Merge Standby-branch to trunk (mostly).

The Standby-branch was branched from the StandaloneZODB-1_0-branch,
which includes the BTrees-fsIndex code.  I didn't include that change
in the merge, but everything else.  Terse summary follows:

BaseStorage.py:
    Add read-only storage feature.
    Add TransactionRecord and DataRecord marker classes for iteration.
    Reformat some lines.

FileStorage.py:
    Add read-only storage feature.
    Greg Ward's ConflictError patch
    Reformat some lines.
    Add lastTransaction(), lastSerialno().
    Add bounds support to iterator().
    Use TransactionRecord and DataRecord.

Connection.py:
DemoStorage.py:
MappingStorage.py:
    Greg Ward's ConflictError patch

POSException.py:
    Greg Ward's ConflictError patch
    Add ReadOnlyError.

src/ZODB/BaseStorage.py

@@ -14,7 +14,7 @@
 """
 # Do this portably in the face of checking out with -kv
 import string
-__version__ = string.split('$Revision: 1.16 $')[-2:][0]
+__version__ = string.split('$Revision: 1.17 $')[-2:][0]
 
 import ThreadLock, bpthread
 import time, UndoLogCompatible
@@ -26,6 +26,7 @@ class BaseStorage(UndoLogCompatible.UndoLogCompatible):
     _transaction=None # Transaction that is being committed
     _serial=z64       # Transaction serial number
     _tstatus=' '      # Transaction status, used for copying data
+    _is_read_only = 0
 
     def __init__(self, name, base=None):
         
@@ -42,8 +43,10 @@ class BaseStorage(UndoLogCompatible.UndoLogCompatible):
         t=time.time()
         t=self._ts=apply(TimeStamp,(time.gmtime(t)[:5]+(t%60,)))
         self._serial=`t`
-        if base is None: self._oid='\0\0\0\0\0\0\0\0'
-        else:            self._oid=base._oid
+        if base is None:
+            self._oid='\0\0\0\0\0\0\0\0'
+        else:
+            self._oid=base._oid
 
     def abortVersion(self, src, transaction):
         if transaction is not self._transaction:
@@ -55,15 +58,24 @@ class BaseStorage(UndoLogCompatible.UndoLogCompatible):
             raise POSException.StorageTransactionError(self, transaction)
         return []
 
-    def close(self): pass
+    def close(self):
+        pass
 
-    def getName(self): return self.__name__
-    def getSize(self): return len(self)*300 # WAG!
-    def history(self, oid, version, length=1): pass
+    def getName(self):
+        return self.__name__
+    
+    def getSize(self):
+        return len(self)*300 # WAG!
+    
+    def history(self, oid, version, length=1):
+        pass
                     
-    def modifiedInVersion(self, oid): return ''
+    def modifiedInVersion(self, oid):
+        return ''
 
     def new_oid(self, last=None):
+        if self._is_read_only:
+            raise POSException.ReadOnlyError()
         if last is None:
             self._lock_acquire()
             try:
@@ -79,10 +91,17 @@ class BaseStorage(UndoLogCompatible.UndoLogCompatible):
             if d < 255: return last[:-1]+chr(d+1)+'\0'*(8-len(last))
             else:       return self.new_oid(last[:-1])
 
-    def registerDB(self, db, limit): pass # we don't care
-
-    def supportsUndo(self): return 0
-    def supportsVersions(self): return 0
+    def registerDB(self, db, limit):
+        pass # we don't care
+
+    def isReadOnly(self):
+        return self._is_read_only
+    
+    def supportsUndo(self):
+        return 0
+    
+    def supportsVersions(self):
+        return 0
         
     def tpc_abort(self, transaction):
         self._lock_acquire()
@@ -171,15 +190,22 @@ class BaseStorage(UndoLogCompatible.UndoLogCompatible):
         pass
 
     def undo(self, transaction_id):
+        if self._is_read_only:
+            raise POSException.ReadOnlyError()
         raise POSException.UndoError, 'non-undoable transaction'
 
-    def undoLog(self, first, last, filter=None): return ()
+    def undoLog(self, first, last, filter=None):
+        return ()
 
-    def versionEmpty(self, version): return 1
+    def versionEmpty(self, version):
+        return 1
 
-    def versions(self, max=None): return ()
+    def versions(self, max=None):
+        return ()
 
-    def pack(self, t, referencesf): pass
+    def pack(self, t, referencesf):
+        if self._is_read_only:
+            raise POSException.ReadOnlyError()
 
     def getSerial(self, oid):
         self._lock_acquire()
@@ -232,3 +258,9 @@ class BaseStorage(UndoLogCompatible.UndoLogCompatible):
                 
             self.tpc_vote(transaction)
             self.tpc_finish(transaction)
+
+class TransactionRecord:
+    """Abstract base class for iterator protocol"""
+
+class DataRecord:
+    """Abstract base class for iterator protocol"""

src/ZODB/Connection.py

@@ -12,11 +12,11 @@
 ##############################################################################
 """Database connection support
 
-$Id: Connection.py,v 1.61 2001/11/28 15:51:18 matt Exp $"""
-__version__='$Revision: 1.61 $'[11:-2]
+$Id: Connection.py,v 1.62 2002/01/17 17:34:33 jeremy Exp $"""
+__version__='$Revision: 1.62 $'[11:-2]
 
 from cPickleCache import PickleCache
-from POSException import ConflictError
+from POSException import ConflictError, ReadConflictError
 from ExtensionClass import Base
 import ExportImport, TmpStore
 from zLOG import LOG, ERROR, BLATHER
@@ -248,7 +248,7 @@ class Connection(ExportImport.ExportImport):
                 or
                 invalid(None)
                 ):
-                raise ConflictError, `oid`
+                raise ConflictError(object=object)
             self._invalidating.append(oid)
 
         else:
@@ -315,7 +315,7 @@ class Connection(ExportImport.ExportImport):
                     or
                     invalid(None)
                     ):
-                    raise ConflictError, `oid`
+                    raise ConflictError(object=object)
                 self._invalidating.append(oid)
                 
             klass = object.__class__
@@ -459,7 +459,7 @@ class Connection(ExportImport.ExportImport):
             if invalid(oid) or invalid(None):
                 if not hasattr(object.__class__, '_p_independent'):
                     get_transaction().register(self)
-                    raise ConflictError(`oid`, `object.__class__`)
+                    raise ReadConflictError(object=object)
                 invalid=1
             else:
                 invalid=0
@@ -484,7 +484,7 @@ class Connection(ExportImport.ExportImport):
                     except KeyError: pass
                 else:
                     get_transaction().register(self)
-                    raise ConflictError(`oid`, `object.__class__`)
+                    raise ConflictError(object=object)
 
         except ConflictError:
             raise
@@ -544,7 +544,7 @@ class Connection(ExportImport.ExportImport):
 
     def tpc_begin(self, transaction, sub=None):
         if self._invalid(None): # Some nitwit invalidated everything!
-            raise ConflictError, "transaction already invalidated"
+            raise ConflictError("transaction already invalidated")
         self._invalidating=[]
         self._creating=[]
 

src/ZODB/DemoStorage.py

@@ -78,7 +78,7 @@ method::
 and call it to monitor the storage.
 
 """
-__version__='$Revision: 1.8 $'[11:-2]
+__version__='$Revision: 1.9 $'[11:-2]
 
 import base64, time, string
 from ZODB import POSException, BaseStorage, utils
@@ -244,7 +244,8 @@ class DemoStorage(BaseStorage.BaseStorage):
                 else:
                     nv=old
 
-                if serial != oserial: raise POSException.ConflictError
+                if serial != oserial:
+                    raise POSException.ConflictError(serials=(oserial, serial))
                 
             serial=self._serial
             r=[oid, serial, old, version and (version, nv) or None, data]

src/ZODB/MappingStorage.py

@@ -86,7 +86,7 @@ method::
 and call it to minotor the storage.
 
 """
-__version__='$Revision: 1.4 $'[11:-2]
+__version__='$Revision: 1.5 $'[11:-2]
 
 import POSException, BaseStorage, string, utils
 from TimeStamp import TimeStamp
@@ -136,7 +136,8 @@ class MappingStorage(BaseStorage.BaseStorage):
             if self._index.has_key(oid):
                 old=self._index[oid]
                 oserial=old[:8]
-                if serial != oserial: raise POSException.ConflictError
+                if serial != oserial:
+                    raise POSException.ConflictError(serials=(oserial, serial))
                 
             serial=self._serial
             self._tindex.append((oid,serial+data))

src/ZODB/POSException.py

@@ -10,14 +10,14 @@
 # FOR A PARTICULAR PURPOSE
 # 
 ##############################################################################
-'''BoboPOS-defined exceptions
+"""BoboPOS-defined exceptions
 
-$Id: POSException.py,v 1.8 2001/11/28 15:51:20 matt Exp $'''
-__version__='$Revision: 1.8 $'[11:-2]
+$Id: POSException.py,v 1.9 2002/01/17 17:34:33 jeremy Exp $"""
+__version__ = '$Revision: 1.9 $'.split()[-2:][0]
 
 from string import join
-StringType=type('')
-DictType=type({})
+from types import StringType, DictType
+from ZODB import utils
 
 class POSError(Exception):
     """Persistent object system error
@@ -28,10 +28,94 @@ class TransactionError(POSError):
     """
 
 class ConflictError(TransactionError):
-    """Two transactions tried to modify the same object at once
+    """Two transactions tried to modify the same object at once.  This
+    transaction should be resubmitted.
+
+    Instance attributes:
+      oid : string
+        the OID (8-byte packed string) of the object in conflict
+      class_name : string
+        the fully-qualified name of that object's class
+      message : string
+        a human-readable explanation of the error
+      serials : (string, string)
+        a pair of 8-byte packed strings; these are the serial numbers
+        (old and new) of the object in conflict.  (Serial numbers are
+        closely related [equal?] to transaction IDs; a ConflictError may
+        be triggered by a serial number mismatch.)
+
+    The caller should pass either object or oid as a keyword argument,
+    but not both of them.  If object is passed, it should be a
+    persistent object with an _p_oid attribute.
+    """
 
-    This transaction should be resubmitted.
+    def __init__(self, message=None, object=None, oid=None, serials=None):
+        if message is None:
+            self.message = "database conflict error"
+        else:
+            self.message = message
+
+        if object is None:
+            self.oid = None
+            self.class_name = None
+        else:
+            self.oid = object._p_oid
+            klass = object.__class__
+            self.class_name = klass.__module__ + "." + klass.__name__
+
+        if oid is not None:
+            assert self.oid is None
+            self.oid = oid
+
+        self.serials = serials
+
+    def __str__(self):
+        extras = []
+        if self.oid:
+            extras.append("oid %016x" % utils.U64(self.oid))
+        if self.class_name:
+            extras.append("class %s" % self.class_name)
+        if self.serials:
+            extras.append("serial was %016x, now %016x" %
+                          tuple(map(utils.U64, self.serials)))
+        if extras:
+            return "%s (%s)" % (self.message, ", ".join(extras))
+        else:
+            return self.message
+
+    def get_oid(self):
+        return self.oid
+
+    def get_class_name(self):
+        return self.class_name
+
+    def get_old_serial(self):
+        return self.serials[0]
+
+    def get_new_serial(self):
+        return self.serials[1]
+
+    def get_serials(self):
+        return self.serials
+
+
+class ReadConflictError(ConflictError):
+    """A conflict detected at read time -- attempt to read an object
+    that has changed in another transaction (eg. another thread
+    or process).
     """
+    def __init__(self, message=None, object=None, serials=None):
+        if message is None:
+            message = "database read conflict error"
+        ConflictError.__init__(self, message=message, object=object,
+                               serials=serials)
+
+class BTreesConflictError(ConflictError):
+    """A special subclass for BTrees conflict errors, which return
+    an undocumented four-tuple."""
+    def __init__(self, *btree_args):
+        ConflictError.__init__(self, message="BTrees conflict error")
+        self.btree = btree_args
 
 class VersionError(POSError):
     """An error in handling versions occurred
@@ -84,6 +168,10 @@ class MountedStorageError(StorageError):
     """Unable to access mounted storage.
     """
 
+class ReadOnlyError(StorageError):
+    """Unable to modify objects in a read-only storage.
+    """
+
 class ExportError(POSError):
     """An export file doesn't have the right format.
     """