1 /*

     2  * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 package java.lang.invoke;

    26 

    27 import sun.invoke.util.Wrapper;

    28 

    29 import static java.lang.invoke.MethodHandleNatives.mapLookupExceptionToError;

    30 import static java.util.Objects.requireNonNull;

    31 

    32 /**

    33  * Bootstrap methods for dynamically-computed constants.

    34  *

    35  * <p>The bootstrap methods in this class will throw a

    36  * {@code NullPointerException} for any reference argument that is {@code null},

    37  * unless the argument is specified to be unused or specified to accept a

    38  * {@code null} value.

    39  *

    40  * @since 10

    41  */

    42 public final class ConstantBootstraps {

    43     // implements the upcall from the JVM, MethodHandleNatives.linkDynamicConstant:

    44     /*non-public*/

    45     static Object makeConstant(MethodHandle bootstrapMethod,

    46                                // Callee information:

    47                                String name, Class<?> type,

    48                                // Extra arguments for BSM, if any:

    49                                Object info,

    50                                // Caller information:

    51                                Class<?> callerClass) {

    52         // BSMI.invoke handles all type checking and exception translation.

    53         // If type is not a reference type, the JVM is expecting a boxed

    54         // version, and will manage unboxing on the other side.

    55         return BootstrapMethodInvoker.invoke(

    56                 type, bootstrapMethod, name, type, info, callerClass);

    57     }

    58 

    59     /**

    60      * Returns a {@code null} object reference for the reference type specified

    61      * by {@code type}.

    62      *

    63      * @param lookup unused

    64      * @param name unused

    65      * @param type a reference type

    66      * @return a {@code null} value

    67      * @throws IllegalArgumentException if {@code type} is not a reference type

    68      */

    69     public static Object nullConstant(MethodHandles.Lookup lookup, String name, Class<?> type) {

    70         if (requireNonNull(type).isPrimitive()) {

    71             throw new IllegalArgumentException(String.format("not reference: %s", type));

    72         }

    73 

    74         return null;

    75     }

    76 

    77     /**

    78      * Returns a {@link Class} mirror for the primitive type whose type

    79      * descriptor is specified by {@code name}.

    80      *

    81      * @param lookup unused

    82      * @param name the descriptor (JVMS 4.3) of the desired primitive type

    83      * @param type the required result type (must be {@code Class.class})

    84      * @return the {@link Class} mirror

    85      * @throws IllegalArgumentException if the name is not a descriptor for a

    86      * primitive type or the type is not {@code Class.class}

    87      */

    88     public static Class<?> primitiveClass(MethodHandles.Lookup lookup, String name, Class<?> type) {

    89         requireNonNull(name);

    90         requireNonNull(type);

    91         if (type != Class.class) {

    92             throw new IllegalArgumentException();

    93         }

    94         if (name.length() == 0 || name.length() > 1) {

    95             throw new IllegalArgumentException(String.format("not primitive: %s", name));

    96         }

    97 

    98         return Wrapper.forPrimitiveType(name.charAt(0)).primitiveType();

    99     }

   100 

   101     /**

   102      * Returns an {@code enum} constant of the type specified by {@code type}

   103      * with the name specified by {@code name}.

   104      *

   105      * @param lookup the lookup context describing the class performing the

   106      * operation (normally stacked by the JVM)

   107      * @param type the {@code Class} object describing the enum type for which

   108      * a constant is to be returned

   109      * @param name the name of the constant to return, which must exactly match

   110      * an enum constant in the specified type.

   111      * @param <E> The enum type for which a constant value is to be returned

   112      * @return the enum constant of the specified enum type with the

   113      * specified name

   114      * @throws IllegalAccessError if the declaring class or the field is not

   115      * accessible to the class performing the operation

   116      * @throws IllegalArgumentException if the specified enum type has

   117      * no constant with the specified name, or the specified

   118      * class object does not represent an enum type

   119      * @see Enum#valueOf(Class, String)

   120      */

   121     public static <E extends Enum<E>> E enumConstant(MethodHandles.Lookup lookup, String name, Class<E> type) {

   122         requireNonNull(lookup);

   123         requireNonNull(name);

   124         requireNonNull(type);

   125         validateClassAccess(lookup, type);

   126 

   127         return Enum.valueOf(type, name);

   128     }

   129 

   130     /**

   131      * Returns the value of a static final field.

   132      *

   133      * @param lookup the lookup context describing the class performing the

   134      * operation (normally stacked by the JVM)

   135      * @param name the name of the field

   136      * @param type the type of the field

   137      * @param declaringClass the class in which the field is declared

   138      * @return the value of the field

   139      * @throws IllegalAccessError if the declaring class or the field is not

   140      * accessible to the class performing the operation

   141      * @throws NoSuchFieldError if the specified field does not exist

   142      * @throws IncompatibleClassChangeError if the specified field is not

   143      * {@code final}

   144      */

   145     public static Object getStaticFinal(MethodHandles.Lookup lookup, String name, Class<?> type,

   146                                         Class<?> declaringClass) {

   147         requireNonNull(lookup);

   148         requireNonNull(name);

   149         requireNonNull(type);

   150         requireNonNull(declaringClass);

   151 

   152         MethodHandle mh;

   153         try {

   154             mh = lookup.findStaticGetter(declaringClass, name, type);

   155             MemberName member = mh.internalMemberName();

   156             if (!member.isFinal()) {

   157                 throw new IncompatibleClassChangeError("not a final field: " + name);

   158             }

   159         }

   160         catch (ReflectiveOperationException ex) {

   161             throw mapLookupExceptionToError(ex);

   162         }

   163 

   164         // Since mh is a handle to a static field only instances of

   165         // VirtualMachineError are anticipated to be thrown, such as a

   166         // StackOverflowError or an InternalError from the j.l.invoke code

   167         try {

   168             return mh.invoke();

   169         }

   170         catch (RuntimeException | Error e) {

   171             throw e;

   172         }

   173         catch (Throwable e) {

   174             throw new LinkageError("Unexpected throwable", e);

   175         }

   176     }

   177 

   178     /**

   179      * Returns the value of a static final field declared in the class which

   180      * is the same as the field's type (or, for primitive-valued fields,

   181      * declared in the wrapper class.)  This is a simplified form of

   182      * {@link #getStaticFinal(MethodHandles.Lookup, String, Class, Class)}

   183      * for the case where a class declares distinguished constant instances of

   184      * itself.

   185      *

   186      * @param lookup the lookup context describing the class performing the

   187      * operation (normally stacked by the JVM)

   188      * @param name the name of the field

   189      * @param type the type of the field

   190      * @return the value of the field

   191      * @throws IllegalAccessError if the declaring class or the field is not

   192      * accessible to the class performing the operation

   193      * @throws NoSuchFieldError if the specified field does not exist

   194      * @throws IncompatibleClassChangeError if the specified field is not

   195      * {@code final}

   196      * @see #getStaticFinal(MethodHandles.Lookup, String, Class, Class)

   197      */

   198     public static Object getStaticFinal(MethodHandles.Lookup lookup, String name, Class<?> type) {

   199         requireNonNull(type);

   200 

   201         Class<?> declaring = type.isPrimitive()

   202                              ? Wrapper.forPrimitiveType(type).wrapperType()

   203                              : type;

   204         return getStaticFinal(lookup, name, type, declaring);

   205     }

   206 

   207 

   208     /**

   209      * Returns the result of invoking a method handle with the provided

   210      * arguments.

   211      *

   212      * @param lookup the lookup context describing the class performing the

   213      * operation (normally stacked by the JVM)

   214      * @param name unused

   215      * @param type the type of the value to be returned, which must be

   216      * compatible with the return type of the method handle

   217      * @param handle the method handle to be invoked

   218      * @param args the arguments to pass to the method handle, as if with

   219      * {@link MethodHandle#invokeWithArguments}.  Each argument may be

   220      * {@code null}.

   221      * @return the result of invoking the method handle

   222      * @throws WrongMethodTypeException if the handle's return type cannot be

   223      * adjusted to the desired type

   224      * @throws ClassCastException if an argument cannot be converted by

   225      * reference casting

   226      * @throws Throwable anything thrown by the method handle invocation

   227      */

   228     public static Object invoke(MethodHandles.Lookup lookup, String name, Class<?> type,

   229                                 MethodHandle handle, Object... args) throws Throwable {

   230         requireNonNull(type);

   231         requireNonNull(handle);

   232         requireNonNull(args);

   233 

   234         if (type != handle.type().returnType()) {

   235             handle = handle.asType(handle.type().changeReturnType(type));

   236         }

   237 

   238         return handle.invokeWithArguments(args);

   239     }

   240 

   241     /**

   242      * Finds a {@link VarHandle} for an instance field.

   243      *

   244      * @param lookup the lookup context describing the class performing the

   245      * operation (normally stacked by the JVM)

   246      * @param name the name of the field

   247      * @param type the required result type (must be {@code Class<VarHandle>})

   248      * @param declaringClass the class in which the field is declared

   249      * @param fieldType the type of the field

   250      * @return the {@link VarHandle}

   251      * @throws IllegalAccessError if the declaring class or the field is not

   252      * accessible to the class performing the operation

   253      * @throws NoSuchFieldError if the specified field does not exist

   254      * @throws IllegalArgumentException if the type is not {@code VarHandle}

   255      */

   256     public static VarHandle fieldVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type,

   257                                            Class<?> declaringClass, Class<?> fieldType) {

   258         requireNonNull(lookup);

   259         requireNonNull(name);

   260         requireNonNull(type);

   261         requireNonNull(declaringClass);

   262         requireNonNull(fieldType);

   263         if (type != VarHandle.class) {

   264             throw new IllegalArgumentException();

   265         }

   266 

   267         try {

   268             return lookup.findVarHandle(declaringClass, name, fieldType);

   269         }

   270         catch (ReflectiveOperationException e) {

   271             throw mapLookupExceptionToError(e);

   272         }

   273     }

   274 

   275     /**

   276      * Finds a {@link VarHandle} for a static field.

   277      *

   278      * @param lookup the lookup context describing the class performing the

   279      * operation (normally stacked by the JVM)

   280      * @param name the name of the field

   281      * @param type the required result type (must be {@code Class<VarHandle>})

   282      * @param declaringClass the class in which the field is declared

   283      * @param fieldType the type of the field

   284      * @return the {@link VarHandle}

   285      * @throws IllegalAccessError if the declaring class or the field is not

   286      * accessible to the class performing the operation

   287      * @throws NoSuchFieldError if the specified field does not exist

   288      * @throws IllegalArgumentException if the type is not {@code VarHandle}

   289      */

   290     public static VarHandle staticFieldVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type,

   291                                                  Class<?> declaringClass, Class<?> fieldType) {

   292         requireNonNull(lookup);

   293         requireNonNull(name);

   294         requireNonNull(type);

   295         requireNonNull(declaringClass);

   296         requireNonNull(fieldType);

   297         if (type != VarHandle.class) {

   298             throw new IllegalArgumentException();

   299         }

   300 

   301         try {

   302             return lookup.findStaticVarHandle(declaringClass, name, fieldType);

   303         }

   304         catch (ReflectiveOperationException e) {

   305             throw mapLookupExceptionToError(e);

   306         }

   307     }

   308 

   309     /**

   310      * Finds a {@link VarHandle} for an array type.

   311      *

   312      * @param lookup the lookup context describing the class performing the

   313      * operation (normally stacked by the JVM)

   314      * @param name unused

   315      * @param type the required result type (must be {@code Class<VarHandle>})

   316      * @param arrayClass the type of the array

   317      * @return the {@link VarHandle}

   318      * @throws IllegalAccessError if the component type of the array is not

   319      * accessible to the class performing the operation

   320      * @throws IllegalArgumentException if the type is not {@code VarHandle}

   321      */

   322     public static VarHandle arrayVarHandle(MethodHandles.Lookup lookup, String name, Class<VarHandle> type,

   323                                            Class<?> arrayClass) {

   324         requireNonNull(lookup);

   325         requireNonNull(type);

   326         requireNonNull(arrayClass);

   327         if (type != VarHandle.class) {

   328             throw new IllegalArgumentException();

   329         }

   330 

   331         return MethodHandles.arrayElementVarHandle(validateClassAccess(lookup, arrayClass));

   332     }

   333 

   334     private static <T> Class<T> validateClassAccess(MethodHandles.Lookup lookup, Class<T> type) {

   335         try {

   336             lookup.accessClass(type);

   337             return type;

   338         }

   339         catch (ReflectiveOperationException ex) {

   340             throw mapLookupExceptionToError(ex);

   341         }

   342     }

   343 }