#!/usr/bin/python

# Copyright (C) 2004 Dan Carpenter
# This code is released under the GNU General Public License (GPL)

import sys
import os
import md5

# get the filename
if len(sys.argv) != 2:
    print "Usage:  %s <filename>" %(sys.argv[0])
    sys.exit(1)
fname = sys.argv[1]
if not os.access(fname, os.R_OK):
    print "Error:  Cannot open %s for reading" %(fname)
    sys.exit(1)
f = file(fname)

hashes = [[]]

# hash all the 4k chunks
# empty files should still generate valid signatures.
txt = f.read(4096)
hashes[0].append(md5.md5(txt).digest())
while 1:
    txt = f.read(4096)
    if not len(txt):
        break
    hashes[0].append(md5.md5(txt).digest())


# calculate all the remaining hashes
j = 0
while len(hashes[j]) > 1:
    hashes.append([])
    i = 0
    while i < len(hashes[j]):
        tmp = hashes[j][i:i + 2]
        txt = ""
        for t in tmp:
            txt += t
        hashes[j + 1].append(md5.md5(txt).digest())
        i += 2
    j += 1


# change the final hash to hex for printing
output = ""
for byte in hashes[-1][0]:
    output += "%x" %(ord(byte))
print "%s" %(output)