OverloadedMethod.java

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/*
   Copyright 2009-2013 Attila Szegedi

   Licensed under both the Apache License, Version 2.0 (the "Apache License")
   and the BSD License (the "BSD License"), with licensee being free to
   choose either of the two at their discretion.

   You may not use this file except in compliance with either the Apache
   License or the BSD License.

   If you choose to use this file in compliance with the Apache License, the
   following notice applies to you:

       You may obtain a copy of the Apache License at

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

       Unless required by applicable law or agreed to in writing, software
       distributed under the License is distributed on an "AS IS" BASIS,
       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
       implied. See the License for the specific language governing
       permissions and limitations under the License.

   If you choose to use this file in compliance with the BSD License, the
   following notice applies to you:

       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
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       * 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
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*/

package jdk.internal.dynalink.beans;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import jdk.internal.dynalink.linker.LinkerServices;
import jdk.internal.dynalink.support.Lookup;
import jdk.internal.dynalink.support.TypeUtilities;

/**
 * Represents a subset of overloaded methods for a certain method name on a certain class. It can be either a fixarg or
 * a vararg subset depending on the subclass. The method is for a fixed number of arguments though (as it is generated
 * for a concrete call site). As such, all methods in the subset can be invoked with the specified number of arguments
 * (exactly matching for fixargs, or having less than or equal fixed arguments, for varargs).
 *
 * @author Attila Szegedi
 */
class OverloadedMethod {
    private final Map<ClassString, MethodHandle> argTypesToMethods = new ConcurrentHashMap<>();
    private final OverloadedDynamicMethod parent;
    private final MethodType callSiteType;
    private final MethodHandle invoker;
    private final LinkerServices linkerServices;
    private final ArrayList<MethodHandle> fixArgMethods;
    private final ArrayList<MethodHandle> varArgMethods;

    OverloadedMethod(final List<MethodHandle> methodHandles, final OverloadedDynamicMethod parent, final MethodType callSiteType,
            final LinkerServices linkerServices) {
        this.parent = parent;
        final Class<?> commonRetType = getCommonReturnType(methodHandles);
        this.callSiteType = callSiteType.changeReturnType(commonRetType);
        this.linkerServices = linkerServices;

        fixArgMethods = new ArrayList<>(methodHandles.size());
        varArgMethods = new ArrayList<>(methodHandles.size());
        final int argNum = callSiteType.parameterCount();
        for(MethodHandle mh: methodHandles) {
            if(mh.isVarargsCollector()) {
                final MethodHandle asFixed = mh.asFixedArity();
                if(argNum == asFixed.type().parameterCount()) {
                    fixArgMethods.add(asFixed);
                }
                varArgMethods.add(mh);
            } else {
                fixArgMethods.add(mh);
            }
        }
        fixArgMethods.trimToSize();
        varArgMethods.trimToSize();

        final MethodHandle bound = SELECT_METHOD.bindTo(this);
        final MethodHandle collecting = SingleDynamicMethod.collectArguments(bound, argNum).asType(
                callSiteType.changeReturnType(MethodHandle.class));
        invoker = linkerServices.asTypeLosslessReturn(MethodHandles.foldArguments(
                MethodHandles.exactInvoker(this.callSiteType), collecting), callSiteType);
    }

    MethodHandle getInvoker() {
        return invoker;
    }

    private static final MethodHandle SELECT_METHOD = Lookup.findOwnSpecial(MethodHandles.lookup(), "selectMethod",
            MethodHandle.class, Object[].class);

    @SuppressWarnings("unused")
    private MethodHandle selectMethod(final Object[] args) throws NoSuchMethodException {
        final Class<?>[] argTypes = new Class<?>[args.length];
        for(int i = 0; i < argTypes.length; ++i) {
            final Object arg = args[i];
            argTypes[i] = arg == null ? ClassString.NULL_CLASS : arg.getClass();
        }
        final ClassString classString = new ClassString(argTypes);
        MethodHandle method = argTypesToMethods.get(classString);
        if(method == null) {
            List<MethodHandle> methods = classString.getMaximallySpecifics(fixArgMethods, linkerServices, false);
            if(methods.isEmpty()) {
                methods = classString.getMaximallySpecifics(varArgMethods, linkerServices, true);
            }
            switch(methods.size()) {
                case 0: {
                    method = getNoSuchMethodThrower(argTypes);
                    break;
                }
                case 1: {
                    method = SingleDynamicMethod.getInvocation(methods.get(0), callSiteType, linkerServices);
                    break;
                }
                default: {
                    // This is unfortunate - invocation time ambiguity. We can still save the day if
                    method = getAmbiguousMethodThrower(argTypes, methods);
                    break;
                }
            }
            // Avoid keeping references to unrelated classes; this ruins the performance a bit, but avoids class loader
            // memory leaks.
            if(classString.isVisibleFrom(parent.getClassLoader())) {
                argTypesToMethods.put(classString, method);
            }
        }
        return method;
    }

    private MethodHandle getNoSuchMethodThrower(final Class<?>[] argTypes) {
        return adaptThrower(MethodHandles.insertArguments(THROW_NO_SUCH_METHOD, 0, this, argTypes));
    }

    private static final MethodHandle THROW_NO_SUCH_METHOD = Lookup.findOwnSpecial(MethodHandles.lookup(),
            "throwNoSuchMethod", void.class, Class[].class);

    @SuppressWarnings("unused")
    private void throwNoSuchMethod(final Class<?>[] argTypes) throws NoSuchMethodException {
        if(varArgMethods.isEmpty()) {
            throw new NoSuchMethodException("None of the fixed arity signatures " + getSignatureList(fixArgMethods) +
                    " of method " + parent.getName() + " match the argument types " + argTypesString(argTypes));
        }
        throw new NoSuchMethodException("None of the fixed arity signatures " + getSignatureList(fixArgMethods) +
                " or the variable arity signatures " + getSignatureList(varArgMethods) + " of the method " +
                parent.getName() + " match the argument types " + argTypesString(argTypes));
    }

    private MethodHandle getAmbiguousMethodThrower(final Class<?>[] argTypes, final List<MethodHandle> methods) {
        return adaptThrower(MethodHandles.insertArguments(THROW_AMBIGUOUS_METHOD, 0, this, argTypes, methods));
    }

    private MethodHandle adaptThrower(final MethodHandle rawThrower) {
        return MethodHandles.dropArguments(rawThrower, 0, callSiteType.parameterList()).asType(callSiteType);
    }

    private static final MethodHandle THROW_AMBIGUOUS_METHOD = Lookup.findOwnSpecial(MethodHandles.lookup(),
            "throwAmbiguousMethod", void.class, Class[].class, List.class);

    @SuppressWarnings("unused")
    private void throwAmbiguousMethod(final Class<?>[] argTypes, final List<MethodHandle> methods) throws NoSuchMethodException {
        final String arity = methods.get(0).isVarargsCollector() ? "variable" : "fixed";
        throw new NoSuchMethodException("Can't unambiguously select between " + arity + " arity signatures " +
                getSignatureList(methods) + " of the method " + parent.getName() + " for argument types " +
                argTypesString(argTypes));
    }

    private static String argTypesString(final Class<?>[] classes) {
        final StringBuilder b = new StringBuilder().append('[');
        appendTypes(b, classes, false);
        return b.append(']').toString();
    }

    private static String getSignatureList(final List<MethodHandle> methods) {
        final StringBuilder b = new StringBuilder().append('[');
        final Iterator<MethodHandle> it = methods.iterator();
        if(it.hasNext()) {
            appendSig(b, it.next());
            while(it.hasNext()) {
                appendSig(b.append(", "), it.next());
            }
        }
        return b.append(']').toString();
    }

    private static void appendSig(final StringBuilder b, final MethodHandle m) {
        b.append('(');
        appendTypes(b, m.type().parameterArray(), m.isVarargsCollector());
        b.append(')');
    }

    private static void appendTypes(final StringBuilder b, final Class<?>[] classes, final boolean varArg) {
        final int l = classes.length;
        if(!varArg) {
            if(l > 1) {
                b.append(classes[1].getCanonicalName());
                for(int i = 2; i < l; ++i) {
                    b.append(", ").append(classes[i].getCanonicalName());
                }
            }
        } else {
            for(int i = 1; i < l - 1; ++i) {
                b.append(classes[i].getCanonicalName()).append(", ");
            }
            b.append(classes[l - 1].getComponentType().getCanonicalName()).append("...");
        }
    }

    private static Class<?> getCommonReturnType(final List<MethodHandle> methodHandles) {
        final Iterator<MethodHandle> it = methodHandles.iterator();
        Class<?> retType = it.next().type().returnType();
        while(it.hasNext()) {
            retType = TypeUtilities.getCommonLosslessConversionType(retType, it.next().type().returnType());
        }
        return retType;
    }
}