--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/dancres/blitz/oid/Allocator.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,31 @@
+package org.dancres.blitz.oid;
+
+import java.io.IOException;
+
+/**
+   <p>An Allocator generates a series of UIDImpl's each of which is
+   guarenteed to be unique within the scope of the Allocator.  Note that
+   allocated id's are not re-used so an Allocator can, potentially, become
+   exhausted.  This can be avoided by allowing the allocator sufficient
+   space to allocate from by increasing the maximum number of available
+   allocator ids.</p>
+
+   <p>Allocator's are self-recovering.  They check <code>BootContext</code>
+   for the presence of a <code>SyncBarrier</code> instance which indicates
+   the maximum number of log operations between checkpoints.  This number
+   represents the maximum number of entry writes or notify registrations which
+   could have been carried out without the appropriate Allocator instances
+   being sync'd to disk.  Thus, the allocator simply ensures that all it's
+   oid generators are incremented by the value of the SyncBarrier and sync'd
+   back to disk.  This guarentees that there will be no oid overlap and
+   means that "user code" need not be involved in the recovery process.</p>
+ */
+public interface Allocator {
+    public OID getNextId() throws IOException;
+
+    /**
+       @return the maximum number of zone id's this Allocator instance
+       is allowed to use.
+     */
+    public int getMaxZoneId();
+}