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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;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodType;
import java.util.Iterator;
import java.util.TreeSet;
/**
* This is a list of code versions of a function.
* The list is sorted in ascending order of generic descriptors
*/
@SuppressWarnings("serial")
final class CompiledFunctions extends TreeSet<CompiledFunction> {
private CompiledFunction generic;
CompiledFunction best(final MethodType type) {
final Iterator<CompiledFunction> iter = iterator();
while (iter.hasNext()) {
final CompiledFunction next = iter.next();
if (next.typeCompatible(type)) {
return next;
}
}
return generic();
}
boolean needsCallee() {
return ScriptFunctionData.needsCallee(mostGeneric().getInvoker());
}
CompiledFunction mostGeneric() {
return last();
}
CompiledFunction generic() {
CompiledFunction gen = this.generic;
if (gen == null) {
gen = this.generic = makeGeneric(mostGeneric());
}
return gen;
}
private static CompiledFunction makeGeneric(final CompiledFunction func) {
final MethodHandle invoker = composeGenericMethod(func.getInvoker());
final MethodHandle constructor = func.hasConstructor() ? composeGenericMethod(func.getConstructor()) : null;
return new CompiledFunction(invoker.type(), invoker, constructor);
}
/**
* Takes a method handle, and returns a potentially different method handle that can be used in
* {@code ScriptFunction#invoke(Object, Object...)} or {code ScriptFunction#construct(Object, Object...)}.
* The returned method handle will be sure to return {@code Object}, and will have all its parameters turned into
* {@code Object} as well, except for the following ones:
* <ul>
* <li>a last parameter of type {@code Object[]} which is used for vararg functions,</li>
* <li>the first argument, which is forced to be {@link ScriptFunction}, in case the function receives itself
* (callee) as an argument.</li>
* </ul>
*
* @param mh the original method handle
*
* @return the new handle, conforming to the rules above.
*/
private static MethodHandle composeGenericMethod(final MethodHandle mh) {
final MethodType type = mh.type();
final boolean isVarArg = ScriptFunctionData.isVarArg(mh);
final int paramCount = isVarArg ? type.parameterCount() - 1 : type.parameterCount();
MethodType newType = MethodType.genericMethodType(paramCount, isVarArg);
if (ScriptFunctionData.needsCallee(mh)) {
newType = newType.changeParameterType(0, ScriptFunction.class);
}
return type.equals(newType) ? mh : mh.asType(newType);
}
/**
* Is the given type even more specific than this entire list? That means
* we have an opportunity for more specific versions of the method
* through lazy code generation
*
* @param type type to check against
* @return true if the given type is more specific than all invocations available
*/
boolean isLessSpecificThan(final MethodType type) {
return best(type).moreGenericThan(type);
}
}
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