dt_file_ver_cmp.py

# file_ver_cmp.py
#
# Copyright (C) 2008, 2010 Fabian Knittel <fabian.knittel@avona.com>
#
# 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, 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA.

import os
import re

def split_ver(ver):
    return ver.split('-', 1)

def split_file_ver(base, suffix, name):
    """Split off base and suffix from the file-name and return the file's
    version."""
    return name[len(base):-len(suffix)]

def cmp_maybe_int(val1, val2):
    """Compare two string values. In case they're numeric, compare the
    numeric values, otherwise do a alphanumeric compare. In case only one of
    them is numeric, the numeric value wins.
    """
    try:
        int_val1 = int(val1)
    except:
        int_val1 = None
    try:
        int_val2 = int(val2)
    except:
        int_val2 = None

    if int_val1 is not None or int_val2 is not None:
        return cmp(int_val1, int_val2)
    return cmp(val1, val2)

def cmp_dotted_ver(ver1, ver2):
    # Trivial case.
    if ver1 == ver2:
        return 0

    # Compare each component.
    vers1 = ver1.split('.')
    vers2 = ver2.split('.')
    i = 0
    while i < len(vers1) and i < len(vers2):
        if vers1[i] != vers2[i]:
            return cmp_maybe_int(vers1[i], vers2[i])
        i += 1

    # The longer version with otherwise equal components is the newer / higher
    # version.
    if len(vers1) > len(vers2):
        return 1
    else:
        return -1

def cmp_ver(ver1, ver2):
    # Trivial case.
    if ver1 == ver2:
        return 0

    front1, back1 = split_ver(ver1)
    front2, back2 = split_ver(ver2)
    # If the front version is equal, compare the appended version.
    if front1 == front2:
        return cmp_maybe_int(back1, back2)

    return cmp_dotted_ver(front1, front2)

def cmp_files(base, suffix, name1, name2):
    if name1 == name2:
        return 0
    ver1 = split_file_ver(base, suffix, name1)
    ver2 = split_file_ver(base, suffix, name2)
    return cmp_ver(ver1, ver2)

def highest_file_ver(base, suffix, files):
    highest_file = files[0]
    for file in files[1:]:
        if cmp_files(base, suffix, file, highest_file) == 1:
            highest_file = file
    return highest_file

def find_highest_file_ver(base, suffix, search_dir):
    regex = '^%s.+%s$' % (base, suffix)
    prog = re.compile(regex)
    files = filter(prog.search, os.listdir(search_dir))
    if len(files) > 0:
        return os.path.join(search_dir, highest_file_ver(base, suffix, files))
    else:
        return None

# vim:set ft=python sw=4 et: