1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/rt/emul/compact/src/main/java/java/lang/invoke/VolatileCallSite.java	Sat Aug 09 11:11:13 2014 +0200
     1.3 @@ -0,0 +1,109 @@
     1.4 +/*
     1.5 + * Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
     1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
     1.7 + *
     1.8 + * This code is free software; you can redistribute it and/or modify it
     1.9 + * under the terms of the GNU General Public License version 2 only, as
    1.10 + * published by the Free Software Foundation.  Oracle designates this
    1.11 + * particular file as subject to the "Classpath" exception as provided
    1.12 + * by Oracle in the LICENSE file that accompanied this code.
    1.13 + *
    1.14 + * This code is distributed in the hope that it will be useful, but WITHOUT
    1.15 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    1.16 + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    1.17 + * version 2 for more details (a copy is included in the LICENSE file that
    1.18 + * accompanied this code).
    1.19 + *
    1.20 + * You should have received a copy of the GNU General Public License version
    1.21 + * 2 along with this work; if not, write to the Free Software Foundation,
    1.22 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
    1.23 + *
    1.24 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
    1.25 + * or visit www.oracle.com if you need additional information or have any
    1.26 + * questions.
    1.27 + */
    1.28 +
    1.29 +package java.lang.invoke;
    1.30 +
    1.31 +/**
    1.32 + * A {@code VolatileCallSite} is a {@link CallSite} whose target acts like a volatile variable.
    1.33 + * An {@code invokedynamic} instruction linked to a {@code VolatileCallSite} sees updates
    1.34 + * to its call site target immediately, even if the update occurs in another thread.
    1.35 + * There may be a performance penalty for such tight coupling between threads.
    1.36 + * <p>
    1.37 + * Unlike {@code MutableCallSite}, there is no
    1.38 + * {@linkplain MutableCallSite#syncAll syncAll operation} on volatile
    1.39 + * call sites, since every write to a volatile variable is implicitly
    1.40 + * synchronized with reader threads.
    1.41 + * <p>
    1.42 + * In other respects, a {@code VolatileCallSite} is interchangeable
    1.43 + * with {@code MutableCallSite}.
    1.44 + * @see MutableCallSite
    1.45 + * @author John Rose, JSR 292 EG
    1.46 + */
    1.47 +public class VolatileCallSite extends CallSite {
    1.48 +    /**
    1.49 +     * Creates a call site with a volatile binding to its target.
    1.50 +     * The initial target is set to a method handle
    1.51 +     * of the given type which will throw an {@code IllegalStateException} if called.
    1.52 +     * @param type the method type that this call site will have
    1.53 +     * @throws NullPointerException if the proposed type is null
    1.54 +     */
    1.55 +    public VolatileCallSite(MethodType type) {
    1.56 +        super(type);
    1.57 +    }
    1.58 +
    1.59 +    /**
    1.60 +     * Creates a call site with a volatile binding to its target.
    1.61 +     * The target is set to the given value.
    1.62 +     * @param target the method handle that will be the initial target of the call site
    1.63 +     * @throws NullPointerException if the proposed target is null
    1.64 +     */
    1.65 +    public VolatileCallSite(MethodHandle target) {
    1.66 +        super(target);
    1.67 +    }
    1.68 +
    1.69 +    /**
    1.70 +     * Returns the target method of the call site, which behaves
    1.71 +     * like a {@code volatile} field of the {@code VolatileCallSite}.
    1.72 +     * <p>
    1.73 +     * The interactions of {@code getTarget} with memory are the same
    1.74 +     * as of a read from a {@code volatile} field.
    1.75 +     * <p>
    1.76 +     * In particular, the current thread is required to issue a fresh
    1.77 +     * read of the target from memory, and must not fail to see
    1.78 +     * a recent update to the target by another thread.
    1.79 +     *
    1.80 +     * @return the linkage state of this call site, a method handle which can change over time
    1.81 +     * @see #setTarget
    1.82 +     */
    1.83 +    @Override public final MethodHandle getTarget() {
    1.84 +        return getTargetVolatile();
    1.85 +    }
    1.86 +
    1.87 +    /**
    1.88 +     * Updates the target method of this call site, as a volatile variable.
    1.89 +     * The type of the new target must agree with the type of the old target.
    1.90 +     * <p>
    1.91 +     * The interactions with memory are the same as of a write to a volatile field.
    1.92 +     * In particular, any threads is guaranteed to see the updated target
    1.93 +     * the next time it calls {@code getTarget}.
    1.94 +     * @param newTarget the new target
    1.95 +     * @throws NullPointerException if the proposed new target is null
    1.96 +     * @throws WrongMethodTypeException if the proposed new target
    1.97 +     *         has a method type that differs from the previous target
    1.98 +     * @see #getTarget
    1.99 +     */
   1.100 +    @Override public void setTarget(MethodHandle newTarget) {
   1.101 +        checkTargetChange(getTargetVolatile(), newTarget);
   1.102 +        setTargetVolatile(newTarget);
   1.103 +    }
   1.104 +
   1.105 +    /**
   1.106 +     * {@inheritDoc}
   1.107 +     */
   1.108 +    @Override
   1.109 +    public final MethodHandle dynamicInvoker() {
   1.110 +        return makeDynamicInvoker();
   1.111 +    }
   1.112 +}