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/*
* 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 jdk.nashorn.internal.runtime.linker;
import static jdk.nashorn.internal.lookup.Lookup.MH;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.ref.WeakReference;
import jdk.internal.dynalink.CallSiteDescriptor;
import jdk.nashorn.internal.codegen.ObjectClassGenerator;
import jdk.nashorn.internal.objects.Global;
import jdk.nashorn.internal.runtime.Property;
import jdk.nashorn.internal.runtime.PropertyMap;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptObject;
/**
* Constructor of method handles used to guard call sites.
*/
public final class NashornGuards {
private static final MethodHandle IS_SCRIPTOBJECT = findOwnMH("isScriptObject", boolean.class, Object.class);
private static final MethodHandle IS_SCRIPTFUNCTION = findOwnMH("isScriptFunction", boolean.class, Object.class);
private static final MethodHandle IS_MAP = findOwnMH("isMap", boolean.class, Object.class, PropertyMap.class);
private static final MethodHandle SAME_OBJECT = findOwnMH("sameObject", boolean.class, Object.class, WeakReference.class);
private static final MethodHandle IS_INSTANCEOF_2 = findOwnMH("isInstanceOf2", boolean.class, Object.class, Class.class, Class.class);
// don't create me!
private NashornGuards() {
}
/**
* Get the guard that checks if an item is a {@code ScriptObject}
* @return method handle for guard
*/
public static MethodHandle getScriptObjectGuard() {
return IS_SCRIPTOBJECT;
}
/**
* Get the guard that checks if an item is a {@code ScriptFunction}
* @return method handle for guard
*/
public static MethodHandle getScriptFunctionGuard() {
return IS_SCRIPTFUNCTION;
}
/**
* Get the guard that checks if a {@link PropertyMap} is equal to
* a known map, using reference comparison
*
* @param map The map to check against. This will be bound to the guard method handle
*
* @return method handle for guard
*/
public static MethodHandle getMapGuard(final PropertyMap map) {
return MH.insertArguments(IS_MAP, 1, map);
}
/**
* Determine whether the given callsite needs a guard.
* @param property the property, or null
* @param desc the callsite descriptor
* @return true if a guard should be used for this callsite
*/
static boolean needsGuard(final Property property, final CallSiteDescriptor desc) {
return property == null || property.isConfigurable()
|| property.isBound() || !ObjectClassGenerator.OBJECT_FIELDS_ONLY
|| !NashornCallSiteDescriptor.isFastScope(desc) || property.canChangeType();
}
/**
* Get the guard for a property access. This returns an identity guard for non-configurable global properties
* and a map guard for everything else.
*
* @param sobj the first object in the prototype chain
* @param property the property
* @param desc the callsite descriptor
* @return method handle for guard
*/
public static MethodHandle getGuard(final ScriptObject sobj, final Property property, final CallSiteDescriptor desc) {
if (!needsGuard(property, desc)) {
return null;
}
if (NashornCallSiteDescriptor.isScope(desc)) {
if (property != null && property.isBound()) {
// This is a declared top level variables in main script or eval, use identity guard.
return getIdentityGuard(sobj);
}
if (!(sobj instanceof Global) && (property == null || property.isConfigurable())) {
// Undeclared variables in nested evals need stronger guards
return combineGuards(getIdentityGuard(sobj), getMapGuard(sobj.getMap()));
}
}
return getMapGuard(sobj.getMap());
}
/**
* Get a guard that checks referential identity of the current object.
*
* @param sobj the self object
* @return true if same self object instance
*/
public static MethodHandle getIdentityGuard(final ScriptObject sobj) {
return MH.insertArguments(SAME_OBJECT, 1, new WeakReference<>(sobj));
}
/**
* Get a guard that checks if in item is an instance of either of two classes.
*
* @param class1 the first class
* @param class2 the second class
* @return method handle for guard
*/
public static MethodHandle getInstanceOf2Guard(final Class<?> class1, final Class<?> class2) {
return MH.insertArguments(IS_INSTANCEOF_2, 1, class1, class2);
}
/**
* Combine two method handles of type {@code (Object)boolean} using logical AND.
*
* @param guard1 the first guard
* @param guard2 the second guard, only invoked if guard1 returns true
* @return true if both guard1 and guard2 returned true
*/
public static MethodHandle combineGuards(final MethodHandle guard1, final MethodHandle guard2) {
return MH.guardWithTest(guard1, guard2, MH.dropArguments(MH.constant(boolean.class, false), 0, Object.class));
}
@SuppressWarnings("unused")
private static boolean isScriptObject(final Object self) {
return self instanceof ScriptObject;
}
@SuppressWarnings("unused")
private static boolean isScriptFunction(final Object self) {
return self instanceof ScriptFunction;
}
@SuppressWarnings("unused")
private static boolean isMap(final Object self, final PropertyMap map) {
return self instanceof ScriptObject && ((ScriptObject)self).getMap() == map;
}
@SuppressWarnings("unused")
private static boolean sameObject(final Object self, final WeakReference<ScriptObject> ref) {
return self == ref.get();
}
@SuppressWarnings("unused")
private static boolean isInstanceOf2(final Object self, final Class<?> class1, final Class<?> class2) {
return class1.isInstance(self) || class2.isInstance(self);
}
private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {
return MH.findStatic(MethodHandles.lookup(), NashornGuards.class, name, MH.type(rtype, types));
}
}
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