/*

 * Copyright (c) 2008, 2009, 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 sun.dyn;

import java.dyn.*;

/**

 * Construction and caching of often-used invokers.

 * @author jrose

 */

public class Invokers {

    // exact type (sans leading taget MH) for the outgoing call

    private final MethodType targetType;

    // exact invoker for the outgoing call

    private /*lazy*/ MethodHandle exactInvoker;

    // erased (partially untyped but with primitives) invoker for the outgoing call

    private /*lazy*/ MethodHandle erasedInvoker;

    /*lazy*/ MethodHandle erasedInvokerWithDrops;  // for InvokeGeneric

    // generic (untyped) invoker for the outgoing call

    private /*lazy*/ MethodHandle genericInvoker;

    // generic (untyped) invoker for the outgoing call; accepts a single Object[]

    private final /*lazy*/ MethodHandle[] varargsInvokers;

    /** Compute and cache information common to all collecting adapters

     *  that implement members of the erasure-family of the given erased type.

     */

    public Invokers(Access token, MethodType targetType) {

        Access.check(token);

        this.targetType = targetType;

        this.varargsInvokers = new MethodHandle[targetType.parameterCount()+1];

    }

    public static MethodType invokerType(MethodType targetType) {

        return targetType.insertParameterTypes(0, MethodHandle.class);

    }

    public MethodHandle exactInvoker() {

        MethodHandle invoker = exactInvoker;

        if (invoker != null)  return invoker;

        try {

            invoker = MethodHandleImpl.IMPL_LOOKUP.findVirtual(MethodHandle.class, "invoke", targetType);

        } catch (NoAccessException ex) {

            throw new InternalError("JVM cannot find invoker for "+targetType);

        }

        assert(invokerType(targetType) == invoker.type());

        exactInvoker = invoker;

        return invoker;

    }

    public MethodHandle genericInvoker() {

        MethodHandle invoker1 = exactInvoker();

        MethodHandle invoker = genericInvoker;

        if (invoker != null)  return invoker;

        MethodType genericType = targetType.generic();

        invoker = MethodHandles.convertArguments(invoker1, invokerType(genericType));

        genericInvoker = invoker;

        return invoker;

    }

    public MethodHandle erasedInvoker() {

        MethodHandle invoker1 = exactInvoker();

        MethodHandle invoker = erasedInvoker;

        if (invoker != null)  return invoker;

        MethodType erasedType = targetType.erase();

        if (erasedType == targetType.generic())

            invoker = genericInvoker();

        else

            invoker = MethodHandles.convertArguments(invoker1, invokerType(erasedType));

        erasedInvoker = invoker;

        return invoker;

    }

    public MethodHandle varargsInvoker(int objectArgCount) {

        MethodHandle vaInvoker = varargsInvokers[objectArgCount];

        if (vaInvoker != null)  return vaInvoker;

        MethodHandle gInvoker = genericInvoker();

        MethodType vaType = MethodType.genericMethodType(objectArgCount, true);

        vaInvoker = MethodHandles.spreadArguments(gInvoker, invokerType(vaType));

        varargsInvokers[objectArgCount] = vaInvoker;

        return vaInvoker;

    }

    public String toString() {

        return "Invokers"+targetType;

    }

}