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# -*- coding: utf-8 -*-
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#
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# Copyright 2012 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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#   1. Redistributions of source code must retain the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer.
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#
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#   2. Redistributions in binary form must reproduce the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer in the documentation and/or other materials
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#      provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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"""This module provides various helper functions to be used by other parts of
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the package.
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"""
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import sh
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import hashlib
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import time
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import os
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class FatalError(Exception):
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    """Fatal Error exception of snf-image-creator"""
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    pass
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def get_command(command):
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    """Return a file system binary command"""
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    def find_sbin_command(command, exception):
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        search_paths = ['/usr/local/sbin', '/usr/sbin', '/sbin']
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        for fullpath in map(lambda x: "%s/%s" % (x, command), search_paths):
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            if os.path.exists(fullpath) and os.access(fullpath, os.X_OK):
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                return sh.Command(fullpath)
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        raise exception
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    try:
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        return sh.__getattr__(command)
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    except sh.CommandNotFound as e:
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        return find_sbin_command(command, e)
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def try_fail_repeat(command, *args):
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    """Execute a command multiple times until it succeeds"""
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    times = (0.1, 0.5, 1, 2)
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    i = iter(times)
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    while True:
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        try:
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            command(*args)
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            return
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        except sh.ErrorReturnCode:
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            try:
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                wait = i.next()
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            except StopIteration:
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                break
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            time.sleep(wait)
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    raise FatalError("Command: `%s %s' failed" % (command, " ".join(args)))
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def free_space(dirname):
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    """Compute the free space in a directory"""
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    stat = os.statvfs(dirname)
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    return stat.f_bavail * stat.f_frsize
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class MD5:
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    """Represents MD5 computations"""
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    def __init__(self, output):
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        """Create an MD5 instance"""
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        self.out = output
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    def compute(self, filename, size):
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        """Compute the MD5 checksum of a file"""
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        MB = 2 ** 20
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        BLOCKSIZE = 4 * MB  # 4MB
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        prog_size = ((size + MB - 1) // MB)  # in MB
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        progressbar = self.out.Progress(prog_size, "Calculating md5sum", 'mb')
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        md5 = hashlib.md5()
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        with open(filename, "r") as src:
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            left = size
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            while left > 0:
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                length = min(left, BLOCKSIZE)
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                data = src.read(length)
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                md5.update(data)
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                left -= length
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                progressbar.goto((size - left) // MB)
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        checksum = md5.hexdigest()
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        progressbar.success(checksum)
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        return checksum
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# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :