#!/usr/bin/python
#
# create-file -- create a file full of zeroes
# Copyright (C) 2009  Lars Wirzenius
#
# 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 3 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, see <http://www.gnu.org/licenses/>.


import optparse
import os


def parse_size(size):
    sizes = (
        ("k", 1000),
        ("m", 1000**2),
        ("g", 1000**3),

        ("kb", 1000),
        ("mb", 1000**2),
        ("gb", 1000**3),

        ("kib", 1024),
        ("mib", 1024**2),
        ("gib", 1024**3),
        )
    size = size.lower()
    for suffix, x in sizes:
        if size.endswith(suffix):
            amount = int(size[:-len(suffix)].strip())
            return amount * x
    return int(size.strip())


def parse_args():
    parser = optparse.OptionParser()
    
    parser.epilog = ("SIZE is a size. Default is in bytes, use suffixes "
                     "kB/MB/GB for multiples of 1000, KiB/MiB/GiB for "
                     "multiples of 1024. Only integers supported.")
    
    parser.add_option("--sparse", action="store_true",
                      help="create a sparse file")
                     
    parser.add_option("--size", metavar="SIZE", default="0",
                      help="create a file of size SIZE")

    options, filenames = parser.parse_args()
    options.size = parse_size(options.size)

    return options, filenames


def create_file(filename, options):
    fd = os.open(filename, os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0666)
    if options.sparse:
        if options.size > 0:
            os.lseek(fd, options.size - 1, os.SEEK_SET)
            os.write(fd, "\0")
    else:
        bytes = options.size
        data = "\0" * 1024**2
        while bytes >= len(data):
            os.write(fd, data)
            bytes -= len(data)
        if bytes > 0:
            os.write(fd, data[:bytes])
    os.close(fd)


def main():
    options, filenames = parse_args()
    for filename in filenames:
        create_file(filename, options)


if __name__ == "__main__":
    main()