# Copyright 2012 GRNET S.A. All rights reserved.
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#      disclaimer.
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#   2. Redistributions in binary form must reproduce the above
#      copyright notice, this list of conditions and the following
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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import sys
import pbs
import hashlib


class FatalError(Exception):
    pass


def get_command(command):
    def find_sbin_command(command, exception):
        search_paths = ['/usr/local/sbin', '/usr/sbin', '/sbin']
        for fullpath in map(lambda x: "%s/%s" % (x, command), search_paths):
            if os.path.exists(fullpath) and os.access(fullpath, os.X_OK):
                return pbs.Command(fullpath)
        raise exception

    try:
        return pbs.__getattr__(command)
    except pbs.CommadNotFount as e:
        return find_sbin_command(command, e)


class MD5:
    def __init__(self, output):
        self.out = output

    def compute(self, filename, size):

        MB = 2 ** 20
        BLOCKSIZE = 4 * MB  # 4MB

        prog_size = ((size + MB - 1) // MB)  # in MB
        progressbar = self.out.Progress(prog_size, "Calculating md5sum", 'mb')
        md5 = hashlib.md5()
        with open(filename, "r") as src:
            left = size
            while left > 0:
                length = min(left, BLOCKSIZE)
                data = src.read(length)
                md5.update(data)
                left -= length
                progressbar.goto((size - left) // MB)

        checksum = md5.hexdigest()
        progressbar.success(checksum)

        return checksum

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