| /* |
| * Copyright (c) 2008, 2013, 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 sun.invoke.util; |
| |
| import java.lang.invoke.MethodType; |
| import sun.invoke.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. |
| * <p> |
| * If both types are references, we apply the verifier's subclass check |
| * (or subtyping, if keepInterfaces). |
| * If the src type is a type guaranteed to be null (Void) it can be converted |
| * to any other reference type. |
| * <p> |
| * If both types are primitives, we apply the verifier's primitive conversions. |
| * These do not include Java conversions such as long to double, since those |
| * require computation and (in general) stack depth changes. |
| * But very simple 32-bit viewing changes, such as byte to int, |
| * are null conversions, because they do not require any computation. |
| * These conversions are from any type to a wider type up to 32 bits, |
| * as long as the conversion is not signed to unsigned (byte to char). |
| * <p> |
| * The primitive type 'void' does not interconvert with any other type, |
| * even though it is legal to drop any type from the stack and "return void". |
| * The stack effects, though are different between void and any other type, |
| * so it is safer to report a non-trivial conversion. |
| * |
| * @param src the type of a stacked value |
| * @param dst the type by which we'd like to treat it |
| * @param keepInterfaces if false, we treat any interface as if it were Object |
| * @return whether the retyping can be done without motion or reformatting |
| */ |
| public static boolean isNullConversion(Class<?> src, Class<?> dst, boolean keepInterfaces) { |
| if (src == dst) return true; |
| // Verifier allows any interface to be treated as Object: |
| if (!keepInterfaces) { |
| if (dst.isInterface()) dst = Object.class; |
| if (src.isInterface()) src = Object.class; |
| if (src == dst) return true; // check again |
| } |
| if (isNullType(src)) return !dst.isPrimitive(); |
| if (!src.isPrimitive()) return dst.isAssignableFrom(src); |
| if (!dst.isPrimitive()) return false; |
| // Verifier allows an int to carry byte, short, char, or even boolean: |
| Wrapper sw = Wrapper.forPrimitiveType(src); |
| if (dst == int.class) return sw.isSubwordOrInt(); |
| Wrapper dw = Wrapper.forPrimitiveType(dst); |
| if (!sw.isSubwordOrInt()) return false; |
| if (!dw.isSubwordOrInt()) return false; |
| if (!dw.isSigned() && sw.isSigned()) return false; |
| return dw.bitWidth() > sw.bitWidth(); |
| } |
| |
| /** |
| * Specialization of isNullConversion to reference types. |
| * @param src the type of a stacked value |
| * @param dst 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) { |
| // Any reference statically typed as Void is guaranteed to be null. |
| // Therefore, it can be safely treated as a value of any |
| // other type that admits null, i.e., a reference type. |
| if (type == Void.class) return true; |
| // Locally known null-only class: |
| if (type == Empty.class) return true; |
| return false; |
| } |
| |
| /** |
| * 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, boolean keepInterfaces) { |
| 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), keepInterfaces)) |
| return false; |
| return isNullConversion(recv.returnType(), call.returnType(), keepInterfaces); |
| } |
| |
| /** |
| * 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: |
| * <ul><li>checkcast |
| * </li><li>conversion between any two integral types (but not floats) |
| * </li><li>unboxing from a wrapper to its corresponding primitive type |
| * </li><li>conversion in either direction between float and double |
| * </li></ul> |
| * (Autoboxing is not supported here; it must be done via Java code.) |
| * Returns 0 otherwise. |
| */ |
| public static int canPassUnchecked(Class<?> src, Class<?> dst) { |
| if (src == dst) |
| return 1; |
| |
| if (dst.isPrimitive()) { |
| if (dst == void.class) |
| // Return anything to a caller expecting void. |
| // This is a property of the implementation, which links |
| // return values via a register rather than via a stack push. |
| // This makes it possible to ignore cleanly. |
| return 1; |
| if (src == void.class) |
| return 0; // void-to-something? |
| if (!src.isPrimitive()) |
| // Cannot pass a reference to any primitive type (exc. void). |
| return 0; |
| Wrapper sw = Wrapper.forPrimitiveType(src); |
| Wrapper dw = Wrapper.forPrimitiveType(dst); |
| if (sw.isSubwordOrInt() && dw.isSubwordOrInt()) { |
| if (sw.bitWidth() >= dw.bitWidth()) |
| return -1; // truncation may be required |
| if (!dw.isSigned() && sw.isSigned()) |
| return -1; // sign elimination may be required |
| return 1; |
| } |
| if (src == float.class || dst == float.class) { |
| if (src == double.class || dst == double.class) |
| return -1; // floating conversion may be required |
| else |
| return 0; // other primitive conversions NYI |
| } else { |
| // all fixed-point conversions are supported |
| return 0; |
| } |
| } else if (src.isPrimitive()) { |
| // Cannot pass a primitive to any reference type. |
| // (Maybe allow null.class?) |
| return 0; |
| } |
| |
| // Handle reference types in the rest of the block: |
| |
| // The verifier treats interfaces exactly like Object. |
| if (isNullReferenceConversion(src, dst)) |
| // pass any reference to object or an arb. interface |
| return 1; |
| // else it's a definite "maybe" (cast is required) |
| return -1; |
| } |
| |
| public static boolean isSpreadArgType(Class<?> spreadArg) { |
| return spreadArg.isArray(); |
| } |
| public static Class<?> spreadArgElementType(Class<?> spreadArg, int i) { |
| return spreadArg.getComponentType(); |
| } |
| } |
