# Copyright (C) 2014 Bastian Kleineidam
#
# 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 Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
Cache check results.
"""
from ..decorators import synchronized
from ..lock import get_lock
# lock object
cache_lock = get_lock("results_cache_lock")
[docs]
class ResultCache:
"""
Thread-safe cache of UrlData.to_wire() results.
the cache is limited in size since we rather recheck the same URL
multiple times instead of running out of memory.
format: {cache key (string) -> result (UrlData.towire())}
"""
def __init__(self, result_cache_size):
"""Initialize result cache."""
# mapping {URL -> cached result}
self.cache = {}
self.max_size = result_cache_size
[docs]
@synchronized(cache_lock)
def get_result(self, key):
"""Return cached result or None if not found."""
return self.cache.get(key)
[docs]
@synchronized(cache_lock)
def add_result(self, key, result):
"""Add result object to cache with given key.
The request is ignored when the cache is already full or the key
is None.
"""
if len(self.cache) > self.max_size:
return
if key is not None:
self.cache[key] = result
[docs]
def has_result(self, key):
"""Non-thread-safe function for fast containment checks."""
return key in self.cache
[docs]
def has_non_empty_result(self, key):
"""Non-thread-safe function for fast containment checks."""
return self.cache.get(key)
def __len__(self):
"""Get number of cached elements. This is not thread-safe and is
likely to change before the returned value is used."""
return len(self.cache)