lcs

#!/usr/bin/env python3

import binascii
import functools
import re
import glob
import sys
import os
from itertools import islice
import fnmatch

if len(sys.argv) != 3: 
    print ("Usage: lcs2.py [file extension without period] [number of bytes to read]")
    sys.exit()
    
def findfiles(which, where='.'):
    '''Returns list of filenames from `where` path matched by 'which'
       shell pattern. Matching is case-insensitive.'''
    rule = re.compile(fnmatch.translate(which), re.IGNORECASE)
    return [name for name in os.listdir(where) if rule.match(name)]

format=str(sys.argv[1])
#print (format)
if sys.argv[1] == "all":
    #print ("Arvg is all")
    format_use="*"
else:
    format_use="*"+format
    
bytes_to_read=int(sys.argv[2])
bytes_to_print=str(sys.argv[2])
file_list = findfiles(format_use)
file_list.sort()

match_count=0
no_match_count=0

with open(file_list[0], "rb") as f:
    start_bytes = (f.read(bytes_to_read))
    print ("\n\nFirst " + bytes_to_print + " binary bytes of " + file_list[0] + " are: " + str(start_bytes))
    S1 = str((binascii.hexlify(start_bytes)))
    S1 = S1.replace('b\'','')
    S1 = S1.replace('\'','')
    print("First " + bytes_to_print + " hexadecimal bytes of " + file_list[0] + " are: " + str(S1) + "\n")

    
with open(file_list[1], "rb") as f:
    start_bytes = (f.read(bytes_to_read))
    print ("First " + bytes_to_print + " Binary bytes of " + file_list[1] + " are: " + str(start_bytes))
    S2 = str((binascii.hexlify(start_bytes)))
    S2 = S2.replace('b\'','')
    S2 = S2.replace('\'','')
    print ("First " + bytes_to_print + " hexadecimal bytes of " + file_list[1] + " are: " + str(S2) + "\n")
    
def lcs(s1, s2):
  m = [[0] * (1 + len(s2)) for i in range(1 + len(s1))]
  longest, x_longest = 0, 0
  for x in range(1, 1 + len(s1)):
    for y in range(1, 1 + len(s2)):
      if s1[x - 1] == s2[y - 1]:
        m[x][y] = m[x - 1][y - 1] + 1
        if m[x][y] > longest:
          longest = m[x][y]
          x_longest = x
      else:
        m[x][y] = 0
  return s1[x_longest - longest: x_longest]

common_sequence = lcs(S1, S2)
a = re.search(common_sequence, S1)
if len(str(a.group())) <= 3:
    print ("ALERT - LONGEST COMMON SEQUENCE IS TOO SHORT!.")

if a:
    a2 = str(a.group()).replace('\'','')
    print("Found the common sequence " + str(a2) + " at location " + str(a.span()) + "\n")
    #print (a.group())
    to_ascii=str(a2)
    #print ("to ascii is " + to_ascii)
    #print (len(to_ascii))
    #print(binascii.unhexlify(to_ascii))
    if len(to_ascii)%2==0: 
        #print (len(to_ascii))
        ascii_version = binascii.unhexlify(to_ascii)
        ascii_version = str(ascii_version).replace('b\'','')
        ascii_version = str(ascii_version).replace('\'','')
        print ("ASCII version of common sequence is " + str(ascii_version) + "\n")
    else:
        print ("FOUND ODD NUMBER OF CHARACTERS.")
        to_ascii += '0' #ONLY FIXES RIGHT SIDE
        #print("Length is now " + str(len(to_ascii)))
        print (to_ascii)
        ascii_version = binascii.unhexlify(to_ascii)
        ascii_version = str(ascii_version).replace('b\'','')
        ascii_version = str(ascii_version).replace('\'','')
        print ("ASCII version of common sequence is " + str(ascii_version) + "\n")
    print("Checking other files in directory.\n")

for files in file_list:
    with open(files, "rb") as f:
        start_bytes = (f.read(bytes_to_read))
        S1 = str((binascii.hexlify(start_bytes)))
        S1 = S1.replace('b\'','')
        result = re.search(common_sequence, S1)
        if result:
            match_count=match_count+1
            print ("File " + files + " contains the string " + common_sequence + " at location " + str(result.span()))
        else:
            no_match_count=no_match_count+1
            print("File " + files + " DOES NOT CONTAIN THE STRING.")
            
print (str(match_count) + " files with matches.")
print (str(no_match_count) + " files without matches.")