442 lines
19 KiB
Java
442 lines
19 KiB
Java
/*
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* Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang.invoke;
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import sun.invoke.util.Wrapper;
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import static java.lang.invoke.MethodHandleNatives.mapLookupExceptionToError;
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import static java.util.Objects.requireNonNull;
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import java.lang.reflect.Modifier;
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/**
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* Bootstrap methods for dynamically-computed constants.
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*
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* <p>The bootstrap methods in this class will throw a
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* {@code NullPointerException} for any reference argument that is {@code null},
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* unless the argument is specified to be unused or specified to accept a
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* {@code null} value.
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*
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* @since 11
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*/
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public final class ConstantBootstraps {
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/**
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* Do not call.
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*/
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private ConstantBootstraps() {throw new AssertionError();}
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// implements the upcall from the JVM, MethodHandleNatives.linkDynamicConstant:
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/*non-public*/
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// BEGIN Android-removed: Remove unused implementation.
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/*
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static Object makeConstant(MethodHandle bootstrapMethod,
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// Callee information:
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String name, Class<?> type,
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// Extra arguments for BSM, if any:
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Object info,
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// Caller information:
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Class<?> callerClass) {
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// Restrict bootstrap methods to those whose first parameter is Lookup
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// The motivation here is, in the future, to possibly support BSMs
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// that do not accept the meta-data of lookup/name/type, thereby
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// allowing the co-opting of existing methods to be used as BSMs as
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// long as the static arguments can be passed as method arguments
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MethodType mt = bootstrapMethod.type();
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if (mt.parameterCount() < 2 ||
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!MethodHandles.Lookup.class.isAssignableFrom(mt.parameterType(0))) {
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throw new BootstrapMethodError(
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"Invalid bootstrap method declared for resolving a dynamic constant: " + bootstrapMethod);
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}
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// BSMI.invoke handles all type checking and exception translation.
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// If type is not a reference type, the JVM is expecting a boxed
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// version, and will manage unboxing on the other side.
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return BootstrapMethodInvoker.invoke(
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type, bootstrapMethod, name, type, info, callerClass);
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}
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*/
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// END Android-removed: Remove unused implementation.
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/**
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* Returns a {@code null} object reference for the reference type specified
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* by {@code type}.
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*
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* @param lookup unused
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* @param name unused
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* @param type a reference type
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* @return a {@code null} value
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* @throws IllegalArgumentException if {@code type} is not a reference type
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*/
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public static Object nullConstant(MethodHandles.Lookup lookup, String name, Class<?> type) {
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if (requireNonNull(type).isPrimitive()) {
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throw new IllegalArgumentException(String.format("not reference: %s", type));
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}
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return null;
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}
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/**
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* Returns a {@link Class} mirror for the primitive type whose type
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* descriptor is specified by {@code name}.
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*
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* @param lookup unused
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* @param name the descriptor (JVMS 4.3) of the desired primitive type
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* @param type the required result type (must be {@code Class.class})
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* @return the {@link Class} mirror
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* @throws IllegalArgumentException if the name is not a descriptor for a
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* primitive type or the type is not {@code Class.class}
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*/
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public static Class<?> primitiveClass(MethodHandles.Lookup lookup, String name, Class<?> type) {
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requireNonNull(name);
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requireNonNull(type);
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if (type != Class.class) {
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throw new IllegalArgumentException();
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}
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if (name.length() != 1) {
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throw new IllegalArgumentException(String.format("not primitive: %s", name));
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}
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return Wrapper.forPrimitiveType(name.charAt(0)).primitiveType();
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}
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/**
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* Returns an {@code enum} constant of the type specified by {@code type}
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* with the name specified by {@code name}.
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*
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* @param lookup the lookup context describing the class performing the
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* operation (normally stacked by the JVM)
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* @param name the name of the constant to return, which must exactly match
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* an enum constant in the specified type.
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* @param type the {@code Class} object describing the enum type for which
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* a constant is to be returned
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* @param <E> The enum type for which a constant value is to be returned
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* @return the enum constant of the specified enum type with the
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* specified name
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* @throws IllegalAccessError if the declaring class or the field is not
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* accessible to the class performing the operation
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* @throws IllegalArgumentException if the specified enum type has
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* no constant with the specified name, or the specified
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* class object does not represent an enum type
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* @see Enum#valueOf(Class, String)
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*/
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public static <E extends Enum<E>> E enumConstant(MethodHandles.Lookup lookup, String name, Class<E> type) {
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requireNonNull(lookup);
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requireNonNull(name);
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requireNonNull(type);
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validateClassAccess(lookup, type);
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return Enum.valueOf(type, name);
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}
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/**
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* Returns the value of a static final field.
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*
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* @param lookup the lookup context describing the class performing the
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* operation (normally stacked by the JVM)
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* @param name the name of the field
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* @param type the type of the field
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* @param declaringClass the class in which the field is declared
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* @return the value of the field
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* @throws IllegalAccessError if the declaring class or the field is not
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* accessible to the class performing the operation
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* @throws NoSuchFieldError if the specified field does not exist
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* @throws IncompatibleClassChangeError if the specified field is not
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* {@code final}
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*/
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public static Object getStaticFinal(MethodHandles.Lookup lookup, String name, Class<?> type,
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Class<?> declaringClass) {
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requireNonNull(lookup);
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requireNonNull(name);
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requireNonNull(type);
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requireNonNull(declaringClass);
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MethodHandle mh;
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try {
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mh = lookup.findStaticGetter(declaringClass, name, type);
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// Android-changed: Re-implement final modifier check with existing APIs.
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// MemberName member = mh.internalMemberName();
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// if (!member.isFinal()) {
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MethodHandleInfo info = lookup.revealDirect(mh);
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if (!Modifier.isFinal(info.getModifiers())) {
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throw new IncompatibleClassChangeError("not a final field: " + name);
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}
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}
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catch (ReflectiveOperationException ex) {
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throw mapLookupExceptionToError(ex);
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}
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// Since mh is a handle to a static field only instances of
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// VirtualMachineError are anticipated to be thrown, such as a
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// StackOverflowError or an InternalError from the j.l.invoke code
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try {
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return mh.invoke();
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}
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catch (RuntimeException | Error e) {
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throw e;
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}
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catch (Throwable e) {
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throw new LinkageError("Unexpected throwable", e);
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}
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}
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/**
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* Returns the value of a static final field declared in the class which
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* is the same as the field's type (or, for primitive-valued fields,
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* declared in the wrapper class.) This is a simplified form of
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* {@link #getStaticFinal(MethodHandles.Lookup, String, Class, Class)}
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* for the case where a class declares distinguished constant instances of
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* itself.
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*
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* @param lookup the lookup context describing the class performing the
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* operation (normally stacked by the JVM)
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* @param name the name of the field
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* @param type the type of the field
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* @return the value of the field
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* @throws IllegalAccessError if the declaring class or the field is not
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* accessible to the class performing the operation
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* @throws NoSuchFieldError if the specified field does not exist
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* @throws IncompatibleClassChangeError if the specified field is not
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* {@code final}
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* @see #getStaticFinal(MethodHandles.Lookup, String, Class, Class)
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*/
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public static Object getStaticFinal(MethodHandles.Lookup lookup, String name, Class<?> type) {
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requireNonNull(type);
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Class<?> declaring = type.isPrimitive()
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? Wrapper.forPrimitiveType(type).wrapperType()
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: type;
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return getStaticFinal(lookup, name, type, declaring);
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}
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/**
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* Returns the result of invoking a method handle with the provided
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* arguments.
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* <p>
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* This method behaves as if the method handle to be invoked is the result
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* of adapting the given method handle, via {@link MethodHandle#asType}, to
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* adjust the return type to the desired type.
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*
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* @param lookup unused
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* @param name unused
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* @param type the desired type of the value to be returned, which must be
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* compatible with the return type of the method handle
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* @param handle the method handle to be invoked
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* @param args the arguments to pass to the method handle, as if with
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* {@link MethodHandle#invokeWithArguments}. Each argument may be
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* {@code null}.
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* @return the result of invoking the method handle
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* @throws WrongMethodTypeException if the handle's method type cannot be
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* adjusted to take the given number of arguments, or if the handle's return
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* type cannot be adjusted to the desired type
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* @throws ClassCastException if an argument or the result produced by
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* invoking the handle cannot be converted by reference casting
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* @throws Throwable anything thrown by the method handle invocation
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*/
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public static Object invoke(MethodHandles.Lookup lookup, String name, Class<?> type,
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MethodHandle handle, Object... args) throws Throwable {
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requireNonNull(type);
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requireNonNull(handle);
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requireNonNull(args);
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if (type != handle.type().returnType()) {
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// Adjust the return type of the handle to be invoked while
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// preserving variable arity if present
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handle = handle.asType(handle.type().changeReturnType(type)).
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withVarargs(handle.isVarargsCollector());
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}
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return handle.invokeWithArguments(args);
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}
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/**
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* Finds a {@link VarHandle} for an instance field.
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*
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* @param lookup the lookup context describing the class performing the
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* operation (normally stacked by the JVM)
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* @param name the name of the field
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* @param type the required result type (must be {@code Class<VarHandle>})
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* @param declaringClass the class in which the field is declared
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* @param fieldType the type of the field
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* @return the {@link VarHandle}
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* @throws IllegalAccessError if the declaring class or the field is not
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* accessible to the class performing the operation
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* @throws NoSuchFieldError if the specified field does not exist
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* @throws IllegalArgumentException if the type is not {@code VarHandle}
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*/
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public static VarHandle fieldVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type,
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Class<?> declaringClass, Class<?> fieldType) {
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requireNonNull(lookup);
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requireNonNull(name);
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requireNonNull(type);
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requireNonNull(declaringClass);
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requireNonNull(fieldType);
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if (type != VarHandle.class) {
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throw new IllegalArgumentException();
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}
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try {
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return lookup.findVarHandle(declaringClass, name, fieldType);
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}
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catch (ReflectiveOperationException e) {
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throw mapLookupExceptionToError(e);
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}
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}
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/**
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* Finds a {@link VarHandle} for a static field.
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*
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* @param lookup the lookup context describing the class performing the
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* operation (normally stacked by the JVM)
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* @param name the name of the field
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* @param type the required result type (must be {@code Class<VarHandle>})
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* @param declaringClass the class in which the field is declared
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* @param fieldType the type of the field
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* @return the {@link VarHandle}
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* @throws IllegalAccessError if the declaring class or the field is not
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* accessible to the class performing the operation
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* @throws NoSuchFieldError if the specified field does not exist
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* @throws IllegalArgumentException if the type is not {@code VarHandle}
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*/
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public static VarHandle staticFieldVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type,
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Class<?> declaringClass, Class<?> fieldType) {
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requireNonNull(lookup);
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requireNonNull(name);
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requireNonNull(type);
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requireNonNull(declaringClass);
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requireNonNull(fieldType);
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if (type != VarHandle.class) {
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throw new IllegalArgumentException();
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}
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try {
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return lookup.findStaticVarHandle(declaringClass, name, fieldType);
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}
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catch (ReflectiveOperationException e) {
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throw mapLookupExceptionToError(e);
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}
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}
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/**
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* Finds a {@link VarHandle} for an array type.
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*
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* @param lookup the lookup context describing the class performing the
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* operation (normally stacked by the JVM)
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* @param name unused
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* @param type the required result type (must be {@code Class<VarHandle>})
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* @param arrayClass the type of the array
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* @return the {@link VarHandle}
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* @throws IllegalAccessError if the component type of the array is not
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* accessible to the class performing the operation
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* @throws IllegalArgumentException if the type is not {@code VarHandle}
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*/
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public static VarHandle arrayVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type,
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Class<?> arrayClass) {
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requireNonNull(lookup);
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requireNonNull(type);
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requireNonNull(arrayClass);
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if (type != VarHandle.class) {
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throw new IllegalArgumentException();
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}
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return MethodHandles.arrayElementVarHandle(validateClassAccess(lookup, arrayClass));
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}
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/**
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* Applies a conversion from a source type to a destination type.
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* <p>
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* Given a destination type {@code dstType} and an input
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* value {@code value}, one of the following will happen:
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* <ul>
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* <li>If {@code dstType} is {@code void.class},
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* a {@link ClassCastException} is thrown.
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* <li>If {@code dstType} is {@code Object.class}, {@code value} is returned as is.
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* </ul>
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* <p>
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* Otherwise one of the following conversions is applied to {@code value}:
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* <ol>
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* <li>If {@code dstType} is a reference type, a reference cast
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* is applied to {@code value} as if by calling {@code dstType.cast(value)}.
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* <li>If {@code dstType} is a primitive type, then, if the runtime type
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* of {@code value} is a primitive wrapper type (such as {@link Integer}),
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* a Java unboxing conversion is applied {@jls 5.1.8} followed by a
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* Java casting conversion {@jls 5.5} converting either directly to
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* {@code dstType}, or, if {@code dstType} is {@code boolean},
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* to {@code int}, which is then converted to either {@code true}
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* or {@code false} depending on whether the least-significant-bit
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* is 1 or 0 respectively. If the runtime type of {@code value} is
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* not a primitive wrapper type a {@link ClassCastException} is thrown.
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* </ol>
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* <p>
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* The result is the same as when using the following code:
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* <blockquote><pre>{@code
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* MethodHandle id = MethodHandles.identity(dstType);
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* MethodType mt = MethodType.methodType(dstType, Object.class);
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* MethodHandle conv = MethodHandles.explicitCastArguments(id, mt);
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* return conv.invoke(value);
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* }</pre></blockquote>
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*
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* @param lookup unused
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* @param name unused
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* @param dstType the destination type of the conversion
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* @param value the value to be converted
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* @return the converted value
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* @throws ClassCastException when {@code dstType} is {@code void},
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* when a cast per (1) fails, or when {@code dstType} is a primitive type
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* and the runtime type of {@code value} is not a primitive wrapper type
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* (such as {@link Integer})
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*
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* @since 15
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*/
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public static Object explicitCast(MethodHandles.Lookup lookup, String name, Class<?> dstType, Object value)
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throws ClassCastException {
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if (dstType == void.class)
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throw new ClassCastException("Can not convert to void");
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if (dstType == Object.class)
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return value;
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MethodHandle id = MethodHandles.identity(dstType);
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MethodType mt = MethodType.methodType(dstType, Object.class);
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MethodHandle conv = MethodHandles.explicitCastArguments(id, mt);
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try {
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return conv.invoke(value);
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} catch (RuntimeException|Error e) {
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throw e; // let specified CCE and other runtime exceptions/errors through
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} catch (Throwable throwable) {
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throw new InternalError(throwable); // Not specified, throw InternalError
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}
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}
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private static <T> Class<T> validateClassAccess(MethodHandles.Lookup lookup, Class<T> type) {
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try {
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lookup.accessClass(type);
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return type;
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}
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catch (ReflectiveOperationException ex) {
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throw mapLookupExceptionToError(ex);
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}
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}
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}
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