#!/usr/bin/env python
#dxfpurgeblocks.py - program to purge unused blocks in DXF v.2000 files
#Copyright (C) 2005 Fernando Fernandez Pedraza - http://www.fpedraza.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 2
#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, write to the Free Software
#Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

import sys
import os
import string

i=0
n=0
blocks=0
blocksfound=0
block=0
nameline=0
lines=[0]*10000000
blocksdata={}
blocksindrawing={}
blocksdelete={}

import fileinput
for line in fileinput.input(sys.argv[1]):
    i=i+1
    lines[i]=line
    
    #if line contains BLOCKS flag blocks=1 
    if (string.find(line,"BLOCKS")) <> -1:
        blocks=1
        blocksfound=1
        
    if (blocks):
        #if line contains ENDSEC flag blocks=0
        if (string.find(line,"ENDSEC")) > -1:
            blocks=0
    
        if (string.find(line,"AcDbBlockBegin")) > -1:
            block=1
            inblock=1
            blockbegin=i-9
                    
        if (((string.find(line,"AcDbBlockEnd")) > -1) and inblock):
            inblock=0
            blockend=i
            handle=lines[blockbegin+3]
            name=lines[blockbegin+11]
            #ignore some special blocks
            if (string.find(name,"_Space") < 0):
                blocksdata[name]=[blockbegin,blockend]
                
    #when section 'blocks' end
    #search again the blocknames we found.
    #if they appear again we will keep them, else throw away
    if (blocksfound and blocks==0):
    
        if (string.find(line,"AcDbBlockReference") > -1):
            nameline=i+10
              
        #store found blocks
        if i==nameline:
            blocksindrawing[line]=1
     

#build list of blocks to delete
print "blocks in drawing: ", len(blocksindrawing)
for k in blocksdata:
    if (not blocksindrawing.has_key(k)):
        blocksdelete[k]=blocksdata[k]

print "blocks to purge:", len(blocksdelete)

# delete unused blocks from 'BLOCKS' section
for k in blocksdelete:
    n=n+1
    if (n%100==0): print "Deleted", n, "unused blocks"
    for j in range(blocksdelete[k][0],blocksdelete[k][1]+1):
        lines[j]=""

    
f=open("copy_of_"+sys.argv[1],"w")
for i in lines:
    if i: f.write(i)
f.close