8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/lang/invoke/ConstantCallSite.java

@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2010, 2013, 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 java.lang.invoke;
+
+/**
+ * A {@code ConstantCallSite} is a {@link CallSite} whose target is permanent, and can never be changed.
+ * An {@code invokedynamic} instruction linked to a {@code ConstantCallSite} is permanently
+ * bound to the call site's target.
+ * @author John Rose, JSR 292 EG
+ * @since 1.7
+ */
+public class ConstantCallSite extends CallSite {
+    private final boolean isFrozen;
+
+    /**
+     * Creates a call site with a permanent target.
+     * @param target the target to be permanently associated with this call site
+     * @throws NullPointerException if the proposed target is null
+     */
+    public ConstantCallSite(MethodHandle target) {
+        super(target);
+        isFrozen = true;
+    }
+
+    /**
+     * Creates a call site with a permanent target, possibly bound to the call site itself.
+     * <p>
+     * During construction of the call site, the {@code createTargetHook} is invoked to
+     * produce the actual target, as if by a call of the form
+     * {@code (MethodHandle) createTargetHook.invoke(this)}.
+     * <p>
+     * Note that user code cannot perform such an action directly in a subclass constructor,
+     * since the target must be fixed before the {@code ConstantCallSite} constructor returns.
+     * <p>
+     * The hook is said to bind the call site to a target method handle,
+     * and a typical action would be {@code someTarget.bindTo(this)}.
+     * However, the hook is free to take any action whatever,
+     * including ignoring the call site and returning a constant target.
+     * <p>
+     * The result returned by the hook must be a method handle of exactly
+     * the same type as the call site.
+     * <p>
+     * While the hook is being called, the new {@code ConstantCallSite}
+     * object is in a partially constructed state.
+     * In this state,
+     * a call to {@code getTarget}, or any other attempt to use the target,
+     * will result in an {@code IllegalStateException}.
+     * It is legal at all times to obtain the call site's type using the {@code type} method.
+     *
+     * @param targetType the type of the method handle to be permanently associated with this call site
+     * @param createTargetHook a method handle to invoke (on the call site) to produce the call site's target
+     * @throws WrongMethodTypeException if the hook cannot be invoked on the required arguments,
+     *         or if the target returned by the hook is not of the given {@code targetType}
+     * @throws NullPointerException if the hook returns a null value
+     * @throws ClassCastException if the hook returns something other than a {@code MethodHandle}
+     * @throws Throwable anything else thrown by the hook function
+     */
+    protected ConstantCallSite(MethodType targetType, MethodHandle createTargetHook) throws Throwable {
+        super(targetType, createTargetHook);
+        isFrozen = true;
+    }
+
+    /**
+     * Returns the target method of the call site, which behaves
+     * like a {@code final} field of the {@code ConstantCallSite}.
+     * That is, the target is always the original value passed
+     * to the constructor call which created this instance.
+     *
+     * @return the immutable linkage state of this call site, a constant method handle
+     * @throws IllegalStateException if the {@code ConstantCallSite} constructor has not completed
+     */
+    @Override public final MethodHandle getTarget() {
+        if (!isFrozen)  throw new IllegalStateException();
+        return target;
+    }
+
+    /**
+     * Always throws an {@link UnsupportedOperationException}.
+     * This kind of call site cannot change its target.
+     * @param ignore a new target proposed for the call site, which is ignored
+     * @throws UnsupportedOperationException because this kind of call site cannot change its target
+     */
+    @Override public final void setTarget(MethodHandle ignore) {
+        throw new UnsupportedOperationException();
+    }
+
+    /**
+     * Returns this call site's permanent target.
+     * Since that target will never change, this is a correct implementation
+     * of {@link CallSite#dynamicInvoker CallSite.dynamicInvoker}.
+     * @return the immutable linkage state of this call site, a constant method handle
+     * @throws IllegalStateException if the {@code ConstantCallSite} constructor has not completed
+     */
+    @Override
+    public final MethodHandle dynamicInvoker() {
+        return getTarget();
+    }
+}