/*

 * Copyright (c) 2017, 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.util.Wrapper;

import java.lang.invoke.AbstractConstantGroup.BSCIWithCache;

import java.util.Arrays;

import static java.lang.invoke.BootstrapCallInfo.makeBootstrapCallInfo;

import static java.lang.invoke.ConstantGroup.makeConstantGroup;

import static java.lang.invoke.MethodHandleNatives.*;

import static java.lang.invoke.MethodHandleStatics.TRACE_METHOD_LINKAGE;

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

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

final class BootstrapMethodInvoker {

    /**

     * Factored code for invoking a bootstrap method for invokedynamic

     * or a dynamic constant.

     * @param resultType the expected return type (either CallSite or a constant type)

     * @param bootstrapMethod the BSM to call

     * @param name the method name or constant name

     * @param type the method type or constant type

     * @param info information passed up from the JVM, to derive static arguments

     * @param callerClass the class containing the resolved method call or constant load

     * @param <T> the expected return type

     * @return the expected value, either a CallSite or a constant value

     */

    static <T> T invoke(Class<T> resultType,

                        MethodHandle bootstrapMethod,

                        // Callee information:

                        String name, Object type,

                        // Extra arguments for BSM, if any:

                        Object info,

                        // Caller information:

                        Class<?> callerClass) {

        MethodHandles.Lookup caller = IMPL_LOOKUP.in(callerClass);

        Object result;

        boolean pullMode = isPullModeBSM(bootstrapMethod);  // default value is false

        boolean vmIsPushing = !staticArgumentsPulled(info); // default value is true

        MethodHandle pullModeBSM;

        // match the VM with the BSM

        if (vmIsPushing) {

            // VM is pushing arguments at us

            pullModeBSM = null;

            if (pullMode) {

                bootstrapMethod = pushMePullYou(bootstrapMethod, true);

            }

        } else {

            // VM wants us to pull args from it

            pullModeBSM = pullMode ? bootstrapMethod :

                    pushMePullYou(bootstrapMethod, false);

            bootstrapMethod = null;

        }

        try {

            info = maybeReBox(info);

            if (info == null) {

                // VM is allowed to pass up a null meaning no BSM args

                result = bootstrapMethod.invoke(caller, name, type);

            }

            else if (!info.getClass().isArray()) {

                // VM is allowed to pass up a single BSM arg directly

                result = bootstrapMethod.invoke(caller, name, type, info);

            }

            else if (info.getClass() == int[].class) {

                // VM is allowed to pass up a pair {argc, index}

                // referring to 'argc' BSM args at some place 'index'

                // in the guts of the VM (associated with callerClass).

                // The format of this index pair is private to the

                // handshake between the VM and this class only.

                // This supports "pulling" of arguments.

                // The VM is allowed to do this for any reason.

                // The code in this method makes up for any mismatches.

                BootstrapCallInfo<Object> bsci

                    = new VM_BSCI<>(bootstrapMethod, name, type, caller, (int[])info);

                // Pull-mode API is (Lookup, BootstrapCallInfo) -> Object

                result = pullModeBSM.invoke(caller, bsci);

            }

            else {

                // VM is allowed to pass up a full array of resolved BSM args

                Object[] argv = (Object[]) info;

                maybeReBoxElements(argv);

                switch (argv.length) {

                    case 0:

                        result = bootstrapMethod.invoke(caller, name, type);

                        break;

                    case 1:

                        result = bootstrapMethod.invoke(caller, name, type,

                                                        argv[0]);

                        break;

                    case 2:

                        result = bootstrapMethod.invoke(caller, name, type,

                                                        argv[0], argv[1]);

                        break;

                    case 3:

                        break;

                    case 4:

                        result = bootstrapMethod.invoke(caller, name, type,

                                                        argv[0], argv[1], argv[2], argv[3]);

                        break;

                    case 5:

                        result = bootstrapMethod.invoke(caller, name, type,

                                                        argv[0], argv[1], argv[2], argv[3], argv[4]);

                        break;

                    case 6:

                        result = bootstrapMethod.invoke(caller, name, type,

                                                        argv[0], argv[1], argv[2], argv[3], argv[4], argv[5]);

                        break;

                    default:

                        final int NON_SPREAD_ARG_COUNT = 3;  // (caller, name, type)

                        final int MAX_SAFE_SIZE = MethodType.MAX_MH_ARITY / 2 - NON_SPREAD_ARG_COUNT;

                        if (argv.length >= MAX_SAFE_SIZE) {

                            // to be on the safe side, use invokeWithArguments which handles jumbo lists

                            Object[] newargv = new Object[NON_SPREAD_ARG_COUNT + argv.length];

                            newargv[0] = caller;

                            newargv[1] = name;

                            newargv[2] = type;

                            System.arraycopy(argv, 0, newargv, NON_SPREAD_ARG_COUNT, argv.length);

                            result = bootstrapMethod.invokeWithArguments(newargv);

                            break;

                        }

                        MethodType invocationType = MethodType.genericMethodType(NON_SPREAD_ARG_COUNT + argv.length);

                        MethodHandle typedBSM = bootstrapMethod.asType(invocationType);

                        MethodHandle spreader = invocationType.invokers().spreadInvoker(NON_SPREAD_ARG_COUNT);

                        result = spreader.invokeExact(typedBSM, (Object) caller, (Object) name, type, argv);

                }

            }

            if (resultType.isPrimitive()) {

                // Non-reference conversions are more than just plain casts.

                // By pushing the value through a funnel of the form (T x)->x,

                // the boxed result can be widened as needed.  See MH::asType.

                MethodHandle funnel = MethodHandles.identity(resultType);

                result = funnel.invoke(result);

                // Now it is the wrapper type for resultType.

                resultType = Wrapper.asWrapperType(resultType);

            }

            return resultType.cast(result);

        }

        catch (Error e) {

            // Pass through an Error, including BootstrapMethodError, any other

            // form of linkage error, such as IllegalAccessError if the bootstrap

            // method is inaccessible, or say ThreadDeath/OutOfMemoryError

            // See the "Linking Exceptions" section for the invokedynamic

            // instruction in JVMS 6.5.

            throw e;

        }

        catch (Throwable ex) {

            // Wrap anything else in BootstrapMethodError

            throw new BootstrapMethodError("bootstrap method initialization exception", ex);

        }

    }

    /** The JVM produces java.lang.Integer values to box

     *  CONSTANT_Integer boxes but does not intern them.

     *  Let's intern them.  This is slightly wrong for

     *  a {@code CONSTANT_Dynamic} which produces an

     *  un-interned integer (e.g., {@code new Integer(0)}).

     */

    private static Object maybeReBox(Object x) {

        if (x instanceof Integer) {

            int xi = (int) x;

            if (xi == (byte) xi)

                x = xi;  // must rebox; see JLS 5.1.7

        }

        return x;

    }

    private static void maybeReBoxElements(Object[] xa) {

        for (int i = 0; i < xa.length; i++) {

            xa[i] = maybeReBox(xa[i]);

        }

    }

    /** Canonical VM-aware implementation of BootstrapCallInfo.

     * Knows how to dig into the JVM for lazily resolved (pull-mode) constants.

     */

    private static final class VM_BSCI<T> extends BSCIWithCache<T> {

        private final int[] indexInfo;

        private final Class<?> caller;  // for index resolution only

        VM_BSCI(MethodHandle bsm, String name, T type,

                Lookup lookup, int[] indexInfo) {

            super(bsm, name, type, indexInfo[0]);

            if (!lookup.hasPrivateAccess())  //D.I.D.

                throw new AssertionError("bad Lookup object");

            this.caller = lookup.lookupClass();

            this.indexInfo = indexInfo;

            // scoop up all the easy stuff right away:

            prefetchIntoCache(0, size());

        }

        @Override Object fillCache(int i) {

            Object[] buf = { null };

            copyConstants(i, i+1, buf, 0);

            Object res = wrapNull(buf[0]);

            cache[i] = res;

            int next = i + 1;

            if (next < cache.length && cache[next] == null)

                maybePrefetchIntoCache(next, false);  // try to prefetch

            return res;

        }

        @Override public int copyConstants(int start, int end,

                                           Object[] buf, int pos) {

            int i = start, bufi = pos;

            while (i < end) {

                Object x = cache[i];

                if (x == null)  break;

                buf[bufi++] = unwrapNull(x);

                i++;

            }

            // give up at first null and grab the rest in one big block

            if (i >= end)  return i;

            Object[] temp = new Object[end - i];

            if (TRACE_METHOD_LINKAGE) {

                System.out.println("resolving more BSM arguments: " +

                        Arrays.asList(caller.getSimpleName(), Arrays.toString(indexInfo), i, end));

            }

            copyOutBootstrapArguments(caller, indexInfo,

                                      i, end, temp, 0,

                                      true, null);

            for (Object x : temp) {

                x = maybeReBox(x);

                buf[bufi++] = x;

                cache[i++] = wrapNull(x);

            }

            if (end < cache.length && cache[end] == null)

                maybePrefetchIntoCache(end, true);  // try to prefetch

            return i;

        }

        private static final int MIN_PF = 4;

        private void maybePrefetchIntoCache(int i, boolean bulk) {

            int len = cache.length;

            assert(0 <= i && i <= len);

            int pfLimit = i;

            if (bulk)  pfLimit += i;  // exponential prefetch expansion

            // try to prefetch at least MIN_PF elements

            if (pfLimit < i + MIN_PF)  pfLimit = i + MIN_PF;

            if (pfLimit > len || pfLimit < 0)  pfLimit = len;

            // stop prefetching where cache is more full than empty

            int empty = 0, nonEmpty = 0, lastEmpty = i;

            for (int j = i; j < pfLimit; j++) {

                if (cache[j] == null) {

                    empty++;

                    lastEmpty = j;

                } else {

                    nonEmpty++;

                    if (nonEmpty > empty) {

                        pfLimit = lastEmpty + 1;

                        break;

                    }

                    if (pfLimit < len)  pfLimit++;

                }

            }

            if (bulk && empty < MIN_PF && pfLimit < len)

                return;  // not worth the effort

            prefetchIntoCache(i, pfLimit);

        }

        private void prefetchIntoCache(int i, int pfLimit) {

            if (pfLimit <= i)  return;  // corner case

            Object[] temp = new Object[pfLimit - i];

            if (TRACE_METHOD_LINKAGE) {

                System.out.println("prefetching BSM arguments: " +

                        Arrays.asList(caller.getSimpleName(), Arrays.toString(indexInfo), i, pfLimit));

            }

            copyOutBootstrapArguments(caller, indexInfo,

                                      i, pfLimit, temp, 0,

                                      false, NOT_PRESENT);

            for (Object x : temp) {

                if (x != NOT_PRESENT && cache[i] == null) {

                    cache[i] = wrapNull(maybeReBox(x));

                }

                i++;

            }

        }

    }

    /*non-public*/ static final

    class PushAdapter {

        // skeleton for push-mode BSM which wraps a pull-mode BSM:

        static Object pushToBootstrapMethod(MethodHandle pullModeBSM,

                                            MethodHandles.Lookup lookup, String name, Object type,

                                            Object... arguments) throws Throwable {

            ConstantGroup cons = makeConstantGroup(Arrays.asList(arguments));

            BootstrapCallInfo<?> bsci = makeBootstrapCallInfo(pullModeBSM, name, type, cons);

            if (TRACE_METHOD_LINKAGE)

                System.out.println("pull-mode BSM gets pushed arguments from fake BSCI");

            return pullModeBSM.invoke(lookup, bsci);

        }

        static final MethodHandle MH_pushToBootstrapMethod;

        static {

            final Class<?> THIS_CLASS = PushAdapter.class;

            try {

                MH_pushToBootstrapMethod = IMPL_LOOKUP

                    .findStatic(THIS_CLASS, "pushToBootstrapMethod",

                                MethodType.methodType(Object.class, MethodHandle.class,

                                        Lookup.class, String.class, Object.class, Object[].class));

            } catch (Throwable ex) {

                throw new InternalError(ex);

            }

        }

    }

    /*non-public*/ static final

    class PullAdapter {

        // skeleton for pull-mode BSM which wraps a push-mode BSM:

        static Object pullFromBootstrapMethod(MethodHandle pushModeBSM,

                                              MethodHandles.Lookup lookup,

                                              BootstrapCallInfo<?> bsci)

                throws Throwable {

            int argc = bsci.size();

            switch (argc) {

                case 0:

                    return pushModeBSM.invoke(lookup, bsci.invocationName(), bsci.invocationType());

                case 1:

                    return pushModeBSM.invoke(lookup, bsci.invocationName(), bsci.invocationType(),

                            bsci.get(0));

                case 2:

                    return pushModeBSM.invoke(lookup, bsci.invocationName(), bsci.invocationType(),

                            bsci.get(0), bsci.get(1));

                case 3:

                    return pushModeBSM.invoke(lookup, bsci.invocationName(), bsci.invocationType(),

                            bsci.get(0), bsci.get(1), bsci.get(2));

                case 4:

                    return pushModeBSM.invoke(lookup, bsci.invocationName(), bsci.invocationType(),

                            bsci.get(0), bsci.get(1), bsci.get(2), bsci.get(3));

                case 5:

                    return pushModeBSM.invoke(lookup, bsci.invocationName(), bsci.invocationType(),

                            bsci.get(0), bsci.get(1), bsci.get(2), bsci.get(3), bsci.get(4));

                case 6:

                    return pushModeBSM.invoke(lookup, bsci.invocationName(), bsci.invocationType(),

                            bsci.get(0), bsci.get(1), bsci.get(2), bsci.get(3), bsci.get(4), bsci.get(5));

                default:

                    final int NON_SPREAD_ARG_COUNT = 3;  // (lookup, name, type)

                    final int MAX_SAFE_SIZE = MethodType.MAX_MH_ARITY / 2 - NON_SPREAD_ARG_COUNT;

                    if (argc >= MAX_SAFE_SIZE) {

                        // to be on the safe side, use invokeWithArguments which handles jumbo lists

                        Object[] newargv = new Object[NON_SPREAD_ARG_COUNT + argc];

                        newargv[0] = lookup;

                        newargv[1] = bsci.invocationName();

                        newargv[2] = bsci.invocationType();

                        bsci.copyConstants(0, argc, newargv, NON_SPREAD_ARG_COUNT);

                        return pushModeBSM.invokeWithArguments(newargv);

                    }

                    MethodType invocationType = MethodType.genericMethodType(NON_SPREAD_ARG_COUNT + argc);

                    MethodHandle typedBSM = pushModeBSM.asType(invocationType);

                    MethodHandle spreader = invocationType.invokers().spreadInvoker(NON_SPREAD_ARG_COUNT);

                    Object[] argv = new Object[argc];

                    bsci.copyConstants(0, argc, argv, 0);

                    return spreader.invokeExact(typedBSM, (Object) lookup, (Object) bsci.invocationName(), bsci.invocationType(), argv);

                }

        }

        static final MethodHandle MH_pullFromBootstrapMethod;

        static {

            final Class<?> THIS_CLASS = PullAdapter.class;

            try {

                MH_pullFromBootstrapMethod = IMPL_LOOKUP

                    .findStatic(THIS_CLASS, "pullFromBootstrapMethod",

                                MethodType.methodType(Object.class, MethodHandle.class,

                                        Lookup.class, BootstrapCallInfo.class));

            } catch (Throwable ex) {

                throw new InternalError(ex);

            }

        }

    }

    /** Given a push-mode BSM (taking one argument) convert it to a

     *  pull-mode BSM (taking N pre-resolved arguments).

     *  This method is used when, in fact, the JVM is passing up

     *  pre-resolved arguments, but the BSM is expecting lazy stuff.

     *  Or, when goToPushMode is true, do the reverse transform.

     *  (The two transforms are exactly inverse.)

     */

    static MethodHandle pushMePullYou(MethodHandle bsm, boolean goToPushMode) {

        if (TRACE_METHOD_LINKAGE) {

            System.out.println("converting BSM of type " + bsm.type() + " to "

                    + (goToPushMode ? "push mode" : "pull mode"));

        }

        assert(isPullModeBSM(bsm) == goToPushMode); // there must be a change

        if (goToPushMode) {

            return PushAdapter.MH_pushToBootstrapMethod.bindTo(bsm).withVarargs(true);

        } else {

            return PullAdapter.MH_pullFromBootstrapMethod.bindTo(bsm).withVarargs(false);

        }

    }

}