--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/impl/DefaultVirtualFrame.java	Tue Dec 18 15:33:55 2012 +0100
@@ -0,0 +1,194 @@
+/*
+ * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.truffle.api.impl;
+
+import java.util.*;
+
+import com.oracle.truffle.api.*;
+import com.oracle.truffle.api.frame.*;
+
+final class DefaultVirtualFrame implements VirtualFrame {
+
+    private static final Object UNDEFINED_OBJECT = null;
+    private static final Boolean UNDEFINED_BOOLEAN = false;
+    private static final Integer UNDEFINED_INTEGER = 0;
+    private static final Float UNDEFINED_FLOAT = 0.0f;
+    private static final Long UNDEFINED_LONG = 0L;
+    private static final Double UNDEFINED_DOUBLE = 0.0d;
+
+    private final FrameDescriptor descriptor;
+    private final PackedFrame caller;
+    private final Arguments arguments;
+    private FrameVersion currentVersion;
+    protected Object[] locals;
+    protected Class[] tags;
+
+    DefaultVirtualFrame(FrameDescriptor descriptor, PackedFrame caller, Arguments arguments) {
+        this.descriptor = descriptor;
+        this.caller = caller;
+        this.arguments = arguments;
+        this.currentVersion = descriptor.getCurrentVersion();
+        this.locals = new Object[descriptor.getSize()];
+        // The tags are only needed for assertion checking, so initialize the field only when assertions are enabled
+        assert (this.tags = new Class[descriptor.getSize()]) != null;
+    }
+
+    @Override
+    public Arguments getArguments() {
+        return arguments;
+    }
+
+    @Override
+    public PackedFrame getCaller() {
+        return caller;
+    }
+
+    @Override
+    public PackedFrame pack() {
+        return new DefaultPackedFrame(this);
+    }
+
+    @Override
+    public MaterializedFrame materialize() {
+        return new DefaultMaterializedFrame(this);
+    }
+
+    @Override
+    public Object getObject(FrameSlot slot) {
+        return get(slot, Object.class, UNDEFINED_OBJECT);
+    }
+
+    @Override
+    public void setObject(FrameSlot slot, Object value) {
+        set(slot, Object.class, value);
+    }
+
+    @Override
+    public boolean getBoolean(FrameSlot slot) {
+        return (Boolean) get(slot, Float.class, UNDEFINED_BOOLEAN);
+    }
+
+    @Override
+    public void setBoolean(FrameSlot slot, boolean value) {
+        set(slot, Float.class, value);
+    }
+
+    @Override
+    public int getInt(FrameSlot slot) {
+        return (Integer) get(slot, Integer.class, UNDEFINED_INTEGER);
+    }
+
+    @Override
+    public void setInt(FrameSlot slot, int value) {
+        set(slot, Integer.class, value);
+    }
+
+    @Override
+    public long getLong(FrameSlot slot) {
+        return (Long) get(slot, Long.class, UNDEFINED_LONG);
+    }
+
+    @Override
+    public void setLong(FrameSlot slot, long value) {
+        set(slot, Long.class, value);
+    }
+
+    @Override
+    public float getFloat(FrameSlot slot) {
+        return (Float) get(slot, Float.class, UNDEFINED_FLOAT);
+    }
+
+    @Override
+    public void setFloat(FrameSlot slot, float value) {
+        set(slot, Float.class, value);
+    }
+
+    @Override
+    public double getDouble(FrameSlot slot) {
+        return (Double) get(slot, Double.class, UNDEFINED_DOUBLE);
+    }
+
+    @Override
+    public void setDouble(FrameSlot slot, double value) {
+        set(slot, Double.class, value);
+    }
+
+    private Object get(FrameSlot slot, Class< ? > accessType, Object defaultValue) {
+        Object value = locals[slot.getIndex()];
+        assert verifyGet(slot, accessType, value);
+        if (value == null) {
+            return defaultValue;
+        } else {
+            return value;
+        }
+    }
+
+    private boolean verifyGet(FrameSlot slot, Class< ? > accessType, Object value) {
+        assert descriptor.getSlots().get(slot.getIndex()) == slot;
+        Class< ? > tag = tags[slot.getIndex()];
+        if (value == null) {
+            assert tag == null || tag == Object.class;
+        } else {
+            assert tag == accessType : "Local variable " + slot + " was written with set" + tag.getSimpleName() + ", but is read with get" + accessType.getSimpleName();
+        }
+        return true;
+    }
+
+    private void set(FrameSlot slot, Class< ? > accessType, Object value) {
+        assert verifySet(slot, accessType, value);
+        locals[slot.getIndex()] = value;
+    }
+
+    private boolean verifySet(FrameSlot slot, Class< ? > accessType, Object value) {
+        assert descriptor.getSlots().get(slot.getIndex()) == slot;
+        tags[slot.getIndex()] = accessType;
+        assert accessType.isAssignableFrom(slot.getType()) : "Local variable " + slot + ": " + accessType + " is not assignable from " + slot.getType();
+        if (value == null) {
+            assert accessType == Object.class;
+        } else {
+            assert slot.getType().isAssignableFrom(value.getClass()) : "Local variable " + slot + ": " + slot.getType() + " is not assignable from " + value.getClass();
+        }
+        return true;
+    }
+
+    @Override
+    public void updateToLatestVersion() {
+        if (currentVersion.getNext() != null) {
+            doUpdateToLatestVersion();
+        }
+    }
+
+    private void doUpdateToLatestVersion() {
+        FrameVersion version = currentVersion;
+        while (version.getNext() != null) {
+            version = version.getNext();
+            if (version instanceof FrameVersion.TypeChange) {
+                ((FrameVersion.TypeChange) version).applyTransformation(this);
+            } else if (version instanceof FrameVersion.Resize) {
+                int newSize = ((FrameVersion.Resize) version).getNewSize();
+                locals = Arrays.copyOf(locals, newSize);
+            }
+        }
+        currentVersion = version;
+    }
+}