app/django/core/cache/backends/locmem.py
author Todd Larsen <tlarsen@google.com>
Wed, 21 Jan 2009 00:27:39 +0000
changeset 858 e79e7a22326f
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Add an export() view, and implement it as text/text for Document. For every Model except Document, the public() view is displayed for any attempts to access the export() view. Currently, the permissions for export() are the same as for public(). This seems reasonable for Document, since anyone could extract the raw HTML from the page source anyway. The permissions should probably be different for other types of exports, such as vCard or iCard exports of profiles, CSV exports of lists, etc. Patch by: Todd Larsen Review by: to-be-reviewed

"Thread-safe in-memory cache backend."

import time
try:
    import cPickle as pickle
except ImportError:
    import pickle

from django.core.cache.backends.base import BaseCache
from django.utils.synch import RWLock

class CacheClass(BaseCache):
    def __init__(self, _, params):
        BaseCache.__init__(self, params)
        self._cache = {}
        self._expire_info = {}

        max_entries = params.get('max_entries', 300)
        try:
            self._max_entries = int(max_entries)
        except (ValueError, TypeError):
            self._max_entries = 300

        cull_frequency = params.get('cull_frequency', 3)
        try:
            self._cull_frequency = int(cull_frequency)
        except (ValueError, TypeError):
            self._cull_frequency = 3

        self._lock = RWLock()

    def add(self, key, value, timeout=None):
        self._lock.writer_enters()
        try:
            exp = self._expire_info.get(key)
            if exp is None or exp <= time.time():
                try:
                    self._set(key, pickle.dumps(value), timeout)
                    return True
                except pickle.PickleError:
                    pass
            return False
        finally:
            self._lock.writer_leaves()

    def get(self, key, default=None):
        self._lock.reader_enters()
        try:
            exp = self._expire_info.get(key)
            if exp is None:
                return default
            elif exp > time.time():
                try:
                    return pickle.loads(self._cache[key])
                except pickle.PickleError:
                    return default
        finally:
            self._lock.reader_leaves()
        self._lock.writer_enters()
        try:
            del self._cache[key]
            del self._expire_info[key]
            return default
        finally:
            self._lock.writer_leaves()

    def _set(self, key, value, timeout=None):
        if len(self._cache) >= self._max_entries:
            self._cull()
        if timeout is None:
            timeout = self.default_timeout
        self._cache[key] = value
        self._expire_info[key] = time.time() + timeout

    def set(self, key, value, timeout=None):
        self._lock.writer_enters()
        # Python 2.3 and 2.4 don't allow combined try-except-finally blocks.
        try:
            try:
                self._set(key, pickle.dumps(value), timeout)
            except pickle.PickleError:
                pass
        finally:
            self._lock.writer_leaves()

    def has_key(self, key):
        self._lock.reader_enters()
        try:
            exp = self._expire_info.get(key)
            if exp is None:
                return False
            elif exp > time.time():
                return True
        finally:
            self._lock.reader_leaves()

        self._lock.writer_enters()
        try:
            del self._cache[key]
            del self._expire_info[key]
            return False
        finally:
            self._lock.writer_leaves()

    def _cull(self):
        if self._cull_frequency == 0:
            self._cache.clear()
            self._expire_info.clear()
        else:
            doomed = [k for (i, k) in enumerate(self._cache) if i % self._cull_frequency == 0]
            for k in doomed:
                self._delete(k)

    def _delete(self, key):
        try:
            del self._cache[key]
        except KeyError:
            pass
        try:
            del self._expire_info[key]
        except KeyError:
            pass

    def delete(self, key):
        self._lock.writer_enters()
        try:
            self._delete(key)
        finally:
            self._lock.writer_leaves()