#! /usr/bin/env python

# Copyright (C) 2008-2009 by Guy Rutenberg

# This program 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 2 of the License, or
# (at your option) any later version.
#
# This program 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 this program; if not, write to the
# Free Software Foundation, Inc.,
# 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

import hashlib
import tarfile


def tarsum(input_file, hash, output_file):
    """
        input_file  - A FILE object to read the tar file from.
        hash - The name of the hash to use. Must be supported by hashlib.
        output_file - A FILE to write the computed signatures to.
        """
    tar = tarfile.open(mode="r|*", fileobj=input_file)

    chunk_size = 100 * 1024
    store_digests = {}

    for member in tar:
        if not member.isfile():
            continue
        f = tar.extractfile(member)
        h = hashlib.new(hash)
        data = f.read(chunk_size)
        while data:
            h.update(data)
            data = f.read(chunk_size)
        output_file.write("%s  %s\n" % (h.hexdigest(), member.name))


def main():
    parser = OptionParser()

    version = (
        "%prog 0.2.1\n"
        "Copyright (C) 2008-2009 Guy Rutenberg <http://www.guyrutenberg.com/contact-me>"
    )
    usage = ("%prog [options] TARFILE\n"
             "Print a checksum signature for every file in TARFILE.\n"
             "With no FILE, or when FILE is -, read standard input.")
    parser = OptionParser(usage=usage, version=version)
    parser.add_option(
        "-c",
        "--checksum",
        dest="checksum",
        type="string",
        help="use HASH as for caclculating the checksums. [default: %default]",
        metavar="HASH",
        default="md5")
    parser.add_option("-o",
                      "--output",
                      dest="output",
                      type="string",
                      help="save signatures to FILE.",
                      metavar="FILE")

    (option, args) = parser.parse_args()

    output_file = sys.stdout
    if option.output:
        output_file = open(option.output, "w")

    input_file = sys.stdin
    if len(args) == 1 and args[0] != "-":
        input_file = open(args[0], "r")

    tarsum(input_file, option.checksum, output_file)


if __name__ == "__main__":
    from optparse import OptionParser
    import sys

main()