~bzr-pqm/bzr/bzr.dev : contents of bzrlib/lru

~bzr-pqm/bzr/bzr.dev : (revision 3871.3.1)

# Copyright (C) 2006 Canonical Ltd
#
# 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""A simple least-recently-used (LRU) cache."""

from collections import deque
import gc


class LRUCache(object):
    """A class which manages a cache of entries, removing unused ones."""

    def __init__(self, max_cache=100, after_cleanup_size=None):
        self._max_cache = max_cache
        if after_cleanup_size is None:
            self._after_cleanup_size = self._max_cache
        else:
            self._after_cleanup_size = min(after_cleanup_size, self._max_cache)

        self._compact_queue_length = 4*self._max_cache

        self._cache = {}
        self._cleanup = {}
        self._queue = deque() # Track when things are accessed
        self._refcount = {} # number of entries in self._queue for each key

    def __contains__(self, key):
        return key in self._cache

    def __getitem__(self, key):
        val = self._cache[key]
        self._record_access(key)
        return val

    def __len__(self):
        return len(self._cache)

    def add(self, key, value, cleanup=None):
        """Add a new value to the cache.

        Also, if the entry is ever removed from the queue, call cleanup.
        Passing it the key and value being removed.

        :param key: The key to store it under
        :param value: The object to store
        :param cleanup: None or a function taking (key, value) to indicate
                        'value' sohuld be cleaned up.
        """
        if key in self._cache:
            self._remove(key)
        self._cache[key] = value
        self._cleanup[key] = cleanup
        self._record_access(key)

        if len(self._cache) > self._max_cache:
            # Trigger the cleanup
            self.cleanup()

    def get(self, key, default=None):
        if key in self._cache:
            return self[key]
        return default

    def keys(self):
        """Get the list of keys currently cached.

        Note that values returned here may not be available by the time you
        request them later. This is simply meant as a peak into the current
        state.

        :return: An unordered list of keys that are currently cached.
        """
        return self._cache.keys()

    def cleanup(self):
        """Clear the cache until it shrinks to the requested size.

        This does not completely wipe the cache, just makes sure it is under
        the after_cleanup_size.
        """
        # Make sure the cache is shrunk to the correct size
        while len(self._cache) > self._after_cleanup_size:
            self._remove_lru()

    def __setitem__(self, key, value):
        """Add a value to the cache, there will be no cleanup function."""
        self.add(key, value, cleanup=None)

    def _record_access(self, key):
        """Record that key was accessed."""
        self._queue.append(key)
        # Can't use setdefault because you can't += 1 the result
        self._refcount[key] = self._refcount.get(key, 0) + 1

        # If our access queue is too large, clean it up too
        if len(self._queue) > self._compact_queue_length:
            self._compact_queue()

    def _compact_queue(self):
        """Compact the queue, leaving things in sorted last appended order."""
        new_queue = deque()
        for item in self._queue:
            if self._refcount[item] == 1:
                new_queue.append(item)
            else:
                self._refcount[item] -= 1
        self._queue = new_queue
        # All entries should be of the same size. There should be one entry in
        # queue for each entry in cache, and all refcounts should == 1
        if not (len(self._queue) == len(self._cache) ==
                len(self._refcount) == sum(self._refcount.itervalues())):
            raise AssertionError()

    def _remove(self, key):
        """Remove an entry, making sure to maintain the invariants."""
        cleanup = self._cleanup.pop(key)
        val = self._cache.pop(key)
        if cleanup is not None:
            cleanup(key, val)
        return val

    def _remove_lru(self):
        """Remove one entry from the lru, and handle consequences.

        If there are no more references to the lru, then this entry should be
        removed from the cache.
        """
        key = self._queue.popleft()
        self._refcount[key] -= 1
        if not self._refcount[key]:
            del self._refcount[key]
            self._remove(key)

    def clear(self):
        """Clear out all of the cache."""
        # Clean up in LRU order
        while self._cache:
            self._remove_lru()


class LRUSizeCache(LRUCache):
    """An LRUCache that removes things based on the size of the values.

    This differs in that it doesn't care how many actual items there are,
    it just restricts the cache to be cleaned up after so much data is stored.

    The values that are added must support len(value).
    """

    def __init__(self, max_size=1024*1024, after_cleanup_size=None,
                 compute_size=None):
        """Create a new LRUSizeCache.

        :param max_size: The max number of bytes to store before we start
            clearing out entries.
        :param after_cleanup_size: After cleaning up, shrink everything to this
            size.
        :param compute_size: A function to compute the size of the values. We
            use a function here, so that you can pass 'len' if you are just
            using simple strings, or a more complex function if you are using
            something like a list of strings, or even a custom object.
            The function should take the form "compute_size(value) => integer".
            If not supplied, it defaults to 'len()'
        """
        # This approximates that texts are > 0.5k in size. It only really
        # effects when we clean up the queue, so we don't want it to be too
        # large.
        LRUCache.__init__(self, max_cache=int(max_size/512))
        self._max_size = max_size
        if after_cleanup_size is None:
            self._after_cleanup_size = self._max_size
        else:
            self._after_cleanup_size = min(after_cleanup_size, self._max_size)

        self._value_size = 0
        self._compute_size = compute_size
        if compute_size is None:
            self._compute_size = len

    def add(self, key, value, cleanup=None):
        """Add a new value to the cache.

        Also, if the entry is ever removed from the queue, call cleanup.
        Passing it the key and value being removed.

        :param key: The key to store it under
        :param value: The object to store
        :param cleanup: None or a function taking (key, value) to indicate
                        'value' sohuld be cleaned up.
        """
        if key in self._cache:
            self._remove(key)
        value_len = self._compute_size(value)
        if value_len >= self._after_cleanup_size:
            return
        self._value_size += value_len
        self._cache[key] = value
        self._cleanup[key] = cleanup
        self._record_access(key)

        if self._value_size > self._max_size:
            # Time to cleanup
            self.cleanup()

    def cleanup(self):
        """Clear the cache until it shrinks to the requested size.

        This does not completely wipe the cache, just makes sure it is under
        the after_cleanup_size.
        """
        # Make sure the cache is shrunk to the correct size
        while self._value_size > self._after_cleanup_size:
            self._remove_lru()

    def _remove(self, key):
        """Remove an entry, making sure to maintain the invariants."""
        val = LRUCache._remove(self, key)
        self._value_size -= self._compute_size(val)

2993.1.1 by Robert Collins * New module ``lru_cache`` providing a cache for use by tasks that need	1	# Copyright (C) 2006 Canonical Ltd
	2	#
	3	# This program is free software; you can redistribute it and/or modify
	4	# it under the terms of the GNU General Public License as published by
	5	# the Free Software Foundation; either version 2 of the License, or
	6	# (at your option) any later version.
	7	#
	8	# This program is distributed in the hope that it will be useful,
	9	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	11	# GNU General Public License for more details.
	12	#
	13	# You should have received a copy of the GNU General Public License
	14	# along with this program; if not, write to the Free Software
	15	# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	16
	17	"""A simple least-recently-used (LRU) cache."""
	18
	19	from collections import deque
	20	import gc
	21
	22
	23	class LRUCache(object):
	24	"""A class which manages a cache of entries, removing unused ones."""
	25
	26	def __init__(self, max_cache=100, after_cleanup_size=None):
	27	self._max_cache = max_cache
	28	if after_cleanup_size is None:
	29	self._after_cleanup_size = self._max_cache
	30	else:
	31	self._after_cleanup_size = min(after_cleanup_size, self._max_cache)
	32
	33	self._compact_queue_length = 4*self._max_cache
	34
	35	self._cache = {}
	36	self._cleanup = {}
	37	self._queue = deque() # Track when things are accessed
	38	self._refcount = {} # number of entries in self._queue for each key
	39
	40	def __contains__(self, key):
	41	return key in self._cache
	42
	43	def __getitem__(self, key):
	44	val = self._cache[key]
	45	self._record_access(key)
	46	return val
	47
	48	def __len__(self):
	49	return len(self._cache)
	50
	51	def add(self, key, value, cleanup=None):
	52	"""Add a new value to the cache.
	53
	54	Also, if the entry is ever removed from the queue, call cleanup.
	55	Passing it the key and value being removed.
	56
	57	:param key: The key to store it under
	58	:param value: The object to store
	59	:param cleanup: None or a function taking (key, value) to indicate
	60	'value' sohuld be cleaned up.
	61	"""
	62	if key in self._cache:
	63	self._remove(key)
	64	self._cache[key] = value
65	self._cleanup[key] = cleanup
66	self._record_access(key)
67
68	if len(self._cache) > self._max_cache:
69	# Trigger the cleanup
70	self.cleanup()
71
2998.2.1 by John Arbash Meinel Implement LRUCache.get() which acts like dict.get()	72	def get(self, key, default=None):
	73	if key in self._cache:
	74	return self[key]
	75	return default
	76
3763.8.10 by John Arbash Meinel Add a .keys() member to LRUCache and LRUSizeCache.	77	def keys(self):
	78	"""Get the list of keys currently cached.
	79
	80	Note that values returned here may not be available by the time you
	81	request them later. This is simply meant as a peak into the current
	82	state.
	83
	84	:return: An unordered list of keys that are currently cached.
	85	"""
	86	return self._cache.keys()
	87
2993.1.1 by Robert Collins * New module ``lru_cache`` providing a cache for use by tasks that need	88	def cleanup(self):
	89	"""Clear the cache until it shrinks to the requested size.
	90
	91	This does not completely wipe the cache, just makes sure it is under
	92	the after_cleanup_size.
	93	"""
	94	# Make sure the cache is shrunk to the correct size
	95	while len(self._cache) > self._after_cleanup_size:
	96	self._remove_lru()
	97
	98	def __setitem__(self, key, value):
	99	"""Add a value to the cache, there will be no cleanup function."""
	100	self.add(key, value, cleanup=None)
	101
	102	def _record_access(self, key):
	103	"""Record that key was accessed."""
	104	self._queue.append(key)
	105	# Can't use setdefault because you can't += 1 the result
	106	self._refcount[key] = self._refcount.get(key, 0) + 1
	107
	108	# If our access queue is too large, clean it up too
	109	if len(self._queue) > self._compact_queue_length:
	110	self._compact_queue()
	111
	112	def _compact_queue(self):
	113	"""Compact the queue, leaving things in sorted last appended order."""
	114	new_queue = deque()
	115	for item in self._queue:
	116	if self._refcount[item] == 1:
	117	new_queue.append(item)
	118	else:
	119	self._refcount[item] -= 1
	120	self._queue = new_queue
	121	# All entries should be of the same size. There should be one entry in
	122	# queue for each entry in cache, and all refcounts should == 1
3376.2.4 by Martin Pool Remove every assert statement from bzrlib!	123	if not (len(self._queue) == len(self._cache) ==
	124	len(self._refcount) == sum(self._refcount.itervalues())):
	125	raise AssertionError()
2993.1.1 by Robert Collins * New module ``lru_cache`` providing a cache for use by tasks that need	126
	127	def _remove(self, key):
	128	"""Remove an entry, making sure to maintain the invariants."""
	129	cleanup = self._cleanup.pop(key)
	130	val = self._cache.pop(key)
	131	if cleanup is not None:
	132	cleanup(key, val)
	133	return val
	134
	135	def _remove_lru(self):
	136	"""Remove one entry from the lru, and handle consequences.
	137
	138	If there are no more references to the lru, then this entry should be
	139	removed from the cache.
	140	"""
	141	key = self._queue.popleft()
	142	self._refcount[key] -= 1
	143	if not self._refcount[key]:
	144	del self._refcount[key]
	145	self._remove(key)
	146
	147	def clear(self):
	148	"""Clear out all of the cache."""
	149	# Clean up in LRU order
	150	while self._cache:
	151	self._remove_lru()
	152
	153
	154	class LRUSizeCache(LRUCache):
	155	"""An LRUCache that removes things based on the size of the values.
	156
	157	This differs in that it doesn't care how many actual items there are,
	158	it just restricts the cache to be cleaned up after so much data is stored.
	159
	160	The values that are added must support len(value).
	161	"""
	162
	163	def __init__(self, max_size=1024*1024, after_cleanup_size=None,
	164	compute_size=None):
	165	"""Create a new LRUSizeCache.
	166
	167	:param max_size: The max number of bytes to store before we start
	168	clearing out entries.
	169	:param after_cleanup_size: After cleaning up, shrink everything to this
	170	size.
	171	:param compute_size: A function to compute the size of the values. We
	172	use a function here, so that you can pass 'len' if you are just
	173	using simple strings, or a more complex function if you are using
	174	something like a list of strings, or even a custom object.
	175	The function should take the form "compute_size(value) => integer".
	176	If not supplied, it defaults to 'len()'
	177	"""
	178	# This approximates that texts are > 0.5k in size. It only really
	179	# effects when we clean up the queue, so we don't want it to be too
	180	# large.
	181	LRUCache.__init__(self, max_cache=int(max_size/512))
	182	self._max_size = max_size
	183	if after_cleanup_size is None:
	184	self._after_cleanup_size = self._max_size
	185	else:
	186	self._after_cleanup_size = min(after_cleanup_size, self._max_size)
	187
	188	self._value_size = 0
	189	self._compute_size = compute_size
190	if compute_size is None:
191	self._compute_size = len
192
193	def add(self, key, value, cleanup=None):
194	"""Add a new value to the cache.
195
196	Also, if the entry is ever removed from the queue, call cleanup.
197	Passing it the key and value being removed.
198
199	:param key: The key to store it under
200	:param value: The object to store
201	:param cleanup: None or a function taking (key, value) to indicate
202	'value' sohuld be cleaned up.
203	"""
204	if key in self._cache:
205	self._remove(key)
206	value_len = self._compute_size(value)
207	if value_len >= self._after_cleanup_size:
208	return
209	self._value_size += value_len
210	self._cache[key] = value
211	self._cleanup[key] = cleanup
212	self._record_access(key)
213
214	if self._value_size > self._max_size:
215	# Time to cleanup
216	self.cleanup()
217
218	def cleanup(self):
219	"""Clear the cache until it shrinks to the requested size.
220
221	This does not completely wipe the cache, just makes sure it is under
222	the after_cleanup_size.
223	"""
224	# Make sure the cache is shrunk to the correct size
225	while self._value_size > self._after_cleanup_size:
226	self._remove_lru()
227
228	def _remove(self, key):
229	"""Remove an entry, making sure to maintain the invariants."""
230	val = LRUCache._remove(self, key)
231	self._value_size -= self._compute_size(val)