Wed, 20 Aug 2014 10:25:28 +0200
8044638: Tidy up Nashorn codebase for code standards
8055199: Tidy up Nashorn codebase for code standards (August 2014)
Reviewed-by: lagergren, sundar
attila@90 | 1 | /* |
attila@90 | 2 | * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. |
attila@90 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
attila@90 | 4 | * |
attila@90 | 5 | * This code is free software; you can redistribute it and/or modify it |
attila@90 | 6 | * under the terms of the GNU General Public License version 2 only, as |
attila@90 | 7 | * published by the Free Software Foundation. Oracle designates this |
attila@90 | 8 | * particular file as subject to the "Classpath" exception as provided |
attila@90 | 9 | * by Oracle in the LICENSE file that accompanied this code. |
attila@90 | 10 | * |
attila@90 | 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
attila@90 | 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
attila@90 | 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
attila@90 | 14 | * version 2 for more details (a copy is included in the LICENSE file that |
attila@90 | 15 | * accompanied this code). |
attila@90 | 16 | * |
attila@90 | 17 | * You should have received a copy of the GNU General Public License version |
attila@90 | 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
attila@90 | 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
attila@90 | 20 | * |
attila@90 | 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
attila@90 | 22 | * or visit www.oracle.com if you need additional information or have any |
attila@90 | 23 | * questions. |
attila@90 | 24 | */ |
attila@90 | 25 | |
attila@90 | 26 | /* |
attila@90 | 27 | * This file is available under and governed by the GNU General Public |
attila@90 | 28 | * License version 2 only, as published by the Free Software Foundation. |
attila@90 | 29 | * However, the following notice accompanied the original version of this |
attila@90 | 30 | * file, and Oracle licenses the original version of this file under the BSD |
attila@90 | 31 | * license: |
attila@90 | 32 | */ |
attila@90 | 33 | /* |
attila@90 | 34 | Copyright 2009-2013 Attila Szegedi |
attila@90 | 35 | |
attila@90 | 36 | Licensed under both the Apache License, Version 2.0 (the "Apache License") |
attila@90 | 37 | and the BSD License (the "BSD License"), with licensee being free to |
attila@90 | 38 | choose either of the two at their discretion. |
attila@90 | 39 | |
attila@90 | 40 | You may not use this file except in compliance with either the Apache |
attila@90 | 41 | License or the BSD License. |
attila@90 | 42 | |
attila@90 | 43 | If you choose to use this file in compliance with the Apache License, the |
attila@90 | 44 | following notice applies to you: |
attila@90 | 45 | |
attila@90 | 46 | You may obtain a copy of the Apache License at |
attila@90 | 47 | |
attila@90 | 48 | http://www.apache.org/licenses/LICENSE-2.0 |
attila@90 | 49 | |
attila@90 | 50 | Unless required by applicable law or agreed to in writing, software |
attila@90 | 51 | distributed under the License is distributed on an "AS IS" BASIS, |
attila@90 | 52 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
attila@90 | 53 | implied. See the License for the specific language governing |
attila@90 | 54 | permissions and limitations under the License. |
attila@90 | 55 | |
attila@90 | 56 | If you choose to use this file in compliance with the BSD License, the |
attila@90 | 57 | following notice applies to you: |
attila@90 | 58 | |
attila@90 | 59 | Redistribution and use in source and binary forms, with or without |
attila@90 | 60 | modification, are permitted provided that the following conditions are |
attila@90 | 61 | met: |
attila@90 | 62 | * Redistributions of source code must retain the above copyright |
attila@90 | 63 | notice, this list of conditions and the following disclaimer. |
attila@90 | 64 | * Redistributions in binary form must reproduce the above copyright |
attila@90 | 65 | notice, this list of conditions and the following disclaimer in the |
attila@90 | 66 | documentation and/or other materials provided with the distribution. |
attila@90 | 67 | * Neither the name of the copyright holder nor the names of |
attila@90 | 68 | contributors may be used to endorse or promote products derived from |
attila@90 | 69 | this software without specific prior written permission. |
attila@90 | 70 | |
attila@90 | 71 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS |
attila@90 | 72 | IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
attila@90 | 73 | TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A |
attila@90 | 74 | PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER |
attila@90 | 75 | BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
attila@90 | 76 | CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
attila@90 | 77 | SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR |
attila@90 | 78 | BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
attila@90 | 79 | WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
attila@90 | 80 | OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
attila@90 | 81 | ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
attila@90 | 82 | */ |
attila@90 | 83 | |
attila@90 | 84 | package jdk.internal.dynalink; |
attila@90 | 85 | |
attila@90 | 86 | import java.lang.invoke.MethodHandle; |
attila@90 | 87 | import java.lang.invoke.MethodHandles; |
attila@90 | 88 | import java.util.Iterator; |
attila@90 | 89 | import java.util.LinkedList; |
attila@90 | 90 | import java.util.concurrent.atomic.AtomicReference; |
attila@90 | 91 | import jdk.internal.dynalink.linker.GuardedInvocation; |
attila@90 | 92 | import jdk.internal.dynalink.support.AbstractRelinkableCallSite; |
attila@488 | 93 | import jdk.internal.dynalink.support.Lookup; |
attila@90 | 94 | |
attila@90 | 95 | /** |
attila@90 | 96 | * A relinkable call site that maintains a chain of linked method handles. In the default implementation, up to 8 method |
attila@90 | 97 | * handles can be chained, cascading from one to the other through |
attila@90 | 98 | * {@link MethodHandles#guardWithTest(MethodHandle, MethodHandle, MethodHandle)}. When this call site has to link a new |
attila@90 | 99 | * method handle and the length of the chain is already at the maximum, it will throw away the oldest method handle. |
attila@90 | 100 | * Switchpoint-invalidated handles in the chain are removed eagerly (on each linking request, and whenever a |
attila@90 | 101 | * switchpoint-invalidated method handle is traversed during invocation). There is currently no profiling |
attila@90 | 102 | * attached to the handles in the chain, so they are never reordered based on usage; the most recently linked method |
attila@90 | 103 | * handle is always at the start of the chain. |
attila@90 | 104 | */ |
attila@90 | 105 | public class ChainedCallSite extends AbstractRelinkableCallSite { |
attila@488 | 106 | private static final MethodHandle PRUNE = Lookup.findOwnSpecial(MethodHandles.lookup(), "prune", MethodHandle.class, |
attila@488 | 107 | MethodHandle.class); |
attila@488 | 108 | |
attila@90 | 109 | private final AtomicReference<LinkedList<GuardedInvocation>> invocations = new AtomicReference<>(); |
attila@90 | 110 | |
attila@90 | 111 | /** |
attila@90 | 112 | * Creates a new chained call site. |
attila@90 | 113 | * @param descriptor the descriptor for the call site. |
attila@90 | 114 | */ |
attila@962 | 115 | public ChainedCallSite(final CallSiteDescriptor descriptor) { |
attila@90 | 116 | super(descriptor); |
attila@90 | 117 | } |
attila@90 | 118 | |
attila@90 | 119 | /** |
attila@90 | 120 | * The maximum number of method handles in the chain. Defaults to 8. You can override it in a subclass if you need |
attila@90 | 121 | * to change the value. If your override returns a value less than 1, the code will break. |
attila@90 | 122 | * @return the maximum number of method handles in the chain. |
attila@90 | 123 | */ |
attila@90 | 124 | protected int getMaxChainLength() { |
attila@90 | 125 | return 8; |
attila@90 | 126 | } |
attila@90 | 127 | |
attila@90 | 128 | @Override |
attila@962 | 129 | public void relink(final GuardedInvocation guardedInvocation, final MethodHandle fallback) { |
attila@90 | 130 | relinkInternal(guardedInvocation, fallback, false); |
attila@90 | 131 | } |
attila@90 | 132 | |
attila@90 | 133 | @Override |
attila@962 | 134 | public void resetAndRelink(final GuardedInvocation guardedInvocation, final MethodHandle fallback) { |
attila@90 | 135 | relinkInternal(guardedInvocation, fallback, true); |
attila@90 | 136 | } |
attila@90 | 137 | |
attila@962 | 138 | private MethodHandle relinkInternal(final GuardedInvocation invocation, final MethodHandle relink, final boolean reset) { |
attila@90 | 139 | final LinkedList<GuardedInvocation> currentInvocations = invocations.get(); |
attila@90 | 140 | @SuppressWarnings({ "unchecked", "rawtypes" }) |
attila@90 | 141 | final LinkedList<GuardedInvocation> newInvocations = |
attila@90 | 142 | currentInvocations == null || reset ? new LinkedList<>() : (LinkedList)currentInvocations.clone(); |
attila@90 | 143 | |
attila@90 | 144 | // First, prune the chain of invalidated switchpoints. |
attila@962 | 145 | for(final Iterator<GuardedInvocation> it = newInvocations.iterator(); it.hasNext();) { |
attila@90 | 146 | if(it.next().hasBeenInvalidated()) { |
attila@90 | 147 | it.remove(); |
attila@90 | 148 | } |
attila@90 | 149 | } |
attila@90 | 150 | |
attila@90 | 151 | // prune() is allowed to invoke this method with invocation == null meaning we're just pruning the chain and not |
attila@90 | 152 | // adding any new invocations to it. |
attila@90 | 153 | if(invocation != null) { |
attila@90 | 154 | // Remove oldest entry if we're at max length |
attila@90 | 155 | if(newInvocations.size() == getMaxChainLength()) { |
attila@90 | 156 | newInvocations.removeFirst(); |
attila@90 | 157 | } |
attila@90 | 158 | newInvocations.addLast(invocation); |
attila@90 | 159 | } |
attila@90 | 160 | |
attila@90 | 161 | // prune-and-invoke is used as the fallback for invalidated switchpoints. If a switchpoint gets invalidated, we |
attila@90 | 162 | // rebuild the chain and get rid of all invalidated switchpoints instead of letting them linger. |
attila@90 | 163 | final MethodHandle pruneAndInvoke = makePruneAndInvokeMethod(relink); |
attila@90 | 164 | |
attila@90 | 165 | // Fold the new chain |
attila@90 | 166 | MethodHandle target = relink; |
attila@962 | 167 | for(final GuardedInvocation inv: newInvocations) { |
attila@90 | 168 | target = inv.compose(pruneAndInvoke, target); |
attila@90 | 169 | } |
attila@90 | 170 | |
attila@90 | 171 | // If nobody else updated the call site while we were rebuilding the chain, set the target to our chain. In case |
attila@90 | 172 | // we lost the race for multithreaded update, just do nothing. Either the other thread installed the same thing |
attila@90 | 173 | // we wanted to install, or otherwise, we'll be asked to relink again. |
attila@90 | 174 | if(invocations.compareAndSet(currentInvocations, newInvocations)) { |
attila@90 | 175 | setTarget(target); |
attila@90 | 176 | } |
attila@90 | 177 | return target; |
attila@90 | 178 | } |
attila@90 | 179 | |
attila@90 | 180 | /** |
attila@90 | 181 | * Creates a method that rebuilds our call chain, pruning it of any invalidated switchpoints, and then invokes that |
attila@90 | 182 | * chain. |
attila@90 | 183 | * @param relink the ultimate fallback for the chain (the {@code DynamicLinker}'s relink). |
attila@90 | 184 | * @return a method handle for prune-and-invoke |
attila@90 | 185 | */ |
attila@962 | 186 | private MethodHandle makePruneAndInvokeMethod(final MethodHandle relink) { |
attila@90 | 187 | // Bind prune to (this, relink) |
attila@90 | 188 | final MethodHandle boundPrune = MethodHandles.insertArguments(PRUNE, 0, this, relink); |
attila@90 | 189 | // Make it ignore all incoming arguments |
attila@90 | 190 | final MethodHandle ignoreArgsPrune = MethodHandles.dropArguments(boundPrune, 0, type().parameterList()); |
attila@90 | 191 | // Invoke prune, then invoke the call site target with original arguments |
attila@90 | 192 | return MethodHandles.foldArguments(MethodHandles.exactInvoker(type()), ignoreArgsPrune); |
attila@90 | 193 | } |
attila@90 | 194 | |
attila@90 | 195 | @SuppressWarnings("unused") |
attila@962 | 196 | private MethodHandle prune(final MethodHandle relink) { |
attila@90 | 197 | return relinkInternal(null, relink, false); |
attila@90 | 198 | } |
attila@101 | 199 | } |