1 /*
   2  * Copyright (c) 2010, 2013, 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 jdk.nashorn.internal.runtime.linker;
  27 
  28 import java.lang.invoke.MethodHandle;
  29 import java.lang.invoke.MethodHandles;
  30 import java.lang.invoke.MethodType;
  31 import jdk.internal.dynalink.beans.BeansLinker;
  32 import jdk.internal.dynalink.linker.ConversionComparator.Comparison;
  33 import jdk.internal.dynalink.linker.GuardedInvocation;
  34 import jdk.internal.dynalink.linker.GuardingDynamicLinker;
  35 import jdk.internal.dynalink.linker.LinkRequest;
  36 import jdk.internal.dynalink.linker.LinkerServices;
  37 import jdk.internal.dynalink.support.Lookup;
  38 import jdk.nashorn.internal.runtime.ConsString;
  39 
  40 /**
  41  * This linker delegates to a {@code BeansLinker} but passes it a special linker services object that has a modified
  42  * {@code asType} method that will ensure that we never pass internal engine objects that should not be externally
  43  * observable (currently only ConsString) to Java APIs, but rather that we flatten it into a String. We can't just add
  44  * this functionality as custom converters via {@code GuaardingTypeConverterFactory}, since they are not consulted when
  45  * the target method handle parameter signature is {@code Object}.
  46  */
  47 public class NashornBeansLinker implements GuardingDynamicLinker {
  48     private static final MethodHandle EXPORT_ARGUMENT = new Lookup(MethodHandles.lookup()).findOwnStatic("exportArgument", Object.class, Object.class);
  49 
  50     private final BeansLinker beansLinker = new BeansLinker();
  51 
  52     @Override
  53     public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {
  54         return getGuardedInvocation(beansLinker, linkRequest, linkerServices);
  55     }
  56 
  57     /**
  58      * Delegates to the specified linker but injects its linker services wrapper so that it will apply all special
  59      * conversions that this class does.
  60      * @param delegateLinker the linker to which the actual work is delegated to.
  61      * @param linkRequest the delegated link request
  62      * @param linkerServices the original link services that will be augmented with special conversions
  63      * @return the guarded invocation from the delegate, possibly augmented with special conversions
  64      * @throws Exception if the delegate throws an exception
  65      */
  66     public static GuardedInvocation getGuardedInvocation(final GuardingDynamicLinker delegateLinker, final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {
  67         return delegateLinker.getGuardedInvocation(linkRequest, new NashornBeansLinkerServices(linkerServices));
  68     }
  69 
  70     static Object exportArgument(final Object arg) {
  71         return arg instanceof ConsString ? arg.toString() : arg;
  72     }
  73 
  74     private static class NashornBeansLinkerServices implements LinkerServices {
  75         private final LinkerServices linkerServices;
  76 
  77         NashornBeansLinkerServices(final LinkerServices linkerServices) {
  78             this.linkerServices = linkerServices;
  79         }
  80 
  81         @Override
  82         public MethodHandle asType(final MethodHandle handle, final MethodType fromType) {
  83             final MethodHandle typed = linkerServices.asType(handle, fromType);
  84 
  85             final MethodType handleType = handle.type();
  86             final int paramCount = handleType.parameterCount();
  87             assert fromType.parameterCount() == handleType.parameterCount();
  88 
  89             MethodHandle[] filters = null;
  90             for(int i = 0; i < paramCount; ++i) {
  91                 if(shouldConvert(handleType.parameterType(i), fromType.parameterType(i))) {
  92                     if(filters == null) {
  93                         filters = new MethodHandle[paramCount];
  94                     }
  95                     filters[i] = EXPORT_ARGUMENT;
  96                 }
  97             }
  98 
  99             return filters != null ? MethodHandles.filterArguments(typed, 0, filters) : typed;
 100         }
 101 
 102         @Override
 103         public MethodHandle asTypeLosslessReturn(final MethodHandle handle, final MethodType fromType) {
 104             return Implementation.asTypeLosslessReturn(this, handle, fromType);
 105         }
 106 
 107         private static boolean shouldConvert(final Class<?> handleType, final Class<?> fromType) {
 108             return handleType == Object.class && fromType == Object.class;
 109         }
 110 
 111         @Override
 112         public MethodHandle getTypeConverter(final Class<?> sourceType, final Class<?> targetType) {
 113             return linkerServices.getTypeConverter(sourceType, targetType);
 114         }
 115 
 116         @Override
 117         public boolean canConvert(final Class<?> from, final Class<?> to) {
 118             return linkerServices.canConvert(from, to);
 119         }
 120 
 121         @Override
 122         public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest) throws Exception {
 123             return linkerServices.getGuardedInvocation(linkRequest);
 124         }
 125 
 126         @Override
 127         public Comparison compareConversion(final Class<?> sourceType, final Class<?> targetType1, final Class<?> targetType2) {
 128             return linkerServices.compareConversion(sourceType, targetType1, targetType2);
 129         }
 130     }
 131 }