#!/usr/bin/env python3

# prevent local imports
if __name__ == "__main__":
    __import__('sys').path.pop(0)

import io
import os
import struct
import sys
import functools as ft
import operator as op

try:
    import crc32c as crc32c_lib
except ModuleNotFoundError:
    crc32c_lib = None


# open with '-' for stdin/stdout
def openio(path, mode='r', buffering=-1):
    import os
    if path == '-':
        if 'r' in mode:
            return os.fdopen(os.dup(sys.stdin.fileno()), mode, buffering)
        else:
            return os.fdopen(os.dup(sys.stdout.fileno()), mode, buffering)
    else:
        return open(path, mode, buffering)

def crc32c(data, crc=0):
    if crc32c_lib is not None:
        return crc32c_lib.crc32c(data, crc)
    else:
        crc ^= 0xffffffff
        for b in data:
            crc ^= b
            for j in range(8):
                crc = (crc >> 1) ^ ((crc & 1) * 0x82f63b78)
        return 0xffffffff ^ crc

def popc(x):
    return bin(x).count('1')

def parity(x):
    return popc(x) & 1


def main(paths, *,
        hex=False,
        string=False):
    import builtins
    hex_, hex = hex, builtins.hex

    # interpret as sequence of hex bytes
    if hex_:
        bytes_ = [b for path in paths for b in path.split()]
        print('%01x' % parity(crc32c(bytes(int(b, 16) for b in bytes_))))

    # interpret as strings
    elif string:
        for path in paths:
            print('%01x  %s' % (parity(crc32c(path.encode('utf8'))), path))

    # default to interpreting as paths
    else:
        if not paths:
            paths = [None]

        for path in paths:
            with openio(path or '-', 'rb') as f:
                # calculate crc, crc32c preserves parity
                crc = 0
                while True:
                    block = f.read(io.DEFAULT_BUFFER_SIZE)
                    if not block:
                        break

                    crc = crc32c(block, crc)

                # print what we found
                if path is not None:
                    print('%01x  %s' % (parity(crc), path))
                else:
                    print('%01x' % parity(crc))


if __name__ == "__main__":
    import argparse
    import sys
    parser = argparse.ArgumentParser(
            description="Calculates parity.",
            allow_abbrev=False)
    parser.add_argument(
            'paths',
            nargs='*',
            help="Paths to read. Reads stdin by default.")
    parser.add_argument(
            '-x', '--hex',
            action='store_true',
            help="Interpret as a sequence of hex bytes.")
    parser.add_argument(
            '-s', '--string',
            action='store_true',
            help="Interpret as strings.")
    sys.exit(main(**{k: v
            for k, v in vars(parser.parse_intermixed_args()).items()
            if v is not None}))