| /* |
| * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * 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). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| package jdk.dynalink.internal; |
| |
| import java.util.ArrayList; |
| import java.util.HashSet; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Set; |
| import jdk.dynalink.linker.support.TypeUtilities; |
| |
| /** |
| * Various static utility methods for testing type relationships; internal to Dynalink. |
| */ |
| public class InternalTypeUtilities { |
| private InternalTypeUtilities() { |
| } |
| |
| /** |
| * Returns true if either of the types is assignable from the other. |
| * @param c1 one type |
| * @param c2 another type |
| * @return true if either c1 is assignable from c2 or c2 is assignable from c1. |
| */ |
| public static boolean areAssignable(final Class<?> c1, final Class<?> c2) { |
| return c1.isAssignableFrom(c2) || c2.isAssignableFrom(c1); |
| } |
| |
| /** |
| * Return true if it is safe to strongly reference a class from the referred |
| * class loader from a class associated with the referring class loader |
| * without risking a class loader memory leak. Generally, it is only safe |
| * to reference classes from the same or ancestor class loader. {@code null} |
| * indicates the system class loader; classes from it can always be |
| * directly referenced, and it can only directly reference classes from |
| * itself. This method can be used by language runtimes to ensure they are |
| * using weak references in their linkages when they need to link to methods |
| * in unrelated class loaders. |
| * |
| * @param referrerLoader the referrer class loader. |
| * @param referredLoader the referred class loader |
| * @return true if it is safe to strongly reference the class from referred |
| * in referred. |
| * @throws SecurityException if the caller does not have the |
| * {@code RuntimePermission("getClassLoader")} permission and the method |
| * needs to traverse the parent class loader chain. |
| */ |
| public static boolean canReferenceDirectly(final ClassLoader referrerLoader, final ClassLoader referredLoader) { |
| if(referredLoader == null) { |
| // Can always refer directly to a system class |
| return true; |
| } |
| if(referrerLoader == null) { |
| // System classes can't refer directly to any non-system class |
| return false; |
| } |
| // Otherwise, can only refer directly to classes residing in same or |
| // parent class loader. |
| |
| ClassLoader referrer = referrerLoader; |
| do { |
| if(referrer == referredLoader) { |
| return true; |
| } |
| referrer = referrer.getParent(); |
| } while(referrer != null); |
| return false; |
| } |
| |
| /** |
| * Given two types represented by c1 and c2, returns a type that is their |
| * most specific common supertype for purposes of lossless conversions. |
| * |
| * @param c1 one type |
| * @param c2 another type |
| * @return their most common superclass or superinterface for purposes of |
| * lossless conversions. If they have several unrelated superinterfaces as |
| * their most specific common type, or the types themselves are completely |
| * unrelated interfaces, {@link java.lang.Object} is returned. |
| */ |
| public static Class<?> getCommonLosslessConversionType(final Class<?> c1, final Class<?> c2) { |
| if(c1 == c2) { |
| return c1; |
| } else if (c1 == void.class || c2 == void.class) { |
| return Object.class; |
| } else if(TypeUtilities.isConvertibleWithoutLoss(c2, c1)) { |
| return c1; |
| } else if(TypeUtilities.isConvertibleWithoutLoss(c1, c2)) { |
| return c2; |
| } else if(c1.isPrimitive() && c2.isPrimitive()) { |
| if((c1 == byte.class && c2 == char.class) || (c1 == char.class && c2 == byte.class)) { |
| // byte + char = int |
| return int.class; |
| } else if((c1 == short.class && c2 == char.class) || (c1 == char.class && c2 == short.class)) { |
| // short + char = int |
| return int.class; |
| } else if((c1 == int.class && c2 == float.class) || (c1 == float.class && c2 == int.class)) { |
| // int + float = double |
| return double.class; |
| } |
| } |
| // For all other cases. This will handle long + (float|double) = Number case as well as boolean + anything = Object case too. |
| return getMostSpecificCommonTypeUnequalNonprimitives(c1, c2); |
| } |
| |
| private static Class<?> getMostSpecificCommonTypeUnequalNonprimitives(final Class<?> c1, final Class<?> c2) { |
| final Class<?> npc1 = c1.isPrimitive() ? TypeUtilities.getWrapperType(c1) : c1; |
| final Class<?> npc2 = c2.isPrimitive() ? TypeUtilities.getWrapperType(c2) : c2; |
| final Set<Class<?>> a1 = getAssignables(npc1, npc2); |
| final Set<Class<?>> a2 = getAssignables(npc2, npc1); |
| a1.retainAll(a2); |
| if(a1.isEmpty()) { |
| // Can happen when at least one of the arguments is an interface, |
| // as they don't have Object at the root of their hierarchy. |
| return Object.class; |
| } |
| // Gather maximally specific elements. Yes, there can be more than one |
| // thank to interfaces. I.e., if you call this method for String.class |
| // and Number.class, you'll have Comparable, Serializable, and Object |
| // as maximal elements. |
| final List<Class<?>> max = new ArrayList<>(); |
| outer: for(final Class<?> clazz: a1) { |
| for(final Iterator<Class<?>> maxiter = max.iterator(); maxiter.hasNext();) { |
| final Class<?> maxClazz = maxiter.next(); |
| if(TypeUtilities.isSubtype(maxClazz, clazz)) { |
| // It can't be maximal, if there's already a more specific |
| // maximal than it. |
| continue outer; |
| } |
| if(TypeUtilities.isSubtype(clazz, maxClazz)) { |
| // If it's more specific than a currently maximal element, |
| // that currently maximal is no longer a maximal. |
| maxiter.remove(); |
| } |
| } |
| // If we get here, no current maximal is more specific than the |
| // current class, so it is considered maximal as well |
| max.add(clazz); |
| } |
| if(max.size() > 1) { |
| return Object.class; |
| } |
| return max.get(0); |
| } |
| |
| private static Set<Class<?>> getAssignables(final Class<?> c1, final Class<?> c2) { |
| final Set<Class<?>> s = new HashSet<>(); |
| collectAssignables(c1, c2, s); |
| return s; |
| } |
| |
| private static void collectAssignables(final Class<?> c1, final Class<?> c2, final Set<Class<?>> s) { |
| if(c1.isAssignableFrom(c2)) { |
| s.add(c1); |
| } |
| final Class<?> sc = c1.getSuperclass(); |
| if(sc != null) { |
| collectAssignables(sc, c2, s); |
| } |
| final Class<?>[] itf = c1.getInterfaces(); |
| for(int i = 0; i < itf.length; ++i) { |
| collectAssignables(itf[i], c2, s); |
| } |
| } |
| } |