[minion-cvs] Speed up WritethroughCache.load function; add documenta...

[nickm@seul.org (Nick Mathewson)]

Update of /home/minion/cvsroot/src/minion/lib/mixminion
In directory moria.mit.edu:/tmp/cvs-serv16818

Modified Files:
	Filestore.py 
Log Message:
Speed up WritethroughCache.load function; add documentation

Index: Filestore.py
===================================================================
RCS file: /home/minion/cvsroot/src/minion/lib/mixminion/Filestore.py,v
retrieving revision 1.20
retrieving revision 1.21
diff -u -d -r1.20 -r1.21
--- Filestore.py	17 May 2004 05:19:07 -0000	1.20
+++ Filestore.py	27 Jul 2004 03:07:06 -0000	1.21
@@ -19,7 +19,6 @@
 import dumbdbm
 import errno
 import os
-import shelve
 import stat
 import threading
 import time
@@ -831,8 +830,17 @@
         return 1
 
 class WritethroughDict:
-    """DOCDOC"""
+    """A persistant mapping from string to pickleable object.  The entire
+       mapping is cached in memory, but all modifications are written through
+       to disk immediately.
+    """
+    ## Fields:
+    # db: A Python database object, as returned by openDB.
+    # _syncLog: A function to call to flush the database to disk, if possible.
+    # cache: A dictionary mapping strings to the objects in this mapping.
     def __init__(self, filename, purpose):
+        """Open a WritethroughDict to store a mapping in the file 'filename'.
+           Use the string 'purpose' in log and messages about this object."""
         self.db, self._syncLog = openDB(filename,purpose)
         self.cache = {}
         self.load()
@@ -860,9 +868,12 @@
         return self.cache.has_key(k)
 
     def sync(self):
+        """Flush changes in the underlying database to disk."""
         self._syncLog()
 
     def close(self):
+        """Release all resources held by this object.  Users of this class
+           should call this method before exiting if at all possible."""
         self._syncLog()
         self.db.close()
         del self.cache
@@ -879,7 +890,8 @@
         return self.cache.items()
 
     def load(self):
+        """Rescan the underlying database for this mapping."""
         keys = self.db.keys()
         self.cache = cache = {}
         for k in keys:
-            self.cache[k] = cPickle.loads(self.db[k])
+            cache[k] = cPickle.loads(self.db[k])