pattern.py

#!/usr/bin/env python

import sys
from string import ascii_uppercase, ascii_lowercase, digits

MAX_PATTERN_LENGTH = 20280


class MaxLengthException(Exception):
    pass


class WasNotFoundException(Exception):
    pass


def pattern_gen(length):
    """
    Generate a pattern of a given length up to a maximum
    of 20280 - after this the pattern would repeat
    """
    if length >= MAX_PATTERN_LENGTH:
        raise MaxLengthException(
            "ERROR: Pattern length exceeds " "maximum of {0}".format(MAX_PATTERN_LENGTH)
        )

    pattern = ""
    for upper in ascii_uppercase:
        for lower in ascii_lowercase:
            for digit in digits:
                if len(pattern) < length:
                    pattern += upper + lower + digit
                else:
                    out = pattern[:length]
                    return out


def pattern_search(search_pattern):
    """
    Search for search_pattern in pattern. Convert from hex if needed
    Looking for needle in haystack
    """
    needle = search_pattern

    try:
        if needle.startswith("0x"):
            # Strip off '0x', convert to ASCII and reverse
            needle = needle[2:]
            needle = bytearray.fromhex(needle).decode("ascii")
            needle = needle[::-1]
    except (ValueError, TypeError) as e:
        raise

    haystack = ""
    for upper in ascii_uppercase:
        for lower in ascii_lowercase:
            for digit in digits:
                haystack += upper + lower + digit
                found_at = haystack.find(needle)
                if found_at > -1:
                    return found_at

    raise WasNotFoundException(
        "Couldn`t find {0} ({1}) "
        "anywhere in the pattern.".format(search_pattern, needle)
    )


def print_help():
    print("Usage: {0} [LENGTH|PATTERN]\n".format(sys.argv[0]))
    print("Generate a pattern of length LENGTH or search for PATTERN and ")
    print("return its position in the pattern.\n")


if __name__ == "__main__":
    if len(sys.argv) < 2:
        print_help()
        sys.exit(0)

    if sys.argv[1] == "-h" or sys.argv[1] == "--help":
        print_help()
        sys.exit(0)

    if sys.argv[1].isdigit():
        try:
            pat = pattern_gen(int(sys.argv[1]))
            print(pat)
        except MaxLengthException as e:
            print(e)
    else:
        try:
            found = pattern_search(sys.argv[1])
            print(
                "Pattern {0} first occurrence at "
                "position {1} in pattern.".format(sys.argv[1], found)
            )
        except WasNotFoundException as e:
            print(e)
            sys.exit(1)
        except (ValueError, TypeError):
            print("Unable to convert hex input for searching. Invalid hex?")
            sys.exit(1)