#! /usr/bin/env python
# -*- coding: ISO-8859-15 -*-
#
# pkpgcounter : a generic Page Description Language parser
#
# (c) 2003, 2004, 2005, 2006, 2007 Jerome Alet <alet@librelogiciel.com>
# This program 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 of the License, or
# (at your option) any later version.
# 
# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
#
# $Id$
#

"""This modules implements a page counter for DVI documents."""

import sys
import os
import mmap
from struct import unpack

import pdlparser

class Parser(pdlparser.PDLParser) :
    """A parser for DVI documents."""
    totiffcommands = [ 'cat >%(fname)s && dvips -q -o - %(fname)s | gs -sDEVICE=tiff24nc -dPARANOIDSAFER -dNOPAUSE -dBATCH -dQUIET -r%(dpi)i -sOutputFile="%(fname)s" -' ]
    def isValid(self) :        
        """Returns True if data is DVI, else False."""
        try :
            if (ord(self.firstblock[0]) == 0xf7) and (ord(self.lastblock[-1]) == 0xdf) :
                self.logdebug("DEBUG: Input file is in the DVI format.")
                return True
            else :    
                return False
        except IndexError :          
            return False
            
    def getJobSize(self) :
        """Counts pages in a DVI document.
        
           Algorithm by Jerome Alet.
           
           The documentation used for this was :
         
           http://www.math.umd.edu/~asnowden/comp-cont/dvi.html
        """
        infileno = self.infile.fileno()
        minfile = mmap.mmap(infileno, os.fstat(infileno)[6], prot=mmap.PROT_READ, flags=mmap.MAP_SHARED)
        pagecount = 0
        pos = -1
        eofchar = chr(0xdf)
        postchar = chr(0xf8)
        try :
            while minfile[pos] == eofchar :
                pos -= 1
            idbyte = minfile[pos]    
            if idbyte != minfile[1] :
                raise IndexError, "Invalid DVI file."
            pos = unpack(">I", minfile[pos - 4:pos])[0]
            if minfile[pos] != postchar :
                raise IndexError, "Invalid DVI file."
            pagecount = unpack(">H", minfile[pos + 27: pos + 29])[0]
        except IndexError : # EOF ?
            pass
        minfile.close() # reached EOF
        return pagecount
        
if __name__ == "__main__" :    
    pdlparser.test(Parser)