/*

 * Copyright (c) 2008, 2011, 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

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package java.lang.invoke;

import sun.invoke.empty.Empty;

import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;

/**

 * Construction and caching of often-used invokers.

 * @author jrose

 */

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

    // general invoker for the outgoing call

    private /*lazy*/ MethodHandle generalInvoker;

    // general invoker for the outgoing call, uses varargs

    private /*lazy*/ MethodHandle varargsInvoker;

    // general invoker for the outgoing call; accepts a trailing Object[]

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

    // invoker for an unbound callsite

    private /*lazy*/ MethodHandle uninitializedCallSite;

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

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

     */

    /*non-public*/ Invokers(MethodType targetType) {

        this.targetType = targetType;

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

    }

    /*non-public*/ static MethodType invokerType(MethodType targetType) {

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

    }

    /*non-public*/ MethodHandle exactInvoker() {

        MethodHandle invoker = exactInvoker;

        if (invoker != null)  return invoker;

        invoker = lookupInvoker("invokeExact");

        exactInvoker = invoker;

        return invoker;

    }

    /*non-public*/ MethodHandle generalInvoker() {

        MethodHandle invoker = generalInvoker;

        if (invoker != null)  return invoker;

        invoker = lookupInvoker("invoke");

        generalInvoker = invoker;

        return invoker;

    }

    private MethodHandle lookupInvoker(String name) {

        MethodHandle invoker;

        try {

            invoker = IMPL_LOOKUP.findVirtual(MethodHandle.class, name, targetType);

        } catch (ReflectiveOperationException ex) {

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

        }

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

        assert(!invoker.isVarargsCollector());

        return invoker;

    }

    /*non-public*/ MethodHandle erasedInvoker() {

        MethodHandle xinvoker = exactInvoker();

        MethodHandle invoker = erasedInvoker;

        if (invoker != null)  return invoker;

        MethodType erasedType = targetType.erase();

        invoker = xinvoker.asType(invokerType(erasedType));

        erasedInvoker = invoker;

        return invoker;

    }

    /*non-public*/ MethodHandle spreadInvoker(int leadingArgCount) {

        MethodHandle vaInvoker = spreadInvokers[leadingArgCount];

        if (vaInvoker != null)  return vaInvoker;

        MethodHandle gInvoker = generalInvoker();

        int spreadArgCount = targetType.parameterCount() - leadingArgCount;

        vaInvoker = gInvoker.asSpreader(Object[].class, spreadArgCount);

        spreadInvokers[leadingArgCount] = vaInvoker;

        return vaInvoker;

    }

    /*non-public*/ MethodHandle varargsInvoker() {

        MethodHandle vaInvoker = varargsInvoker;

        if (vaInvoker != null)  return vaInvoker;

        vaInvoker = spreadInvoker(0).asType(invokerType(MethodType.genericMethodType(0, true)));

        varargsInvoker = vaInvoker;

        return vaInvoker;

    }

    private static MethodHandle THROW_UCS = null;

    /*non-public*/ MethodHandle uninitializedCallSite() {

        MethodHandle invoker = uninitializedCallSite;

        if (invoker != null)  return invoker;

        if (targetType.parameterCount() > 0) {

            MethodType type0 = targetType.dropParameterTypes(0, targetType.parameterCount());

            Invokers invokers0 = type0.invokers();

            invoker = MethodHandles.dropArguments(invokers0.uninitializedCallSite(),

                                                  0, targetType.parameterList());

            assert(invoker.type().equals(targetType));

            uninitializedCallSite = invoker;

            return invoker;

        }

        if (THROW_UCS == null) {

            try {

                THROW_UCS = IMPL_LOOKUP

                    .findStatic(CallSite.class, "uninitializedCallSite",

                                MethodType.methodType(Empty.class));

            } catch (ReflectiveOperationException ex) {

                throw new RuntimeException(ex);

            }

        }

        invoker = AdapterMethodHandle.makeRetypeRaw(targetType, THROW_UCS);

        assert(invoker.type().equals(targetType));

        uninitializedCallSite = invoker;

        return invoker;

    }

    public String toString() {

        return "Invokers"+targetType;

    }

}