--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/dancres/blitz/entry/Readahead.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,137 @@
+package org.dancres.blitz.entry;
+
+import org.dancres.blitz.ActiveObject;
+import org.dancres.blitz.ActiveObjectRegistry;
+import org.dancres.blitz.Logging;
+import org.dancres.blitz.mangler.MangledEntry;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.io.IOException;
+
+import EDU.oswego.cs.dl.util.concurrent.QueuedExecutor;
+
+/**
+ */
+public class Readahead implements ActiveObject {
+    private static Logger theLogger =
+        Logging.newLogger("org.dancres.blitz.entry.Readahead");
+
+    private static Readahead theReadahead = new Readahead();
+
+    private QueuedExecutor theExecutor;
+
+    private Set theActiveTemplates = new HashSet();
+
+    static Readahead get() {
+        return theReadahead;
+    }
+
+    private Readahead() {
+        ActiveObjectRegistry.add(this);
+    }
+
+    /**
+     * @return <code>true</code> if the readahead will go active
+     */
+    boolean add(MangledEntry aTemplate, int aReadahead) {
+        if ((! aTemplate.isSnapshot()) &&
+            (! aTemplate.isWildcard())) {
+            if (theLogger.isLoggable(Level.FINEST))
+                theLogger.log(Level.FINEST,
+                    "Readahead not snapshot/wildcard: " + aTemplate.getType());
+            return false;
+        }
+
+        if (aReadahead == 0) {
+            if (theLogger.isLoggable(Level.FINEST))
+                theLogger.log(Level.FINEST,
+                    "Readahead not set: " + aTemplate.getType());
+            return false;
+        }
+
+        synchronized(theActiveTemplates) {
+            if (! theActiveTemplates.contains(aTemplate)) {
+                if (theLogger.isLoggable(Level.FINEST))
+                    theLogger.log(Level.FINEST,
+                        "Readahead going active: " + aReadahead);
+                theActiveTemplates.add(aTemplate);
+
+                try {
+                    theExecutor.execute(new ReadTask(aTemplate, aReadahead));
+                } catch (InterruptedException anIE) {
+                    // Doesn't matter it's just a readahead
+                }
+
+                return true;
+            } else
+                return false;
+        }
+    }
+
+    void remove(MangledEntry aTemplate) {
+        synchronized(theActiveTemplates) {
+            theActiveTemplates.remove(aTemplate);
+        }
+    }
+
+    public void begin() {
+        theExecutor = new QueuedExecutor();
+    }
+
+    public void halt() {
+        theExecutor.shutdownNow();
+    }
+
+    static class ReadTask implements Runnable {
+        private MangledEntry theTemplate;
+        private int theReadahead;
+
+        ReadTask(MangledEntry aTemplate, int aReadahead) {
+            theTemplate = aTemplate;
+            theReadahead = aReadahead;
+        }
+
+        public void run() {
+            try {
+                String myType = theTemplate.getType();
+
+                EntryReposRecovery myRepos =
+                        EntryRepositoryFactory.get().getAdmin(myType);
+
+                // System.err.println("Attempting readahead of 10");
+
+                myRepos.find(theTemplate, new CountingVisitor(theReadahead));
+            } catch (IOException anIOE) {
+                    theLogger.log(Level.SEVERE,
+                            "Readahead failed with", anIOE);
+            } finally {
+                Readahead.get().remove(theTemplate);
+            }
+        }
+    }
+
+    static class CountingVisitor implements SearchVisitor {
+        private int theRequiredOffers;
+        private int theTotalOffers;
+
+        CountingVisitor(int aRequired) {
+            theRequiredOffers = aRequired;
+        }
+
+        public boolean isDeleter() {
+            return false;
+        }
+
+        public int offer(SearchOffer anOffer) {
+            ++theTotalOffers;
+
+            if (theTotalOffers == theRequiredOffers)
+                return STOP;
+            else
+                return TRY_AGAIN;
+        }
+    }
+}