util.py

'''
Created on May 24, 2013
@author: Jonathan Pelletier (jonathan.pelletier1@gmail.com)

This file is part of EMVZombie.

EMVZombie 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 3 of the License, or
(at your option) any later version.

EMVZombie 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 EMVZombie.  If not, see <http://www.gnu.org/licenses/>.
'''

import sys

# Miscellaneous  helper functions use throughout all modules

def die(msg):
    print msg
    sys.exit(-1)

def usign(val):
    """Returns the unsigned value of the given integer on 8 bits."""
    return (val + (1 << 8)) % (1 << 8)
    
def resp2str(val):
    """returns a human readable string from a card command response."""
    return "".join([hex(i)[2:].zfill(2) for i in val])

def str2ba(val):
    """returns a byte array from a human readable string.
    
    Example
    =======
    >>> str2ba('A0000000031010')
    '\xA0\x00\x00\x00\x03\x10\x10'
    >>> str2ba('A0000000032010')
    '\xA0\x00\x00\x00\x03\x20\x10'
    
    """
    part = partition(val, 2)
    return "".join([chr(int(i,16)) for i in part])

def partition(val, n):
    """ Returns a sequence of non overlapping lists of n items taken from val. 
    
    Example
    =======
    >>> partition('aabbccddeeff',2)
    ('aa','bb','cc','dd','ff')
    >>> partition('aaabbbcccddd',3)
    ('aaa','ccc','ddd')
    
        
    """
    # stop recursive cases
    if len(val) <= n:
        return tuple([val])
    # the partition of a list is a list made of the first n element + 
    # the partition of the remaining elements.
    else:
        r = partition(val[n:],n)
        v = [val[:n]]
        v.extend(r)
        return tuple(v)
    
def human(ite):
    """Takes an iterable of byte[] and return a list containing the hex 
    representations of these byte[]."""
    
    return [resp2str(val) for val in ite]