merge two partial files in binary mode like uncompleted torrent download.

merge_partial_files.py

#!/usr/bin/python

import sys,getopt

def str_or(s1,s2):    
        # convert strings to a list of character pair tuples
        # go through each tuple, converting them to ASCII code (ord)
        # perform or on the ASCII code
        # then convert the result back to ASCII (chr)
        # merge the resulting array of characters as a string
        return ''.join(chr(ord(a) | ord(b)) for a,b in zip(s1,s2))

filename1 = None
filename2 = None
filename_out = None
blocksize = 1024

opts,args = getopt.getopt(sys.argv[1:],'a:b:o:')
for o,a in opts:
	if o == '-a':
		filename1 = a
        if o == '-b':
                filename2 = a
        if o == '-o':
                filename_out = a
    
if not filename1 or not filename2:
        print '-a file -b file -o outfile'
        exit()

offset = 0
f1 = open(filename1, 'rb')
f2 = open(filename2, 'rb')
fout = None
if filename_out:
        fout = open(filename_out, 'wb')

while True:
	block1 = f1.read(blocksize)
        block2 = f2.read(blocksize)

        if block1 == '' and block2 == '':
                break

	if block1 != block2:
                print block1.encode('hex')
                print '-'*80
                print block2.encode('hex')
                block = str_or(block1, block2)
        else:
                block = block1
        if fout:
                fout.write(block)