--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.api.interop/src/com/oracle/truffle/api/interop/Message.java	Mon Jun 08 04:50:13 2015 +0200
@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2014, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.interop;
+
+import com.oracle.truffle.api.nodes.Node;
+import com.oracle.truffle.api.interop.ForeignAccess.Factory;
+
+/**
+ * Inter-operability is based on sending messages. Standard messages are defined as as constants
+ * like {@link #IS_NULL} or factory methods in this class, but one can always define their own,
+ * specialized messages.
+ */
+public abstract class Message {
+    /**
+     * Message to read a field.
+     */
+    public static final Message READ = Read.INSTANCE;
+
+    /**
+     * Converts {@link TruffleObject truffle value} to Java primitive type. Primitive types are
+     * subclasses of {@link Number}, {@link Boolean}, {@link Character} and {@link String}. Related
+     * to {@link #IS_BOXED} message.
+     */
+    public static final Message UNBOX = Unbox.INSTANCE;
+
+    /**
+     * Message to write a field.
+     */
+    public static Message WRITE = Write.INSTANCE;
+
+    /**
+     * Creates an execute message. All messages created by this method are
+     * {@link Object#equals(java.lang.Object) equal} to each other regardless of the value of
+     * <code>argumentsLength</code>.
+     *
+     * @param argumentsLength number of parameters to pass to the target
+     * @return execute message
+     */
+    public static Message createExecute(int argumentsLength) {
+        return Execute.create(false, argumentsLength);
+    }
+
+    /**
+     * Message to check for executability.
+     * <p>
+     * Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
+     * this message should yield value of {@link Boolean}.
+     */
+    public static final Message IS_EXECUTABLE = IsExecutable.INSTANCE;
+
+    /**
+     * Creates an execute message. All messages created by this method are
+     * {@link Object#equals(java.lang.Object) equal} to each other regardless of the value of
+     * <code>argumentsLength</code>. The expected behavior of this message is to perform
+     * {@link #READ} first and on the result invoke {@link #createExecute(int)}.
+     *
+     * @param argumentsLength number of parameters to pass to the target
+     * @return read & execute message
+     */
+    public static Message createInvoke(int argumentsLength) {
+        return Execute.create(true, argumentsLength);
+    }
+
+    /**
+     * Check for <code>null</code> message. The Truffle languages are suggested to have their own
+     * object representing <code>null</code> like values in their languages. For purposes of
+     * inter-operability it is essential to canonicalize such values from time to time - sending
+     * this message is a way to recognize such <code>null</code> representing values.
+     * <p>
+     * Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
+     * this message should yield value of {@link Boolean}.
+     */
+    public static final Message IS_NULL = IsNull.INSTANCE;
+
+    /**
+     * Message to check for having a size.
+     * <p>
+     * Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
+     * this message should yield value of {@link Boolean}.
+     */
+    public static final Message HAS_SIZE = HasSize.INSTANCE;
+
+    /**
+     * Getter of the size. If {@link #HAS_SIZE supported}, this message allows to obtain a size (of
+     * an array).
+     * <p>
+     * Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
+     * this message should yield value of {@link Integer}.
+     */
+    public static final Message GET_SIZE = GetSize.INSTANCE;
+
+    /**
+     * Check for value being boxed. Can you value be converted to one of the basic Java types? Many
+     * languages have a special representation for types like number, string, etc. To ensure
+     * inter-operability, these types should support unboxing - if they do, they should handle this
+     * message.
+     * <p>
+     * Calling {@link Factory#accessMessage(com.oracle.truffle.api.interop.Message) the target}
+     * created for this message should yield value of {@link Boolean}.
+     */
+    public static final Message IS_BOXED = IsBoxed.INSTANCE;
+
+    /**
+     * Compares types of two messages. Messages are encouraged to implement this method. All
+     * standard ones ({@link #IS_NULL}, {@link #READ}, etc.) do so. Messages obtained via the same
+     * {@link #createExecute(int) method} are equal, messages obtained by different methods or
+     * fields are not.
+     *
+     * @param message the object to compare to
+     * @return true, if the structure of the message is that same as of <code>this</code> one.
+     */
+    @Override
+    public abstract boolean equals(Object message);
+
+    /**
+     * When re-implementing {@link #equals(java.lang.Object)}, it is generally recommended to also
+     * implement <code>hashCode()</code>.
+     * 
+     * @return hash code
+     */
+    @Override
+    public abstract int hashCode();
+
+    /**
+     * Creates an AST node for this message. The node can be inserted into AST of your language and
+     * will handle communication with the foreign language.
+     *
+     * @return node to be inserted into your AST and passed back to
+     *         {@link ForeignAccess#execute(com.oracle.truffle.api.nodes.Node, com.oracle.truffle.api.frame.VirtualFrame, com.oracle.truffle.api.interop.TruffleObject, java.lang.Object[])}
+     *         method.
+     */
+    public final Node createNode() {
+        return new ForeignObjectAccessHeadNode(this);
+    }
+
+}