1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/sun/invoke/util/VerifyType.java Sat Aug 09 11:11:13 2014 +0200
1.3 @@ -0,0 +1,194 @@
1.4 +/*
1.5 + * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation. Oracle designates this
1.11 + * particular file as subject to the "Classpath" exception as provided
1.12 + * by Oracle in the LICENSE file that accompanied this code.
1.13 + *
1.14 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 + * version 2 for more details (a copy is included in the LICENSE file that
1.18 + * accompanied this code).
1.19 + *
1.20 + * You should have received a copy of the GNU General Public License version
1.21 + * 2 along with this work; if not, write to the Free Software Foundation,
1.22 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 + *
1.24 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.25 + * or visit www.oracle.com if you need additional information or have any
1.26 + * questions.
1.27 + */
1.28 +
1.29 +package sun.invoke.util;
1.30 +
1.31 +import java.lang.invoke.MethodType;
1.32 +import sun.invoke.empty.Empty;
1.33 +
1.34 +/**
1.35 + * This class centralizes information about the JVM verifier
1.36 + * and its requirements about type correctness.
1.37 + * @author jrose
1.38 + */
1.39 +public class VerifyType {
1.40 +
1.41 + private VerifyType() { } // cannot instantiate
1.42 +
1.43 + /**
1.44 + * True if a value can be stacked as the source type and unstacked as the
1.45 + * destination type, without violating the JVM's type consistency.
1.46 + *
1.47 + * @param src the type of a stacked value
1.48 + * @param dst the type by which we'd like to treat it
1.49 + * @return whether the retyping can be done without motion or reformatting
1.50 + */
1.51 + public static boolean isNullConversion(Class<?> src, Class<?> dst) {
1.52 + if (src == dst) return true;
1.53 + // Verifier allows any interface to be treated as Object:
1.54 + if (dst.isInterface()) dst = Object.class;
1.55 + if (src.isInterface()) src = Object.class;
1.56 + if (src == dst) return true; // check again
1.57 + if (dst == void.class) return true; // drop any return value
1.58 + if (isNullType(src)) return !dst.isPrimitive();
1.59 + if (!src.isPrimitive()) return dst.isAssignableFrom(src);
1.60 + if (!dst.isPrimitive()) return false;
1.61 + // Verifier allows an int to carry byte, short, char, or even boolean:
1.62 + Wrapper sw = Wrapper.forPrimitiveType(src);
1.63 + if (dst == int.class) return sw.isSubwordOrInt();
1.64 + Wrapper dw = Wrapper.forPrimitiveType(dst);
1.65 + if (!sw.isSubwordOrInt()) return false;
1.66 + if (!dw.isSubwordOrInt()) return false;
1.67 + if (!dw.isSigned() && sw.isSigned()) return false;
1.68 + return dw.bitWidth() > sw.bitWidth();
1.69 + }
1.70 +
1.71 + /**
1.72 + * Specialization of isNullConversion to reference types.
1.73 + * @param src the type of a stacked value
1.74 + * @param dst the reference type by which we'd like to treat it
1.75 + * @return whether the retyping can be done without a cast
1.76 + */
1.77 + public static boolean isNullReferenceConversion(Class<?> src, Class<?> dst) {
1.78 + assert(!dst.isPrimitive());
1.79 + if (dst.isInterface()) return true; // verifier allows this
1.80 + if (isNullType(src)) return true;
1.81 + return dst.isAssignableFrom(src);
1.82 + }
1.83 +
1.84 + /**
1.85 + * Is the given type java.lang.Null or an equivalent null-only type?
1.86 + */
1.87 + public static boolean isNullType(Class<?> type) {
1.88 + if (type == null) return false;
1.89 + return type == NULL_CLASS
1.90 + // This one may also be used as a null type.
1.91 + // TO DO: Decide if we really want to legitimize it here.
1.92 + // Probably we do, unless java.lang.Null really makes it into Java 7
1.93 + //|| type == Void.class
1.94 + // Locally known null-only class:
1.95 + || type == Empty.class
1.96 + ;
1.97 + }
1.98 + private static final Class<?> NULL_CLASS;
1.99 + static {
1.100 + Class<?> nullClass = null;
1.101 + try {
1.102 + nullClass = Class.forName("java.lang.Null");
1.103 + } catch (ClassNotFoundException ex) {
1.104 + // OK, we'll cope
1.105 + }
1.106 + NULL_CLASS = nullClass;
1.107 + }
1.108 +
1.109 + /**
1.110 + * True if a method handle can receive a call under a slightly different
1.111 + * method type, without moving or reformatting any stack elements.
1.112 + *
1.113 + * @param call the type of call being made
1.114 + * @param recv the type of the method handle receiving the call
1.115 + * @return whether the retyping can be done without motion or reformatting
1.116 + */
1.117 + public static boolean isNullConversion(MethodType call, MethodType recv) {
1.118 + if (call == recv) return true;
1.119 + int len = call.parameterCount();
1.120 + if (len != recv.parameterCount()) return false;
1.121 + for (int i = 0; i < len; i++)
1.122 + if (!isNullConversion(call.parameterType(i), recv.parameterType(i)))
1.123 + return false;
1.124 + return isNullConversion(recv.returnType(), call.returnType());
1.125 + }
1.126 +
1.127 + /**
1.128 + * Determine if the JVM verifier allows a value of type call to be
1.129 + * passed to a formal parameter (or return variable) of type recv.
1.130 + * Returns 1 if the verifier allows the types to match without conversion.
1.131 + * Returns -1 if the types can be made to match by a JVM-supported adapter.
1.132 + * Cases supported are:
1.133 + * <ul><li>checkcast
1.134 + * </li><li>conversion between any two integral types (but not floats)
1.135 + * </li><li>unboxing from a wrapper to its corresponding primitive type
1.136 + * </li><li>conversion in either direction between float and double
1.137 + * </li></ul>
1.138 + * (Autoboxing is not supported here; it must be done via Java code.)
1.139 + * Returns 0 otherwise.
1.140 + */
1.141 + public static int canPassUnchecked(Class<?> src, Class<?> dst) {
1.142 + if (src == dst)
1.143 + return 1;
1.144 +
1.145 + if (dst.isPrimitive()) {
1.146 + if (dst == void.class)
1.147 + // Return anything to a caller expecting void.
1.148 + // This is a property of the implementation, which links
1.149 + // return values via a register rather than via a stack push.
1.150 + // This makes it possible to ignore cleanly.
1.151 + return 1;
1.152 + if (src == void.class)
1.153 + return 0; // void-to-something?
1.154 + if (!src.isPrimitive())
1.155 + // Cannot pass a reference to any primitive type (exc. void).
1.156 + return 0;
1.157 + Wrapper sw = Wrapper.forPrimitiveType(src);
1.158 + Wrapper dw = Wrapper.forPrimitiveType(dst);
1.159 + if (sw.isSubwordOrInt() && dw.isSubwordOrInt()) {
1.160 + if (sw.bitWidth() >= dw.bitWidth())
1.161 + return -1; // truncation may be required
1.162 + if (!dw.isSigned() && sw.isSigned())
1.163 + return -1; // sign elimination may be required
1.164 + return 1;
1.165 + }
1.166 + if (src == float.class || dst == float.class) {
1.167 + if (src == double.class || dst == double.class)
1.168 + return -1; // floating conversion may be required
1.169 + else
1.170 + return 0; // other primitive conversions NYI
1.171 + } else {
1.172 + // all fixed-point conversions are supported
1.173 + return 0;
1.174 + }
1.175 + } else if (src.isPrimitive()) {
1.176 + // Cannot pass a primitive to any reference type.
1.177 + // (Maybe allow null.class?)
1.178 + return 0;
1.179 + }
1.180 +
1.181 + // Handle reference types in the rest of the block:
1.182 +
1.183 + // The verifier treats interfaces exactly like Object.
1.184 + if (isNullReferenceConversion(src, dst))
1.185 + // pass any reference to object or an arb. interface
1.186 + return 1;
1.187 + // else it's a definite "maybe" (cast is required)
1.188 + return -1;
1.189 + }
1.190 +
1.191 + public static boolean isSpreadArgType(Class<?> spreadArg) {
1.192 + return spreadArg.isArray();
1.193 + }
1.194 + public static Class<?> spreadArgElementType(Class<?> spreadArg, int i) {
1.195 + return spreadArg.getComponentType();
1.196 + }
1.197 +}