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import os
from os.path import join, normcase, normpath, abspath, isabs, sep
from django.utils.encoding import force_unicode
# Define our own abspath function that can handle joining
# unicode paths to a current working directory that has non-ASCII
# characters in it. This isn't necessary on Windows since the
# Windows version of abspath handles this correctly. The Windows
# abspath also handles drive letters differently than the pure
# Python implementation, so it's best not to replace it.
if os.name == 'nt':
abspathu = abspath
else:
def abspathu(path):
"""
Version of os.path.abspath that uses the unicode representation
of the current working directory, thus avoiding a UnicodeDecodeError
in join when the cwd has non-ASCII characters.
"""
if not isabs(path):
path = join(os.getcwdu(), path)
return normpath(path)
def safe_join(base, *paths):
"""
Joins one or more path components to the base path component intelligently.
Returns a normalized, absolute version of the final path.
The final path must be located inside of the base path component (otherwise
a ValueError is raised).
"""
# We need to use normcase to ensure we don't false-negative on case
# insensitive operating systems (like Windows).
base = force_unicode(base)
paths = [force_unicode(p) for p in paths]
final_path = normcase(abspathu(join(base, *paths)))
base_path = normcase(abspathu(base))
base_path_len = len(base_path)
# Ensure final_path starts with base_path and that the next character after
# the final path is os.sep (or nothing, in which case final_path must be
# equal to base_path).
if not final_path.startswith(base_path) \
or final_path[base_path_len:base_path_len+1] not in ('', sep):
raise ValueError('the joined path is located outside of the base path'
' component')
return final_path
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