/* * Copyright 2008-2009 Sun Microsystems, Inc. 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. Sun designates this * particular file as subject to the "Classpath" exception as provided * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, * CA 95054 USA or visit www.sun.com if you need additional information or * have any questions. */ package sun.dyn.util; import java.dyn.MethodType; import sun.dyn.empty.Empty; /** * This class centralizes information about the JVM verifier * and its requirements about type correctness. * @author jrose */ public class VerifyType { private VerifyType() { } // cannot instantiate /** * True if a value can be stacked as the source type and unstacked as the * destination type, without violating the JVM's type consistency. * * @param call the type of a stacked value * @param recv the type by which we'd like to treat it * @return whether the retyping can be done without motion or reformatting */ public static boolean isNullConversion(Class> src, Class> dst) { if (src == dst) return true; // Verifier allows any interface to be treated as Object: if (dst.isInterface()) dst = Object.class; if (src.isInterface()) src = Object.class; if (src == dst) return true; // check again if (dst == void.class) return true; // drop any return value if (isNullType(src)) return !dst.isPrimitive(); if (!src.isPrimitive()) return dst.isAssignableFrom(src); // Verifier allows an int to carry byte, short, char, or even boolean: if (dst == int.class) return Wrapper.forPrimitiveType(src).isSubwordOrInt(); return false; } /** * Specialization of isNullConversion to reference types. * @param call the type of a stacked value * @param recv the reference type by which we'd like to treat it * @return whether the retyping can be done without a cast */ public static boolean isNullReferenceConversion(Class> src, Class> dst) { assert(!dst.isPrimitive()); if (dst.isInterface()) return true; // verifier allows this if (isNullType(src)) return true; return dst.isAssignableFrom(src); } /** * Is the given type java.lang.Null or an equivalent null-only type? */ public static boolean isNullType(Class> type) { if (type == null) return false; return type == NULL_CLASS // This one may also be used as a null type. // TO DO: Decide if we really want to legitimize it here. // Probably we do, unless java.lang.Null really makes it into Java 7 //|| type == Void.class // Locally known null-only class: || type == Empty.class ; } private static final Class> NULL_CLASS; static { Class> nullClass = null; try { nullClass = Class.forName("java.lang.Null"); } catch (ClassNotFoundException ex) { // OK, we'll cope } NULL_CLASS = nullClass; } /** * True if a method handle can receive a call under a slightly different * method type, without moving or reformatting any stack elements. * * @param call the type of call being made * @param recv the type of the method handle receiving the call * @return whether the retyping can be done without motion or reformatting */ public static boolean isNullConversion(MethodType call, MethodType recv) { if (call == recv) return true; int len = call.parameterCount(); if (len != recv.parameterCount()) return false; for (int i = 0; i < len; i++) if (!isNullConversion(call.parameterType(i), recv.parameterType(i))) return false; return isNullConversion(recv.returnType(), call.returnType()); } //TO DO: isRawConversion /** * Determine if the JVM verifier allows a value of type call to be * passed to a formal parameter (or return variable) of type recv. * Returns 1 if the verifier allows the types to match without conversion. * Returns -1 if the types can be made to match by a JVM-supported adapter. * Cases supported are: *