OverloadedDynamicMethod.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.

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package jdk.dynalink.beans;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodType;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.text.Collator;
import java.util.ArrayList;
import java.util.IdentityHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.SecureLookupSupplier;
import jdk.dynalink.beans.ApplicableOverloadedMethods.ApplicabilityTest;
import jdk.dynalink.internal.AccessControlContextFactory;
import jdk.dynalink.internal.InternalTypeUtilities;
import jdk.dynalink.linker.LinkerServices;

/**
 * Represents a group of {@link SingleDynamicMethod} objects that represents all overloads of a particular name (or all
 * constructors) for a particular class. Correctly handles overload resolution, variable arity methods, and caller
 * sensitive methods within the overloads.
 */
class OverloadedDynamicMethod extends DynamicMethod {
    /**
     * Holds a list of all methods.
     */
    private final LinkedList<SingleDynamicMethod> methods = new LinkedList<>();

    /**
     * Creates a new overloaded dynamic method.
     *
     * @param clazz the class this method belongs to
     * @param name the name of the method
     */
    OverloadedDynamicMethod(final Class<?> clazz, final String name) {
        super(getClassAndMethodName(clazz, name));
    }

    @Override
    SingleDynamicMethod getMethodForExactParamTypes(final String paramTypes) {
        final LinkedList<SingleDynamicMethod> matchingMethods = new LinkedList<>();
        for(final SingleDynamicMethod method: methods) {
            final SingleDynamicMethod matchingMethod = method.getMethodForExactParamTypes(paramTypes);
            if(matchingMethod != null) {
                matchingMethods.add(matchingMethod);
            }
        }
        switch(matchingMethods.size()) {
            case 0: {
                return null;
            }
            case 1: {
                return matchingMethods.getFirst();
            }
            default: {
                throw new BootstrapMethodError("Can't choose among " + matchingMethods + " for argument types "
                        + paramTypes + " for method " + getName());
            }
        }
    }

    @Override
    MethodHandle getInvocation(final CallSiteDescriptor callSiteDescriptor, final LinkerServices linkerServices) {
        final MethodType callSiteType = callSiteDescriptor.getMethodType();
        // First, find all methods applicable to the call site by subtyping (JLS 15.12.2.2)
        final ApplicableOverloadedMethods subtypingApplicables = getApplicables(callSiteType,
                ApplicableOverloadedMethods.APPLICABLE_BY_SUBTYPING);
        // Next, find all methods applicable by method invocation conversion to the call site (JLS 15.12.2.3).
        final ApplicableOverloadedMethods methodInvocationApplicables = getApplicables(callSiteType,
                ApplicableOverloadedMethods.APPLICABLE_BY_METHOD_INVOCATION_CONVERSION);
        // Finally, find all methods applicable by variable arity invocation. (JLS 15.12.2.4).
        final ApplicableOverloadedMethods variableArityApplicables = getApplicables(callSiteType,
                ApplicableOverloadedMethods.APPLICABLE_BY_VARIABLE_ARITY);

        // Find the methods that are maximally specific based on the call site signature
        List<SingleDynamicMethod> maximallySpecifics = subtypingApplicables.findMaximallySpecificMethods();
        if(maximallySpecifics.isEmpty()) {
            maximallySpecifics = methodInvocationApplicables.findMaximallySpecificMethods();
            if(maximallySpecifics.isEmpty()) {
                maximallySpecifics = variableArityApplicables.findMaximallySpecificMethods();
            }
        }

        // Now, get a list of the rest of the methods; those that are *not* applicable to the call site signature based
        // on JLS rules. As paradoxical as that might sound, we have to consider these for dynamic invocation, as they
        // might match more concrete types passed in invocations. That's why we provisionally call them "invokables".
        // This is typical for very generic signatures at call sites. Typical example: call site specifies
        // (Object, Object), and we have a method whose parameter types are (String, int). None of the JLS applicability
        // rules will trigger, but we must consider the method, as it can be the right match for a concrete invocation.
        @SuppressWarnings({ "unchecked", "rawtypes" })
        final List<SingleDynamicMethod> invokables = (List)methods.clone();
        invokables.removeAll(subtypingApplicables.getMethods());
        invokables.removeAll(methodInvocationApplicables.getMethods());
        invokables.removeAll(variableArityApplicables.getMethods());
        invokables.removeIf(m -> !isApplicableDynamically(linkerServices, callSiteType, m));

        // If no additional methods can apply at invocation time, and there's more than one maximally specific method
        // based on call site signature, that is a link-time ambiguity. In a static scenario, javac would report an
        // ambiguity error.
        if(invokables.isEmpty() && maximallySpecifics.size() > 1) {
            throw new BootstrapMethodError("Can't choose among " + maximallySpecifics + " for argument types "
                    + callSiteType);
        }

        // Merge them all.
        invokables.addAll(maximallySpecifics);
        switch(invokables.size()) {
            case 0: {
                // No overloads can ever match the call site type
                return null;
            }
            case 1: {
                // Very lucky, we ended up with a single candidate method handle based on the call site signature; we
                // can link it very simply by delegating to the SingleDynamicMethod.
                return invokables.iterator().next().getInvocation(callSiteDescriptor, linkerServices);
            }
            default: {
                // We have more than one candidate. We have no choice but to link to a method that resolves overloads on
                // every invocation (alternatively, we could opportunistically link the one method that resolves for the
                // current arguments, but we'd need to install a fairly complex guard for that and when it'd fail, we'd
                // go back all the way to candidate selection. Note that we're resolving any potential caller sensitive
                // methods here to their handles, as the OverloadedMethod instance is specific to a call site, so it
                // has an already determined Lookup.
                final List<MethodHandle> methodHandles = new ArrayList<>(invokables.size());
                for(final SingleDynamicMethod method: invokables) {
                    methodHandles.add(method.getTarget(callSiteDescriptor));
                }
                return new OverloadedMethod(methodHandles, this, getCallSiteClassLoader(callSiteDescriptor), callSiteType, linkerServices, callSiteDescriptor).getInvoker();
            }
        }
    }

    @SuppressWarnings("removal")
    private static final AccessControlContext GET_CALL_SITE_CLASS_LOADER_CONTEXT =
            AccessControlContextFactory.createAccessControlContext(
                    "getClassLoader", SecureLookupSupplier.GET_LOOKUP_PERMISSION_NAME);

    @SuppressWarnings("removal")
    private static ClassLoader getCallSiteClassLoader(final CallSiteDescriptor callSiteDescriptor) {
        return AccessController.doPrivileged(
            (PrivilegedAction<ClassLoader>) () -> callSiteDescriptor.getLookup().lookupClass().getClassLoader(),
            GET_CALL_SITE_CLASS_LOADER_CONTEXT);
    }

    @Override
    public boolean contains(final SingleDynamicMethod m) {
        for(final SingleDynamicMethod method: methods) {
            if(method.contains(m)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public boolean isConstructor() {
        assert !methods.isEmpty();
        return methods.getFirst().isConstructor();
    }

    @Override
    public String toString() {
        // First gather the names and sort them. This makes it consistent and easier to read.
        final List<String> names = new ArrayList<>(methods.size());
        int len = 0;
        for (final SingleDynamicMethod m: methods) {
            final String name = m.getName();
            len += name.length();
            names.add(name);
        }
        // Case insensitive sorting, so e.g. "Object" doesn't come before "boolean".
        final Collator collator = Collator.getInstance();
        collator.setStrength(Collator.SECONDARY);
        names.sort(collator);

        final String className = getClass().getName();
        // Class name length + length of signatures + 2 chars/per signature for indentation and newline +
        // 3 for brackets and initial newline
        final int totalLength = className.length() + len + 2 * names.size() + 3;
        final StringBuilder b = new StringBuilder(totalLength);
        b.append('[').append(className).append('\n');
        for(final String name: names) {
            b.append(' ').append(name).append('\n');
        }
        b.append(']');
        assert b.length() == totalLength;
        return b.toString();
    }

    private static boolean isApplicableDynamically(final LinkerServices linkerServices, final MethodType callSiteType,
            final SingleDynamicMethod m) {
        final MethodType methodType = m.getMethodType();
        final boolean varArgs = m.isVarArgs();
        final int fixedArgLen = methodType.parameterCount() - (varArgs ? 1 : 0);
        final int callSiteArgLen = callSiteType.parameterCount();

        // Arity checks
        if(varArgs) {
            if(callSiteArgLen < fixedArgLen) {
                return false;
            }
        } else if(callSiteArgLen != fixedArgLen) {
            return false;
        }

        // Fixed arguments type checks, starting from 1, as receiver type doesn't participate
        for(int i = 1; i < fixedArgLen; ++i) {
            if(!isApplicableDynamically(linkerServices, callSiteType.parameterType(i), methodType.parameterType(i))) {
                return false;
            }
        }
        if(!varArgs) {
            // Not vararg; both arity and types matched.
            return true;
        }

        final Class<?> varArgArrayType = methodType.parameterType(fixedArgLen);
        final Class<?> varArgType = varArgArrayType.getComponentType();

        if(fixedArgLen == callSiteArgLen - 1) {
            // Exactly one vararg; check both array type matching and array component type matching.
            final Class<?> callSiteArgType = callSiteType.parameterType(fixedArgLen);
            return isApplicableDynamically(linkerServices, callSiteArgType, varArgArrayType)
                    || isApplicableDynamically(linkerServices, callSiteArgType, varArgType);
        }

        // Either zero, or more than one vararg; check if all actual vararg types match the vararg array component type.
        for(int i = fixedArgLen; i < callSiteArgLen; ++i) {
            if(!isApplicableDynamically(linkerServices, callSiteType.parameterType(i), varArgType)) {
                return false;
            }
        }

        return true;
    }

    private static boolean isApplicableDynamically(final LinkerServices linkerServices, final Class<?> callSiteType,
            final Class<?> methodType) {
        return isPotentiallyConvertible(callSiteType, methodType)
                || linkerServices.canConvert(callSiteType, methodType);
    }

    private ApplicableOverloadedMethods getApplicables(final MethodType callSiteType, final ApplicabilityTest test) {
        return new ApplicableOverloadedMethods(methods, callSiteType, test);
    }

    /**
     * Add a method to this overloaded method's set.
     *
     * @param method a method to add
     */
    public void addMethod(final SingleDynamicMethod method) {
        assert constructorFlagConsistent(method);
        methods.add(method);
    }

    private boolean constructorFlagConsistent(final SingleDynamicMethod method) {
        return methods.isEmpty() || methods.getFirst().isConstructor() == method.isConstructor();
    }

    /**
     * Determines whether one type can be potentially converted to another type at runtime. Allows a conversion between
     * any subtype and supertype in either direction, and also allows a conversion between any two primitive types, as
     * well as between any primitive type and any reference type that can hold a boxed primitive.
     *
     * @param callSiteType the parameter type at the call site
     * @param methodType the parameter type in the method declaration
     * @return true if callSiteType is potentially convertible to the methodType.
     */
    private static boolean isPotentiallyConvertible(final Class<?> callSiteType, final Class<?> methodType) {
        // Widening or narrowing reference conversion
        if(InternalTypeUtilities.areAssignable(callSiteType, methodType)) {
            return true;
        }
        if(callSiteType.isPrimitive()) {
            // Allow any conversion among primitives, as well as from any
            // primitive to any type that can receive a boxed primitive.
            // TODO: narrow this a bit, i.e. allow, say, boolean to Character?
            // MethodHandles.convertArguments() allows it, so we might need to
            // too.
            return methodType.isPrimitive() || isAssignableFromBoxedPrimitive(methodType);
        }
        if(methodType.isPrimitive()) {
            // Allow conversion from any reference type that can contain a
            // boxed primitive to any primitive.
            // TODO: narrow this a bit too?
            return isAssignableFromBoxedPrimitive(callSiteType);
        }
        return false;
    }

    private static final Set<Class<?>> PRIMITIVE_WRAPPER_TYPES = createPrimitiveWrapperTypes();

    private static Set<Class<?>> createPrimitiveWrapperTypes() {
        final Map<Class<?>, Class<?>> classes = new IdentityHashMap<>();
        addClassHierarchy(classes, Boolean.class);
        addClassHierarchy(classes, Byte.class);
        addClassHierarchy(classes, Character.class);
        addClassHierarchy(classes, Short.class);
        addClassHierarchy(classes, Integer.class);
        addClassHierarchy(classes, Long.class);
        addClassHierarchy(classes, Float.class);
        addClassHierarchy(classes, Double.class);
        return classes.keySet();
    }

    private static void addClassHierarchy(final Map<Class<?>, Class<?>> map, final Class<?> clazz) {
        if(clazz == null) {
            return;
        }
        map.put(clazz, clazz);
        addClassHierarchy(map, clazz.getSuperclass());
        for(final Class<?> itf: clazz.getInterfaces()) {
            addClassHierarchy(map, itf);
        }
    }

    /**
     * Returns true if the class can be assigned from any boxed primitive.
     *
     * @param clazz the class
     * @return true if the class can be assigned from any boxed primitive. Basically, it is true if the class is any
     * primitive wrapper class, or a superclass or superinterface of any primitive wrapper class.
     */
    private static boolean isAssignableFromBoxedPrimitive(final Class<?> clazz) {
        return PRIMITIVE_WRAPPER_TYPES.contains(clazz);
    }
}