 #include <extractor.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <signal.h>
 #include <unistd.h>
 
 /**
  * Entry in the mapping from control data to LE types.
  */
 struct Matches
 {
   /**
    * Key in the Pdfian control file.
    */
   const char *text;
 
   /**
    * Corresponding type in LE.
    */
   enum EXTRACTOR_MetaType type;
 };
 
 
 /**
  * Map from pdf-control entries to LE types.
  *
  * See output of 'pdfinfo'.
  */
 static struct Matches tmap[] = {
   {"Title",        EXTRACTOR_METATYPE_TITLE},
   {"Subject",      EXTRACTOR_METATYPE_SUBJECT},
   {"Keywords",     EXTRACTOR_METATYPE_KEYWORDS},
   {"Author",       EXTRACTOR_METATYPE_AUTHOR_NAME},
   {"Creator",      EXTRACTOR_METATYPE_CREATOR},
   {"Producer",     EXTRACTOR_METATYPE_PRODUCED_BY_SOFTWARE},
   {"CreationDate", EXTRACTOR_METATYPE_CREATION_DATE},
   {"ModDate",      EXTRACTOR_METATYPE_MODIFICATION_DATE},
   {"PDF version",  EXTRACTOR_METATYPE_ENCODER_VERSION},
   {"Pages",        EXTRACTOR_METATYPE_PAGE_COUNT},
   {NULL, 0}
 };
 
 
 /**
  * Process the "stdout" file from pdfinfo.
  *
  * @param fout stdout of pdfinfo
  * @param proc function to call with meta data
  * @param proc_cls closure for @e proc
  */
 static void
 process_stdout (FILE *fout,
                 EXTRACTOR_MetaDataProcessor proc,
                 void *proc_cls)
 {
   unsigned int i;
   char line[1025];
   const char *psuffix;
   const char *colon;
 
   while (! feof (fout))
   {
     if (NULL == fgets (line, sizeof (line) - 1, fout))
       break;
     if (0 == strlen (line))
       continue;
     if ('\n' == line[strlen (line) - 1])
       line[strlen (line) - 1] = '\0';
     colon = strchr (line, (int) ':');
     if (NULL == colon)
       break;
     psuffix = colon + 1;
     while (isblank ((unsigned char) psuffix[0]))
       psuffix++;
     if (0 == strlen (psuffix))
       continue;
     for (i = 0; NULL != tmap[i].text; i++)
     {
       if (0 != strncasecmp (line,
                             tmap[i].text,
                             colon - line))
         continue;
       if (0 != proc (proc_cls,
                      "pdf",
                      tmap[i].type,
                      EXTRACTOR_METAFORMAT_UTF8,
                      "text/plain",
                      psuffix,
                      strlen (psuffix) + 1))
         return;
       break;
     }
   }
 }
 
 
 /**
  * Main entry method for the PDF extraction plugin.
  *
  * @param ec extraction context provided to the plugin
  */
 void
 EXTRACTOR_pdf_extract_method (struct EXTRACTOR_ExtractContext *ec)
 {
   uint64_t fsize;
   void *data;
   pid_t pid;
   int in[2];
   int out[2];
   FILE *fout;
   uint64_t pos;
 
   fsize = ec->get_size (ec->cls);
   if (fsize < 128)
     return;
   if (4 !=
       ec->read (ec->cls, &data, 4))
     return;
   if (0 != strncmp ("%PDF", data, 4))
     return;
   if (0 !=
       ec->seek (ec->cls, 0, SEEK_SET))
     return;
   if (0 != pipe (in))
     return;
   if (0 != pipe (out))
   {
     close (in[0]);
     close (in[1]);
     return;
   }
   pid = fork ();
   if (-1 == pid)
   {
     close (in[0]);
     close (in[1]);
     close (out[0]);
     close (out[1]);
     return;
   }
   if (0 == pid)
   {
     char *const args[] = {
       "pdfinfo",
       "-",
       NULL
     };
     /* am child, exec 'pdfinfo' */
     close (0);
     close (1);
     if ( (-1 == dup2 (in[0], 0)) ||
          (-1 == dup2 (out[1], 1)) )
       exit (1);
     close (in[0]);
     close (in[1]);
     close (out[0]);
     close (out[1]);
     execvp ("pdfinfo", args);
     exit (1);
   }
   /* am parent, send file */
   close (in[0]);
   close (out[1]);
   fout = fdopen (out[0], "r");
   if (NULL == fout)
   {
     close (in[1]);
     close (out[0]);
     kill (pid, SIGKILL);
     waitpid (pid, NULL, 0);
     return;
   }
   pos = 0;
   while (pos < fsize)
   {
     ssize_t got;
     size_t wpos;
 
     data = NULL;
     got = ec->read (ec->cls,
                     &data,
                     fsize - pos);
     if ( (-1 == got) ||
          (NULL == data) )
       break;
     wpos = 0;
     while (wpos < got)
     {
       ssize_t out;
 
       out = write (in[1], data + wpos, got - wpos);
       if (out <= 0)
         break;
       wpos += out;
     }
     if (wpos < got)
       break;
     pos += got;
   }
   close (in[1]);
   process_stdout (fout, ec->proc, ec->cls);
   fclose (fout);
   kill (pid, SIGKILL);
   waitpid (pid, NULL, 0);
 }
 
 
 /* end of pdf_extractor.c */