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

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     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

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    25 

    26 /*

    27  * This file is available under and governed by the GNU General Public

    28  * License version 2 only, as published by the Free Software Foundation.

    29  * However, the following notice accompanied the original version of this

    30  * file, and Oracle licenses the original version of this file under the BSD

    31  * license:

    32  */

    33 /*

    34    Copyright 2009-2013 Attila Szegedi

    35 

    36    Licensed under both the Apache License, Version 2.0 (the "Apache License")

    37    and the BSD License (the "BSD License"), with licensee being free to

    38    choose either of the two at their discretion.

    39 

    40    You may not use this file except in compliance with either the Apache

    41    License or the BSD License.

    42 

    43    If you choose to use this file in compliance with the Apache License, the

    44    following notice applies to you:

    45 

    46        You may obtain a copy of the Apache License at

    47 

    48            http://www.apache.org/licenses/LICENSE-2.0

    49 

    50        Unless required by applicable law or agreed to in writing, software

    51        distributed under the License is distributed on an "AS IS" BASIS,

    52        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or

    53        implied. See the License for the specific language governing

    54        permissions and limitations under the License.

    55 

    56    If you choose to use this file in compliance with the BSD License, the

    57    following notice applies to you:

    58 

    59        Redistribution and use in source and binary forms, with or without

    60        modification, are permitted provided that the following conditions are

    61        met:

    62        * Redistributions of source code must retain the above copyright

    63          notice, this list of conditions and the following disclaimer.

    64        * Redistributions in binary form must reproduce the above copyright

    65          notice, this list of conditions and the following disclaimer in the

    66          documentation and/or other materials provided with the distribution.

    67        * Neither the name of the copyright holder nor the names of

    68          contributors may be used to endorse or promote products derived from

    69          this software without specific prior written permission.

    70 

    71        THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

    72        IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

    73        TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

    74        PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER

    75        BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

    76        CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

    77        SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR

    78        BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

    79        WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

    80        OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF

    81        ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    82 */

    83 

    84 package jdk.dynalink;

    85 

    86 import java.lang.invoke.MethodHandles;

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

    88 import java.lang.invoke.MethodType;

    89 import java.util.Objects;

    90 import java.util.function.Supplier;

    91 

    92 /**

    93  * Call site descriptors contain all the information necessary for linking a

    94  * call site. This information is normally passed as parameters to bootstrap

    95  * methods and consists of the {@code MethodHandles.Lookup} object on the caller

    96  * class in which the call site occurs, the dynamic operation at the call

    97  * site, and the method type of the call site. {@code CallSiteDescriptor}

    98  * objects are used in Dynalink to capture and store these parameters for

    99  * subsequent use by the {@link DynamicLinker}.

   100  * <p>

   101  * The constructors of built-in {@link RelinkableCallSite} implementations all

   102  * take a call site descriptor.

   103  * <p>

   104  * Call site descriptors must be immutable. You can use this class as-is or you

   105  * can subclass it, especially if you need to add further information to the

   106  * descriptors (typically, values passed in additional parameters to the

   107  * bootstrap method. Since the descriptors must be immutable, you can set up a

   108  * cache for equivalent descriptors to have the call sites share them.

   109  * <p>

   110  * The class extends {@link SecureLookupSupplier} for security-checked access to

   111  * the {@code MethodHandles.Lookup} object it carries. This lookup should be used

   112  * to find method handles to set as targets of the call site described by this

   113  * descriptor.

   114  */

   115 public class CallSiteDescriptor extends SecureLookupSupplier {

   116     private final Operation operation;

   117     private final MethodType methodType;

   118 

   119     /**

   120      * Creates a new call site descriptor.

   121      * @param lookup the lookup object describing the class the call site belongs to.

   122      * When creating descriptors from a {@link java.lang.invoke} bootstrap method,

   123      * it should be the lookup passed to the bootstrap.

   124      * @param operation the dynamic operation at the call site.

   125      * @param methodType the method type of the call site. When creating

   126      * descriptors from a {@link java.lang.invoke} bootstrap method, it should be

   127      * the method type passed to the bootstrap.

   128      */

   129     public CallSiteDescriptor(final Lookup lookup, final Operation operation, final MethodType methodType) {

   130         super(lookup);

   131         this.operation = Objects.requireNonNull(operation, "name");

   132         this.methodType = Objects.requireNonNull(methodType, "methodType");

   133     }

   134 

   135     /**

   136      * Returns the operation at the call site.

   137      * @return the operation at the call site.

   138      */

   139     public final Operation getOperation() {

   140         return operation;

   141     }

   142 

   143     /**

   144      * The type of the method at the call site.

   145      *

   146      * @return type of the method at the call site.

   147      */

   148     public final MethodType getMethodType() {

   149         return methodType;

   150     }

   151 

   152     /**

   153      * Finds or creates a call site descriptor that only differs in its

   154      * method type from this descriptor.

   155      * Invokes {@link #changeMethodTypeInternal(MethodType)}.

   156      *

   157      * @param newMethodType the new method type

   158      * @return a call site descriptor with changed method type.

   159      * @throws NullPointerException if {@code newMethodType} is null.

   160      */

   161     public final CallSiteDescriptor changeMethodType(final MethodType newMethodType) {

   162         final CallSiteDescriptor changed = changeMethodTypeInternal(newMethodType);

   163 

   164         if (getClass() != CallSiteDescriptor.class) {

   165             assertChangeInvariants(changed, "changeMethodTypeInternal");

   166             alwaysAssert(operation == changed.operation, () -> "changeMethodTypeInternal must not change the descriptor's operation");

   167             alwaysAssert(newMethodType == changed.methodType, () -> "changeMethodTypeInternal didn't set the correct new method type");

   168         }

   169         return changed;

   170     }

   171 

   172     /**

   173      * Finds or creates a call site descriptor that only differs in its

   174      * method type from this descriptor. Subclasses must override this method

   175      * to return an object of their exact class. If an overridden method changes

   176      * something other than the method type in the descriptor (its class, lookup,

   177      * or operation), or returns null, an {@code AssertionError} will be thrown

   178      * from {@link #changeMethodType(MethodType)}.

   179      *

   180      * @param newMethodType the new method type

   181      * @return a call site descriptor with the changed method type.

   182      */

   183     protected CallSiteDescriptor changeMethodTypeInternal(final MethodType newMethodType) {

   184         return new CallSiteDescriptor(getLookupPrivileged(), operation, newMethodType);

   185     }

   186 

   187     /**

   188      * Finds or creates a call site descriptor that only differs in its

   189      * operation from this descriptor.

   190      * Invokes {@link #changeOperationInternal(Operation)}.

   191      *

   192      * @param newOperation the new operation

   193      * @return a call site descriptor with the changed operation.

   194      * @throws NullPointerException if {@code newOperation} is null.

   195      * @throws SecurityException if the descriptor's lookup isn't the

   196      * {@link MethodHandles#publicLookup()}, and a security manager is present,

   197      * and a check for {@code RuntimePermission("dynalink.getLookup")} fails.

   198      * This is necessary as changing the operation in the call site descriptor

   199      * allows fabrication of descriptors for arbitrary operations with the lookup.

   200      */

   201     public final CallSiteDescriptor changeOperation(final Operation newOperation) {

   202         getLookup(); // force security check

   203         final CallSiteDescriptor changed = changeOperationInternal(newOperation);

   204 

   205         if (getClass() != CallSiteDescriptor.class) {

   206             assertChangeInvariants(changed, "changeOperationInternal");

   207             alwaysAssert(methodType == changed.methodType, () -> "changeOperationInternal must not change the descriptor's method type");

   208             alwaysAssert(newOperation == changed.operation, () -> "changeOperationInternal didn't set the correct new operation");

   209         }

   210         return changed;

   211     }

   212 

   213     /**

   214      * Finds or creates a call site descriptor that only differs in its

   215      * operation from this descriptor. Subclasses must override this method

   216      * to return an object of their exact class. If an overridden method changes

   217      * something other than the operation in the descriptor (its class, lookup,

   218      * or method type), or returns null, an {@code AssertionError} will be thrown

   219      * from {@link #changeOperation(Operation)}.

   220      *

   221      * @param newOperation the new operation

   222      * @return a call site descriptor with the changed operation.

   223      */

   224     protected CallSiteDescriptor changeOperationInternal(final Operation newOperation) {

   225         return new CallSiteDescriptor(getLookupPrivileged(), newOperation, methodType);

   226     }

   227 

   228     /**

   229      * Returns true if this call site descriptor is equal to the passed object.

   230      * It is considered equal if the other object is of the exact same class,

   231      * their operations and method types are equal, and their lookups have the

   232      * same {@link java.lang.invoke.MethodHandles.Lookup#lookupClass()} and

   233      * {@link java.lang.invoke.MethodHandles.Lookup#lookupModes()}.

   234      */

   235     @Override

   236     public boolean equals(final Object obj) {

   237         if (obj == this) {

   238             return true;

   239         } else if (obj == null) {

   240             return false;

   241         } else if (obj.getClass() != getClass()) {

   242             return false;

   243         }

   244         final CallSiteDescriptor other = (CallSiteDescriptor)obj;

   245         return operation.equals(other.operation) &&

   246                methodType.equals(other.methodType) &&

   247                lookupsEqual(getLookupPrivileged(), other.getLookupPrivileged());

   248     }

   249 

   250     /**

   251      * Compares two lookup objects for value-based equality. They are considered

   252      * equal if they have the same

   253      * {@link java.lang.invoke.MethodHandles.Lookup#lookupClass()} and

   254      * {@link java.lang.invoke.MethodHandles.Lookup#lookupModes()}.

   255      * @param l1 first lookup

   256      * @param l2 second lookup

   257      * @return true if the two lookups are equal, false otherwise.

   258      */

   259     private static boolean lookupsEqual(final Lookup l1, final Lookup l2) {

   260         return l1.lookupClass() == l2.lookupClass() && l1.lookupModes() == l2.lookupModes();

   261     }

   262 

   263     /**

   264      * Returns a value-based hash code of this call site descriptor computed

   265      * from its operation, method type, and lookup object's lookup class and

   266      * lookup modes.

   267      * @return value-based hash code for this call site descriptor.

   268      */

   269     @Override

   270     public int hashCode() {

   271         return operation.hashCode() + 31 * methodType.hashCode() + 31 * 31 * lookupHashCode(getLookupPrivileged());

   272     }

   273 

   274     /**

   275      * Returns a value-based hash code for the passed lookup object. It is

   276      * based on the lookup object's

   277      * {@link java.lang.invoke.MethodHandles.Lookup#lookupClass()} and

   278      * {@link java.lang.invoke.MethodHandles.Lookup#lookupModes()} values.

   279      * @param lookup the lookup object.

   280      * @return a hash code for the object..

   281      */

   282     private static int lookupHashCode(final Lookup lookup) {

   283         return lookup.lookupClass().hashCode() + 31 * lookup.lookupModes();

   284     }

   285 

   286     /**

   287      * Returns the string representation of this call site descriptor, of the

   288      * format {@code name(parameterTypes)returnType@lookup}.

   289      */

   290     @Override

   291     public String toString() {

   292         final String mt = methodType.toString();

   293         final String l = getLookupPrivileged().toString();

   294         final String o = operation.toString();

   295         final StringBuilder b = new StringBuilder(o.length() + mt.length() + 1 + l.length());

   296         return b.append(o).append(mt).append('@').append(l).toString();

   297     }

   298 

   299     private void assertChangeInvariants(final CallSiteDescriptor changed, final String caller) {

   300         alwaysAssert(changed != null, () -> caller + " must not return null.");

   301         alwaysAssert(getClass() == changed.getClass(), () -> caller + " must not change the descriptor's class");

   302         alwaysAssert(lookupsEqual(getLookupPrivileged(), changed.getLookupPrivileged()), () -> caller + " must not change the descriptor's lookup");

   303     }

   304 

   305     private static void alwaysAssert(final boolean cond, final Supplier<String> errorMessage) {

   306         if (!cond) {

   307             throw new AssertionError(errorMessage.get());

   308         }

   309     }

   310 }