OverloadedMethod.java

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/*
   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
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   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
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*/

package jdk.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.dynalink.SecureLookupSupplier;
import jdk.dynalink.internal.InternalTypeUtilities;
import jdk.dynalink.linker.LinkerServices;
import jdk.dynalink.linker.support.Lookup;

/**
 * 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).
 */
class OverloadedMethod {
    private final Map<ClassString, MethodHandle> argTypesToMethods = new ConcurrentHashMap<>();
    private final OverloadedDynamicMethod parent;
    private final ClassLoader callSiteClassLoader;
    private final MethodType callSiteType;
    private final MethodHandle invoker;
    private final LinkerServices linkerServices;
    private final SecureLookupSupplier lookupSupplier;
    private final ArrayList<MethodHandle> fixArgMethods;
    private final ArrayList<MethodHandle> varArgMethods;

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

        fixArgMethods = new ArrayList<>(methodHandles.size());
        varArgMethods = new ArrayList<>(methodHandles.size());
        final int argNum = callSiteType.parameterCount();
        for(final 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) {
        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: {
                    final List<MethodHandle> fmethods = methods;
                    method = linkerServices.getWithLookup(
                            ()->SingleDynamicMethod.getInvocation(fmethods.get(0), callSiteType, linkerServices),
                            lookupSupplier);
                    break;
                }
                default: {
                    // This is unfortunate - invocation time ambiguity.
                    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(callSiteClassLoader)) {
                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 = InternalTypeUtilities.getCommonLosslessConversionType(retType, it.next().type().returnType());
        }
        return retType;
    }
}