1 /*

     2  * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package java.dyn;

    27 

    28 import sun.dyn.util.*;

    29 import static java.dyn.MethodHandles.Lookup.IMPL_LOOKUP;

    30 

    31 /**

    32  * Adapters which manage MethodHandle.invokeGeneric calls.

    33  * The JVM calls one of these when the exact type match fails.

    34  * @author jrose

    35  */

    36 class InvokeGeneric {

    37     // erased type for the call, which originates from an invokeGeneric site

    38     private final MethodType erasedCallerType;

    39     // an invoker of type (MT, MH; A...) -> R

    40     private final MethodHandle initialInvoker;

    41 

    42     /** Compute and cache information for this adapter, so that it can

    43      *  call out to targets of the erasure-family of the given erased type.

    44      */

    45     /*non-public*/ InvokeGeneric(MethodType erasedCallerType) throws ReflectiveOperationException {

    46         assert(erasedCallerType.equals(erasedCallerType.erase()));

    47         this.erasedCallerType = erasedCallerType;

    48         this.initialInvoker = makeInitialInvoker();

    49         assert initialInvoker.type().equals(erasedCallerType

    50                                             .insertParameterTypes(0, MethodType.class, MethodHandle.class))

    51             : initialInvoker.type();

    52     }

    53 

    54     private static MethodHandles.Lookup lookup() {

    55         return IMPL_LOOKUP;

    56     }

    57 

    58     /** Return the adapter information for this type's erasure. */

    59     /*non-public*/ static MethodHandle genericInvokerOf(MethodType erasedCallerType) throws ReflectiveOperationException {

    60         InvokeGeneric gen = new InvokeGeneric(erasedCallerType);

    61         return gen.initialInvoker;

    62     }

    63 

    64     private MethodHandle makeInitialInvoker() throws ReflectiveOperationException {

    65         // postDispatch = #(MH'; MT, MH; A...){MH'(MT, MH; A)}

    66         MethodHandle postDispatch = makePostDispatchInvoker();

    67         MethodHandle invoker;

    68         if (returnConversionPossible()) {

    69             invoker = MethodHandles.foldArguments(postDispatch,

    70                                                   dispatcher("dispatchWithConversion"));

    71         } else {

    72             invoker = MethodHandles.foldArguments(postDispatch, dispatcher("dispatch"));

    73         }

    74         return invoker;

    75     }

    76 

    77     private static final Class<?>[] EXTRA_ARGS = { MethodType.class, MethodHandle.class };

    78     private MethodHandle makePostDispatchInvoker() {

    79         // Take (MH'; MT, MH; A...) and run MH'(MT, MH; A...).

    80         MethodType invokerType = erasedCallerType.insertParameterTypes(0, EXTRA_ARGS);

    81         return invokerType.invokers().exactInvoker();

    82     }

    83     private MethodHandle dropDispatchArguments(MethodHandle targetInvoker) {

    84         assert(targetInvoker.type().parameterType(0) == MethodHandle.class);

    85         return MethodHandles.dropArguments(targetInvoker, 1, EXTRA_ARGS);

    86     }

    87 

    88     private MethodHandle dispatcher(String dispatchName) throws ReflectiveOperationException {

    89         return lookup().bind(this, dispatchName,

    90                              MethodType.methodType(MethodHandle.class,

    91                                                    MethodType.class, MethodHandle.class));

    92     }

    93 

    94     static final boolean USE_AS_TYPE_PATH = true;

    95 

    96     /** Return a method handle to invoke on the callerType, target, and remaining arguments.

    97      *  The method handle must finish the call.

    98      *  This is the first look at the caller type and target.

    99      */

   100     private MethodHandle dispatch(MethodType callerType, MethodHandle target) {

   101         MethodType targetType = target.type();

   102         if (USE_AS_TYPE_PATH || target.isVarargsCollector()) {

   103             MethodHandle newTarget = target.asType(callerType);

   104             targetType = callerType;

   105             Invokers invokers = targetType.invokers();

   106             MethodHandle invoker = invokers.erasedInvokerWithDrops;

   107             if (invoker == null) {

   108                 invokers.erasedInvokerWithDrops = invoker =

   109                     dropDispatchArguments(invokers.erasedInvoker());

   110             }

   111             return invoker.bindTo(newTarget);

   112         }

   113         throw new RuntimeException("NYI");

   114     }

   115 

   116     private MethodHandle dispatchWithConversion(MethodType callerType, MethodHandle target) {

   117         MethodHandle finisher = dispatch(callerType, target);

   118         if (returnConversionNeeded(callerType, target))

   119             finisher = addReturnConversion(finisher, callerType.returnType());  //FIXME: slow

   120         return finisher;

   121     }

   122 

   123     private boolean returnConversionPossible() {

   124         Class<?> needType = erasedCallerType.returnType();

   125         return !needType.isPrimitive();

   126     }

   127     private boolean returnConversionNeeded(MethodType callerType, MethodHandle target) {

   128         Class<?> needType = callerType.returnType();

   129         if (needType == erasedCallerType.returnType())

   130             return false;  // no conversions possible, since must be primitive or Object

   131         Class<?> haveType = target.type().returnType();

   132         if (VerifyType.isNullConversion(haveType, needType))

   133             return false;

   134         return true;

   135     }

   136     private MethodHandle addReturnConversion(MethodHandle target, Class<?> type) {

   137         if (true) throw new RuntimeException("NYI");

   138         // FIXME: This is slow because it creates a closure node on every call that requires a return cast.

   139         MethodType targetType = target.type();

   140         MethodHandle caster = ValueConversions.identity(type);

   141         caster = caster.asType(MethodType.methodType(type, targetType.returnType()));

   142         // Drop irrelevant arguments, because we only care about the return value:

   143         caster = MethodHandles.dropArguments(caster, 1, targetType.parameterList());

   144         MethodHandle result = MethodHandles.foldArguments(caster, target);

   145         return result.asType(target.type());

   146     }

   147 

   148     public String toString() {

   149         return "InvokeGeneric"+erasedCallerType;

   150     }

   151 }