--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/dancres/blitz/disk/SyncFinalizer.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,80 @@
+package org.dancres.blitz.disk;
+
+import java.util.logging.Level;
+
+import com.sleepycat.je.Environment;
+import com.sleepycat.je.DatabaseException;
+import com.sleepycat.je.CheckpointConfig;
+
+import org.dancres.blitz.task.Task;
+
+/**
+   <p>We pass one of these to the WriteDaemon which calls back on it once
+   it has "forced" all write requests lodged before the call to force.  This
+   ensures we checkpoint Db having flushed the relevant updates.</p>
+
+   <p>Optionally, the SyncFinalizer can callback a user-defined
+   task to perform additional work post sync.  If this mechanism is used, the
+   thread which calls <code>waitForCompletion()</code> will not be blocked
+   because all work will be done asynchronously.  Otherwise, the calling thread
+   is blocked until completion.</p>
+ */
+class SyncFinalizer implements Task {
+    private boolean isDone = false;
+    private Runnable theCompletionTask;
+    private Environment theEnv;
+
+    SyncFinalizer(Environment anEnv, Runnable aCompletionTask) {
+        theEnv = anEnv;
+        theCompletionTask = aCompletionTask;
+    }
+
+    public void run() {
+        try {
+            theEnv.sync();
+
+            CheckpointConfig myConfig = new CheckpointConfig();
+            myConfig.setForce(true);
+            theEnv.checkpoint(myConfig);
+
+        } catch (DatabaseException aDbe) {
+            WriteDaemon.theLogger.log(Level.SEVERE,
+                                      "Warning, failed to checkpoint", aDbe);
+        }
+
+        if (theCompletionTask != null)
+            theCompletionTask.run();
+        else 
+            synchronized(this) {
+                isDone = true;
+                notify();
+            }
+    }
+
+    /**
+       Only blocks when there's no completion task.  i.e. The completion task
+       is assumed to imply that the caller requires asynchronous completion
+       and does not wish to block.
+     */
+    void waitForCompletion() {
+        // No completion task means block.
+        //
+        if (theCompletionTask == null) {
+            long myStart = System.currentTimeMillis();
+
+            synchronized(this) {
+                while (!isDone) {
+                    try {
+                        wait();
+                    } catch (InterruptedException anIE) {
+                    }
+                }
+            }
+
+            long myEnd = System.currentTimeMillis();
+            WriteDaemon.theLogger.log(Level.FINE,
+                                      "Queue blocked for: " +
+                                      (myEnd - myStart));
+        }
+    }
+}