Change DemoStorage to use BTrees.OOBTree instead of BTree.

Raise correct exceptions in abortVersion() and commitVersion().

Spread out some code that had the vertical white space removed.

Fix the versions() implementation so that it works if the optional max
argument is not passed by the caller.

Fix commitVersion() so that it works for committing from one version
to the other.  The previous version always committed to the
non-version data even if a destination version was specified.

Fix typos.

src/ZODB/DemoStorage.py

@@ -137,7 +137,7 @@ The pickle data will be None for a record for an object created in
 an aborted version.
 
 It is instructive to watch what happens to the internal data structures
-as changes are made.  Foe example, in Zope, you can create an external
+as changes are made.  For example, in Zope, you can create an external
 method::
 
   import Zope
@@ -147,14 +147,16 @@ method::
 
       return Zope.DB._storage._splat()
 
-and call it to minotor the storage.
+and call it to monitor the storage.
 
 """
-__version__='$Revision: 1.6 $'[11:-2]
+__version__='$Revision: 1.7 $'[11:-2]
 
-import base64, POSException, BTree, BaseStorage, time, string, utils
+import base64, time, string
+from ZODB import POSException, BaseStorage, utils
 from TimeStamp import TimeStamp
 from cPickle import loads
+from BTrees import OOBTree
 
 class DemoStorage(BaseStorage.BaseStorage):
 
@@ -163,7 +165,7 @@ class DemoStorage(BaseStorage.BaseStorage):
         BaseStorage.BaseStorage.__init__(self, name, base)
 
         # We use a BTree because the items are sorted!
-        self._data=BTree.BTree()
+        self._data=OOBTree.OOBTree()
         self._index={}
         self._vindex={}
         self._base=base
@@ -198,6 +200,8 @@ class DemoStorage(BaseStorage.BaseStorage):
     def abortVersion(self, src, transaction):
         if transaction is not self._transaction:
             raise POSException.StorageTransactionError(self, transaction)
+        if not src:
+            raise POSException.VersionCommitError("Invalid version")
         
         self._lock_acquire()
         try:
@@ -224,6 +228,12 @@ class DemoStorage(BaseStorage.BaseStorage):
         if transaction is not self._transaction:
             raise POSException.StorageTransactionError(self, transaction)
         
+        if not src:
+            raise POSException.VersionCommitError("Invalid source version")
+        if src == dest:
+            raise POSException.VersionCommitError(
+                "Can't commit to same version: %s" % repr(src))
+
         self._lock_acquire()
         try:
             v=self._vindex.get(src, None)
@@ -233,8 +243,14 @@ class DemoStorage(BaseStorage.BaseStorage):
             oids=[]
             for r in v.values():
                 oid, serial, pre, vdata, p = r
+                assert vdata is not None
                 oids.append(oid)
-                tindex.append([oid, serial, r, None, p])
+                if dest:
+                    new_vdata = dest, vdata[1]
+                else:
+                    new_vdata = None
+                tindex.append([oid, serial, r, new_vdata, p])
+                
 
             return oids
 
@@ -243,18 +259,23 @@ class DemoStorage(BaseStorage.BaseStorage):
     def load(self, oid, version):
         self._lock_acquire()
         try:
-            try: oid, serial, pre, vdata, p = self._index[oid]
-            except:
-                if self._base: return self._base.load(oid, '')
+            try:
+                oid, serial, pre, vdata, p = self._index[oid]
+            except KeyError:
+                if self._base:
+                    return self._base.load(oid, '')
                 raise KeyError, oid
 
             if vdata:
                 oversion, nv = vdata
                 if oversion != version:
-                    if nv: oid, serial, pre, vdata, p = nv
-                    else: raise KeyError, oid
+                    if nv:
+                        oid, serial, pre, vdata, p = nv
+                    else:
+                        raise KeyError, oid
 
-            if p is None: raise KeyError, oid
+            if p is None:
+                raise KeyError, oid
             
             return p, serial
         finally: self._lock_release()
@@ -298,14 +319,14 @@ class DemoStorage(BaseStorage.BaseStorage):
                 if serial != oserial: raise POSException.ConflictError
                 
             serial=self._serial
-            r=[oid, serial, old, version and (version,nv) or None, data]
+            r=[oid, serial, old, version and (version, nv) or None, data]
             self._tindex.append(r)
 
             s=self._tsize
             s=s+72+(data and (16+len(data)) or 4)
             if version: s=s+32+len(version)
 
-            if s > self._quota:
+            if self._quota is not None and s > self._quota:
                 raise POSException.StorageError, (
                     '''<b>Quota Exceeded</b><br>
                     The maximum quota for this demonstration storage
@@ -435,13 +456,13 @@ class DemoStorage(BaseStorage.BaseStorage):
         return not self._vindex.get(version, None)
 
     def versions(self, max=None):
-        r=[]
-        a=r.append
-        for version in self._vindex.keys()[:max]:
-            if self.versionEmpty(version): continue
-            a(version)
-            if max and len(r) >= max: return r
-
+        r = []
+        for v in self._vindex.keys():
+            if self.versionEmpty(v):
+                continue
+            r.append(v)
+            if max is not None and len(r) >= max:
+                break
         return r
 
     def _build_indexes(self, stop='\377\377\377\377\377\377\377\377'):