--- a/jdk/src/share/classes/java/dyn/Switcher.java Wed Mar 02 12:00:41 2011 -0800
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,130 +0,0 @@
-/*
- * Copyright (c) 2010, 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.dyn;
-
-/**
- * <p>
- * A {@code Switcher} is an object which can publish state transitions to other threads.
- * A switcher is initially in the <em>valid</em> state, but may at any time be
- * changed to the <em>invalid</em> state. Invalidation cannot be reversed.
- * <p>
- * A single switcher may be used to create any number of guarded method handle pairs.
- * Each guarded pair is wrapped in a new method handle {@code M},
- * which is permanently associated with the switcher that created it.
- * Each pair consists of a target {@code T} and a fallback {@code F}.
- * While the switcher is valid, invocations to {@code M} are delegated to {@code T}.
- * After it is invalidated, invocations are delegated to {@code F}.
- * <p>
- * Invalidation is global and immediate, as if the switcher contained a
- * volatile boolean variable consulted on every call to {@code M}.
- * The invalidation is also permanent, which means the switcher
- * can change state only once.
- * <p>
- * Here is an example of a switcher in action:
- * <blockquote><pre>
-MethodType MT_str2 = MethodType.methodType(String.class, String.class);
-MethodHandle MH_strcat = MethodHandles.lookup()
- .findVirtual(String.class, "concat", MT_str2);
-Switcher switcher = new Switcher();
-// the following steps may be repeated to re-use the same switcher:
-MethodHandle worker1 = strcat;
-MethodHandle worker2 = MethodHandles.permuteArguments(strcat, MT_str2, 1, 0);
-MethodHandle worker = switcher.guardWithTest(worker1, worker2);
-assertEquals("method", (String) worker.invokeExact("met", "hod"));
-switcher.invalidate();
-assertEquals("hodmet", (String) worker.invokeExact("met", "hod"));
- * </pre></blockquote>
- * <p>
- * <em>Implementation Note:</em>
- * A switcher behaves as if implemented on top of {@link MutableCallSite},
- * approximately as follows:
- * <blockquote><pre>
-public class Switcher {
- private static final MethodHandle
- K_true = MethodHandles.constant(boolean.class, true),
- K_false = MethodHandles.constant(boolean.class, false);
- private final MutableCallSite mcs;
- private final MethodHandle mcsInvoker;
- public Switcher() {
- this.mcs = new MutableCallSite(K_true);
- this.mcsInvoker = mcs.dynamicInvoker();
- }
- public MethodHandle guardWithTest(
- MethodHandle target, MethodHandle fallback) {
- // Note: mcsInvoker is of type boolean().
- // Target and fallback may take any arguments, but must have the same type.
- return MethodHandles.guardWithTest(this.mcsInvoker, target, fallback);
- }
- public static void invalidateAll(Switcher[] switchers) {
- List<MutableCallSite> mcss = new ArrayList<>();
- for (Switcher s : switchers) mcss.add(s.mcs);
- for (MutableCallSite mcs : mcss) mcs.setTarget(K_false);
- MutableCallSite.sync(mcss.toArray(new MutableCallSite[0]));
- }
-}
- * </pre></blockquote>
- * @author Remi Forax, JSR 292 EG
- */
-public class Switcher {
- private static final MethodHandle
- K_true = MethodHandles.constant(boolean.class, true),
- K_false = MethodHandles.constant(boolean.class, false);
-
- private final MutableCallSite mcs;
- private final MethodHandle mcsInvoker;
-
- /** Create a switcher. */
- public Switcher() {
- this.mcs = new MutableCallSite(K_true);
- this.mcsInvoker = mcs.dynamicInvoker();
- }
-
- /**
- * Return a method handle which always delegates either to the target or the fallback.
- * The method handle will delegate to the target exactly as long as the switcher is valid.
- * After that, it will permanently delegate to the fallback.
- * <p>
- * The target and fallback must be of exactly the same method type,
- * and the resulting combined method handle will also be of this type.
- * @see MethodHandles#guardWithTest
- */
- public MethodHandle guardWithTest(MethodHandle target, MethodHandle fallback) {
- if (mcs.getTarget() == K_false)
- return fallback; // already invalid
- return MethodHandles.guardWithTest(mcsInvoker, target, fallback);
- }
-
- /** Set all of the given switchers into the invalid state. */
- public static void invalidateAll(Switcher[] switchers) {
- MutableCallSite[] sites = new MutableCallSite[switchers.length];
- int fillp = 0;
- for (Switcher switcher : switchers) {
- sites[fillp++] = switcher.mcs;
- switcher.mcs.setTarget(K_false);
- }
- MutableCallSite.sync(sites);
- }
-}