ClassString.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * 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).
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 *
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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file, and Oracle licenses the original version of this file under the BSD
 * license:
 */
/*
   Copyright 2009-2013 Attila Szegedi

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:
   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.
   * Neither the name of the copyright holder nor the names of
     contributors may be used to endorse or promote products derived from
     this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
   BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
   BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package jdk.dynalink.beans;

import java.lang.invoke.MethodHandle;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import jdk.dynalink.internal.AccessControlContextFactory;
import jdk.dynalink.internal.InternalTypeUtilities;
import jdk.dynalink.linker.LinkerServices;
import jdk.dynalink.linker.support.TypeUtilities;

/**
 * Represents a sequence of {@link Class} objects, useful for representing method signatures. Provides value
 * semantics for using them as map keys, as well as specificity calculations and applicability checks as per
 * JLS.
 */
final class ClassString {
    @SuppressWarnings("removal")
    private static final AccessControlContext GET_CLASS_LOADER_CONTEXT =
            AccessControlContextFactory.createAccessControlContext("getClassLoader");

    /**
     * An anonymous inner class used solely to represent the "type" of null values for method applicability checking.
     */
    static final Class<?> NULL_CLASS = (new Object() { /* Intentionally empty */ }).getClass();

    private final Class<?>[] classes;
    private int hashCode;

    ClassString(final Class<?>[] classes) {
        this.classes = classes;
    }

    @Override
    public boolean equals(final Object other) {
        if(!(other instanceof ClassString)) {
            return false;
        }
        final Class<?>[] otherClasses = ((ClassString)other).classes;
        if(otherClasses.length != classes.length) {
            return false;
        }
        for(int i = 0; i < otherClasses.length; ++i) {
            if(otherClasses[i] != classes[i]) {
                return false;
            }
        }
        return true;
    }

    @Override
    public int hashCode() {
        if(hashCode == 0) {
            int h = 0;
            for(final Class<?> cls: classes) {
                h ^= cls.hashCode();
            }
            hashCode = h;
        }
        return hashCode;
    }

    @Override
    public String toString() {
        return "ClassString[" + Arrays.toString(classes) + "]";
    }

    @SuppressWarnings("removal")
    boolean isVisibleFrom(final ClassLoader classLoader) {
        return AccessController.doPrivileged((PrivilegedAction<Boolean>) () -> {
            for(final Class<?> clazz: classes) {
                if(!InternalTypeUtilities.canReferenceDirectly(classLoader, clazz.getClassLoader())) {
                    return false;
                }
            }
            return true;
        }, GET_CLASS_LOADER_CONTEXT);
    }

    List<MethodHandle> getMaximallySpecifics(final List<MethodHandle> methods, final LinkerServices linkerServices, final boolean varArg) {
        return MaximallySpecific.getMaximallySpecificMethodHandles(getApplicables(methods, linkerServices, varArg),
                varArg, classes, linkerServices);
    }

    /**
     * Returns all methods that are applicable to actual parameter classes represented by this ClassString object.
     */
    LinkedList<MethodHandle> getApplicables(final List<MethodHandle> methods, final LinkerServices linkerServices, final boolean varArg) {
        final LinkedList<MethodHandle> list = new LinkedList<>();
        for(final MethodHandle member: methods) {
            if(isApplicable(member, linkerServices, varArg)) {
                list.add(member);
            }
        }
        return list;
    }

    /**
     * Returns true if the supplied method is applicable to actual parameter classes represented by this ClassString
     * object.
     *
     */
    private boolean isApplicable(final MethodHandle method, final LinkerServices linkerServices, final boolean varArg) {
        final Class<?>[] formalTypes = method.type().parameterArray();
        final int cl = classes.length;
        final int fl = formalTypes.length - (varArg ? 1 : 0);
        if(varArg) {
            if(cl < fl) {
                return false;
            }
        } else {
            if(cl != fl) {
                return false;
            }
        }
        // Starting from 1 as we ignore the receiver type
        for(int i = 1; i < fl; ++i) {
            if(!canConvert(linkerServices, classes[i], formalTypes[i])) {
                return false;
            }
        }
        if(varArg) {
            final Class<?> varArgType = formalTypes[fl].getComponentType();
            for(int i = fl; i < cl; ++i) {
                if(!canConvert(linkerServices, classes[i], varArgType)) {
                    return false;
                }
            }
        }
        return true;
    }

    private static boolean canConvert(final LinkerServices ls, final Class<?> from, final Class<?> to) {
        if(from == NULL_CLASS) {
            return !to.isPrimitive();
        }
        return ls == null ? TypeUtilities.isMethodInvocationConvertible(from, to) : ls.canConvert(from, to);
    }
}