[Assorted-commits] SF.net SVN: assorted: [228] python-commons/trunk/src/commons/files.py

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

Revision: 228
          http://assorted.svn.sourceforge.net/assorted/?rev=228&view=rev
Author:   yangzhang
Date:     2008-01-12 18:30:11 -0800 (Sat, 12 Jan 2008)

Log Message:
-----------
added disk double buffer

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

Modified: python-commons/trunk/src/commons/files.py
===================================================================
--- python-commons/trunk/src/commons/files.py	2008-01-13 02:29:58 UTC (rev 227)
+++ python-commons/trunk/src/commons/files.py	2008-01-13 02:30:11 UTC (rev 228)
@@ -11,6 +11,8 @@
 from L{invalid_filename_chars}.
 """
 
+from __future__ import with_statement
+
 import os, re, tempfile
 
 def soft_makedirs( path ):
@@ -76,3 +78,28 @@
     pattern = invalid_filename_chars_regex
     return re.sub( pattern, '_', filename )
 
+class disk_double_buffer( object ):
+    """
+    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
+        # initialize empty reader file
+        with file( self.paths[ self.r ], 'w' ): pass
+        self.reload_files()
+    def reload_files( self ):
+        self.writer = file( self.paths[ self.w ], 'w' )
+        self.reader = file( self.paths[ self.r ] )
+    def switch( self ):
+        self.r, self.w = self.w, self.r
+        self.close()
+        self.reload_files()
+    def write( self, x ):
+        self.writer.write( x )
+    def read( self, len = 8192 ):
+        return self.reader.read( len )
+    def close( self ):
+        self.reader.close()
+        self.writer.close()


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