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# Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org)
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR
# ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""Contains a substitute for Python 2.6's os.path.relpath()."""
import os
# This function is a replacement for os.path.relpath(), which is only
# available in Python 2.6:
#
# http://docs.python.org/library/os.path.html#os.path.relpath
#
# It should behave essentially the same as os.path.relpath(), except for
# returning None on paths not contained in abs_start_path.
def relpath(path, start_path, os_path_abspath=None):
"""Return a path relative to the given start path, or None.
Returns None if the path is not contained in the directory start_path.
Args:
path: An absolute or relative path to convert to a relative path.
start_path: The path relative to which the given path should be
converted.
os_path_abspath: A replacement function for unit testing. This
function should strip trailing slashes just like
os.path.abspath(). Defaults to os.path.abspath.
"""
if os_path_abspath is None:
os_path_abspath = os.path.abspath
# Since os_path_abspath() calls os.path.normpath()--
#
# (see http://docs.python.org/library/os.path.html#os.path.abspath )
#
# it also removes trailing slashes and converts forward and backward
# slashes to the preferred slash os.sep.
start_path = os_path_abspath(start_path)
path = os_path_abspath(path)
if not path.lower().startswith(start_path.lower()):
# Then path is outside the directory given by start_path.
return None
rel_path = path[len(start_path):]
if not rel_path:
# Then the paths are the same.
pass
elif rel_path[0] == os.sep:
# It is probably sufficient to remove just the first character
# since os.path.normpath() collapses separators, but we use
# lstrip() just to be sure.
rel_path = rel_path.lstrip(os.sep)
else:
# We are in the case typified by the following example:
#
# start_path = "/tmp/foo"
# path = "/tmp/foobar"
# rel_path = "bar"
return None
return rel_path
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