1770 lines
90 KiB
Java
1770 lines
90 KiB
Java
/*
|
|
* 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 java.lang.invoke;
|
|
|
|
import java.util.Arrays;
|
|
import java.util.Objects;
|
|
|
|
import dalvik.system.EmulatedStackFrame;
|
|
|
|
import static java.lang.invoke.MethodHandleStatics.*;
|
|
|
|
/**
|
|
* A method handle is a typed, directly executable reference to an underlying method,
|
|
* constructor, field, or similar low-level operation, with optional
|
|
* transformations of arguments or return values.
|
|
* These transformations are quite general, and include such patterns as
|
|
* {@linkplain #asType conversion},
|
|
* {@linkplain #bindTo insertion},
|
|
* {@linkplain java.lang.invoke.MethodHandles#dropArguments deletion},
|
|
* and {@linkplain java.lang.invoke.MethodHandles#filterArguments substitution}.
|
|
*
|
|
* <h1>Method handle contents</h1>
|
|
* Method handles are dynamically and strongly typed according to their parameter and return types.
|
|
* They are not distinguished by the name or the defining class of their underlying methods.
|
|
* A method handle must be invoked using a symbolic type descriptor which matches
|
|
* the method handle's own {@linkplain #type type descriptor}.
|
|
* <p>
|
|
* Every method handle reports its type descriptor via the {@link #type type} accessor.
|
|
* This type descriptor is a {@link java.lang.invoke.MethodType MethodType} object,
|
|
* whose structure is a series of classes, one of which is
|
|
* the return type of the method (or {@code void.class} if none).
|
|
* <p>
|
|
* A method handle's type controls the types of invocations it accepts,
|
|
* and the kinds of transformations that apply to it.
|
|
* <p>
|
|
* A method handle contains a pair of special invoker methods
|
|
* called {@link #invokeExact invokeExact} and {@link #invoke invoke}.
|
|
* Both invoker methods provide direct access to the method handle's
|
|
* underlying method, constructor, field, or other operation,
|
|
* as modified by transformations of arguments and return values.
|
|
* Both invokers accept calls which exactly match the method handle's own type.
|
|
* The plain, inexact invoker also accepts a range of other call types.
|
|
* <p>
|
|
* Method handles are immutable and have no visible state.
|
|
* Of course, they can be bound to underlying methods or data which exhibit state.
|
|
* With respect to the Java Memory Model, any method handle will behave
|
|
* as if all of its (internal) fields are final variables. This means that any method
|
|
* handle made visible to the application will always be fully formed.
|
|
* This is true even if the method handle is published through a shared
|
|
* variable in a data race.
|
|
* <p>
|
|
* Method handles cannot be subclassed by the user.
|
|
* Implementations may (or may not) create internal subclasses of {@code MethodHandle}
|
|
* which may be visible via the {@link java.lang.Object#getClass Object.getClass}
|
|
* operation. The programmer should not draw conclusions about a method handle
|
|
* from its specific class, as the method handle class hierarchy (if any)
|
|
* may change from time to time or across implementations from different vendors.
|
|
*
|
|
* <h1>Method handle compilation</h1>
|
|
* A Java method call expression naming {@code invokeExact} or {@code invoke}
|
|
* can invoke a method handle from Java source code.
|
|
* From the viewpoint of source code, these methods can take any arguments
|
|
* and their result can be cast to any return type.
|
|
* Formally this is accomplished by giving the invoker methods
|
|
* {@code Object} return types and variable arity {@code Object} arguments,
|
|
* but they have an additional quality called <em>signature polymorphism</em>
|
|
* which connects this freedom of invocation directly to the JVM execution stack.
|
|
* <p>
|
|
* As is usual with virtual methods, source-level calls to {@code invokeExact}
|
|
* and {@code invoke} compile to an {@code invokevirtual} instruction.
|
|
* More unusually, the compiler must record the actual argument types,
|
|
* and may not perform method invocation conversions on the arguments.
|
|
* Instead, it must push them on the stack according to their own unconverted types.
|
|
* The method handle object itself is pushed on the stack before the arguments.
|
|
* The compiler then calls the method handle with a symbolic type descriptor which
|
|
* describes the argument and return types.
|
|
* <p>
|
|
* To issue a complete symbolic type descriptor, the compiler must also determine
|
|
* the return type. This is based on a cast on the method invocation expression,
|
|
* if there is one, or else {@code Object} if the invocation is an expression
|
|
* or else {@code void} if the invocation is a statement.
|
|
* The cast may be to a primitive type (but not {@code void}).
|
|
* <p>
|
|
* As a corner case, an uncasted {@code null} argument is given
|
|
* a symbolic type descriptor of {@code java.lang.Void}.
|
|
* The ambiguity with the type {@code Void} is harmless, since there are no references of type
|
|
* {@code Void} except the null reference.
|
|
*
|
|
* <h1>Method handle invocation</h1>
|
|
* The first time a {@code invokevirtual} instruction is executed
|
|
* it is linked, by symbolically resolving the names in the instruction
|
|
* and verifying that the method call is statically legal.
|
|
* This is true of calls to {@code invokeExact} and {@code invoke}.
|
|
* In this case, the symbolic type descriptor emitted by the compiler is checked for
|
|
* correct syntax and names it contains are resolved.
|
|
* Thus, an {@code invokevirtual} instruction which invokes
|
|
* a method handle will always link, as long
|
|
* as the symbolic type descriptor is syntactically well-formed
|
|
* and the types exist.
|
|
* <p>
|
|
* When the {@code invokevirtual} is executed after linking,
|
|
* the receiving method handle's type is first checked by the JVM
|
|
* to ensure that it matches the symbolic type descriptor.
|
|
* If the type match fails, it means that the method which the
|
|
* caller is invoking is not present on the individual
|
|
* method handle being invoked.
|
|
* <p>
|
|
* In the case of {@code invokeExact}, the type descriptor of the invocation
|
|
* (after resolving symbolic type names) must exactly match the method type
|
|
* of the receiving method handle.
|
|
* In the case of plain, inexact {@code invoke}, the resolved type descriptor
|
|
* must be a valid argument to the receiver's {@link #asType asType} method.
|
|
* Thus, plain {@code invoke} is more permissive than {@code invokeExact}.
|
|
* <p>
|
|
* After type matching, a call to {@code invokeExact} directly
|
|
* and immediately invoke the method handle's underlying method
|
|
* (or other behavior, as the case may be).
|
|
* <p>
|
|
* A call to plain {@code invoke} works the same as a call to
|
|
* {@code invokeExact}, if the symbolic type descriptor specified by the caller
|
|
* exactly matches the method handle's own type.
|
|
* If there is a type mismatch, {@code invoke} attempts
|
|
* to adjust the type of the receiving method handle,
|
|
* as if by a call to {@link #asType asType},
|
|
* to obtain an exactly invokable method handle {@code M2}.
|
|
* This allows a more powerful negotiation of method type
|
|
* between caller and callee.
|
|
* <p>
|
|
* (<em>Note:</em> The adjusted method handle {@code M2} is not directly observable,
|
|
* and implementations are therefore not required to materialize it.)
|
|
*
|
|
* <h1>Invocation checking</h1>
|
|
* In typical programs, method handle type matching will usually succeed.
|
|
* But if a match fails, the JVM will throw a {@link WrongMethodTypeException},
|
|
* either directly (in the case of {@code invokeExact}) or indirectly as if
|
|
* by a failed call to {@code asType} (in the case of {@code invoke}).
|
|
* <p>
|
|
* Thus, a method type mismatch which might show up as a linkage error
|
|
* in a statically typed program can show up as
|
|
* a dynamic {@code WrongMethodTypeException}
|
|
* in a program which uses method handles.
|
|
* <p>
|
|
* Because method types contain "live" {@code Class} objects,
|
|
* method type matching takes into account both types names and class loaders.
|
|
* Thus, even if a method handle {@code M} is created in one
|
|
* class loader {@code L1} and used in another {@code L2},
|
|
* method handle calls are type-safe, because the caller's symbolic type
|
|
* descriptor, as resolved in {@code L2},
|
|
* is matched against the original callee method's symbolic type descriptor,
|
|
* as resolved in {@code L1}.
|
|
* The resolution in {@code L1} happens when {@code M} is created
|
|
* and its type is assigned, while the resolution in {@code L2} happens
|
|
* when the {@code invokevirtual} instruction is linked.
|
|
* <p>
|
|
* Apart from the checking of type descriptors,
|
|
* a method handle's capability to call its underlying method is unrestricted.
|
|
* If a method handle is formed on a non-public method by a class
|
|
* that has access to that method, the resulting handle can be used
|
|
* in any place by any caller who receives a reference to it.
|
|
* <p>
|
|
* Unlike with the Core Reflection API, where access is checked every time
|
|
* a reflective method is invoked,
|
|
* method handle access checking is performed
|
|
* <a href="MethodHandles.Lookup.html#access">when the method handle is created</a>.
|
|
* In the case of {@code ldc} (see below), access checking is performed as part of linking
|
|
* the constant pool entry underlying the constant method handle.
|
|
* <p>
|
|
* Thus, handles to non-public methods, or to methods in non-public classes,
|
|
* should generally be kept secret.
|
|
* They should not be passed to untrusted code unless their use from
|
|
* the untrusted code would be harmless.
|
|
*
|
|
* <h1>Method handle creation</h1>
|
|
* Java code can create a method handle that directly accesses
|
|
* any method, constructor, or field that is accessible to that code.
|
|
* This is done via a reflective, capability-based API called
|
|
* {@link java.lang.invoke.MethodHandles.Lookup MethodHandles.Lookup}
|
|
* For example, a static method handle can be obtained
|
|
* from {@link java.lang.invoke.MethodHandles.Lookup#findStatic Lookup.findStatic}.
|
|
* There are also conversion methods from Core Reflection API objects,
|
|
* such as {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect}.
|
|
* <p>
|
|
* Like classes and strings, method handles that correspond to accessible
|
|
* fields, methods, and constructors can also be represented directly
|
|
* in a class file's constant pool as constants to be loaded by {@code ldc} bytecodes.
|
|
* A new type of constant pool entry, {@code CONSTANT_MethodHandle},
|
|
* refers directly to an associated {@code CONSTANT_Methodref},
|
|
* {@code CONSTANT_InterfaceMethodref}, or {@code CONSTANT_Fieldref}
|
|
* constant pool entry.
|
|
* (For full details on method handle constants,
|
|
* see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)
|
|
* <p>
|
|
* Method handles produced by lookups or constant loads from methods or
|
|
* constructors with the variable arity modifier bit ({@code 0x0080})
|
|
* have a corresponding variable arity, as if they were defined with
|
|
* the help of {@link #asVarargsCollector asVarargsCollector}.
|
|
* <p>
|
|
* A method reference may refer either to a static or non-static method.
|
|
* In the non-static case, the method handle type includes an explicit
|
|
* receiver argument, prepended before any other arguments.
|
|
* In the method handle's type, the initial receiver argument is typed
|
|
* according to the class under which the method was initially requested.
|
|
* (E.g., if a non-static method handle is obtained via {@code ldc},
|
|
* the type of the receiver is the class named in the constant pool entry.)
|
|
* <p>
|
|
* Method handle constants are subject to the same link-time access checks
|
|
* their corresponding bytecode instructions, and the {@code ldc} instruction
|
|
* will throw corresponding linkage errors if the bytecode behaviors would
|
|
* throw such errors.
|
|
* <p>
|
|
* As a corollary of this, access to protected members is restricted
|
|
* to receivers only of the accessing class, or one of its subclasses,
|
|
* and the accessing class must in turn be a subclass (or package sibling)
|
|
* of the protected member's defining class.
|
|
* If a method reference refers to a protected non-static method or field
|
|
* of a class outside the current package, the receiver argument will
|
|
* be narrowed to the type of the accessing class.
|
|
* <p>
|
|
* When a method handle to a virtual method is invoked, the method is
|
|
* always looked up in the receiver (that is, the first argument).
|
|
* <p>
|
|
* A non-virtual method handle to a specific virtual method implementation
|
|
* can also be created. These do not perform virtual lookup based on
|
|
* receiver type. Such a method handle simulates the effect of
|
|
* an {@code invokespecial} instruction to the same method.
|
|
*
|
|
* <h1>Usage examples</h1>
|
|
* Here are some examples of usage:
|
|
* <blockquote><pre>{@code
|
|
Object x, y; String s; int i;
|
|
MethodType mt; MethodHandle mh;
|
|
MethodHandles.Lookup lookup = MethodHandles.lookup();
|
|
// mt is (char,char)String
|
|
mt = MethodType.methodType(String.class, char.class, char.class);
|
|
mh = lookup.findVirtual(String.class, "replace", mt);
|
|
s = (String) mh.invokeExact("daddy",'d','n');
|
|
// invokeExact(Ljava/lang/String;CC)Ljava/lang/String;
|
|
assertEquals(s, "nanny");
|
|
// weakly typed invocation (using MHs.invoke)
|
|
s = (String) mh.invokeWithArguments("sappy", 'p', 'v');
|
|
assertEquals(s, "savvy");
|
|
// mt is (Object[])List
|
|
mt = MethodType.methodType(java.util.List.class, Object[].class);
|
|
mh = lookup.findStatic(java.util.Arrays.class, "asList", mt);
|
|
assert(mh.isVarargsCollector());
|
|
x = mh.invoke("one", "two");
|
|
// invoke(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/Object;
|
|
assertEquals(x, java.util.Arrays.asList("one","two"));
|
|
// mt is (Object,Object,Object)Object
|
|
mt = MethodType.genericMethodType(3);
|
|
mh = mh.asType(mt);
|
|
x = mh.invokeExact((Object)1, (Object)2, (Object)3);
|
|
// invokeExact(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
|
|
assertEquals(x, java.util.Arrays.asList(1,2,3));
|
|
// mt is ()int
|
|
mt = MethodType.methodType(int.class);
|
|
mh = lookup.findVirtual(java.util.List.class, "size", mt);
|
|
i = (int) mh.invokeExact(java.util.Arrays.asList(1,2,3));
|
|
// invokeExact(Ljava/util/List;)I
|
|
assert(i == 3);
|
|
mt = MethodType.methodType(void.class, String.class);
|
|
mh = lookup.findVirtual(java.io.PrintStream.class, "println", mt);
|
|
mh.invokeExact(System.out, "Hello, world.");
|
|
// invokeExact(Ljava/io/PrintStream;Ljava/lang/String;)V
|
|
* }</pre></blockquote>
|
|
* Each of the above calls to {@code invokeExact} or plain {@code invoke}
|
|
* generates a single invokevirtual instruction with
|
|
* the symbolic type descriptor indicated in the following comment.
|
|
* In these examples, the helper method {@code assertEquals} is assumed to
|
|
* be a method which calls {@link java.util.Objects#equals(Object,Object) Objects.equals}
|
|
* on its arguments, and asserts that the result is true.
|
|
*
|
|
* <h1>Exceptions</h1>
|
|
* The methods {@code invokeExact} and {@code invoke} are declared
|
|
* to throw {@link java.lang.Throwable Throwable},
|
|
* which is to say that there is no static restriction on what a method handle
|
|
* can throw. Since the JVM does not distinguish between checked
|
|
* and unchecked exceptions (other than by their class, of course),
|
|
* there is no particular effect on bytecode shape from ascribing
|
|
* checked exceptions to method handle invocations. But in Java source
|
|
* code, methods which perform method handle calls must either explicitly
|
|
* throw {@code Throwable}, or else must catch all
|
|
* throwables locally, rethrowing only those which are legal in the context,
|
|
* and wrapping ones which are illegal.
|
|
*
|
|
* <h1><a name="sigpoly"></a>Signature polymorphism</h1>
|
|
* The unusual compilation and linkage behavior of
|
|
* {@code invokeExact} and plain {@code invoke}
|
|
* is referenced by the term <em>signature polymorphism</em>.
|
|
* As defined in the Java Language Specification,
|
|
* a signature polymorphic method is one which can operate with
|
|
* any of a wide range of call signatures and return types.
|
|
* <p>
|
|
* In source code, a call to a signature polymorphic method will
|
|
* compile, regardless of the requested symbolic type descriptor.
|
|
* As usual, the Java compiler emits an {@code invokevirtual}
|
|
* instruction with the given symbolic type descriptor against the named method.
|
|
* The unusual part is that the symbolic type descriptor is derived from
|
|
* the actual argument and return types, not from the method declaration.
|
|
* <p>
|
|
* When the JVM processes bytecode containing signature polymorphic calls,
|
|
* it will successfully link any such call, regardless of its symbolic type descriptor.
|
|
* (In order to retain type safety, the JVM will guard such calls with suitable
|
|
* dynamic type checks, as described elsewhere.)
|
|
* <p>
|
|
* Bytecode generators, including the compiler back end, are required to emit
|
|
* untransformed symbolic type descriptors for these methods.
|
|
* Tools which determine symbolic linkage are required to accept such
|
|
* untransformed descriptors, without reporting linkage errors.
|
|
*
|
|
* <h1>Interoperation between method handles and the Core Reflection API</h1>
|
|
* Using factory methods in the {@link java.lang.invoke.MethodHandles.Lookup Lookup} API,
|
|
* any class member represented by a Core Reflection API object
|
|
* can be converted to a behaviorally equivalent method handle.
|
|
* For example, a reflective {@link java.lang.reflect.Method Method} can
|
|
* be converted to a method handle using
|
|
* {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect}.
|
|
* The resulting method handles generally provide more direct and efficient
|
|
* access to the underlying class members.
|
|
* <p>
|
|
* As a special case,
|
|
* when the Core Reflection API is used to view the signature polymorphic
|
|
* methods {@code invokeExact} or plain {@code invoke} in this class,
|
|
* they appear as ordinary non-polymorphic methods.
|
|
* Their reflective appearance, as viewed by
|
|
* {@link java.lang.Class#getDeclaredMethod Class.getDeclaredMethod},
|
|
* is unaffected by their special status in this API.
|
|
* For example, {@link java.lang.reflect.Method#getModifiers Method.getModifiers}
|
|
* will report exactly those modifier bits required for any similarly
|
|
* declared method, including in this case {@code native} and {@code varargs} bits.
|
|
* <p>
|
|
* As with any reflected method, these methods (when reflected) may be
|
|
* invoked via {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}.
|
|
* However, such reflective calls do not result in method handle invocations.
|
|
* Such a call, if passed the required argument
|
|
* (a single one, of type {@code Object[]}), will ignore the argument and
|
|
* will throw an {@code UnsupportedOperationException}.
|
|
* <p>
|
|
* Since {@code invokevirtual} instructions can natively
|
|
* invoke method handles under any symbolic type descriptor, this reflective view conflicts
|
|
* with the normal presentation of these methods via bytecodes.
|
|
* Thus, these two native methods, when reflectively viewed by
|
|
* {@code Class.getDeclaredMethod}, may be regarded as placeholders only.
|
|
* <p>
|
|
* In order to obtain an invoker method for a particular type descriptor,
|
|
* use {@link java.lang.invoke.MethodHandles#exactInvoker MethodHandles.exactInvoker},
|
|
* or {@link java.lang.invoke.MethodHandles#invoker MethodHandles.invoker}.
|
|
* The {@link java.lang.invoke.MethodHandles.Lookup#findVirtual Lookup.findVirtual}
|
|
* API is also able to return a method handle
|
|
* to call {@code invokeExact} or plain {@code invoke},
|
|
* for any specified type descriptor .
|
|
*
|
|
* <h1>Interoperation between method handles and Java generics</h1>
|
|
* A method handle can be obtained on a method, constructor, or field
|
|
* which is declared with Java generic types.
|
|
* As with the Core Reflection API, the type of the method handle
|
|
* will constructed from the erasure of the source-level type.
|
|
* When a method handle is invoked, the types of its arguments
|
|
* or the return value cast type may be generic types or type instances.
|
|
* If this occurs, the compiler will replace those
|
|
* types by their erasures when it constructs the symbolic type descriptor
|
|
* for the {@code invokevirtual} instruction.
|
|
* <p>
|
|
* Method handles do not represent
|
|
* their function-like types in terms of Java parameterized (generic) types,
|
|
* because there are three mismatches between function-like types and parameterized
|
|
* Java types.
|
|
* <ul>
|
|
* <li>Method types range over all possible arities,
|
|
* from no arguments to up to the <a href="MethodHandle.html#maxarity">maximum number</a> of allowed arguments.
|
|
* Generics are not variadic, and so cannot represent this.</li>
|
|
* <li>Method types can specify arguments of primitive types,
|
|
* which Java generic types cannot range over.</li>
|
|
* <li>Higher order functions over method handles (combinators) are
|
|
* often generic across a wide range of function types, including
|
|
* those of multiple arities. It is impossible to represent such
|
|
* genericity with a Java type parameter.</li>
|
|
* </ul>
|
|
*
|
|
* <h1><a name="maxarity"></a>Arity limits</h1>
|
|
* The JVM imposes on all methods and constructors of any kind an absolute
|
|
* limit of 255 stacked arguments. This limit can appear more restrictive
|
|
* in certain cases:
|
|
* <ul>
|
|
* <li>A {@code long} or {@code double} argument counts (for purposes of arity limits) as two argument slots.
|
|
* <li>A non-static method consumes an extra argument for the object on which the method is called.
|
|
* <li>A constructor consumes an extra argument for the object which is being constructed.
|
|
* <li>Since a method handle’s {@code invoke} method (or other signature-polymorphic method) is non-virtual,
|
|
* it consumes an extra argument for the method handle itself, in addition to any non-virtual receiver object.
|
|
* </ul>
|
|
* These limits imply that certain method handles cannot be created, solely because of the JVM limit on stacked arguments.
|
|
* For example, if a static JVM method accepts exactly 255 arguments, a method handle cannot be created for it.
|
|
* Attempts to create method handles with impossible method types lead to an {@link IllegalArgumentException}.
|
|
* In particular, a method handle’s type must not have an arity of the exact maximum 255.
|
|
*
|
|
* @see MethodType
|
|
* @see MethodHandles
|
|
* @author John Rose, JSR 292 EG
|
|
*/
|
|
public abstract class MethodHandle {
|
|
// Android-removed: MethodHandleImpl.initStatics() unused on Android.
|
|
// static { MethodHandleImpl.initStatics(); }
|
|
|
|
/**
|
|
* Internal marker interface which distinguishes (to the Java compiler)
|
|
* those methods which are <a href="MethodHandle.html#sigpoly">signature polymorphic</a>.
|
|
*
|
|
* @hide
|
|
*/
|
|
@java.lang.annotation.Target({java.lang.annotation.ElementType.METHOD})
|
|
@java.lang.annotation.Retention(java.lang.annotation.RetentionPolicy.RUNTIME)
|
|
// Android-changed: Made public @hide as otherwise it breaks the stubs generation.
|
|
// @interface PolymorphicSignature { }
|
|
public @interface PolymorphicSignature { }
|
|
|
|
/**
|
|
* The type of this method handle, this corresponds to the exact type of the method
|
|
* being invoked.
|
|
*/
|
|
private final MethodType type;
|
|
|
|
// Android-removed: LambdaForm is unused on Android.
|
|
// They will be substituted with appropriate implementation / delegate classes.
|
|
/*
|
|
/*private* final LambdaForm form;
|
|
// form is not private so that invokers can easily fetch it
|
|
*/
|
|
/*private*/ MethodHandle asTypeCache;
|
|
// asTypeCache is not private so that invokers can easily fetch it
|
|
/*
|
|
// Android-removed: customizationCount is unused on Android.
|
|
/*non-public* byte customizationCount;
|
|
// customizationCount should be accessible from invokers
|
|
*/
|
|
|
|
/**
|
|
* The spread invoker associated with this type with zero trailing arguments.
|
|
* This is used to speed up invokeWithArguments.
|
|
*/
|
|
private MethodHandle cachedSpreadInvoker;
|
|
|
|
/**
|
|
* The INVOKE* constants and SGET/SPUT and IGET/IPUT constants specify the behaviour of this
|
|
* method handle with respect to the ArtField* or the ArtMethod* that it operates on. These
|
|
* behaviours are equivalent to the dex bytecode behaviour on the respective method_id or
|
|
* field_id in the equivalent instruction.
|
|
*
|
|
* INVOKE_TRANSFORM is a special type of handle which doesn't encode any dex bytecode behaviour,
|
|
* instead it transforms the list of input arguments or performs other higher order operations
|
|
* before (optionally) delegating to another method handle.
|
|
*/
|
|
|
|
/** @hide */ public static final int INVOKE_VIRTUAL = 0;
|
|
/** @hide */ public static final int INVOKE_SUPER = 1;
|
|
/** @hide */ public static final int INVOKE_DIRECT = 2;
|
|
/** @hide */ public static final int INVOKE_STATIC = 3;
|
|
/** @hide */ public static final int INVOKE_INTERFACE = 4;
|
|
/** @hide */ public static final int INVOKE_TRANSFORM = 5;
|
|
/** @hide */ public static final int INVOKE_VAR_HANDLE = 6;
|
|
/** @hide */ public static final int INVOKE_VAR_HANDLE_EXACT = 7;
|
|
/** @hide */ public static final int IGET = 8;
|
|
/** @hide */ public static final int IPUT = 9;
|
|
/** @hide */ public static final int SGET = 10;
|
|
/** @hide */ public static final int SPUT = 11;
|
|
|
|
// The kind of this method handle (used by the runtime). This is one of the INVOKE_*
|
|
// constants or SGET/SPUT, IGET/IPUT.
|
|
/** @hide */ protected final int handleKind;
|
|
|
|
// The ArtMethod* or ArtField* associated with this method handle (used by the runtime).
|
|
/** @hide */ protected final long artFieldOrMethod;
|
|
|
|
/** @hide */
|
|
protected MethodHandle(long artFieldOrMethod, int handleKind, MethodType type) {
|
|
this.artFieldOrMethod = artFieldOrMethod;
|
|
this.handleKind = handleKind;
|
|
this.type = type;
|
|
}
|
|
// END Android-added: Android specific implementation.
|
|
|
|
/**
|
|
* Reports the type of this method handle.
|
|
* Every invocation of this method handle via {@code invokeExact} must exactly match this type.
|
|
* @return the method handle type
|
|
*/
|
|
public MethodType type() {
|
|
return type;
|
|
}
|
|
|
|
// BEGIN Android-removed: LambdaForm unsupported on Android.
|
|
/*
|
|
/**
|
|
* Package-private constructor for the method handle implementation hierarchy.
|
|
* Method handle inheritance will be contained completely within
|
|
* the {@code java.lang.invoke} package.
|
|
*
|
|
// @param type type (permanently assigned) of the new method handle
|
|
/*non-public* MethodHandle(MethodType type, LambdaForm form) {
|
|
type.getClass(); // explicit NPE
|
|
form.getClass(); // explicit NPE
|
|
this.type = type;
|
|
this.form = form.uncustomize();
|
|
|
|
this.form.prepare(); // TO DO: Try to delay this step until just before invocation.
|
|
}
|
|
*/
|
|
// END Android-removed: LambdaForm unsupported on Android.
|
|
|
|
/**
|
|
* Invokes the method handle, allowing any caller type descriptor, but requiring an exact type match.
|
|
* The symbolic type descriptor at the call site of {@code invokeExact} must
|
|
* exactly match this method handle's {@link #type type}.
|
|
* No conversions are allowed on arguments or return values.
|
|
* <p>
|
|
* When this method is observed via the Core Reflection API,
|
|
* it will appear as a single native method, taking an object array and returning an object.
|
|
* If this native method is invoked directly via
|
|
* {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}, via JNI,
|
|
* or indirectly via {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect},
|
|
* it will throw an {@code UnsupportedOperationException}.
|
|
* @param args the signature-polymorphic parameter list, statically represented using varargs
|
|
* @return the signature-polymorphic result, statically represented using {@code Object}
|
|
* @throws WrongMethodTypeException if the target's type is not identical with the caller's symbolic type descriptor
|
|
* @throws Throwable anything thrown by the underlying method propagates unchanged through the method handle call
|
|
*/
|
|
public final native @PolymorphicSignature Object invokeExact(Object... args) throws Throwable;
|
|
|
|
/**
|
|
* Invokes the method handle, allowing any caller type descriptor,
|
|
* and optionally performing conversions on arguments and return values.
|
|
* <p>
|
|
* If the call site's symbolic type descriptor exactly matches this method handle's {@link #type type},
|
|
* the call proceeds as if by {@link #invokeExact invokeExact}.
|
|
* <p>
|
|
* Otherwise, the call proceeds as if this method handle were first
|
|
* adjusted by calling {@link #asType asType} to adjust this method handle
|
|
* to the required type, and then the call proceeds as if by
|
|
* {@link #invokeExact invokeExact} on the adjusted method handle.
|
|
* <p>
|
|
* There is no guarantee that the {@code asType} call is actually made.
|
|
* If the JVM can predict the results of making the call, it may perform
|
|
* adaptations directly on the caller's arguments,
|
|
* and call the target method handle according to its own exact type.
|
|
* <p>
|
|
* The resolved type descriptor at the call site of {@code invoke} must
|
|
* be a valid argument to the receivers {@code asType} method.
|
|
* In particular, the caller must specify the same argument arity
|
|
* as the callee's type,
|
|
* if the callee is not a {@linkplain #asVarargsCollector variable arity collector}.
|
|
* <p>
|
|
* When this method is observed via the Core Reflection API,
|
|
* it will appear as a single native method, taking an object array and returning an object.
|
|
* If this native method is invoked directly via
|
|
* {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}, via JNI,
|
|
* or indirectly via {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect},
|
|
* it will throw an {@code UnsupportedOperationException}.
|
|
* @param args the signature-polymorphic parameter list, statically represented using varargs
|
|
* @return the signature-polymorphic result, statically represented using {@code Object}
|
|
* @throws WrongMethodTypeException if the target's type cannot be adjusted to the caller's symbolic type descriptor
|
|
* @throws ClassCastException if the target's type can be adjusted to the caller, but a reference cast fails
|
|
* @throws Throwable anything thrown by the underlying method propagates unchanged through the method handle call
|
|
*/
|
|
public final native @PolymorphicSignature Object invoke(Object... args) throws Throwable;
|
|
|
|
// BEGIN Android-removed: RI implementation unused on Android.
|
|
/*
|
|
/**
|
|
* Private method for trusted invocation of a method handle respecting simplified signatures.
|
|
* Type mismatches will not throw {@code WrongMethodTypeException}, but could crash the JVM.
|
|
* <p>
|
|
* The caller signature is restricted to the following basic types:
|
|
* Object, int, long, float, double, and void return.
|
|
* <p>
|
|
* The caller is responsible for maintaining type correctness by ensuring
|
|
* that the each outgoing argument value is a member of the range of the corresponding
|
|
* callee argument type.
|
|
* (The caller should therefore issue appropriate casts and integer narrowing
|
|
* operations on outgoing argument values.)
|
|
* The caller can assume that the incoming result value is part of the range
|
|
* of the callee's return type.
|
|
* @param args the signature-polymorphic parameter list, statically represented using varargs
|
|
* @return the signature-polymorphic result, statically represented using {@code Object}
|
|
*
|
|
/*non-public* final native @PolymorphicSignature Object invokeBasic(Object... args) throws Throwable;
|
|
|
|
/**
|
|
* Private method for trusted invocation of a MemberName of kind {@code REF_invokeVirtual}.
|
|
* The caller signature is restricted to basic types as with {@code invokeBasic}.
|
|
* The trailing (not leading) argument must be a MemberName.
|
|
* @param args the signature-polymorphic parameter list, statically represented using varargs
|
|
* @return the signature-polymorphic result, statically represented using {@code Object}
|
|
*
|
|
/*non-public* static native @PolymorphicSignature Object linkToVirtual(Object... args) throws Throwable;
|
|
|
|
/**
|
|
* Private method for trusted invocation of a MemberName of kind {@code REF_invokeStatic}.
|
|
* The caller signature is restricted to basic types as with {@code invokeBasic}.
|
|
* The trailing (not leading) argument must be a MemberName.
|
|
* @param args the signature-polymorphic parameter list, statically represented using varargs
|
|
* @return the signature-polymorphic result, statically represented using {@code Object}
|
|
*
|
|
/*non-public* static native @PolymorphicSignature Object linkToStatic(Object... args) throws Throwable;
|
|
|
|
/**
|
|
* Private method for trusted invocation of a MemberName of kind {@code REF_invokeSpecial}.
|
|
* The caller signature is restricted to basic types as with {@code invokeBasic}.
|
|
* The trailing (not leading) argument must be a MemberName.
|
|
* @param args the signature-polymorphic parameter list, statically represented using varargs
|
|
* @return the signature-polymorphic result, statically represented using {@code Object}
|
|
*
|
|
/*non-public* static native @PolymorphicSignature Object linkToSpecial(Object... args) throws Throwable;
|
|
|
|
/**
|
|
* Private method for trusted invocation of a MemberName of kind {@code REF_invokeInterface}.
|
|
* The caller signature is restricted to basic types as with {@code invokeBasic}.
|
|
* The trailing (not leading) argument must be a MemberName.
|
|
* @param args the signature-polymorphic parameter list, statically represented using varargs
|
|
* @return the signature-polymorphic result, statically represented using {@code Object}
|
|
*
|
|
/*non-public* static native @PolymorphicSignature Object linkToInterface(Object... args) throws Throwable;
|
|
*/
|
|
// END Android-removed: RI implementation unused on Android.
|
|
|
|
/**
|
|
* Performs a variable arity invocation, passing the arguments in the given list
|
|
* to the method handle, as if via an inexact {@link #invoke invoke} from a call site
|
|
* which mentions only the type {@code Object}, and whose arity is the length
|
|
* of the argument list.
|
|
* <p>
|
|
* Specifically, execution proceeds as if by the following steps,
|
|
* although the methods are not guaranteed to be called if the JVM
|
|
* can predict their effects.
|
|
* <ul>
|
|
* <li>Determine the length of the argument array as {@code N}.
|
|
* For a null reference, {@code N=0}. </li>
|
|
* <li>Determine the general type {@code TN} of {@code N} arguments as
|
|
* as {@code TN=MethodType.genericMethodType(N)}.</li>
|
|
* <li>Force the original target method handle {@code MH0} to the
|
|
* required type, as {@code MH1 = MH0.asType(TN)}. </li>
|
|
* <li>Spread the array into {@code N} separate arguments {@code A0, ...}. </li>
|
|
* <li>Invoke the type-adjusted method handle on the unpacked arguments:
|
|
* MH1.invokeExact(A0, ...). </li>
|
|
* <li>Take the return value as an {@code Object} reference. </li>
|
|
* </ul>
|
|
* <p>
|
|
* Because of the action of the {@code asType} step, the following argument
|
|
* conversions are applied as necessary:
|
|
* <ul>
|
|
* <li>reference casting
|
|
* <li>unboxing
|
|
* <li>widening primitive conversions
|
|
* </ul>
|
|
* <p>
|
|
* The result returned by the call is boxed if it is a primitive,
|
|
* or forced to null if the return type is void.
|
|
* <p>
|
|
* This call is equivalent to the following code:
|
|
* <blockquote><pre>{@code
|
|
* MethodHandle invoker = MethodHandles.spreadInvoker(this.type(), 0);
|
|
* Object result = invoker.invokeExact(this, arguments);
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* Unlike the signature polymorphic methods {@code invokeExact} and {@code invoke},
|
|
* {@code invokeWithArguments} can be accessed normally via the Core Reflection API and JNI.
|
|
* It can therefore be used as a bridge between native or reflective code and method handles.
|
|
*
|
|
* @param arguments the arguments to pass to the target
|
|
* @return the result returned by the target
|
|
* @throws ClassCastException if an argument cannot be converted by reference casting
|
|
* @throws WrongMethodTypeException if the target's type cannot be adjusted to take the given number of {@code Object} arguments
|
|
* @throws Throwable anything thrown by the target method invocation
|
|
* @see MethodHandles#spreadInvoker
|
|
*/
|
|
public Object invokeWithArguments(Object... arguments) throws Throwable {
|
|
MethodType invocationType = MethodType.genericMethodType(arguments == null ? 0 : arguments.length);
|
|
// BEGIN Android-changed: Android specific implementation.
|
|
// return invocationType.invokers().spreadInvoker(0).invokeExact(asType(invocationType), arguments);
|
|
MethodHandle invoker = cachedSpreadInvoker;
|
|
if (invoker == null || !invoker.type().equals(invocationType)) {
|
|
invoker = MethodHandles.spreadInvoker(invocationType, 0);
|
|
cachedSpreadInvoker = invoker;
|
|
}
|
|
return invoker.invoke(asType(invocationType), arguments);
|
|
// END Android-changed: Android specific implementation.
|
|
}
|
|
|
|
/**
|
|
* Performs a variable arity invocation, passing the arguments in the given array
|
|
* to the method handle, as if via an inexact {@link #invoke invoke} from a call site
|
|
* which mentions only the type {@code Object}, and whose arity is the length
|
|
* of the argument array.
|
|
* <p>
|
|
* This method is also equivalent to the following code:
|
|
* <blockquote><pre>{@code
|
|
* invokeWithArguments(arguments.toArray()
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param arguments the arguments to pass to the target
|
|
* @return the result returned by the target
|
|
* @throws NullPointerException if {@code arguments} is a null reference
|
|
* @throws ClassCastException if an argument cannot be converted by reference casting
|
|
* @throws WrongMethodTypeException if the target's type cannot be adjusted to take the given number of {@code Object} arguments
|
|
* @throws Throwable anything thrown by the target method invocation
|
|
*/
|
|
public Object invokeWithArguments(java.util.List<?> arguments) throws Throwable {
|
|
return invokeWithArguments(arguments.toArray());
|
|
}
|
|
|
|
/**
|
|
* Produces an adapter method handle which adapts the type of the
|
|
* current method handle to a new type.
|
|
* The resulting method handle is guaranteed to report a type
|
|
* which is equal to the desired new type.
|
|
* <p>
|
|
* If the original type and new type are equal, returns {@code this}.
|
|
* <p>
|
|
* The new method handle, when invoked, will perform the following
|
|
* steps:
|
|
* <ul>
|
|
* <li>Convert the incoming argument list to match the original
|
|
* method handle's argument list.
|
|
* <li>Invoke the original method handle on the converted argument list.
|
|
* <li>Convert any result returned by the original method handle
|
|
* to the return type of new method handle.
|
|
* </ul>
|
|
* <p>
|
|
* This method provides the crucial behavioral difference between
|
|
* {@link #invokeExact invokeExact} and plain, inexact {@link #invoke invoke}.
|
|
* The two methods
|
|
* perform the same steps when the caller's type descriptor exactly m atches
|
|
* the callee's, but when the types differ, plain {@link #invoke invoke}
|
|
* also calls {@code asType} (or some internal equivalent) in order
|
|
* to match up the caller's and callee's types.
|
|
* <p>
|
|
* If the current method is a variable arity method handle
|
|
* argument list conversion may involve the conversion and collection
|
|
* of several arguments into an array, as
|
|
* {@linkplain #asVarargsCollector described elsewhere}.
|
|
* In every other case, all conversions are applied <em>pairwise</em>,
|
|
* which means that each argument or return value is converted to
|
|
* exactly one argument or return value (or no return value).
|
|
* The applied conversions are defined by consulting the
|
|
* the corresponding component types of the old and new
|
|
* method handle types.
|
|
* <p>
|
|
* Let <em>T0</em> and <em>T1</em> be corresponding new and old parameter types,
|
|
* or old and new return types. Specifically, for some valid index {@code i}, let
|
|
* <em>T0</em>{@code =newType.parameterType(i)} and <em>T1</em>{@code =this.type().parameterType(i)}.
|
|
* Or else, going the other way for return values, let
|
|
* <em>T0</em>{@code =this.type().returnType()} and <em>T1</em>{@code =newType.returnType()}.
|
|
* If the types are the same, the new method handle makes no change
|
|
* to the corresponding argument or return value (if any).
|
|
* Otherwise, one of the following conversions is applied
|
|
* if possible:
|
|
* <ul>
|
|
* <li>If <em>T0</em> and <em>T1</em> are references, then a cast to <em>T1</em> is applied.
|
|
* (The types do not need to be related in any particular way.
|
|
* This is because a dynamic value of null can convert to any reference type.)
|
|
* <li>If <em>T0</em> and <em>T1</em> are primitives, then a Java method invocation
|
|
* conversion (JLS 5.3) is applied, if one exists.
|
|
* (Specifically, <em>T0</em> must convert to <em>T1</em> by a widening primitive conversion.)
|
|
* <li>If <em>T0</em> is a primitive and <em>T1</em> a reference,
|
|
* a Java casting conversion (JLS 5.5) is applied if one exists.
|
|
* (Specifically, the value is boxed from <em>T0</em> to its wrapper class,
|
|
* which is then widened as needed to <em>T1</em>.)
|
|
* <li>If <em>T0</em> is a reference and <em>T1</em> a primitive, an unboxing
|
|
* conversion will be applied at runtime, possibly followed
|
|
* by a Java method invocation conversion (JLS 5.3)
|
|
* on the primitive value. (These are the primitive widening conversions.)
|
|
* <em>T0</em> must be a wrapper class or a supertype of one.
|
|
* (In the case where <em>T0</em> is Object, these are the conversions
|
|
* allowed by {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}.)
|
|
* The unboxing conversion must have a possibility of success, which means that
|
|
* if <em>T0</em> is not itself a wrapper class, there must exist at least one
|
|
* wrapper class <em>TW</em> which is a subtype of <em>T0</em> and whose unboxed
|
|
* primitive value can be widened to <em>T1</em>.
|
|
* <li>If the return type <em>T1</em> is marked as void, any returned value is discarded
|
|
* <li>If the return type <em>T0</em> is void and <em>T1</em> a reference, a null value is introduced.
|
|
* <li>If the return type <em>T0</em> is void and <em>T1</em> a primitive,
|
|
* a zero value is introduced.
|
|
* </ul>
|
|
* (<em>Note:</em> Both <em>T0</em> and <em>T1</em> may be regarded as static types,
|
|
* because neither corresponds specifically to the <em>dynamic type</em> of any
|
|
* actual argument or return value.)
|
|
* <p>
|
|
* The method handle conversion cannot be made if any one of the required
|
|
* pairwise conversions cannot be made.
|
|
* <p>
|
|
* At runtime, the conversions applied to reference arguments
|
|
* or return values may require additional runtime checks which can fail.
|
|
* An unboxing operation may fail because the original reference is null,
|
|
* causing a {@link java.lang.NullPointerException NullPointerException}.
|
|
* An unboxing operation or a reference cast may also fail on a reference
|
|
* to an object of the wrong type,
|
|
* causing a {@link java.lang.ClassCastException ClassCastException}.
|
|
* Although an unboxing operation may accept several kinds of wrappers,
|
|
* if none are available, a {@code ClassCastException} will be thrown.
|
|
*
|
|
* @param newType the expected type of the new method handle
|
|
* @return a method handle which delegates to {@code this} after performing
|
|
* any necessary argument conversions, and arranges for any
|
|
* necessary return value conversions
|
|
* @throws NullPointerException if {@code newType} is a null reference
|
|
* @throws WrongMethodTypeException if the conversion cannot be made
|
|
* @see MethodHandles#explicitCastArguments
|
|
*/
|
|
public MethodHandle asType(MethodType newType) {
|
|
// Fast path alternative to a heavyweight {@code asType} call.
|
|
// Return 'this' if the conversion will be a no-op.
|
|
// Android-changed: use equals() rather than = since MethodTypes are not interned.
|
|
if (newType.equals(type)) {
|
|
return this;
|
|
}
|
|
// Return 'this.asTypeCache' if the conversion is already memoized.
|
|
MethodHandle atc = asTypeCached(newType);
|
|
if (atc != null) {
|
|
return atc;
|
|
}
|
|
return asTypeUncached(newType);
|
|
}
|
|
|
|
private MethodHandle asTypeCached(MethodType newType) {
|
|
MethodHandle atc = asTypeCache;
|
|
// Android-changed: use equals() rather than = since MethodTypes are not interned.
|
|
if (atc != null && newType.equals(atc.type)) {
|
|
return atc;
|
|
}
|
|
return null;
|
|
}
|
|
|
|
/** Override this to change asType behavior. */
|
|
/*non-public*/ MethodHandle asTypeUncached(MethodType newType) {
|
|
if (!type.isConvertibleTo(newType))
|
|
throw new WrongMethodTypeException("cannot convert "+this+" to "+newType);
|
|
// BEGIN Android-changed: Android specific implementation.
|
|
// return asTypeCache = MethodHandleImpl.makePairwiseConvert(this, newType, true);
|
|
return asTypeCache = new Transformers.AsTypeAdapter(this, newType);
|
|
// END Android-changed: Android specific implementation.
|
|
}
|
|
|
|
/**
|
|
* Makes an <em>array-spreading</em> method handle, which accepts a trailing array argument
|
|
* and spreads its elements as positional arguments.
|
|
* The new method handle adapts, as its <i>target</i>,
|
|
* the current method handle. The type of the adapter will be
|
|
* the same as the type of the target, except that the final
|
|
* {@code arrayLength} parameters of the target's type are replaced
|
|
* by a single array parameter of type {@code arrayType}.
|
|
* <p>
|
|
* If the array element type differs from any of the corresponding
|
|
* argument types on the original target,
|
|
* the original target is adapted to take the array elements directly,
|
|
* as if by a call to {@link #asType asType}.
|
|
* <p>
|
|
* When called, the adapter replaces a trailing array argument
|
|
* by the array's elements, each as its own argument to the target.
|
|
* (The order of the arguments is preserved.)
|
|
* They are converted pairwise by casting and/or unboxing
|
|
* to the types of the trailing parameters of the target.
|
|
* Finally the target is called.
|
|
* What the target eventually returns is returned unchanged by the adapter.
|
|
* <p>
|
|
* Before calling the target, the adapter verifies that the array
|
|
* contains exactly enough elements to provide a correct argument count
|
|
* to the target method handle.
|
|
* (The array may also be null when zero elements are required.)
|
|
* <p>
|
|
* When the adapter is called, the length of the supplied {@code array}
|
|
* argument is queried as if by {@code array.length} or {@code arraylength}
|
|
* bytecode. If the adapter accepts a zero-length trailing array argument,
|
|
* the supplied {@code array} argument can either be a zero-length array or
|
|
* {@code null}; otherwise, the adapter will throw a {@code NullPointerException}
|
|
* if the array is {@code null} and throw an {@link IllegalArgumentException}
|
|
* if the array does not have the correct number of elements.
|
|
* <p>
|
|
* Here are some simple examples of array-spreading method handles:
|
|
* <blockquote><pre>{@code
|
|
MethodHandle equals = publicLookup()
|
|
.findVirtual(String.class, "equals", methodType(boolean.class, Object.class));
|
|
assert( (boolean) equals.invokeExact("me", (Object)"me"));
|
|
assert(!(boolean) equals.invokeExact("me", (Object)"thee"));
|
|
// spread both arguments from a 2-array:
|
|
MethodHandle eq2 = equals.asSpreader(Object[].class, 2);
|
|
assert( (boolean) eq2.invokeExact(new Object[]{ "me", "me" }));
|
|
assert(!(boolean) eq2.invokeExact(new Object[]{ "me", "thee" }));
|
|
// try to spread from anything but a 2-array:
|
|
for (int n = 0; n <= 10; n++) {
|
|
Object[] badArityArgs = (n == 2 ? new Object[0] : new Object[n]);
|
|
try { assert((boolean) eq2.invokeExact(badArityArgs) && false); }
|
|
catch (IllegalArgumentException ex) { } // OK
|
|
}
|
|
// spread both arguments from a String array:
|
|
MethodHandle eq2s = equals.asSpreader(String[].class, 2);
|
|
assert( (boolean) eq2s.invokeExact(new String[]{ "me", "me" }));
|
|
assert(!(boolean) eq2s.invokeExact(new String[]{ "me", "thee" }));
|
|
// spread second arguments from a 1-array:
|
|
MethodHandle eq1 = equals.asSpreader(Object[].class, 1);
|
|
assert( (boolean) eq1.invokeExact("me", new Object[]{ "me" }));
|
|
assert(!(boolean) eq1.invokeExact("me", new Object[]{ "thee" }));
|
|
// spread no arguments from a 0-array or null:
|
|
MethodHandle eq0 = equals.asSpreader(Object[].class, 0);
|
|
assert( (boolean) eq0.invokeExact("me", (Object)"me", new Object[0]));
|
|
assert(!(boolean) eq0.invokeExact("me", (Object)"thee", (Object[])null));
|
|
// asSpreader and asCollector are approximate inverses:
|
|
for (int n = 0; n <= 2; n++) {
|
|
for (Class<?> a : new Class<?>[]{Object[].class, String[].class, CharSequence[].class}) {
|
|
MethodHandle equals2 = equals.asSpreader(a, n).asCollector(a, n);
|
|
assert( (boolean) equals2.invokeWithArguments("me", "me"));
|
|
assert(!(boolean) equals2.invokeWithArguments("me", "thee"));
|
|
}
|
|
}
|
|
MethodHandle caToString = publicLookup()
|
|
.findStatic(Arrays.class, "toString", methodType(String.class, char[].class));
|
|
assertEquals("[A, B, C]", (String) caToString.invokeExact("ABC".toCharArray()));
|
|
MethodHandle caString3 = caToString.asCollector(char[].class, 3);
|
|
assertEquals("[A, B, C]", (String) caString3.invokeExact('A', 'B', 'C'));
|
|
MethodHandle caToString2 = caString3.asSpreader(char[].class, 2);
|
|
assertEquals("[A, B, C]", (String) caToString2.invokeExact('A', "BC".toCharArray()));
|
|
* }</pre></blockquote>
|
|
* @param arrayType usually {@code Object[]}, the type of the array argument from which to extract the spread arguments
|
|
* @param arrayLength the number of arguments to spread from an incoming array argument
|
|
* @return a new method handle which spreads its final array argument,
|
|
* before calling the original method handle
|
|
* @throws NullPointerException if {@code arrayType} is a null reference
|
|
* @throws IllegalArgumentException if {@code arrayType} is not an array type,
|
|
* or if target does not have at least
|
|
* {@code arrayLength} parameter types,
|
|
* or if {@code arrayLength} is negative,
|
|
* or if the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
* @throws WrongMethodTypeException if the implied {@code asType} call fails
|
|
* @see #asCollector
|
|
*/
|
|
public MethodHandle asSpreader(Class<?> arrayType, int arrayLength) {
|
|
return asSpreader(type().parameterCount() - arrayLength, arrayType, arrayLength);
|
|
}
|
|
|
|
/**
|
|
* Makes an <em>array-spreading</em> method handle, which accepts an array argument at a given position and spreads
|
|
* its elements as positional arguments in place of the array. The new method handle adapts, as its <i>target</i>,
|
|
* the current method handle. The type of the adapter will be the same as the type of the target, except that the
|
|
* {@code arrayLength} parameters of the target's type, starting at the zero-based position {@code spreadArgPos},
|
|
* are replaced by a single array parameter of type {@code arrayType}.
|
|
* <p>
|
|
* This method behaves very much like {@link #asSpreader(Class, int)}, but accepts an additional {@code spreadArgPos}
|
|
* argument to indicate at which position in the parameter list the spreading should take place.
|
|
*
|
|
* @apiNote Example:
|
|
* <blockquote><pre>{@code
|
|
MethodHandle compare = LOOKUP.findStatic(Objects.class, "compare", methodType(int.class, Object.class, Object.class, Comparator.class));
|
|
MethodHandle compare2FromArray = compare.asSpreader(0, Object[].class, 2);
|
|
Object[] ints = new Object[]{3, 9, 7, 7};
|
|
Comparator<Integer> cmp = (a, b) -> a - b;
|
|
assertTrue((int) compare2FromArray.invoke(Arrays.copyOfRange(ints, 0, 2), cmp) < 0);
|
|
assertTrue((int) compare2FromArray.invoke(Arrays.copyOfRange(ints, 1, 3), cmp) > 0);
|
|
assertTrue((int) compare2FromArray.invoke(Arrays.copyOfRange(ints, 2, 4), cmp) == 0);
|
|
* }</pre></blockquote>
|
|
* @param spreadArgPos the position (zero-based index) in the argument list at which spreading should start.
|
|
* @param arrayType usually {@code Object[]}, the type of the array argument from which to extract the spread arguments
|
|
* @param arrayLength the number of arguments to spread from an incoming array argument
|
|
* @return a new method handle which spreads an array argument at a given position,
|
|
* before calling the original method handle
|
|
* @throws NullPointerException if {@code arrayType} is a null reference
|
|
* @throws IllegalArgumentException if {@code arrayType} is not an array type,
|
|
* or if target does not have at least
|
|
* {@code arrayLength} parameter types,
|
|
* or if {@code arrayLength} is negative,
|
|
* or if {@code spreadArgPos} has an illegal value (negative, or together with arrayLength exceeding the
|
|
* number of arguments),
|
|
* or if the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
* @throws WrongMethodTypeException if the implied {@code asType} call fails
|
|
*
|
|
* @see #asSpreader(Class, int)
|
|
* @since 9
|
|
*/
|
|
public MethodHandle asSpreader(int spreadArgPos, Class<?> arrayType, int arrayLength) {
|
|
MethodType postSpreadType = asSpreaderChecks(arrayType, spreadArgPos, arrayLength);
|
|
// BEGIN Android-changed: Android specific implementation.
|
|
/*
|
|
MethodHandle afterSpread = this.asType(postSpreadType);
|
|
BoundMethodHandle mh = afterSpread.rebind();
|
|
LambdaForm lform = mh.editor().spreadArgumentsForm(1 + spreadArgPos, arrayType, arrayLength);
|
|
MethodType preSpreadType = postSpreadType.replaceParameterTypes(spreadArgPos, spreadArgPos + arrayLength, arrayType);
|
|
return mh.copyWith(preSpreadType, lform);
|
|
*/
|
|
final int spreadEnd = spreadArgPos + arrayLength;
|
|
final MethodType adapterType =
|
|
postSpreadType.replaceParameterTypes(spreadArgPos, spreadEnd, arrayType);
|
|
return new Transformers.Spreader(
|
|
asType(postSpreadType), adapterType, spreadArgPos, arrayLength);
|
|
// END Android-changed: Android specific implementation.
|
|
}
|
|
|
|
/**
|
|
* See if {@code asSpreader} can be validly called with the given arguments.
|
|
* Return the type of the method handle call after spreading but before conversions.
|
|
*/
|
|
private MethodType asSpreaderChecks(Class<?> arrayType, int pos, int arrayLength) {
|
|
spreadArrayChecks(arrayType, arrayLength);
|
|
int nargs = type().parameterCount();
|
|
if (nargs < arrayLength || arrayLength < 0)
|
|
throw newIllegalArgumentException("bad spread array length");
|
|
if (pos < 0 || pos + arrayLength > nargs) {
|
|
throw newIllegalArgumentException("bad spread position");
|
|
}
|
|
Class<?> arrayElement = arrayType.getComponentType();
|
|
MethodType mtype = type();
|
|
boolean match = true, fail = false;
|
|
for (int i = pos; i < pos + arrayLength; i++) {
|
|
Class<?> ptype = mtype.parameterType(i);
|
|
if (ptype != arrayElement) {
|
|
match = false;
|
|
if (!MethodType.canConvert(arrayElement, ptype)) {
|
|
fail = true;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
if (match) return mtype;
|
|
MethodType needType = mtype.asSpreaderType(arrayType, pos, arrayLength);
|
|
if (!fail) return needType;
|
|
// elicit an error:
|
|
this.asType(needType);
|
|
throw newInternalError("should not return");
|
|
}
|
|
|
|
private void spreadArrayChecks(Class<?> arrayType, int arrayLength) {
|
|
Class<?> arrayElement = arrayType.getComponentType();
|
|
if (arrayElement == null)
|
|
throw newIllegalArgumentException("not an array type", arrayType);
|
|
if ((arrayLength & 0x7F) != arrayLength) {
|
|
if ((arrayLength & 0xFF) != arrayLength)
|
|
throw newIllegalArgumentException("array length is not legal", arrayLength);
|
|
assert(arrayLength >= 128);
|
|
if (arrayElement == long.class ||
|
|
arrayElement == double.class)
|
|
throw newIllegalArgumentException("array length is not legal for long[] or double[]", arrayLength);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Adapts this method handle to be {@linkplain #asVarargsCollector variable arity}
|
|
* if the boolean flag is true, else {@linkplain #asFixedArity fixed arity}.
|
|
* If the method handle is already of the proper arity mode, it is returned
|
|
* unchanged.
|
|
* @apiNote
|
|
* <p>This method is sometimes useful when adapting a method handle that
|
|
* may be variable arity, to ensure that the resulting adapter is also
|
|
* variable arity if and only if the original handle was. For example,
|
|
* this code changes the first argument of a handle {@code mh} to {@code int} without
|
|
* disturbing its variable arity property:
|
|
* {@code mh.asType(mh.type().changeParameterType(0,int.class))
|
|
* .withVarargs(mh.isVarargsCollector())}
|
|
* <p>
|
|
* This call is approximately equivalent to the following code:
|
|
* <blockquote><pre>{@code
|
|
* if (makeVarargs == isVarargsCollector())
|
|
* return this;
|
|
* else if (makeVarargs)
|
|
* return asVarargsCollector(type().lastParameterType());
|
|
* else
|
|
* return return asFixedArity();
|
|
* }</pre></blockquote>
|
|
* @param makeVarargs true if the return method handle should have variable arity behavior
|
|
* @return a method handle of the same type, with possibly adjusted variable arity behavior
|
|
* @throws IllegalArgumentException if {@code makeVarargs} is true and
|
|
* this method handle does not have a trailing array parameter
|
|
* @since 9
|
|
* @see #asVarargsCollector
|
|
* @see #asFixedArity
|
|
*/
|
|
public MethodHandle withVarargs(boolean makeVarargs) {
|
|
assert(!isVarargsCollector()); // subclass responsibility
|
|
if (makeVarargs) {
|
|
return asVarargsCollector(type().lastParameterType());
|
|
} else {
|
|
return this;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Makes an <em>array-collecting</em> method handle, which accepts a given number of trailing
|
|
* positional arguments and collects them into an array argument.
|
|
* The new method handle adapts, as its <i>target</i>,
|
|
* the current method handle. The type of the adapter will be
|
|
* the same as the type of the target, except that a single trailing
|
|
* parameter (usually of type {@code arrayType}) is replaced by
|
|
* {@code arrayLength} parameters whose type is element type of {@code arrayType}.
|
|
* <p>
|
|
* If the array type differs from the final argument type on the original target,
|
|
* the original target is adapted to take the array type directly,
|
|
* as if by a call to {@link #asType asType}.
|
|
* <p>
|
|
* When called, the adapter replaces its trailing {@code arrayLength}
|
|
* arguments by a single new array of type {@code arrayType}, whose elements
|
|
* comprise (in order) the replaced arguments.
|
|
* Finally the target is called.
|
|
* What the target eventually returns is returned unchanged by the adapter.
|
|
* <p>
|
|
* (The array may also be a shared constant when {@code arrayLength} is zero.)
|
|
* <p>
|
|
* (<em>Note:</em> The {@code arrayType} is often identical to the last
|
|
* parameter type of the original target.
|
|
* It is an explicit argument for symmetry with {@code asSpreader}, and also
|
|
* to allow the target to use a simple {@code Object} as its last parameter type.)
|
|
* <p>
|
|
* In order to create a collecting adapter which is not restricted to a particular
|
|
* number of collected arguments, use {@link #asVarargsCollector asVarargsCollector} instead.
|
|
* <p>
|
|
* Here are some examples of array-collecting method handles:
|
|
* <blockquote><pre>{@code
|
|
MethodHandle deepToString = publicLookup()
|
|
.findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
|
|
assertEquals("[won]", (String) deepToString.invokeExact(new Object[]{"won"}));
|
|
MethodHandle ts1 = deepToString.asCollector(Object[].class, 1);
|
|
assertEquals(methodType(String.class, Object.class), ts1.type());
|
|
//assertEquals("[won]", (String) ts1.invokeExact( new Object[]{"won"})); //FAIL
|
|
assertEquals("[[won]]", (String) ts1.invokeExact((Object) new Object[]{"won"}));
|
|
// arrayType can be a subtype of Object[]
|
|
MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
|
|
assertEquals(methodType(String.class, String.class, String.class), ts2.type());
|
|
assertEquals("[two, too]", (String) ts2.invokeExact("two", "too"));
|
|
MethodHandle ts0 = deepToString.asCollector(Object[].class, 0);
|
|
assertEquals("[]", (String) ts0.invokeExact());
|
|
// collectors can be nested, Lisp-style
|
|
MethodHandle ts22 = deepToString.asCollector(Object[].class, 3).asCollector(String[].class, 2);
|
|
assertEquals("[A, B, [C, D]]", ((String) ts22.invokeExact((Object)'A', (Object)"B", "C", "D")));
|
|
// arrayType can be any primitive array type
|
|
MethodHandle bytesToString = publicLookup()
|
|
.findStatic(Arrays.class, "toString", methodType(String.class, byte[].class))
|
|
.asCollector(byte[].class, 3);
|
|
assertEquals("[1, 2, 3]", (String) bytesToString.invokeExact((byte)1, (byte)2, (byte)3));
|
|
MethodHandle longsToString = publicLookup()
|
|
.findStatic(Arrays.class, "toString", methodType(String.class, long[].class))
|
|
.asCollector(long[].class, 1);
|
|
assertEquals("[123]", (String) longsToString.invokeExact((long)123));
|
|
* }</pre></blockquote>
|
|
* @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
|
|
* @param arrayLength the number of arguments to collect into a new array argument
|
|
* @return a new method handle which collects some trailing argument
|
|
* into an array, before calling the original method handle
|
|
* @throws NullPointerException if {@code arrayType} is a null reference
|
|
* @throws IllegalArgumentException if {@code arrayType} is not an array type
|
|
* or {@code arrayType} is not assignable to this method handle's trailing parameter type,
|
|
* or {@code arrayLength} is not a legal array size,
|
|
* or the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
* @throws WrongMethodTypeException if the implied {@code asType} call fails
|
|
* @see #asSpreader
|
|
* @see #asVarargsCollector
|
|
*/
|
|
public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
|
|
return asCollector(type().parameterCount() - 1, arrayType, arrayLength);
|
|
}
|
|
|
|
/**
|
|
* Makes an <em>array-collecting</em> method handle, which accepts a given number of positional arguments starting
|
|
* at a given position, and collects them into an array argument. The new method handle adapts, as its
|
|
* <i>target</i>, the current method handle. The type of the adapter will be the same as the type of the target,
|
|
* except that the parameter at the position indicated by {@code collectArgPos} (usually of type {@code arrayType})
|
|
* is replaced by {@code arrayLength} parameters whose type is element type of {@code arrayType}.
|
|
* <p>
|
|
* This method behaves very much like {@link #asCollector(Class, int)}, but differs in that its {@code
|
|
* collectArgPos} argument indicates at which position in the parameter list arguments should be collected. This
|
|
* index is zero-based.
|
|
*
|
|
* @apiNote Examples:
|
|
* <blockquote><pre>{@code
|
|
StringWriter swr = new StringWriter();
|
|
MethodHandle swWrite = LOOKUP.findVirtual(StringWriter.class, "write", methodType(void.class, char[].class, int.class, int.class)).bindTo(swr);
|
|
MethodHandle swWrite4 = swWrite.asCollector(0, char[].class, 4);
|
|
swWrite4.invoke('A', 'B', 'C', 'D', 1, 2);
|
|
assertEquals("BC", swr.toString());
|
|
swWrite4.invoke('P', 'Q', 'R', 'S', 0, 4);
|
|
assertEquals("BCPQRS", swr.toString());
|
|
swWrite4.invoke('W', 'X', 'Y', 'Z', 3, 1);
|
|
assertEquals("BCPQRSZ", swr.toString());
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
* @param collectArgPos the zero-based position in the parameter list at which to start collecting.
|
|
* @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
|
|
* @param arrayLength the number of arguments to collect into a new array argument
|
|
* @return a new method handle which collects some arguments
|
|
* into an array, before calling the original method handle
|
|
* @throws NullPointerException if {@code arrayType} is a null reference
|
|
* @throws IllegalArgumentException if {@code arrayType} is not an array type
|
|
* or {@code arrayType} is not assignable to this method handle's array parameter type,
|
|
* or {@code arrayLength} is not a legal array size,
|
|
* or {@code collectArgPos} has an illegal value (negative, or greater than the number of arguments),
|
|
* or the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
* @throws WrongMethodTypeException if the implied {@code asType} call fails
|
|
*
|
|
* @see #asCollector(Class, int)
|
|
* @since 9
|
|
*/
|
|
public MethodHandle asCollector(int collectArgPos, Class<?> arrayType, int arrayLength) {
|
|
asCollectorChecks(arrayType, collectArgPos, arrayLength);
|
|
// BEGIN Android-changed: Android specific implementation.
|
|
/*
|
|
BoundMethodHandle mh = rebind();
|
|
MethodType resultType = type().asCollectorType(arrayType, collectArgPos, arrayLength);
|
|
MethodHandle newArray = MethodHandleImpl.varargsArray(arrayType, arrayLength);
|
|
LambdaForm lform = mh.editor().collectArgumentArrayForm(1 + collectArgPos, newArray);
|
|
if (lform != null) {
|
|
return mh.copyWith(resultType, lform);
|
|
}
|
|
lform = mh.editor().collectArgumentsForm(1 + collectArgPos, newArray.type().basicType());
|
|
return mh.copyWithExtendL(resultType, lform, newArray);
|
|
*/
|
|
return new Transformers.Collector(this, arrayType, collectArgPos, arrayLength);
|
|
// END Android-changed: Android specific implementation.
|
|
}
|
|
|
|
/**
|
|
* See if {@code asCollector} can be validly called with the given arguments.
|
|
* Return false if the last parameter is not an exact match to arrayType.
|
|
*/
|
|
/*non-public*/ boolean asCollectorChecks(Class<?> arrayType, int pos, int arrayLength) {
|
|
spreadArrayChecks(arrayType, arrayLength);
|
|
int nargs = type().parameterCount();
|
|
if (pos < 0 || pos >= nargs) {
|
|
throw newIllegalArgumentException("bad collect position");
|
|
}
|
|
if (nargs != 0) {
|
|
Class<?> param = type().parameterType(pos);
|
|
if (param == arrayType) return true;
|
|
if (param.isAssignableFrom(arrayType)) return false;
|
|
}
|
|
throw newIllegalArgumentException("array type not assignable to argument", this, arrayType);
|
|
}
|
|
|
|
/**
|
|
* Makes a <em>variable arity</em> adapter which is able to accept
|
|
* any number of trailing positional arguments and collect them
|
|
* into an array argument.
|
|
* <p>
|
|
* The type and behavior of the adapter will be the same as
|
|
* the type and behavior of the target, except that certain
|
|
* {@code invoke} and {@code asType} requests can lead to
|
|
* trailing positional arguments being collected into target's
|
|
* trailing parameter.
|
|
* Also, the
|
|
* {@linkplain MethodType#lastParameterType last parameter type}
|
|
* of the adapter will be
|
|
* {@code arrayType}, even if the target has a different
|
|
* last parameter type.
|
|
* <p>
|
|
* This transformation may return {@code this} if the method handle is
|
|
* already of variable arity and its trailing parameter type
|
|
* is identical to {@code arrayType}.
|
|
* <p>
|
|
* When called with {@link #invokeExact invokeExact}, the adapter invokes
|
|
* the target with no argument changes.
|
|
* (<em>Note:</em> This behavior is different from a
|
|
* {@linkplain #asCollector fixed arity collector},
|
|
* since it accepts a whole array of indeterminate length,
|
|
* rather than a fixed number of arguments.)
|
|
* <p>
|
|
* When called with plain, inexact {@link #invoke invoke}, if the caller
|
|
* type is the same as the adapter, the adapter invokes the target as with
|
|
* {@code invokeExact}.
|
|
* (This is the normal behavior for {@code invoke} when types match.)
|
|
* <p>
|
|
* Otherwise, if the caller and adapter arity are the same, and the
|
|
* trailing parameter type of the caller is a reference type identical to
|
|
* or assignable to the trailing parameter type of the adapter,
|
|
* the arguments and return values are converted pairwise,
|
|
* as if by {@link #asType asType} on a fixed arity
|
|
* method handle.
|
|
* <p>
|
|
* Otherwise, the arities differ, or the adapter's trailing parameter
|
|
* type is not assignable from the corresponding caller type.
|
|
* In this case, the adapter replaces all trailing arguments from
|
|
* the original trailing argument position onward, by
|
|
* a new array of type {@code arrayType}, whose elements
|
|
* comprise (in order) the replaced arguments.
|
|
* <p>
|
|
* The caller type must provides as least enough arguments,
|
|
* and of the correct type, to satisfy the target's requirement for
|
|
* positional arguments before the trailing array argument.
|
|
* Thus, the caller must supply, at a minimum, {@code N-1} arguments,
|
|
* where {@code N} is the arity of the target.
|
|
* Also, there must exist conversions from the incoming arguments
|
|
* to the target's arguments.
|
|
* As with other uses of plain {@code invoke}, if these basic
|
|
* requirements are not fulfilled, a {@code WrongMethodTypeException}
|
|
* may be thrown.
|
|
* <p>
|
|
* In all cases, what the target eventually returns is returned unchanged by the adapter.
|
|
* <p>
|
|
* In the final case, it is exactly as if the target method handle were
|
|
* temporarily adapted with a {@linkplain #asCollector fixed arity collector}
|
|
* to the arity required by the caller type.
|
|
* (As with {@code asCollector}, if the array length is zero,
|
|
* a shared constant may be used instead of a new array.
|
|
* If the implied call to {@code asCollector} would throw
|
|
* an {@code IllegalArgumentException} or {@code WrongMethodTypeException},
|
|
* the call to the variable arity adapter must throw
|
|
* {@code WrongMethodTypeException}.)
|
|
* <p>
|
|
* The behavior of {@link #asType asType} is also specialized for
|
|
* variable arity adapters, to maintain the invariant that
|
|
* plain, inexact {@code invoke} is always equivalent to an {@code asType}
|
|
* call to adjust the target type, followed by {@code invokeExact}.
|
|
* Therefore, a variable arity adapter responds
|
|
* to an {@code asType} request by building a fixed arity collector,
|
|
* if and only if the adapter and requested type differ either
|
|
* in arity or trailing argument type.
|
|
* The resulting fixed arity collector has its type further adjusted
|
|
* (if necessary) to the requested type by pairwise conversion,
|
|
* as if by another application of {@code asType}.
|
|
* <p>
|
|
* When a method handle is obtained by executing an {@code ldc} instruction
|
|
* of a {@code CONSTANT_MethodHandle} constant, and the target method is marked
|
|
* as a variable arity method (with the modifier bit {@code 0x0080}),
|
|
* the method handle will accept multiple arities, as if the method handle
|
|
* constant were created by means of a call to {@code asVarargsCollector}.
|
|
* <p>
|
|
* In order to create a collecting adapter which collects a predetermined
|
|
* number of arguments, and whose type reflects this predetermined number,
|
|
* use {@link #asCollector asCollector} instead.
|
|
* <p>
|
|
* No method handle transformations produce new method handles with
|
|
* variable arity, unless they are documented as doing so.
|
|
* Therefore, besides {@code asVarargsCollector} and {@code withVarargs},
|
|
* all methods in {@code MethodHandle} and {@code MethodHandles}
|
|
* will return a method handle with fixed arity,
|
|
* except in the cases where they are specified to return their original
|
|
* operand (e.g., {@code asType} of the method handle's own type).
|
|
* <p>
|
|
* Calling {@code asVarargsCollector} on a method handle which is already
|
|
* of variable arity will produce a method handle with the same type and behavior.
|
|
* It may (or may not) return the original variable arity method handle.
|
|
* <p>
|
|
* Here is an example, of a list-making variable arity method handle:
|
|
* <blockquote><pre>{@code
|
|
MethodHandle deepToString = publicLookup()
|
|
.findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
|
|
MethodHandle ts1 = deepToString.asVarargsCollector(Object[].class);
|
|
assertEquals("[won]", (String) ts1.invokeExact( new Object[]{"won"}));
|
|
assertEquals("[won]", (String) ts1.invoke( new Object[]{"won"}));
|
|
assertEquals("[won]", (String) ts1.invoke( "won" ));
|
|
assertEquals("[[won]]", (String) ts1.invoke((Object) new Object[]{"won"}));
|
|
// findStatic of Arrays.asList(...) produces a variable arity method handle:
|
|
MethodHandle asList = publicLookup()
|
|
.findStatic(Arrays.class, "asList", methodType(List.class, Object[].class));
|
|
assertEquals(methodType(List.class, Object[].class), asList.type());
|
|
assert(asList.isVarargsCollector());
|
|
assertEquals("[]", asList.invoke().toString());
|
|
assertEquals("[1]", asList.invoke(1).toString());
|
|
assertEquals("[two, too]", asList.invoke("two", "too").toString());
|
|
String[] argv = { "three", "thee", "tee" };
|
|
assertEquals("[three, thee, tee]", asList.invoke(argv).toString());
|
|
assertEquals("[three, thee, tee]", asList.invoke((Object[])argv).toString());
|
|
List ls = (List) asList.invoke((Object)argv);
|
|
assertEquals(1, ls.size());
|
|
assertEquals("[three, thee, tee]", Arrays.toString((Object[])ls.get(0)));
|
|
* }</pre></blockquote>
|
|
* <p style="font-size:smaller;">
|
|
* <em>Discussion:</em>
|
|
* These rules are designed as a dynamically-typed variation
|
|
* of the Java rules for variable arity methods.
|
|
* In both cases, callers to a variable arity method or method handle
|
|
* can either pass zero or more positional arguments, or else pass
|
|
* pre-collected arrays of any length. Users should be aware of the
|
|
* special role of the final argument, and of the effect of a
|
|
* type match on that final argument, which determines whether
|
|
* or not a single trailing argument is interpreted as a whole
|
|
* array or a single element of an array to be collected.
|
|
* Note that the dynamic type of the trailing argument has no
|
|
* effect on this decision, only a comparison between the symbolic
|
|
* type descriptor of the call site and the type descriptor of the method handle.)
|
|
*
|
|
* @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
|
|
* @return a new method handle which can collect any number of trailing arguments
|
|
* into an array, before calling the original method handle
|
|
* @throws NullPointerException if {@code arrayType} is a null reference
|
|
* @throws IllegalArgumentException if {@code arrayType} is not an array type
|
|
* or {@code arrayType} is not assignable to this method handle's trailing parameter type
|
|
* @see #asCollector
|
|
* @see #isVarargsCollector
|
|
* @see #withVarargs
|
|
* @see #asFixedArity
|
|
*/
|
|
public MethodHandle asVarargsCollector(Class<?> arrayType) {
|
|
Objects.requireNonNull(arrayType);
|
|
boolean lastMatch = asCollectorChecks(arrayType, type().parameterCount() - 1, 0);
|
|
if (isVarargsCollector() && lastMatch)
|
|
return this;
|
|
// Android-changed: Android specific implementation.
|
|
// return MethodHandleImpl.makeVarargsCollector(this, arrayType);
|
|
return new Transformers.VarargsCollector(this);
|
|
}
|
|
|
|
/**
|
|
* Determines if this method handle
|
|
* supports {@linkplain #asVarargsCollector variable arity} calls.
|
|
* Such method handles arise from the following sources:
|
|
* <ul>
|
|
* <li>a call to {@linkplain #asVarargsCollector asVarargsCollector}
|
|
* <li>a call to a {@linkplain java.lang.invoke.MethodHandles.Lookup lookup method}
|
|
* which resolves to a variable arity Java method or constructor
|
|
* <li>an {@code ldc} instruction of a {@code CONSTANT_MethodHandle}
|
|
* which resolves to a variable arity Java method or constructor
|
|
* </ul>
|
|
* @return true if this method handle accepts more than one arity of plain, inexact {@code invoke} calls
|
|
* @see #asVarargsCollector
|
|
* @see #asFixedArity
|
|
*/
|
|
public boolean isVarargsCollector() {
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Makes a <em>fixed arity</em> method handle which is otherwise
|
|
* equivalent to the current method handle.
|
|
* <p>
|
|
* If the current method handle is not of
|
|
* {@linkplain #asVarargsCollector variable arity},
|
|
* the current method handle is returned.
|
|
* This is true even if the current method handle
|
|
* could not be a valid input to {@code asVarargsCollector}.
|
|
* <p>
|
|
* Otherwise, the resulting fixed-arity method handle has the same
|
|
* type and behavior of the current method handle,
|
|
* except that {@link #isVarargsCollector isVarargsCollector}
|
|
* will be false.
|
|
* The fixed-arity method handle may (or may not) be the
|
|
* a previous argument to {@code asVarargsCollector}.
|
|
* <p>
|
|
* Here is an example, of a list-making variable arity method handle:
|
|
* <blockquote><pre>{@code
|
|
MethodHandle asListVar = publicLookup()
|
|
.findStatic(Arrays.class, "asList", methodType(List.class, Object[].class))
|
|
.asVarargsCollector(Object[].class);
|
|
MethodHandle asListFix = asListVar.asFixedArity();
|
|
assertEquals("[1]", asListVar.invoke(1).toString());
|
|
Exception caught = null;
|
|
try { asListFix.invoke((Object)1); }
|
|
catch (Exception ex) { caught = ex; }
|
|
assert(caught instanceof ClassCastException);
|
|
assertEquals("[two, too]", asListVar.invoke("two", "too").toString());
|
|
try { asListFix.invoke("two", "too"); }
|
|
catch (Exception ex) { caught = ex; }
|
|
assert(caught instanceof WrongMethodTypeException);
|
|
Object[] argv = { "three", "thee", "tee" };
|
|
assertEquals("[three, thee, tee]", asListVar.invoke(argv).toString());
|
|
assertEquals("[three, thee, tee]", asListFix.invoke(argv).toString());
|
|
assertEquals(1, ((List) asListVar.invoke((Object)argv)).size());
|
|
assertEquals("[three, thee, tee]", asListFix.invoke((Object)argv).toString());
|
|
* }</pre></blockquote>
|
|
*
|
|
* @return a new method handle which accepts only a fixed number of arguments
|
|
* @see #asVarargsCollector
|
|
* @see #isVarargsCollector
|
|
*/
|
|
public MethodHandle asFixedArity() {
|
|
// BEGIN Android-changed: Android specific implementation.
|
|
// assert(!isVarargsCollector());
|
|
// return this;
|
|
|
|
MethodHandle mh = this;
|
|
if (mh.isVarargsCollector()) {
|
|
mh = ((Transformers.VarargsCollector) mh).asFixedArity();
|
|
}
|
|
assert(!mh.isVarargsCollector());
|
|
return mh;
|
|
// END Android-changed: Android specific implementation.
|
|
}
|
|
|
|
/**
|
|
* Binds a value {@code x} to the first argument of a method handle, without invoking it.
|
|
* The new method handle adapts, as its <i>target</i>,
|
|
* the current method handle by binding it to the given argument.
|
|
* The type of the bound handle will be
|
|
* the same as the type of the target, except that a single leading
|
|
* reference parameter will be omitted.
|
|
* <p>
|
|
* When called, the bound handle inserts the given value {@code x}
|
|
* as a new leading argument to the target. The other arguments are
|
|
* also passed unchanged.
|
|
* What the target eventually returns is returned unchanged by the bound handle.
|
|
* <p>
|
|
* The reference {@code x} must be convertible to the first parameter
|
|
* type of the target.
|
|
* <p>
|
|
* (<em>Note:</em> Because method handles are immutable, the target method handle
|
|
* retains its original type and behavior.)
|
|
* @param x the value to bind to the first argument of the target
|
|
* @return a new method handle which prepends the given value to the incoming
|
|
* argument list, before calling the original method handle
|
|
* @throws IllegalArgumentException if the target does not have a
|
|
* leading parameter type that is a reference type
|
|
* @throws ClassCastException if {@code x} cannot be converted
|
|
* to the leading parameter type of the target
|
|
* @see MethodHandles#insertArguments
|
|
*/
|
|
public MethodHandle bindTo(Object x) {
|
|
x = type.leadingReferenceParameter().cast(x); // throw CCE if needed
|
|
// Android-changed: Android specific implementation.
|
|
// return bindArgumentL(0, x);
|
|
return new Transformers.BindTo(this, x);
|
|
}
|
|
|
|
/**
|
|
* Returns a string representation of the method handle,
|
|
* starting with the string {@code "MethodHandle"} and
|
|
* ending with the string representation of the method handle's type.
|
|
* In other words, this method returns a string equal to the value of:
|
|
* <blockquote><pre>{@code
|
|
* "MethodHandle" + type().toString()
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* (<em>Note:</em> Future releases of this API may add further information
|
|
* to the string representation.
|
|
* Therefore, the present syntax should not be parsed by applications.)
|
|
*
|
|
* @return a string representation of the method handle
|
|
*/
|
|
@Override
|
|
public String toString() {
|
|
// Android-removed: Debugging support unused on Android.
|
|
// if (DEBUG_METHOD_HANDLE_NAMES) return "MethodHandle"+debugString();
|
|
return standardString();
|
|
}
|
|
String standardString() {
|
|
return "MethodHandle"+type;
|
|
}
|
|
|
|
// BEGIN Android-removed: Debugging support unused on Android.
|
|
/*
|
|
/** Return a string with a several lines describing the method handle structure.
|
|
* This string would be suitable for display in an IDE debugger.
|
|
*
|
|
String debugString() {
|
|
return type+" : "+internalForm()+internalProperties();
|
|
}
|
|
*/
|
|
// END Android-removed: Debugging support unused on Android.
|
|
|
|
// BEGIN Android-added: Android specific implementation.
|
|
/** @hide */
|
|
public int getHandleKind() {
|
|
if (handleKind == INVOKE_VAR_HANDLE_EXACT || handleKind == INVOKE_VAR_HANDLE) {
|
|
// No need to expose Android implementation detail, avoids larger
|
|
// MethodHandleInfo changes in revealDirect() code path.
|
|
return INVOKE_VIRTUAL;
|
|
}
|
|
return handleKind;
|
|
}
|
|
|
|
/** @hide */
|
|
protected void transform(EmulatedStackFrame arguments) throws Throwable {
|
|
throw new AssertionError("MethodHandle.transform should never be called.");
|
|
}
|
|
|
|
/**
|
|
* Entry back into the runtime to dispatch a MethodHandle with a specific EmulatedStackFrame
|
|
* containing the arguments to provide.
|
|
* @param arguments the stack frame holding arguments for the invocation.
|
|
* @hide
|
|
*/
|
|
/* package-private */ native void invokeExactWithFrame(EmulatedStackFrame arguments)
|
|
throws Throwable;
|
|
|
|
/**
|
|
* Creates a copy of this method handle, copying all relevant data.
|
|
*
|
|
* @hide
|
|
*/
|
|
protected MethodHandle duplicate() {
|
|
try {
|
|
return (MethodHandle) this.clone();
|
|
} catch (CloneNotSupportedException cnse) {
|
|
throw new AssertionError("Subclass of Transformer is not cloneable");
|
|
}
|
|
}
|
|
|
|
/**
|
|
* This is the entry point for all transform calls, and dispatches to the protected
|
|
* transform method. This layer of indirection exists purely for convenience, because
|
|
* we can invoke-direct on a fixed ArtMethod for all transform variants.
|
|
*
|
|
* NOTE: If this extra layer of indirection proves to be a problem, we can get rid
|
|
* of this layer of indirection at the cost of some additional ugliness.
|
|
*/
|
|
private void transformInternal(EmulatedStackFrame arguments) throws Throwable {
|
|
transform(arguments);
|
|
}
|
|
// END Android-added: Android specific implementation.
|
|
|
|
// BEGIN Android-removed: RI implementation unused on Android.
|
|
/*
|
|
//// Implementation methods.
|
|
//// Sub-classes can override these default implementations.
|
|
//// All these methods assume arguments are already validated.
|
|
|
|
// Other transforms to do: convert, explicitCast, permute, drop, filter, fold, GWT, catch
|
|
|
|
BoundMethodHandle bindArgumentL(int pos, Object value) {
|
|
return rebind().bindArgumentL(pos, value);
|
|
}
|
|
|
|
/*non-public*
|
|
MethodHandle setVarargs(MemberName member) throws IllegalAccessException {
|
|
if (!member.isVarargs()) return this;
|
|
Class<?> arrayType = type().lastParameterType();
|
|
if (arrayType.isArray()) {
|
|
return MethodHandleImpl.makeVarargsCollector(this, arrayType);
|
|
}
|
|
throw member.makeAccessException("cannot make variable arity", null);
|
|
}
|
|
|
|
/*non-public*
|
|
MethodHandle viewAsType(MethodType newType, boolean strict) {
|
|
// No actual conversions, just a new view of the same method.
|
|
// Note that this operation must not produce a DirectMethodHandle,
|
|
// because retyped DMHs, like any transformed MHs,
|
|
// cannot be cracked into MethodHandleInfo.
|
|
assert viewAsTypeChecks(newType, strict);
|
|
BoundMethodHandle mh = rebind();
|
|
assert(!((MethodHandle)mh instanceof DirectMethodHandle));
|
|
return mh.copyWith(newType, mh.form);
|
|
}
|
|
|
|
/*non-public*
|
|
boolean viewAsTypeChecks(MethodType newType, boolean strict) {
|
|
if (strict) {
|
|
assert(type().isViewableAs(newType, true))
|
|
: Arrays.asList(this, newType);
|
|
} else {
|
|
assert(type().basicType().isViewableAs(newType.basicType(), true))
|
|
: Arrays.asList(this, newType);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// Decoding
|
|
|
|
/*non-public*
|
|
LambdaForm internalForm() {
|
|
return form;
|
|
}
|
|
|
|
/*non-public*
|
|
MemberName internalMemberName() {
|
|
return null; // DMH returns DMH.member
|
|
}
|
|
|
|
/*non-public*
|
|
Class<?> internalCallerClass() {
|
|
return null; // caller-bound MH for @CallerSensitive method returns caller
|
|
}
|
|
|
|
/*non-public*
|
|
MethodHandleImpl.Intrinsic intrinsicName() {
|
|
// no special intrinsic meaning to most MHs
|
|
return MethodHandleImpl.Intrinsic.NONE;
|
|
}
|
|
|
|
/*non-public*
|
|
MethodHandle withInternalMemberName(MemberName member, boolean isInvokeSpecial) {
|
|
if (member != null) {
|
|
return MethodHandleImpl.makeWrappedMember(this, member, isInvokeSpecial);
|
|
} else if (internalMemberName() == null) {
|
|
// The required internaMemberName is null, and this MH (like most) doesn't have one.
|
|
return this;
|
|
} else {
|
|
// The following case is rare. Mask the internalMemberName by wrapping the MH in a BMH.
|
|
MethodHandle result = rebind();
|
|
assert (result.internalMemberName() == null);
|
|
return result;
|
|
}
|
|
}
|
|
|
|
/*non-public*
|
|
boolean isInvokeSpecial() {
|
|
return false; // DMH.Special returns true
|
|
}
|
|
|
|
/*non-public*
|
|
Object internalValues() {
|
|
return null;
|
|
}
|
|
|
|
/*non-public*
|
|
Object internalProperties() {
|
|
// Override to something to follow this.form, like "\n& FOO=bar"
|
|
return "";
|
|
}
|
|
|
|
//// Method handle implementation methods.
|
|
//// Sub-classes can override these default implementations.
|
|
//// All these methods assume arguments are already validated.
|
|
|
|
/*non-public*
|
|
abstract MethodHandle copyWith(MethodType mt, LambdaForm lf);
|
|
|
|
/** Require this method handle to be a BMH, or else replace it with a "wrapper" BMH.
|
|
* Many transforms are implemented only for BMHs.
|
|
* @return a behaviorally equivalent BMH
|
|
*
|
|
abstract BoundMethodHandle rebind();
|
|
|
|
/**
|
|
* Replace the old lambda form of this method handle with a new one.
|
|
* The new one must be functionally equivalent to the old one.
|
|
* Threads may continue running the old form indefinitely,
|
|
* but it is likely that the new one will be preferred for new executions.
|
|
* Use with discretion.
|
|
*
|
|
/*non-public*
|
|
void updateForm(LambdaForm newForm) {
|
|
assert(newForm.customized == null || newForm.customized == this);
|
|
if (form == newForm) return;
|
|
newForm.prepare(); // as in MethodHandle.<init>
|
|
UNSAFE.putObject(this, FORM_OFFSET, newForm);
|
|
UNSAFE.fullFence();
|
|
}
|
|
|
|
/** Craft a LambdaForm customized for this particular MethodHandle *
|
|
/*non-public*
|
|
void customize() {
|
|
if (form.customized == null) {
|
|
LambdaForm newForm = form.customize(this);
|
|
updateForm(newForm);
|
|
} else {
|
|
assert(form.customized == this);
|
|
}
|
|
}
|
|
|
|
private static final long FORM_OFFSET;
|
|
static {
|
|
try {
|
|
FORM_OFFSET = UNSAFE.objectFieldOffset(MethodHandle.class.getDeclaredField("form"));
|
|
} catch (ReflectiveOperationException ex) {
|
|
throw newInternalError(ex);
|
|
}
|
|
}
|
|
*/
|
|
// END Android-removed: RI implementation unused on Android.
|
|
}
|