# vim: sw=4:expandtab:foldmethod=marker
#
# Copyright (c) 2006, Mathieu Fenniak
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# * Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
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"""
Utility functions for PDF library.
"""
__author__ = "Mathieu Fenniak"
__author_email__ = "mfenniak@pobox.com"

def readUntilWhitespace(stream, maxchars=None):
    txt = ""
    while True:
        tok = stream.read(1)
        if tok.isspace() or not tok:
            break
        txt += tok
        if len(txt) == maxchars:
            break
    return txt

def readNonWhitespace(stream):
    tok = ' '
    while tok == '\n' or tok == '\r' or tok == ' ' or tok == '\t':
        tok = stream.read(1)
    return tok

class ConvertFunctionsToVirtualList(object):
    def __init__(self, lengthFunction, getFunction):
        self.lengthFunction = lengthFunction
        self.getFunction = getFunction

    def __len__(self):
        return self.lengthFunction()

    def __getitem__(self, index):
        if not isinstance(index, int):
            raise TypeError, "sequence indices must be integers"
        len_self = len(self)
        if index < 0:
            # support negative indexes
            index = len_self + index
        if index < 0 or index >= len_self:
            raise IndexError, "sequence index out of range"
        return self.getFunction(index)

def RC4_encrypt(key, plaintext):
    S = [i for i in range(256)]
    j = 0
    for i in range(256):
        j = (j + S[i] + ord(key[i % len(key)])) % 256
        S[i], S[j] = S[j], S[i]
    i, j = 0, 0
    retval = ""
    for x in range(len(plaintext)):
        i = (i + 1) % 256
        j = (j + S[i]) % 256
        S[i], S[j] = S[j], S[i]
        t = S[(S[i] + S[j]) % 256]
        retval += chr(ord(plaintext[x]) ^ t)
    return retval

if __name__ == "__main__":
    # test RC4
    out = RC4_encrypt("Key", "Plaintext")
    print repr(out)
    pt = RC4_encrypt("Key", out)
    print repr(pt)
