[Assorted-commits] SF.net SVN: assorted: [232] python-commons/trunk/src/commons/files.py

[<yan...@us...>]

Revision: 232
          http://assorted.svn.sourceforge.net/assorted/?rev=232&view=rev
Author:   yangzhang
Date:     2008-01-17 15:13:45 -0800 (Thu, 17 Jan 2008)

Log Message:
-----------
added persistence to disk double buffers

Modified Paths:
--------------
    python-commons/trunk/src/commons/files.py

Modified: python-commons/trunk/src/commons/files.py
===================================================================
--- python-commons/trunk/src/commons/files.py	2008-01-17 23:11:45 UTC (rev 231)
+++ python-commons/trunk/src/commons/files.py	2008-01-17 23:13:45 UTC (rev 232)
@@ -15,6 +15,8 @@
 
 import os, re, tempfile
 
+from path import path
+
 def soft_makedirs( path ):
     """
     Emulate C{mkdir -p} (doesn't complain if it already exists).
@@ -83,9 +85,14 @@
     A simple disk double-buffer. One file is for reading, the other is for
     writing, and a facility for swapping the two roles is provided.
     """
-    def __init__( self, path ):
-        self.paths = [ path + '.0', path + '.1' ]
-        self.w, self.r = 0, 1
+    def __init__( self, path_base, do_persist = True ):
+        self.paths = [ path_base + '.0', path_base + '.1' ]
+        self.do_persist = do_persist
+        self.switch_status = path( path_base + '.switched' )
+        if not do_persist or not self.switch_status.exists():
+            self.w, self.r = 0, 1 # default
+        else:
+            self.w, self.r = 1, 0
         # initialize empty reader file
         with file( self.paths[ self.r ], 'w' ): pass
         self.reload_files()
@@ -93,8 +100,11 @@
         self.writer = file( self.paths[ self.w ], 'w' )
         self.reader = file( self.paths[ self.r ] )
     def switch( self ):
+        self.close()
+        if self.do_persist:
+            if self.w == 0: self.switch_status.touch()
+            else:           self.switch_status.remove()
         self.r, self.w = self.w, self.r
-        self.close()
         self.reload_files()
     def write( self, x ):
         self.writer.write( x )


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