[pypy-svn] r40265 - pypy/dist/demo

[hpk at codespeak.net]

Author: hpk
Date: Sun Mar 11 22:18:06 2007
New Revision: 40265

Added:
   pypy/dist/demo/tp-persistence.py   (contents, props changed)
Log:
adding a small orthogonal persistence example based on transparent proxies 



Added: pypy/dist/demo/tp-persistence.py
==============================================================================
--- (empty file)
+++ pypy/dist/demo/tp-persistence.py	Sun Mar 11 22:18:06 2007
@@ -0,0 +1,70 @@
+"""
+
+This small example implements a basic orthogonal persistence 
+mechanism on top of PyPy's transparent proxies. 
+
+"""
+from pypymagic import transparent_proxy, get_transparent_controller
+from types import MethodType
+
+class PersistentListController(object):
+    _changeops = ('__iadd__ __imul__ __delitem__ __setitem__ __delslice__ '
+                  '__imul__ __init__ __setslice__ '
+                  'append extend insert pop remove reverse sort').split()
+
+    def __init__(self, obj, storage): 
+        self._obj = obj 
+        self._storage = storage 
+        self.persist()
+        self.proxy = transparent_proxy(list, self.perform)
+
+    def persist(self):
+        self._storage.pickle(self._obj) 
+
+    def perform(self, operation, *args, **kwargs):
+        result = getattr(self._obj, operation)(*args, **kwargs)
+        if operation in self._changeops: 
+            # state was modified, do maximally eager checkpointing 
+            self.persist()
+        if result is self._obj:
+            # If the result is the proxied list
+            # return the proxy instead.
+            result = self.proxy
+        elif (isinstance(result, MethodType) and
+             result.im_self is self._obj):
+            # Convert methods bound to the proxied list
+            # to methods bound to the proxy.
+            # This is to have calls to the method become calls
+            # to perform.
+            result = MethodType(result.im_func, self.proxy, result.im_class)
+        return result
+
+    @classmethod
+    def load(cls, storage):
+        obj = storage.unpickle(storage)
+        return cls(obj, storage) 
+
+
+class Storage:
+    def __init__(self, path): 
+        self.path = py.path.local(path)
+
+    def pickle(self, obj): 
+        self.path.dump(obj) 
+
+    def unpickle(self, storage): 
+        return self.path.load()
+    
+if __name__ == '__main__': 
+    import py 
+    storage = Storage("/tmp/mystorage")
+            
+    somelist = [1,2,3]
+    newlist = PersistentListController(somelist, storage).proxy 
+    newlist.append(4) 
+    newlist += [5,6,7]
+    #call_some_function(newlist) # will see a regular list
+    del somelist, newlist 
+    restoredlist = PersistentListController.load(storage).proxy
+    print "restored list", restoredlist
+    print restoredlist == [1,2,3,4,5,6,7]