Refactored cache from django/core/cache.py into django/core/cache package, with each backend getting a separate module. This keeps things cleaner and uses less memory, because the backend module is only loaded if it's needed.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2378 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/cache/backends/filebased.py

@@ -0,0 +1,80 @@
+"File-based cache backend"
+
+from django.core.cache.backends.simple import CacheClass as SimpleCacheClass
+import os, time, urllib
+try:
+    import cPickle as pickle
+except ImportError:
+    import pickle
+
+class CacheClass(SimpleCacheClass):
+    def __init__(self, dir, params):
+        self._dir = dir
+        if not os.path.exists(self._dir):
+            self._createdir()
+        SimpleCacheClass.__init__(self, dir, params)
+        del self._cache
+        del self._expire_info
+
+    def get(self, key, default=None):
+        fname = self._key_to_file(key)
+        try:
+            f = open(fname, 'rb')
+            exp = pickle.load(f)
+            now = time.time()
+            if exp < now:
+                f.close()
+                os.remove(fname)
+            else:
+                return pickle.load(f)
+        except (IOError, OSError, EOFError, pickle.PickleError):
+            pass
+        return default
+
+    def set(self, key, value, timeout=None):
+        fname = self._key_to_file(key)
+        if timeout is None:
+            timeout = self.default_timeout
+        try:
+            filelist = os.listdir(self._dir)
+        except (IOError, OSError):
+            self._createdir()
+            filelist = []
+        if len(filelist) > self._max_entries:
+            self._cull(filelist)
+        try:
+            f = open(fname, 'wb')
+            now = time.time()
+            pickle.dump(now + timeout, f, 2)
+            pickle.dump(value, f, 2)
+        except (IOError, OSError):
+            pass
+
+    def delete(self, key):
+        try:
+            os.remove(self._key_to_file(key))
+        except (IOError, OSError):
+            pass
+
+    def has_key(self, key):
+        return os.path.exists(self._key_to_file(key))
+
+    def _cull(self, filelist):
+        if self._cull_frequency == 0:
+            doomed = filelist
+        else:
+            doomed = [k for (i, k) in enumerate(filelist) if i % self._cull_frequency == 0]
+        for fname in doomed:
+            try:
+                os.remove(os.path.join(self._dir, fname))
+            except (IOError, OSError):
+                pass
+
+    def _createdir(self):
+        try:
+            os.makedirs(self._dir)
+        except OSError:
+            raise EnvironmentError, "Cache directory '%s' does not exist and could not be created'" % self._dir
+
+    def _key_to_file(self, key):
+        return os.path.join(self._dir, urllib.quote_plus(key))