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# This file is part of the Frescobaldi project, http://www.frescobaldi.org/
#
# Copyright (c) 2008 - 2014 by Wilbert Berendsen
#
# 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
# 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, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
# See http://www.gnu.org/licenses/ for more information.
"""
Caches information about files, and checks the mtime upon request.
"""
import os
import weakref
class FileCache(object):
"""Caches information about files, and checks the mtime upon request.
Has __setitem__, __getitem__, __delitem__, clear etc. methods like a dict.
"""
def __init__(self):
self._cache = {}
def __getitem__(self, filename):
mtime, value = self._cache[filename]
try:
if mtime == os.path.getmtime(filename):
return value
except (IOError, OSError):
pass
del self._cache[filename]
raise KeyError
def __setitem__(self, filename, value):
try:
self._cache[filename] = (os.path.getmtime(filename), value)
except (IOError, OSError):
pass
def __delitem__(self, filename):
del self._cache[filename]
def __contains__(self, filename):
try:
self[filename]
return True
except KeyError:
return False
def filename(self, value):
"""Returns the filename of the cached value (if available)."""
for filename in self.filenames():
mtime, obj = self._cache[filename]
if obj == value:
return filename
def filenames(self):
"""Yields filenames that are still valid in the cache."""
for filename in list(self._cache):
try:
self[filename]
yield filename
except KeyError:
pass
def clear(self):
self._cache.clear()
class WeakFileCache(FileCache):
"""Caches information about files like FileCache, but with a weak reference.
This means the object is discarded if you don't keep a reference to it
elsewhere.
"""
def __getitem__(self, filename):
mtime, valueref = self._cache[filename]
value = valueref()
if value is not None:
try:
if mtime == os.path.getmtime(filename):
return value
except (IOError, OSError):
pass
del self._cache[filename]
raise KeyError
def __setitem__(self, filename, value):
valueref = weakref.ref(value)
try:
self._cache[filename] = (os.path.getmtime(filename), valueref)
except (IOError, OSError):
pass
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