Introduce java.lang.invoke.MethodHandles.
- Most APIs are currently unimplemented and will be filled in by
subsequent changes.
- This change includes basic tests for the APIs that are currently
implemented.
bug: 30550796
Test: make build-art-host, docs
Test: vogar MethodHandlesTestVerifyAccessTest
Change-Id: Idec3ee8072dc3a5f94b6fb7ddb08cbc25ed96693
diff --git a/luni/src/test/java/libcore/java/lang/invoke/MethodHandlesTest.java b/luni/src/test/java/libcore/java/lang/invoke/MethodHandlesTest.java
new file mode 100644
index 0000000..33555f7
--- /dev/null
+++ b/luni/src/test/java/libcore/java/lang/invoke/MethodHandlesTest.java
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package libcore.java.lang.invoke;
+
+import junit.framework.TestCase;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.util.Vector;
+
+import static java.lang.invoke.MethodHandles.Lookup.*;
+
+public class MethodHandlesTest extends TestCase {
+ private static final int ALL_LOOKUP_MODES = (PUBLIC | PRIVATE | PACKAGE | PROTECTED);
+
+ public void test_publicLookupClassAndModes() {
+ MethodHandles.Lookup publicLookup = MethodHandles.publicLookup();
+ assertSame(Object.class, publicLookup.lookupClass());
+ assertEquals(PUBLIC, publicLookup.lookupModes());
+ }
+
+ public void test_defaultLookupClassAndModes() {
+ MethodHandles.Lookup defaultLookup = MethodHandles.lookup();
+ assertSame(MethodHandlesTest.class, defaultLookup.lookupClass());
+ assertEquals(ALL_LOOKUP_MODES, defaultLookup.lookupModes());
+ }
+
+ public void test_LookupIn() {
+ MethodHandles.Lookup defaultLookup = MethodHandles.lookup();
+
+ // A class in the same package loses the privilege to lookup protected and private
+ // members.
+ MethodHandles.Lookup siblingLookup = defaultLookup.in(PackageSibling.class);
+ assertEquals(ALL_LOOKUP_MODES & ~(PROTECTED | PRIVATE), siblingLookup.lookupModes());
+
+ // The new lookup isn't in the same package, so it loses all its privileges except
+ // for public.
+ MethodHandles.Lookup nonSibling = defaultLookup.in(Vector.class);
+ assertEquals(PUBLIC, nonSibling.lookupModes());
+
+ // Special case, sibling inner classes in the same parent class
+ MethodHandles.Lookup inner2 = Inner1.lookup.in(Inner2.class);
+ assertEquals(PUBLIC | PRIVATE | PACKAGE, inner2.lookupModes());
+
+ try {
+ MethodHandles.lookup().in(null);
+ fail();
+ } catch (NullPointerException expected) {
+ }
+
+ // Callers cannot change the lookup context to anything within the java.lang.invoke package.
+ try {
+ MethodHandles.lookup().in(MethodHandle.class);
+ fail();
+ } catch (IllegalArgumentException expected) {
+ }
+ }
+
+ public static class Inner1 {
+ public static MethodHandles.Lookup lookup = MethodHandles.lookup();
+ }
+
+ public static class Inner2 {
+ }
+}
+
+class PackageSibling {
+}
+
diff --git a/luni/src/test/java/libcore/sun/invoke/util/VerifyAccessTest.java b/luni/src/test/java/libcore/sun/invoke/util/VerifyAccessTest.java
new file mode 100644
index 0000000..0c02754
--- /dev/null
+++ b/luni/src/test/java/libcore/sun/invoke/util/VerifyAccessTest.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package libcore.sun.invoke.util;
+
+
+import junit.framework.TestCase;
+import sun.invoke.util.VerifyAccess;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.util.List;
+import java.util.Locale;
+import java.util.Vector;
+
+
+public class VerifyAccessTest extends TestCase {
+ public void testIsClassAccessible() {
+ // Always returns false when allowedModes == 0. Note that the "modes" allowed here
+ // are different from the ones used in MethodHandles.
+ assertFalse(VerifyAccess.isClassAccessible(Inner1.class, Inner2.class, 0));
+
+ // Classes in the same package are accessible when Lookup.PACKAGE is specified.
+ assertTrue(VerifyAccess.isClassAccessible(Inner1.class, Inner2.class,
+ MethodHandles.Lookup.PACKAGE));
+ assertTrue(VerifyAccess.isClassAccessible(Inner1.class, Sibling.class,
+ MethodHandles.Lookup.PACKAGE));
+
+ // Public classes are always accessible.
+ assertTrue(VerifyAccess.isClassAccessible(String.class, Inner1.class,
+ MethodHandles.Lookup.PACKAGE));
+ }
+
+ public static class Inner1 {
+ }
+
+ public static class Inner2 {
+ }
+
+ public void testIsSamePackageMember() {
+ assertTrue(VerifyAccess.isSamePackageMember(Inner1.class, Inner2.class));
+ assertTrue(VerifyAccess.isSamePackageMember(Inner1.class, VerifyAccessTest.class));
+
+ assertFalse(VerifyAccess.isSamePackageMember(Sibling.class, Inner1.class));
+ }
+
+ public void testIsSamePackage() {
+ // Both classes are in package java.util.
+ assertTrue(VerifyAccess.isSamePackage(Vector.class, List.class));
+ // Make sure this works for inner classes.
+ assertTrue(VerifyAccess.isSamePackage(Vector.class, Locale.Builder.class));
+ // Differing packages: java.lang vs java.util.
+ assertFalse(VerifyAccess.isSamePackage(Vector.class, String.class));
+
+ try {
+ VerifyAccess.isSamePackage(String[].class, List.class);
+ fail();
+ } catch (IllegalArgumentException expected) {
+ }
+ }
+}
+
+class Sibling {
+}
diff --git a/ojluni/src/main/java/java/lang/invoke/MethodHandles.java b/ojluni/src/main/java/java/lang/invoke/MethodHandles.java
new file mode 100644
index 0000000..17adc59
--- /dev/null
+++ b/ojluni/src/main/java/java/lang/invoke/MethodHandles.java
@@ -0,0 +1,2539 @@
+/*
+ * 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.lang.reflect.*;
+import java.util.List;
+import java.util.Arrays;
+
+import dalvik.system.VMStack;
+import sun.invoke.util.VerifyAccess;
+import sun.invoke.util.Wrapper;
+import static java.lang.invoke.MethodHandleStatics.*;
+
+/**
+ * This class consists exclusively of static methods that operate on or return
+ * method handles. They fall into several categories:
+ * <ul>
+ * <li>Lookup methods which help create method handles for methods and fields.
+ * <li>Combinator methods, which combine or transform pre-existing method handles into new ones.
+ * <li>Other factory methods to create method handles that emulate other common JVM operations or control flow patterns.
+ * </ul>
+ * <p>
+ * @author John Rose, JSR 292 EG
+ * @since 1.7
+ */
+public class MethodHandles {
+
+ private MethodHandles() { } // do not instantiate
+
+ // Android-changed: We do not use MemberName / MethodHandleImpl.
+ //
+ // private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();
+ // static { MethodHandleImpl.initStatics(); }
+ // See IMPL_LOOKUP below.
+
+ //// Method handle creation from ordinary methods.
+
+ /**
+ * Returns a {@link Lookup lookup object} with
+ * full capabilities to emulate all supported bytecode behaviors of the caller.
+ * These capabilities include <a href="MethodHandles.Lookup.html#privacc">private access</a> to the caller.
+ * Factory methods on the lookup object can create
+ * <a href="MethodHandleInfo.html#directmh">direct method handles</a>
+ * for any member that the caller has access to via bytecodes,
+ * including protected and private fields and methods.
+ * This lookup object is a <em>capability</em> which may be delegated to trusted agents.
+ * Do not store it in place where untrusted code can access it.
+ * <p>
+ * This method is caller sensitive, which means that it may return different
+ * values to different callers.
+ * <p>
+ * For any given caller class {@code C}, the lookup object returned by this call
+ * has equivalent capabilities to any lookup object
+ * supplied by the JVM to the bootstrap method of an
+ * <a href="package-summary.html#indyinsn">invokedynamic instruction</a>
+ * executing in the same caller class {@code C}.
+ * @return a lookup object for the caller of this method, with private access
+ */
+ // Android-changed: Remove caller sensitive.
+ // @CallerSensitive
+ public static Lookup lookup() {
+ // Android-changed: Do not use Reflection.getCallerClass().
+ return new Lookup(VMStack.getStackClass1());
+ }
+
+ /**
+ * Returns a {@link Lookup lookup object} which is trusted minimally.
+ * It can only be used to create method handles to
+ * publicly accessible fields and methods.
+ * <p>
+ * As a matter of pure convention, the {@linkplain Lookup#lookupClass lookup class}
+ * of this lookup object will be {@link java.lang.Object}.
+ *
+ * <p style="font-size:smaller;">
+ * <em>Discussion:</em>
+ * The lookup class can be changed to any other class {@code C} using an expression of the form
+ * {@link Lookup#in publicLookup().in(C.class)}.
+ * Since all classes have equal access to public names,
+ * such a change would confer no new access rights.
+ * A public lookup object is always subject to
+ * <a href="MethodHandles.Lookup.html#secmgr">security manager checks</a>.
+ * Also, it cannot access
+ * <a href="MethodHandles.Lookup.html#callsens">caller sensitive methods</a>.
+ * @return a lookup object which is trusted minimally
+ */
+ public static Lookup publicLookup() {
+ return Lookup.PUBLIC_LOOKUP;
+ }
+
+ /**
+ * Performs an unchecked "crack" of a
+ * <a href="MethodHandleInfo.html#directmh">direct method handle</a>.
+ * The result is as if the user had obtained a lookup object capable enough
+ * to crack the target method handle, called
+ * {@link java.lang.invoke.MethodHandles.Lookup#revealDirect Lookup.revealDirect}
+ * on the target to obtain its symbolic reference, and then called
+ * {@link java.lang.invoke.MethodHandleInfo#reflectAs MethodHandleInfo.reflectAs}
+ * to resolve the symbolic reference to a member.
+ * <p>
+ * If there is a security manager, its {@code checkPermission} method
+ * is called with a {@code ReflectPermission("suppressAccessChecks")} permission.
+ * @param <T> the desired type of the result, either {@link Member} or a subtype
+ * @param target a direct method handle to crack into symbolic reference components
+ * @param expected a class object representing the desired result type {@code T}
+ * @return a reference to the method, constructor, or field object
+ * @exception SecurityException if the caller is not privileged to call {@code setAccessible}
+ * @exception NullPointerException if either argument is {@code null}
+ * @exception IllegalArgumentException if the target is not a direct method handle
+ * @exception ClassCastException if the member is not of the expected type
+ * @since 1.8
+ */
+ public static <T extends Member> T
+ reflectAs(Class<T> expected, MethodHandle target) {
+ SecurityManager smgr = System.getSecurityManager();
+ if (smgr != null) smgr.checkPermission(ACCESS_PERMISSION);
+ Lookup lookup = Lookup.IMPL_LOOKUP; // use maximally privileged lookup
+ return lookup.revealDirect(target).reflectAs(expected, lookup);
+ }
+ // Copied from AccessibleObject, as used by Method.setAccessible, etc.:
+ static final private java.security.Permission ACCESS_PERMISSION =
+ new ReflectPermission("suppressAccessChecks");
+
+ /**
+ * A <em>lookup object</em> is a factory for creating method handles,
+ * when the creation requires access checking.
+ * Method handles do not perform
+ * access checks when they are called, but rather when they are created.
+ * Therefore, method handle access
+ * restrictions must be enforced when a method handle is created.
+ * The caller class against which those restrictions are enforced
+ * is known as the {@linkplain #lookupClass lookup class}.
+ * <p>
+ * A lookup class which needs to create method handles will call
+ * {@link MethodHandles#lookup MethodHandles.lookup} to create a factory for itself.
+ * When the {@code Lookup} factory object is created, the identity of the lookup class is
+ * determined, and securely stored in the {@code Lookup} object.
+ * The lookup class (or its delegates) may then use factory methods
+ * on the {@code Lookup} object to create method handles for access-checked members.
+ * This includes all methods, constructors, and fields which are allowed to the lookup class,
+ * even private ones.
+ *
+ * <h1><a name="lookups"></a>Lookup Factory Methods</h1>
+ * The factory methods on a {@code Lookup} object correspond to all major
+ * use cases for methods, constructors, and fields.
+ * Each method handle created by a factory method is the functional
+ * equivalent of a particular <em>bytecode behavior</em>.
+ * (Bytecode behaviors are described in section 5.4.3.5 of the Java Virtual Machine Specification.)
+ * Here is a summary of the correspondence between these factory methods and
+ * the behavior the resulting method handles:
+ * <table border=1 cellpadding=5 summary="lookup method behaviors">
+ * <tr>
+ * <th><a name="equiv"></a>lookup expression</th>
+ * <th>member</th>
+ * <th>bytecode behavior</th>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findGetter lookup.findGetter(C.class,"f",FT.class)}</td>
+ * <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findStaticGetter lookup.findStaticGetter(C.class,"f",FT.class)}</td>
+ * <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findSetter lookup.findSetter(C.class,"f",FT.class)}</td>
+ * <td>{@code FT f;}</td><td>{@code this.f = x;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findStaticSetter lookup.findStaticSetter(C.class,"f",FT.class)}</td>
+ * <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findVirtual lookup.findVirtual(C.class,"m",MT)}</td>
+ * <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findStatic lookup.findStatic(C.class,"m",MT)}</td>
+ * <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findSpecial lookup.findSpecial(C.class,"m",MT,this.class)}</td>
+ * <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#findConstructor lookup.findConstructor(C.class,MT)}</td>
+ * <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectGetter lookup.unreflectGetter(aField)}</td>
+ * <td>({@code static})?<br>{@code FT f;}</td><td>{@code (FT) aField.get(thisOrNull);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectSetter lookup.unreflectSetter(aField)}</td>
+ * <td>({@code static})?<br>{@code FT f;}</td><td>{@code aField.set(thisOrNull, arg);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflect lookup.unreflect(aMethod)}</td>
+ * <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectConstructor lookup.unreflectConstructor(aConstructor)}</td>
+ * <td>{@code C(A*);}</td><td>{@code (C) aConstructor.newInstance(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflect lookup.unreflect(aMethod)}</td>
+ * <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>
+ * </tr>
+ * </table>
+ *
+ * Here, the type {@code C} is the class or interface being searched for a member,
+ * documented as a parameter named {@code refc} in the lookup methods.
+ * The method type {@code MT} is composed from the return type {@code T}
+ * and the sequence of argument types {@code A*}.
+ * The constructor also has a sequence of argument types {@code A*} and
+ * is deemed to return the newly-created object of type {@code C}.
+ * Both {@code MT} and the field type {@code FT} are documented as a parameter named {@code type}.
+ * The formal parameter {@code this} stands for the self-reference of type {@code C};
+ * if it is present, it is always the leading argument to the method handle invocation.
+ * (In the case of some {@code protected} members, {@code this} may be
+ * restricted in type to the lookup class; see below.)
+ * The name {@code arg} stands for all the other method handle arguments.
+ * In the code examples for the Core Reflection API, the name {@code thisOrNull}
+ * stands for a null reference if the accessed method or field is static,
+ * and {@code this} otherwise.
+ * The names {@code aMethod}, {@code aField}, and {@code aConstructor} stand
+ * for reflective objects corresponding to the given members.
+ * <p>
+ * In cases where the given member is of variable arity (i.e., a method or constructor)
+ * the returned method handle will also be of {@linkplain MethodHandle#asVarargsCollector variable arity}.
+ * In all other cases, the returned method handle will be of fixed arity.
+ * <p style="font-size:smaller;">
+ * <em>Discussion:</em>
+ * The equivalence between looked-up method handles and underlying
+ * class members and bytecode behaviors
+ * can break down in a few ways:
+ * <ul style="font-size:smaller;">
+ * <li>If {@code C} is not symbolically accessible from the lookup class's loader,
+ * the lookup can still succeed, even when there is no equivalent
+ * Java expression or bytecoded constant.
+ * <li>Likewise, if {@code T} or {@code MT}
+ * is not symbolically accessible from the lookup class's loader,
+ * the lookup can still succeed.
+ * For example, lookups for {@code MethodHandle.invokeExact} and
+ * {@code MethodHandle.invoke} will always succeed, regardless of requested type.
+ * <li>If there is a security manager installed, it can forbid the lookup
+ * on various grounds (<a href="MethodHandles.Lookup.html#secmgr">see below</a>).
+ * By contrast, the {@code ldc} instruction on a {@code CONSTANT_MethodHandle}
+ * constant is not subject to security manager checks.
+ * <li>If the looked-up method has a
+ * <a href="MethodHandle.html#maxarity">very large arity</a>,
+ * the method handle creation may fail, due to the method handle
+ * type having too many parameters.
+ * </ul>
+ *
+ * <h1><a name="access"></a>Access checking</h1>
+ * Access checks are applied in the factory methods of {@code Lookup},
+ * when a method handle is created.
+ * This is a key difference from the Core Reflection API, since
+ * {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
+ * performs access checking against every caller, on every call.
+ * <p>
+ * All access checks start from a {@code Lookup} object, which
+ * compares its recorded lookup class against all requests to
+ * create method handles.
+ * A single {@code Lookup} object can be used to create any number
+ * of access-checked method handles, all checked against a single
+ * lookup class.
+ * <p>
+ * A {@code Lookup} object can be shared with other trusted code,
+ * such as a metaobject protocol.
+ * A shared {@code Lookup} object delegates the capability
+ * to create method handles on private members of the lookup class.
+ * Even if privileged code uses the {@code Lookup} object,
+ * the access checking is confined to the privileges of the
+ * original lookup class.
+ * <p>
+ * A lookup can fail, because
+ * the containing class is not accessible to the lookup class, or
+ * because the desired class member is missing, or because the
+ * desired class member is not accessible to the lookup class, or
+ * because the lookup object is not trusted enough to access the member.
+ * In any of these cases, a {@code ReflectiveOperationException} will be
+ * thrown from the attempted lookup. The exact class will be one of
+ * the following:
+ * <ul>
+ * <li>NoSuchMethodException — if a method is requested but does not exist
+ * <li>NoSuchFieldException — if a field is requested but does not exist
+ * <li>IllegalAccessException — if the member exists but an access check fails
+ * </ul>
+ * <p>
+ * In general, the conditions under which a method handle may be
+ * looked up for a method {@code M} are no more restrictive than the conditions
+ * under which the lookup class could have compiled, verified, and resolved a call to {@code M}.
+ * Where the JVM would raise exceptions like {@code NoSuchMethodError},
+ * a method handle lookup will generally raise a corresponding
+ * checked exception, such as {@code NoSuchMethodException}.
+ * And the effect of invoking the method handle resulting from the lookup
+ * is <a href="MethodHandles.Lookup.html#equiv">exactly equivalent</a>
+ * to executing the compiled, verified, and resolved call to {@code M}.
+ * The same point is true of fields and constructors.
+ * <p style="font-size:smaller;">
+ * <em>Discussion:</em>
+ * Access checks only apply to named and reflected methods,
+ * constructors, and fields.
+ * Other method handle creation methods, such as
+ * {@link MethodHandle#asType MethodHandle.asType},
+ * do not require any access checks, and are used
+ * independently of any {@code Lookup} object.
+ * <p>
+ * If the desired member is {@code protected}, the usual JVM rules apply,
+ * including the requirement that the lookup class must be either be in the
+ * same package as the desired member, or must inherit that member.
+ * (See the Java Virtual Machine Specification, sections 4.9.2, 5.4.3.5, and 6.4.)
+ * In addition, if the desired member is a non-static field or method
+ * in a different package, the resulting method handle may only be applied
+ * to objects of the lookup class or one of its subclasses.
+ * This requirement is enforced by narrowing the type of the leading
+ * {@code this} parameter from {@code C}
+ * (which will necessarily be a superclass of the lookup class)
+ * to the lookup class itself.
+ * <p>
+ * The JVM imposes a similar requirement on {@code invokespecial} instruction,
+ * that the receiver argument must match both the resolved method <em>and</em>
+ * the current class. Again, this requirement is enforced by narrowing the
+ * type of the leading parameter to the resulting method handle.
+ * (See the Java Virtual Machine Specification, section 4.10.1.9.)
+ * <p>
+ * The JVM represents constructors and static initializer blocks as internal methods
+ * with special names ({@code "<init>"} and {@code "<clinit>"}).
+ * The internal syntax of invocation instructions allows them to refer to such internal
+ * methods as if they were normal methods, but the JVM bytecode verifier rejects them.
+ * A lookup of such an internal method will produce a {@code NoSuchMethodException}.
+ * <p>
+ * In some cases, access between nested classes is obtained by the Java compiler by creating
+ * an wrapper method to access a private method of another class
+ * in the same top-level declaration.
+ * For example, a nested class {@code C.D}
+ * can access private members within other related classes such as
+ * {@code C}, {@code C.D.E}, or {@code C.B},
+ * but the Java compiler may need to generate wrapper methods in
+ * those related classes. In such cases, a {@code Lookup} object on
+ * {@code C.E} would be unable to those private members.
+ * A workaround for this limitation is the {@link Lookup#in Lookup.in} method,
+ * which can transform a lookup on {@code C.E} into one on any of those other
+ * classes, without special elevation of privilege.
+ * <p>
+ * The accesses permitted to a given lookup object may be limited,
+ * according to its set of {@link #lookupModes lookupModes},
+ * to a subset of members normally accessible to the lookup class.
+ * For example, the {@link MethodHandles#publicLookup publicLookup}
+ * method produces a lookup object which is only allowed to access
+ * public members in public classes.
+ * The caller sensitive method {@link MethodHandles#lookup lookup}
+ * produces a lookup object with full capabilities relative to
+ * its caller class, to emulate all supported bytecode behaviors.
+ * Also, the {@link Lookup#in Lookup.in} method may produce a lookup object
+ * with fewer access modes than the original lookup object.
+ *
+ * <p style="font-size:smaller;">
+ * <a name="privacc"></a>
+ * <em>Discussion of private access:</em>
+ * We say that a lookup has <em>private access</em>
+ * if its {@linkplain #lookupModes lookup modes}
+ * include the possibility of accessing {@code private} members.
+ * As documented in the relevant methods elsewhere,
+ * only lookups with private access possess the following capabilities:
+ * <ul style="font-size:smaller;">
+ * <li>access private fields, methods, and constructors of the lookup class
+ * <li>create method handles which invoke <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a> methods,
+ * such as {@code Class.forName}
+ * <li>create method handles which {@link Lookup#findSpecial emulate invokespecial} instructions
+ * <li>avoid <a href="MethodHandles.Lookup.html#secmgr">package access checks</a>
+ * for classes accessible to the lookup class
+ * <li>create {@link Lookup#in delegated lookup objects} which have private access to other classes
+ * within the same package member
+ * </ul>
+ * <p style="font-size:smaller;">
+ * Each of these permissions is a consequence of the fact that a lookup object
+ * with private access can be securely traced back to an originating class,
+ * whose <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> and Java language access permissions
+ * can be reliably determined and emulated by method handles.
+ *
+ * <h1><a name="secmgr"></a>Security manager interactions</h1>
+ * Although bytecode instructions can only refer to classes in
+ * a related class loader, this API can search for methods in any
+ * class, as long as a reference to its {@code Class} object is
+ * available. Such cross-loader references are also possible with the
+ * Core Reflection API, and are impossible to bytecode instructions
+ * such as {@code invokestatic} or {@code getfield}.
+ * There is a {@linkplain java.lang.SecurityManager security manager API}
+ * to allow applications to check such cross-loader references.
+ * These checks apply to both the {@code MethodHandles.Lookup} API
+ * and the Core Reflection API
+ * (as found on {@link java.lang.Class Class}).
+ * <p>
+ * If a security manager is present, member lookups are subject to
+ * additional checks.
+ * From one to three calls are made to the security manager.
+ * Any of these calls can refuse access by throwing a
+ * {@link java.lang.SecurityException SecurityException}.
+ * Define {@code smgr} as the security manager,
+ * {@code lookc} as the lookup class of the current lookup object,
+ * {@code refc} as the containing class in which the member
+ * is being sought, and {@code defc} as the class in which the
+ * member is actually defined.
+ * The value {@code lookc} is defined as <em>not present</em>
+ * if the current lookup object does not have
+ * <a href="MethodHandles.Lookup.html#privacc">private access</a>.
+ * The calls are made according to the following rules:
+ * <ul>
+ * <li><b>Step 1:</b>
+ * If {@code lookc} is not present, or if its class loader is not
+ * the same as or an ancestor of the class loader of {@code refc},
+ * then {@link SecurityManager#checkPackageAccess
+ * smgr.checkPackageAccess(refcPkg)} is called,
+ * where {@code refcPkg} is the package of {@code refc}.
+ * <li><b>Step 2:</b>
+ * If the retrieved member is not public and
+ * {@code lookc} is not present, then
+ * {@link SecurityManager#checkPermission smgr.checkPermission}
+ * with {@code RuntimePermission("accessDeclaredMembers")} is called.
+ * <li><b>Step 3:</b>
+ * If the retrieved member is not public,
+ * and if {@code lookc} is not present,
+ * and if {@code defc} and {@code refc} are different,
+ * then {@link SecurityManager#checkPackageAccess
+ * smgr.checkPackageAccess(defcPkg)} is called,
+ * where {@code defcPkg} is the package of {@code defc}.
+ * </ul>
+ * Security checks are performed after other access checks have passed.
+ * Therefore, the above rules presuppose a member that is public,
+ * or else that is being accessed from a lookup class that has
+ * rights to access the member.
+ *
+ * <h1><a name="callsens"></a>Caller sensitive methods</h1>
+ * A small number of Java methods have a special property called caller sensitivity.
+ * A <em>caller-sensitive</em> method can behave differently depending on the
+ * identity of its immediate caller.
+ * <p>
+ * If a method handle for a caller-sensitive method is requested,
+ * the general rules for <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> apply,
+ * but they take account of the lookup class in a special way.
+ * The resulting method handle behaves as if it were called
+ * from an instruction contained in the lookup class,
+ * so that the caller-sensitive method detects the lookup class.
+ * (By contrast, the invoker of the method handle is disregarded.)
+ * Thus, in the case of caller-sensitive methods,
+ * different lookup classes may give rise to
+ * differently behaving method handles.
+ * <p>
+ * In cases where the lookup object is
+ * {@link MethodHandles#publicLookup() publicLookup()},
+ * or some other lookup object without
+ * <a href="MethodHandles.Lookup.html#privacc">private access</a>,
+ * the lookup class is disregarded.
+ * In such cases, no caller-sensitive method handle can be created,
+ * access is forbidden, and the lookup fails with an
+ * {@code IllegalAccessException}.
+ * <p style="font-size:smaller;">
+ * <em>Discussion:</em>
+ * For example, the caller-sensitive method
+ * {@link java.lang.Class#forName(String) Class.forName(x)}
+ * can return varying classes or throw varying exceptions,
+ * depending on the class loader of the class that calls it.
+ * A public lookup of {@code Class.forName} will fail, because
+ * there is no reasonable way to determine its bytecode behavior.
+ * <p style="font-size:smaller;">
+ * If an application caches method handles for broad sharing,
+ * it should use {@code publicLookup()} to create them.
+ * If there is a lookup of {@code Class.forName}, it will fail,
+ * and the application must take appropriate action in that case.
+ * It may be that a later lookup, perhaps during the invocation of a
+ * bootstrap method, can incorporate the specific identity
+ * of the caller, making the method accessible.
+ * <p style="font-size:smaller;">
+ * The function {@code MethodHandles.lookup} is caller sensitive
+ * so that there can be a secure foundation for lookups.
+ * Nearly all other methods in the JSR 292 API rely on lookup
+ * objects to check access requests.
+ */
+ public static final
+ class Lookup {
+ /** The class on behalf of whom the lookup is being performed. */
+ private final Class<?> lookupClass;
+
+ /** The allowed sorts of members which may be looked up (PUBLIC, etc.). */
+ private final int allowedModes;
+
+ /** A single-bit mask representing {@code public} access,
+ * which may contribute to the result of {@link #lookupModes lookupModes}.
+ * The value, {@code 0x01}, happens to be the same as the value of the
+ * {@code public} {@linkplain java.lang.reflect.Modifier#PUBLIC modifier bit}.
+ */
+ public static final int PUBLIC = Modifier.PUBLIC;
+
+ /** A single-bit mask representing {@code private} access,
+ * which may contribute to the result of {@link #lookupModes lookupModes}.
+ * The value, {@code 0x02}, happens to be the same as the value of the
+ * {@code private} {@linkplain java.lang.reflect.Modifier#PRIVATE modifier bit}.
+ */
+ public static final int PRIVATE = Modifier.PRIVATE;
+
+ /** A single-bit mask representing {@code protected} access,
+ * which may contribute to the result of {@link #lookupModes lookupModes}.
+ * The value, {@code 0x04}, happens to be the same as the value of the
+ * {@code protected} {@linkplain java.lang.reflect.Modifier#PROTECTED modifier bit}.
+ */
+ public static final int PROTECTED = Modifier.PROTECTED;
+
+ /** A single-bit mask representing {@code package} access (default access),
+ * which may contribute to the result of {@link #lookupModes lookupModes}.
+ * The value is {@code 0x08}, which does not correspond meaningfully to
+ * any particular {@linkplain java.lang.reflect.Modifier modifier bit}.
+ */
+ public static final int PACKAGE = Modifier.STATIC;
+
+ private static final int ALL_MODES = (PUBLIC | PRIVATE | PROTECTED | PACKAGE);
+ private static final int TRUSTED = -1;
+
+ private static int fixmods(int mods) {
+ mods &= (ALL_MODES - PACKAGE);
+ return (mods != 0) ? mods : PACKAGE;
+ }
+
+ /** Tells which class is performing the lookup. It is this class against
+ * which checks are performed for visibility and access permissions.
+ * <p>
+ * The class implies a maximum level of access permission,
+ * but the permissions may be additionally limited by the bitmask
+ * {@link #lookupModes lookupModes}, which controls whether non-public members
+ * can be accessed.
+ * @return the lookup class, on behalf of which this lookup object finds members
+ */
+ public Class<?> lookupClass() {
+ return lookupClass;
+ }
+
+ // This is just for calling out to MethodHandleImpl.
+ private Class<?> lookupClassOrNull() {
+ return (allowedModes == TRUSTED) ? null : lookupClass;
+ }
+
+ /** Tells which access-protection classes of members this lookup object can produce.
+ * The result is a bit-mask of the bits
+ * {@linkplain #PUBLIC PUBLIC (0x01)},
+ * {@linkplain #PRIVATE PRIVATE (0x02)},
+ * {@linkplain #PROTECTED PROTECTED (0x04)},
+ * and {@linkplain #PACKAGE PACKAGE (0x08)}.
+ * <p>
+ * A freshly-created lookup object
+ * on the {@linkplain java.lang.invoke.MethodHandles#lookup() caller's class}
+ * has all possible bits set, since the caller class can access all its own members.
+ * A lookup object on a new lookup class
+ * {@linkplain java.lang.invoke.MethodHandles.Lookup#in created from a previous lookup object}
+ * may have some mode bits set to zero.
+ * The purpose of this is to restrict access via the new lookup object,
+ * so that it can access only names which can be reached by the original
+ * lookup object, and also by the new lookup class.
+ * @return the lookup modes, which limit the kinds of access performed by this lookup object
+ */
+ public int lookupModes() {
+ return allowedModes & ALL_MODES;
+ }
+
+ /** Embody the current class (the lookupClass) as a lookup class
+ * for method handle creation.
+ * Must be called by from a method in this package,
+ * which in turn is called by a method not in this package.
+ */
+ Lookup(Class<?> lookupClass) {
+ this(lookupClass, ALL_MODES);
+ // make sure we haven't accidentally picked up a privileged class:
+ checkUnprivilegedlookupClass(lookupClass, ALL_MODES);
+ }
+
+ private Lookup(Class<?> lookupClass, int allowedModes) {
+ this.lookupClass = lookupClass;
+ this.allowedModes = allowedModes;
+ }
+
+ /**
+ * Creates a lookup on the specified new lookup class.
+ * The resulting object will report the specified
+ * class as its own {@link #lookupClass lookupClass}.
+ * <p>
+ * However, the resulting {@code Lookup} object is guaranteed
+ * to have no more access capabilities than the original.
+ * In particular, access capabilities can be lost as follows:<ul>
+ * <li>If the new lookup class differs from the old one,
+ * protected members will not be accessible by virtue of inheritance.
+ * (Protected members may continue to be accessible because of package sharing.)
+ * <li>If the new lookup class is in a different package
+ * than the old one, protected and default (package) members will not be accessible.
+ * <li>If the new lookup class is not within the same package member
+ * as the old one, private members will not be accessible.
+ * <li>If the new lookup class is not accessible to the old lookup class,
+ * then no members, not even public members, will be accessible.
+ * (In all other cases, public members will continue to be accessible.)
+ * </ul>
+ *
+ * @param requestedLookupClass the desired lookup class for the new lookup object
+ * @return a lookup object which reports the desired lookup class
+ * @throws NullPointerException if the argument is null
+ */
+ public Lookup in(Class<?> requestedLookupClass) {
+ requestedLookupClass.getClass(); // null check
+ if (allowedModes == TRUSTED) // IMPL_LOOKUP can make any lookup at all
+ return new Lookup(requestedLookupClass, ALL_MODES);
+ if (requestedLookupClass == this.lookupClass)
+ return this; // keep same capabilities
+ int newModes = (allowedModes & (ALL_MODES & ~PROTECTED));
+ if ((newModes & PACKAGE) != 0
+ && !VerifyAccess.isSamePackage(this.lookupClass, requestedLookupClass)) {
+ newModes &= ~(PACKAGE|PRIVATE);
+ }
+ // Allow nestmate lookups to be created without special privilege:
+ if ((newModes & PRIVATE) != 0
+ && !VerifyAccess.isSamePackageMember(this.lookupClass, requestedLookupClass)) {
+ newModes &= ~PRIVATE;
+ }
+ if ((newModes & PUBLIC) != 0
+ && !VerifyAccess.isClassAccessible(requestedLookupClass, this.lookupClass, allowedModes)) {
+ // The requested class it not accessible from the lookup class.
+ // No permissions.
+ newModes = 0;
+ }
+ checkUnprivilegedlookupClass(requestedLookupClass, newModes);
+ return new Lookup(requestedLookupClass, newModes);
+ }
+
+ // Make sure outer class is initialized first.
+ //
+ // Android-changed: Removed unnecessary reference to IMPL_NAMES.
+ // static { IMPL_NAMES.getClass(); }
+
+ /** Version of lookup which is trusted minimally.
+ * It can only be used to create method handles to
+ * publicly accessible members.
+ */
+ static final Lookup PUBLIC_LOOKUP = new Lookup(Object.class, PUBLIC);
+
+ /** Package-private version of lookup which is trusted. */
+ static final Lookup IMPL_LOOKUP = new Lookup(Object.class, TRUSTED);
+
+ private static void checkUnprivilegedlookupClass(Class<?> lookupClass, int allowedModes) {
+ String name = lookupClass.getName();
+ if (name.startsWith("java.lang.invoke."))
+ throw newIllegalArgumentException("illegal lookupClass: "+lookupClass);
+
+ // For caller-sensitive MethodHandles.lookup()
+ // disallow lookup more restricted packages
+ //
+ // Android-changed: The bootstrap classloader isn't null.
+ if (allowedModes == ALL_MODES &&
+ lookupClass.getClassLoader() == Object.class.getClassLoader()) {
+ if (name.startsWith("java.") ||
+ (name.startsWith("sun.") && !name.startsWith("sun.invoke."))) {
+ throw newIllegalArgumentException("illegal lookupClass: " + lookupClass);
+ }
+ }
+ }
+
+ /**
+ * Displays the name of the class from which lookups are to be made.
+ * (The name is the one reported by {@link java.lang.Class#getName() Class.getName}.)
+ * If there are restrictions on the access permitted to this lookup,
+ * this is indicated by adding a suffix to the class name, consisting
+ * of a slash and a keyword. The keyword represents the strongest
+ * allowed access, and is chosen as follows:
+ * <ul>
+ * <li>If no access is allowed, the suffix is "/noaccess".
+ * <li>If only public access is allowed, the suffix is "/public".
+ * <li>If only public and package access are allowed, the suffix is "/package".
+ * <li>If only public, package, and private access are allowed, the suffix is "/private".
+ * </ul>
+ * If none of the above cases apply, it is the case that full
+ * access (public, package, private, and protected) is allowed.
+ * In this case, no suffix is added.
+ * This is true only of an object obtained originally from
+ * {@link java.lang.invoke.MethodHandles#lookup MethodHandles.lookup}.
+ * Objects created by {@link java.lang.invoke.MethodHandles.Lookup#in Lookup.in}
+ * always have restricted access, and will display a suffix.
+ * <p>
+ * (It may seem strange that protected access should be
+ * stronger than private access. Viewed independently from
+ * package access, protected access is the first to be lost,
+ * because it requires a direct subclass relationship between
+ * caller and callee.)
+ * @see #in
+ */
+ @Override
+ public String toString() {
+ String cname = lookupClass.getName();
+ switch (allowedModes) {
+ case 0: // no privileges
+ return cname + "/noaccess";
+ case PUBLIC:
+ return cname + "/public";
+ case PUBLIC|PACKAGE:
+ return cname + "/package";
+ case ALL_MODES & ~PROTECTED:
+ return cname + "/private";
+ case ALL_MODES:
+ return cname;
+ case TRUSTED:
+ return "/trusted"; // internal only; not exported
+ default: // Should not happen, but it's a bitfield...
+ cname = cname + "/" + Integer.toHexString(allowedModes);
+ assert(false) : cname;
+ return cname;
+ }
+ }
+
+ /**
+ * Produces a method handle for a static method.
+ * The type of the method handle will be that of the method.
+ * (Since static methods do not take receivers, there is no
+ * additional receiver argument inserted into the method handle type,
+ * as there would be with {@link #findVirtual findVirtual} or {@link #findSpecial findSpecial}.)
+ * The method and all its argument types must be accessible to the lookup object.
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the method's variable arity modifier bit ({@code 0x0080}) is set.
+ * <p>
+ * If the returned method handle is invoked, the method's class will
+ * be initialized, if it has not already been initialized.
+ * <p><b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle MH_asList = publicLookup().findStatic(Arrays.class,
+ "asList", methodType(List.class, Object[].class));
+assertEquals("[x, y]", MH_asList.invoke("x", "y").toString());
+ * }</pre></blockquote>
+ * @param refc the class from which the method is accessed
+ * @param name the name of the method
+ * @param type the type of the method
+ * @return the desired method handle
+ * @throws NoSuchMethodException if the method does not exist
+ * @throws IllegalAccessException if access checking fails,
+ * or if the method is not {@code static},
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public
+ MethodHandle findStatic(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findStatic is not implemented");
+ }
+
+ /**
+ * Produces a method handle for a virtual method.
+ * The type of the method handle will be that of the method,
+ * with the receiver type (usually {@code refc}) prepended.
+ * The method and all its argument types must be accessible to the lookup object.
+ * <p>
+ * When called, the handle will treat the first argument as a receiver
+ * and dispatch on the receiver's type to determine which method
+ * implementation to enter.
+ * (The dispatching action is identical with that performed by an
+ * {@code invokevirtual} or {@code invokeinterface} instruction.)
+ * <p>
+ * The first argument will be of type {@code refc} if the lookup
+ * class has full privileges to access the member. Otherwise
+ * the member must be {@code protected} and the first argument
+ * will be restricted in type to the lookup class.
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the method's variable arity modifier bit ({@code 0x0080}) is set.
+ * <p>
+ * Because of the general <a href="MethodHandles.Lookup.html#equiv">equivalence</a> between {@code invokevirtual}
+ * instructions and method handles produced by {@code findVirtual},
+ * if the class is {@code MethodHandle} and the name string is
+ * {@code invokeExact} or {@code invoke}, the resulting
+ * method handle is equivalent to one produced by
+ * {@link java.lang.invoke.MethodHandles#exactInvoker MethodHandles.exactInvoker} or
+ * {@link java.lang.invoke.MethodHandles#invoker MethodHandles.invoker}
+ * with the same {@code type} argument.
+ *
+ * <b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle MH_concat = publicLookup().findVirtual(String.class,
+ "concat", methodType(String.class, String.class));
+MethodHandle MH_hashCode = publicLookup().findVirtual(Object.class,
+ "hashCode", methodType(int.class));
+MethodHandle MH_hashCode_String = publicLookup().findVirtual(String.class,
+ "hashCode", methodType(int.class));
+assertEquals("xy", (String) MH_concat.invokeExact("x", "y"));
+assertEquals("xy".hashCode(), (int) MH_hashCode.invokeExact((Object)"xy"));
+assertEquals("xy".hashCode(), (int) MH_hashCode_String.invokeExact("xy"));
+// interface method:
+MethodHandle MH_subSequence = publicLookup().findVirtual(CharSequence.class,
+ "subSequence", methodType(CharSequence.class, int.class, int.class));
+assertEquals("def", MH_subSequence.invoke("abcdefghi", 3, 6).toString());
+// constructor "internal method" must be accessed differently:
+MethodType MT_newString = methodType(void.class); //()V for new String()
+try { assertEquals("impossible", lookup()
+ .findVirtual(String.class, "<init>", MT_newString));
+ } catch (NoSuchMethodException ex) { } // OK
+MethodHandle MH_newString = publicLookup()
+ .findConstructor(String.class, MT_newString);
+assertEquals("", (String) MH_newString.invokeExact());
+ * }</pre></blockquote>
+ *
+ * @param refc the class or interface from which the method is accessed
+ * @param name the name of the method
+ * @param type the type of the method, with the receiver argument omitted
+ * @return the desired method handle
+ * @throws NoSuchMethodException if the method does not exist
+ * @throws IllegalAccessException if access checking fails,
+ * or if the method is {@code static}
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle findVirtual(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findVirtual is not implemented");
+ }
+
+ /**
+ * Produces a method handle which creates an object and initializes it, using
+ * the constructor of the specified type.
+ * The parameter types of the method handle will be those of the constructor,
+ * while the return type will be a reference to the constructor's class.
+ * The constructor and all its argument types must be accessible to the lookup object.
+ * <p>
+ * The requested type must have a return type of {@code void}.
+ * (This is consistent with the JVM's treatment of constructor type descriptors.)
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the constructor's variable arity modifier bit ({@code 0x0080}) is set.
+ * <p>
+ * If the returned method handle is invoked, the constructor's class will
+ * be initialized, if it has not already been initialized.
+ * <p><b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle MH_newArrayList = publicLookup().findConstructor(
+ ArrayList.class, methodType(void.class, Collection.class));
+Collection orig = Arrays.asList("x", "y");
+Collection copy = (ArrayList) MH_newArrayList.invokeExact(orig);
+assert(orig != copy);
+assertEquals(orig, copy);
+// a variable-arity constructor:
+MethodHandle MH_newProcessBuilder = publicLookup().findConstructor(
+ ProcessBuilder.class, methodType(void.class, String[].class));
+ProcessBuilder pb = (ProcessBuilder)
+ MH_newProcessBuilder.invoke("x", "y", "z");
+assertEquals("[x, y, z]", pb.command().toString());
+ * }</pre></blockquote>
+ * @param refc the class or interface from which the method is accessed
+ * @param type the type of the method, with the receiver argument omitted, and a void return type
+ * @return the desired method handle
+ * @throws NoSuchMethodException if the constructor does not exist
+ * @throws IllegalAccessException if access checking fails
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle findConstructor(Class<?> refc, MethodType type) throws NoSuchMethodException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findConstructor is not implemented");
+ }
+
+ /**
+ * Produces an early-bound method handle for a virtual method.
+ * It will bypass checks for overriding methods on the receiver,
+ * <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial}
+ * instruction from within the explicitly specified {@code specialCaller}.
+ * The type of the method handle will be that of the method,
+ * with a suitably restricted receiver type prepended.
+ * (The receiver type will be {@code specialCaller} or a subtype.)
+ * The method and all its argument types must be accessible
+ * to the lookup object.
+ * <p>
+ * Before method resolution,
+ * if the explicitly specified caller class is not identical with the
+ * lookup class, or if this lookup object does not have
+ * <a href="MethodHandles.Lookup.html#privacc">private access</a>
+ * privileges, the access fails.
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the method's variable arity modifier bit ({@code 0x0080}) is set.
+ * <p style="font-size:smaller;">
+ * <em>(Note: JVM internal methods named {@code "<init>"} are not visible to this API,
+ * even though the {@code invokespecial} instruction can refer to them
+ * in special circumstances. Use {@link #findConstructor findConstructor}
+ * to access instance initialization methods in a safe manner.)</em>
+ * <p><b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+static class Listie extends ArrayList {
+ public String toString() { return "[wee Listie]"; }
+ static Lookup lookup() { return MethodHandles.lookup(); }
+}
+...
+// no access to constructor via invokeSpecial:
+MethodHandle MH_newListie = Listie.lookup()
+ .findConstructor(Listie.class, methodType(void.class));
+Listie l = (Listie) MH_newListie.invokeExact();
+try { assertEquals("impossible", Listie.lookup().findSpecial(
+ Listie.class, "<init>", methodType(void.class), Listie.class));
+ } catch (NoSuchMethodException ex) { } // OK
+// access to super and self methods via invokeSpecial:
+MethodHandle MH_super = Listie.lookup().findSpecial(
+ ArrayList.class, "toString" , methodType(String.class), Listie.class);
+MethodHandle MH_this = Listie.lookup().findSpecial(
+ Listie.class, "toString" , methodType(String.class), Listie.class);
+MethodHandle MH_duper = Listie.lookup().findSpecial(
+ Object.class, "toString" , methodType(String.class), Listie.class);
+assertEquals("[]", (String) MH_super.invokeExact(l));
+assertEquals(""+l, (String) MH_this.invokeExact(l));
+assertEquals("[]", (String) MH_duper.invokeExact(l)); // ArrayList method
+try { assertEquals("inaccessible", Listie.lookup().findSpecial(
+ String.class, "toString", methodType(String.class), Listie.class));
+ } catch (IllegalAccessException ex) { } // OK
+Listie subl = new Listie() { public String toString() { return "[subclass]"; } };
+assertEquals(""+l, (String) MH_this.invokeExact(subl)); // Listie method
+ * }</pre></blockquote>
+ *
+ * @param refc the class or interface from which the method is accessed
+ * @param name the name of the method (which must not be "<init>")
+ * @param type the type of the method, with the receiver argument omitted
+ * @param specialCaller the proposed calling class to perform the {@code invokespecial}
+ * @return the desired method handle
+ * @throws NoSuchMethodException if the method does not exist
+ * @throws IllegalAccessException if access checking fails
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle findSpecial(Class<?> refc, String name, MethodType type,
+ Class<?> specialCaller) throws NoSuchMethodException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findSpecial is not implemented");
+ }
+
+ /**
+ * Produces a method handle giving read access to a non-static field.
+ * The type of the method handle will have a return type of the field's
+ * value type.
+ * The method handle's single argument will be the instance containing
+ * the field.
+ * Access checking is performed immediately on behalf of the lookup class.
+ * @param refc the class or interface from which the method is accessed
+ * @param name the field's name
+ * @param type the field's type
+ * @return a method handle which can load values from the field
+ * @throws NoSuchFieldException if the field does not exist
+ * @throws IllegalAccessException if access checking fails, or if the field is {@code static}
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle findGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findGetter is not implemented");
+ }
+
+ /**
+ * Produces a method handle giving write access to a non-static field.
+ * The type of the method handle will have a void return type.
+ * The method handle will take two arguments, the instance containing
+ * the field, and the value to be stored.
+ * The second argument will be of the field's value type.
+ * Access checking is performed immediately on behalf of the lookup class.
+ * @param refc the class or interface from which the method is accessed
+ * @param name the field's name
+ * @param type the field's type
+ * @return a method handle which can store values into the field
+ * @throws NoSuchFieldException if the field does not exist
+ * @throws IllegalAccessException if access checking fails, or if the field is {@code static}
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle findSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findSetter is not implemented");
+ }
+
+ /**
+ * Produces a method handle giving read access to a static field.
+ * The type of the method handle will have a return type of the field's
+ * value type.
+ * The method handle will take no arguments.
+ * Access checking is performed immediately on behalf of the lookup class.
+ * <p>
+ * If the returned method handle is invoked, the field's class will
+ * be initialized, if it has not already been initialized.
+ * @param refc the class or interface from which the method is accessed
+ * @param name the field's name
+ * @param type the field's type
+ * @return a method handle which can load values from the field
+ * @throws NoSuchFieldException if the field does not exist
+ * @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle findStaticGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findStaticGetter is not implemented");
+ }
+
+ /**
+ * Produces a method handle giving write access to a static field.
+ * The type of the method handle will have a void return type.
+ * The method handle will take a single
+ * argument, of the field's value type, the value to be stored.
+ * Access checking is performed immediately on behalf of the lookup class.
+ * <p>
+ * If the returned method handle is invoked, the field's class will
+ * be initialized, if it has not already been initialized.
+ * @param refc the class or interface from which the method is accessed
+ * @param name the field's name
+ * @param type the field's type
+ * @return a method handle which can store values into the field
+ * @throws NoSuchFieldException if the field does not exist
+ * @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle findStaticSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.findStaticSetter is not implemented");
+ }
+
+ /**
+ * Produces an early-bound method handle for a non-static method.
+ * The receiver must have a supertype {@code defc} in which a method
+ * of the given name and type is accessible to the lookup class.
+ * The method and all its argument types must be accessible to the lookup object.
+ * The type of the method handle will be that of the method,
+ * without any insertion of an additional receiver parameter.
+ * The given receiver will be bound into the method handle,
+ * so that every call to the method handle will invoke the
+ * requested method on the given receiver.
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the method's variable arity modifier bit ({@code 0x0080}) is set
+ * <em>and</em> the trailing array argument is not the only argument.
+ * (If the trailing array argument is the only argument,
+ * the given receiver value will be bound to it.)
+ * <p>
+ * This is equivalent to the following code:
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle mh0 = lookup().findVirtual(defc, name, type);
+MethodHandle mh1 = mh0.bindTo(receiver);
+MethodType mt1 = mh1.type();
+if (mh0.isVarargsCollector())
+ mh1 = mh1.asVarargsCollector(mt1.parameterType(mt1.parameterCount()-1));
+return mh1;
+ * }</pre></blockquote>
+ * where {@code defc} is either {@code receiver.getClass()} or a super
+ * type of that class, in which the requested method is accessible
+ * to the lookup class.
+ * (Note that {@code bindTo} does not preserve variable arity.)
+ * @param receiver the object from which the method is accessed
+ * @param name the name of the method
+ * @param type the type of the method, with the receiver argument omitted
+ * @return the desired method handle
+ * @throws NoSuchMethodException if the method does not exist
+ * @throws IllegalAccessException if access checking fails
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws NullPointerException if any argument is null
+ * @see MethodHandle#bindTo
+ * @see #findVirtual
+ */
+ public MethodHandle bind(Object receiver, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.bind is not implemented");
+ }
+
+ /**
+ * Makes a <a href="MethodHandleInfo.html#directmh">direct method handle</a>
+ * to <i>m</i>, if the lookup class has permission.
+ * If <i>m</i> is non-static, the receiver argument is treated as an initial argument.
+ * If <i>m</i> is virtual, overriding is respected on every call.
+ * Unlike the Core Reflection API, exceptions are <em>not</em> wrapped.
+ * The type of the method handle will be that of the method,
+ * with the receiver type prepended (but only if it is non-static).
+ * If the method's {@code accessible} flag is not set,
+ * access checking is performed immediately on behalf of the lookup class.
+ * If <i>m</i> is not public, do not share the resulting handle with untrusted parties.
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the method's variable arity modifier bit ({@code 0x0080}) is set.
+ * <p>
+ * If <i>m</i> is static, and
+ * if the returned method handle is invoked, the method's class will
+ * be initialized, if it has not already been initialized.
+ * @param m the reflected method
+ * @return a method handle which can invoke the reflected method
+ * @throws IllegalAccessException if access checking fails
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @throws NullPointerException if the argument is null
+ */
+ public MethodHandle unreflect(Method m) throws IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.unreflect is not implemented");
+ }
+
+ /**
+ * Produces a method handle for a reflected method.
+ * It will bypass checks for overriding methods on the receiver,
+ * <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial}
+ * instruction from within the explicitly specified {@code specialCaller}.
+ * The type of the method handle will be that of the method,
+ * with a suitably restricted receiver type prepended.
+ * (The receiver type will be {@code specialCaller} or a subtype.)
+ * If the method's {@code accessible} flag is not set,
+ * access checking is performed immediately on behalf of the lookup class,
+ * as if {@code invokespecial} instruction were being linked.
+ * <p>
+ * Before method resolution,
+ * if the explicitly specified caller class is not identical with the
+ * lookup class, or if this lookup object does not have
+ * <a href="MethodHandles.Lookup.html#privacc">private access</a>
+ * privileges, the access fails.
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the method's variable arity modifier bit ({@code 0x0080}) is set.
+ * @param m the reflected method
+ * @param specialCaller the class nominally calling the method
+ * @return a method handle which can invoke the reflected method
+ * @throws IllegalAccessException if access checking fails
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @throws NullPointerException if any argument is null
+ */
+ public MethodHandle unreflectSpecial(Method m, Class<?> specialCaller) throws IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.unreflectSpecial is not implemented");
+ }
+
+ /**
+ * Produces a method handle for a reflected constructor.
+ * The type of the method handle will be that of the constructor,
+ * with the return type changed to the declaring class.
+ * The method handle will perform a {@code newInstance} operation,
+ * creating a new instance of the constructor's class on the
+ * arguments passed to the method handle.
+ * <p>
+ * If the constructor's {@code accessible} flag is not set,
+ * access checking is performed immediately on behalf of the lookup class.
+ * <p>
+ * The returned method handle will have
+ * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
+ * the constructor's variable arity modifier bit ({@code 0x0080}) is set.
+ * <p>
+ * If the returned method handle is invoked, the constructor's class will
+ * be initialized, if it has not already been initialized.
+ * @param c the reflected constructor
+ * @return a method handle which can invoke the reflected constructor
+ * @throws IllegalAccessException if access checking fails
+ * or if the method's variable arity modifier bit
+ * is set and {@code asVarargsCollector} fails
+ * @throws NullPointerException if the argument is null
+ */
+ public MethodHandle unreflectConstructor(Constructor<?> c) throws IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.unreflectConstructor is not implemented");
+ }
+
+ /**
+ * Produces a method handle giving read access to a reflected field.
+ * The type of the method handle will have a return type of the field's
+ * value type.
+ * If the field is static, the method handle will take no arguments.
+ * Otherwise, its single argument will be the instance containing
+ * the field.
+ * If the field's {@code accessible} flag is not set,
+ * access checking is performed immediately on behalf of the lookup class.
+ * <p>
+ * If the field is static, and
+ * if the returned method handle is invoked, the field's class will
+ * be initialized, if it has not already been initialized.
+ * @param f the reflected field
+ * @return a method handle which can load values from the reflected field
+ * @throws IllegalAccessException if access checking fails
+ * @throws NullPointerException if the argument is null
+ */
+ public MethodHandle unreflectGetter(Field f) throws IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.unreflectGetter is not implemented");
+ }
+
+ /**
+ * Produces a method handle giving write access to a reflected field.
+ * The type of the method handle will have a void return type.
+ * If the field is static, the method handle will take a single
+ * argument, of the field's value type, the value to be stored.
+ * Otherwise, the two arguments will be the instance containing
+ * the field, and the value to be stored.
+ * If the field's {@code accessible} flag is not set,
+ * access checking is performed immediately on behalf of the lookup class.
+ * <p>
+ * If the field is static, and
+ * if the returned method handle is invoked, the field's class will
+ * be initialized, if it has not already been initialized.
+ * @param f the reflected field
+ * @return a method handle which can store values into the reflected field
+ * @throws IllegalAccessException if access checking fails
+ * @throws NullPointerException if the argument is null
+ */
+ public MethodHandle unreflectSetter(Field f) throws IllegalAccessException {
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.Lookup.unreflectSetter is not implemented");
+ }
+
+ /**
+ * Cracks a <a href="MethodHandleInfo.html#directmh">direct method handle</a>
+ * created by this lookup object or a similar one.
+ * Security and access checks are performed to ensure that this lookup object
+ * is capable of reproducing the target method handle.
+ * This means that the cracking may fail if target is a direct method handle
+ * but was created by an unrelated lookup object.
+ * This can happen if the method handle is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a>
+ * and was created by a lookup object for a different class.
+ * @param target a direct method handle to crack into symbolic reference components
+ * @return a symbolic reference which can be used to reconstruct this method handle from this lookup object
+ * @exception SecurityException if a security manager is present and it
+ * <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+ * @throws IllegalArgumentException if the target is not a direct method handle or if access checking fails
+ * @exception NullPointerException if the target is {@code null}
+ * @see MethodHandleInfo
+ * @since 1.8
+ */
+ public MethodHandleInfo revealDirect(MethodHandle target) {
+ // TODO(narayan): Implement this method.
+ //
+ // Notes: Only works for direct method handles. Must check access.
+ //
+ throw new UnsupportedOperationException("MethodHandles.Lookup.revealDirect is not implemented");
+ }
+ }
+
+ /**
+ * Produces a method handle giving read access to elements of an array.
+ * The type of the method handle will have a return type of the array's
+ * element type. Its first argument will be the array type,
+ * and the second will be {@code int}.
+ * @param arrayClass an array type
+ * @return a method handle which can load values from the given array type
+ * @throws NullPointerException if the argument is null
+ * @throws IllegalArgumentException if arrayClass is not an array type
+ */
+ public static
+ MethodHandle arrayElementGetter(Class<?> arrayClass) throws IllegalArgumentException {
+ // return MethodHandleImpl.makeArrayElementAccessor(arrayClass, false);
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.arrayElementGetter is not implemented");
+ }
+
+ /**
+ * Produces a method handle giving write access to elements of an array.
+ * The type of the method handle will have a void return type.
+ * Its last argument will be the array's element type.
+ * The first and second arguments will be the array type and int.
+ * @param arrayClass the class of an array
+ * @return a method handle which can store values into the array type
+ * @throws NullPointerException if the argument is null
+ * @throws IllegalArgumentException if arrayClass is not an array type
+ */
+ public static
+ MethodHandle arrayElementSetter(Class<?> arrayClass) throws IllegalArgumentException {
+ // return MethodHandleImpl.makeArrayElementAccessor(arrayClass, true);
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.arrayElementSetter is not implemented");
+ }
+
+ /// method handle invocation (reflective style)
+
+ /**
+ * Produces a method handle which will invoke any method handle of the
+ * given {@code type}, with a given number of trailing arguments replaced by
+ * a single trailing {@code Object[]} array.
+ * The resulting invoker will be a method handle with the following
+ * arguments:
+ * <ul>
+ * <li>a single {@code MethodHandle} target
+ * <li>zero or more leading values (counted by {@code leadingArgCount})
+ * <li>an {@code Object[]} array containing trailing arguments
+ * </ul>
+ * <p>
+ * The invoker will invoke its target like a call to {@link MethodHandle#invoke invoke} with
+ * the indicated {@code type}.
+ * That is, if the target is exactly of the given {@code type}, it will behave
+ * like {@code invokeExact}; otherwise it behave as if {@link MethodHandle#asType asType}
+ * is used to convert the target to the required {@code type}.
+ * <p>
+ * The type of the returned invoker will not be the given {@code type}, but rather
+ * will have all parameters except the first {@code leadingArgCount}
+ * replaced by a single array of type {@code Object[]}, which will be
+ * the final parameter.
+ * <p>
+ * Before invoking its target, the invoker will spread the final array, apply
+ * reference casts as necessary, and unbox and widen primitive arguments.
+ * If, when the invoker is called, the supplied array argument does
+ * not have the correct number of elements, the invoker will throw
+ * an {@link IllegalArgumentException} instead of invoking the target.
+ * <p>
+ * This method is equivalent to the following code (though it may be more efficient):
+ * <blockquote><pre>{@code
+MethodHandle invoker = MethodHandles.invoker(type);
+int spreadArgCount = type.parameterCount() - leadingArgCount;
+invoker = invoker.asSpreader(Object[].class, spreadArgCount);
+return invoker;
+ * }</pre></blockquote>
+ * This method throws no reflective or security exceptions.
+ * @param type the desired target type
+ * @param leadingArgCount number of fixed arguments, to be passed unchanged to the target
+ * @return a method handle suitable for invoking any method handle of the given type
+ * @throws NullPointerException if {@code type} is null
+ * @throws IllegalArgumentException if {@code leadingArgCount} is not in
+ * the range from 0 to {@code type.parameterCount()} inclusive,
+ * or if the resulting method handle's type would have
+ * <a href="MethodHandle.html#maxarity">too many parameters</a>
+ */
+ static public
+ MethodHandle spreadInvoker(MethodType type, int leadingArgCount) {
+ if (leadingArgCount < 0 || leadingArgCount > type.parameterCount())
+ throw newIllegalArgumentException("bad argument count", leadingArgCount);
+ type = type.asSpreaderType(Object[].class, type.parameterCount() - leadingArgCount);
+ // return type.invokers().spreadInvoker(leadingArgCount);
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.spreadInvoker is not implemented");
+ }
+
+ /**
+ * Produces a special <em>invoker method handle</em> which can be used to
+ * invoke any method handle of the given type, as if by {@link MethodHandle#invokeExact invokeExact}.
+ * The resulting invoker will have a type which is
+ * exactly equal to the desired type, except that it will accept
+ * an additional leading argument of type {@code MethodHandle}.
+ * <p>
+ * This method is equivalent to the following code (though it may be more efficient):
+ * {@code publicLookup().findVirtual(MethodHandle.class, "invokeExact", type)}
+ *
+ * <p style="font-size:smaller;">
+ * <em>Discussion:</em>
+ * Invoker method handles can be useful when working with variable method handles
+ * of unknown types.
+ * For example, to emulate an {@code invokeExact} call to a variable method
+ * handle {@code M}, extract its type {@code T},
+ * look up the invoker method {@code X} for {@code T},
+ * and call the invoker method, as {@code X.invoke(T, A...)}.
+ * (It would not work to call {@code X.invokeExact}, since the type {@code T}
+ * is unknown.)
+ * If spreading, collecting, or other argument transformations are required,
+ * they can be applied once to the invoker {@code X} and reused on many {@code M}
+ * method handle values, as long as they are compatible with the type of {@code X}.
+ * <p style="font-size:smaller;">
+ * <em>(Note: The invoker method is not available via the Core Reflection API.
+ * An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
+ * on the declared {@code invokeExact} or {@code invoke} method will raise an
+ * {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)</em>
+ * <p>
+ * This method throws no reflective or security exceptions.
+ * @param type the desired target type
+ * @return a method handle suitable for invoking any method handle of the given type
+ * @throws IllegalArgumentException if the resulting method handle's type would have
+ * <a href="MethodHandle.html#maxarity">too many parameters</a>
+ */
+ static public
+ MethodHandle exactInvoker(MethodType type) {
+ // return type.invokers().exactInvoker();
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.exactInvoker is not implemented");
+ }
+
+ /**
+ * Produces a special <em>invoker method handle</em> which can be used to
+ * invoke any method handle compatible with the given type, as if by {@link MethodHandle#invoke invoke}.
+ * The resulting invoker will have a type which is
+ * exactly equal to the desired type, except that it will accept
+ * an additional leading argument of type {@code MethodHandle}.
+ * <p>
+ * Before invoking its target, if the target differs from the expected type,
+ * the invoker will apply reference casts as
+ * necessary and box, unbox, or widen primitive values, as if by {@link MethodHandle#asType asType}.
+ * Similarly, the return value will be converted as necessary.
+ * If the target is a {@linkplain MethodHandle#asVarargsCollector variable arity method handle},
+ * the required arity conversion will be made, again as if by {@link MethodHandle#asType asType}.
+ * <p>
+ * This method is equivalent to the following code (though it may be more efficient):
+ * {@code publicLookup().findVirtual(MethodHandle.class, "invoke", type)}
+ * <p style="font-size:smaller;">
+ * <em>Discussion:</em>
+ * A {@linkplain MethodType#genericMethodType general method type} is one which
+ * mentions only {@code Object} arguments and return values.
+ * An invoker for such a type is capable of calling any method handle
+ * of the same arity as the general type.
+ * <p style="font-size:smaller;">
+ * <em>(Note: The invoker method is not available via the Core Reflection API.
+ * An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
+ * on the declared {@code invokeExact} or {@code invoke} method will raise an
+ * {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)</em>
+ * <p>
+ * This method throws no reflective or security exceptions.
+ * @param type the desired target type
+ * @return a method handle suitable for invoking any method handle convertible to the given type
+ * @throws IllegalArgumentException if the resulting method handle's type would have
+ * <a href="MethodHandle.html#maxarity">too many parameters</a>
+ */
+ static public
+ MethodHandle invoker(MethodType type) {
+ // return type.invokers().genericInvoker();
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.invoker is not implemented");
+ }
+
+ // Android-changed: Basic invokers are not supported.
+ //
+ // static /*non-public*/
+ // MethodHandle basicInvoker(MethodType type) {
+ // return type.invokers().basicInvoker();
+ // }
+
+ /// method handle modification (creation from other method handles)
+
+ /**
+ * Produces a method handle which adapts the type of the
+ * given method handle to a new type by pairwise argument and return type conversion.
+ * The original type and new type must have the same number of arguments.
+ * 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 target.
+ * <p>
+ * The same conversions are allowed as for {@link MethodHandle#asType MethodHandle.asType},
+ * and some additional conversions are also applied if those conversions fail.
+ * Given types <em>T0</em>, <em>T1</em>, one of the following conversions is applied
+ * if possible, before or instead of any conversions done by {@code asType}:
+ * <ul>
+ * <li>If <em>T0</em> and <em>T1</em> are references, and <em>T1</em> is an interface type,
+ * then the value of type <em>T0</em> is passed as a <em>T1</em> without a cast.
+ * (This treatment of interfaces follows the usage of the bytecode verifier.)
+ * <li>If <em>T0</em> is boolean and <em>T1</em> is another primitive,
+ * the boolean is converted to a byte value, 1 for true, 0 for false.
+ * (This treatment follows the usage of the bytecode verifier.)
+ * <li>If <em>T1</em> is boolean and <em>T0</em> is another primitive,
+ * <em>T0</em> is converted to byte via Java casting conversion (JLS 5.5),
+ * and the low order bit of the result is tested, as if by {@code (x & 1) != 0}.
+ * <li>If <em>T0</em> and <em>T1</em> are primitives other than boolean,
+ * then a Java casting conversion (JLS 5.5) is applied.
+ * (Specifically, <em>T0</em> will convert to <em>T1</em> by
+ * widening and/or narrowing.)
+ * <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 casting conversion (JLS 5.5) on the primitive value,
+ * possibly followed by a conversion from byte to boolean by testing
+ * the low-order bit.
+ * <li>If <em>T0</em> is a reference and <em>T1</em> a primitive,
+ * and if the reference is null at runtime, a zero value is introduced.
+ * </ul>
+ * @param target the method handle to invoke after arguments are retyped
+ * @param newType the expected type of the new method handle
+ * @return a method handle which delegates to the target after performing
+ * any necessary argument conversions, and arranges for any
+ * necessary return value conversions
+ * @throws NullPointerException if either argument is null
+ * @throws WrongMethodTypeException if the conversion cannot be made
+ * @see MethodHandle#asType
+ */
+ public static
+ MethodHandle explicitCastArguments(MethodHandle target, MethodType newType) {
+ explicitCastArgumentsChecks(target, newType);
+ // use the asTypeCache when possible:
+ MethodType oldType = target.type();
+ if (oldType == newType) return target;
+ if (oldType.explicitCastEquivalentToAsType(newType)) {
+ return target.asFixedArity().asType(newType);
+ }
+
+ // return MethodHandleImpl.makePairwiseConvert(target, newType, false);
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.explicitCastArguments is not implemented");
+ }
+
+ private static void explicitCastArgumentsChecks(MethodHandle target, MethodType newType) {
+ if (target.type().parameterCount() != newType.parameterCount()) {
+ throw new WrongMethodTypeException("cannot explicitly cast " + target + " to " + newType);
+ }
+ }
+
+ /**
+ * Produces a method handle which adapts the calling sequence of the
+ * given method handle to a new type, by reordering the arguments.
+ * The resulting method handle is guaranteed to report a type
+ * which is equal to the desired new type.
+ * <p>
+ * The given array controls the reordering.
+ * Call {@code #I} the number of incoming parameters (the value
+ * {@code newType.parameterCount()}, and call {@code #O} the number
+ * of outgoing parameters (the value {@code target.type().parameterCount()}).
+ * Then the length of the reordering array must be {@code #O},
+ * and each element must be a non-negative number less than {@code #I}.
+ * For every {@code N} less than {@code #O}, the {@code N}-th
+ * outgoing argument will be taken from the {@code I}-th incoming
+ * argument, where {@code I} is {@code reorder[N]}.
+ * <p>
+ * No argument or return value conversions are applied.
+ * The type of each incoming argument, as determined by {@code newType},
+ * must be identical to the type of the corresponding outgoing parameter
+ * or parameters in the target method handle.
+ * The return type of {@code newType} must be identical to the return
+ * type of the original target.
+ * <p>
+ * The reordering array need not specify an actual permutation.
+ * An incoming argument will be duplicated if its index appears
+ * more than once in the array, and an incoming argument will be dropped
+ * if its index does not appear in the array.
+ * As in the case of {@link #dropArguments(MethodHandle,int,List) dropArguments},
+ * incoming arguments which are not mentioned in the reordering array
+ * are may be any type, as determined only by {@code newType}.
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodType intfn1 = methodType(int.class, int.class);
+MethodType intfn2 = methodType(int.class, int.class, int.class);
+MethodHandle sub = ... (int x, int y) -> (x-y) ...;
+assert(sub.type().equals(intfn2));
+MethodHandle sub1 = permuteArguments(sub, intfn2, 0, 1);
+MethodHandle rsub = permuteArguments(sub, intfn2, 1, 0);
+assert((int)rsub.invokeExact(1, 100) == 99);
+MethodHandle add = ... (int x, int y) -> (x+y) ...;
+assert(add.type().equals(intfn2));
+MethodHandle twice = permuteArguments(add, intfn1, 0, 0);
+assert(twice.type().equals(intfn1));
+assert((int)twice.invokeExact(21) == 42);
+ * }</pre></blockquote>
+ * @param target the method handle to invoke after arguments are reordered
+ * @param newType the expected type of the new method handle
+ * @param reorder an index array which controls the reordering
+ * @return a method handle which delegates to the target after it
+ * drops unused arguments and moves and/or duplicates the other arguments
+ * @throws NullPointerException if any argument is null
+ * @throws IllegalArgumentException if the index array length is not equal to
+ * the arity of the target, or if any index array element
+ * not a valid index for a parameter of {@code newType},
+ * or if two corresponding parameter types in
+ * {@code target.type()} and {@code newType} are not identical,
+ */
+ public static
+ MethodHandle permuteArguments(MethodHandle target, MethodType newType, int... reorder) {
+ reorder = reorder.clone(); // get a private copy
+ MethodType oldType = target.type();
+ permuteArgumentChecks(reorder, newType, oldType);
+
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.permuteArguments is not implemented");
+ }
+
+ // Android-changed: findFirstDupOrDrop is unused and removed.
+ // private static int findFirstDupOrDrop(int[] reorder, int newArity);
+
+ private static boolean permuteArgumentChecks(int[] reorder, MethodType newType, MethodType oldType) {
+ if (newType.returnType() != oldType.returnType())
+ throw newIllegalArgumentException("return types do not match",
+ oldType, newType);
+ if (reorder.length == oldType.parameterCount()) {
+ int limit = newType.parameterCount();
+ boolean bad = false;
+ for (int j = 0; j < reorder.length; j++) {
+ int i = reorder[j];
+ if (i < 0 || i >= limit) {
+ bad = true; break;
+ }
+ Class<?> src = newType.parameterType(i);
+ Class<?> dst = oldType.parameterType(j);
+ if (src != dst)
+ throw newIllegalArgumentException("parameter types do not match after reorder",
+ oldType, newType);
+ }
+ if (!bad) return true;
+ }
+ throw newIllegalArgumentException("bad reorder array: "+Arrays.toString(reorder));
+ }
+
+ /**
+ * Produces a method handle of the requested return type which returns the given
+ * constant value every time it is invoked.
+ * <p>
+ * Before the method handle is returned, the passed-in value is converted to the requested type.
+ * If the requested type is primitive, widening primitive conversions are attempted,
+ * else reference conversions are attempted.
+ * <p>The returned method handle is equivalent to {@code identity(type).bindTo(value)}.
+ * @param type the return type of the desired method handle
+ * @param value the value to return
+ * @return a method handle of the given return type and no arguments, which always returns the given value
+ * @throws NullPointerException if the {@code type} argument is null
+ * @throws ClassCastException if the value cannot be converted to the required return type
+ * @throws IllegalArgumentException if the given type is {@code void.class}
+ */
+ public static
+ MethodHandle constant(Class<?> type, Object value) {
+ if (type.isPrimitive()) {
+ if (type == void.class)
+ throw newIllegalArgumentException("void type");
+ Wrapper w = Wrapper.forPrimitiveType(type);
+ value = w.convert(value, type);
+ if (w.zero().equals(value))
+ return zero(w, type);
+ return insertArguments(identity(type), 0, value);
+ } else {
+ if (value == null)
+ return zero(Wrapper.OBJECT, type);
+ return identity(type).bindTo(value);
+ }
+ }
+
+ /**
+ * Produces a method handle which returns its sole argument when invoked.
+ * @param type the type of the sole parameter and return value of the desired method handle
+ * @return a unary method handle which accepts and returns the given type
+ * @throws NullPointerException if the argument is null
+ * @throws IllegalArgumentException if the given type is {@code void.class}
+ */
+ public static
+ MethodHandle identity(Class<?> type) {
+ Wrapper btw = (type.isPrimitive() ? Wrapper.forPrimitiveType(type) : Wrapper.OBJECT);
+ int pos = btw.ordinal();
+ MethodHandle ident = IDENTITY_MHS[pos];
+ if (ident == null) {
+ ident = setCachedMethodHandle(IDENTITY_MHS, pos, makeIdentity(btw.primitiveType()));
+ }
+ if (ident.type().returnType() == type)
+ return ident;
+ // something like identity(Foo.class); do not bother to intern these
+ assert(btw == Wrapper.OBJECT);
+ return makeIdentity(type);
+ }
+ private static final MethodHandle[] IDENTITY_MHS = new MethodHandle[Wrapper.values().length];
+ private static MethodHandle makeIdentity(Class<?> ptype) {
+ // MethodType mtype = MethodType.methodType(ptype, ptype);
+ // LambdaForm lform = LambdaForm.identityForm(BasicType.basicType(ptype));
+ // return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.IDENTITY);
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.makeIdentity is not implemented");
+ }
+
+ private static MethodHandle zero(Wrapper btw, Class<?> rtype) {
+ int pos = btw.ordinal();
+ MethodHandle zero = ZERO_MHS[pos];
+ if (zero == null) {
+ zero = setCachedMethodHandle(ZERO_MHS, pos, makeZero(btw.primitiveType()));
+ }
+ if (zero.type().returnType() == rtype)
+ return zero;
+ assert(btw == Wrapper.OBJECT);
+ return makeZero(rtype);
+ }
+ private static final MethodHandle[] ZERO_MHS = new MethodHandle[Wrapper.values().length];
+ private static MethodHandle makeZero(Class<?> rtype) {
+ // MethodType mtype = MethodType.methodType(rtype);
+ // LambdaForm lform = LambdaForm.zeroForm(BasicType.basicType(rtype));
+ // return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.ZERO);
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.makeZero is not implemented");
+ }
+
+ synchronized private static MethodHandle setCachedMethodHandle(MethodHandle[] cache, int pos, MethodHandle value) {
+ // Simulate a CAS, to avoid racy duplication of results.
+ MethodHandle prev = cache[pos];
+ if (prev != null) return prev;
+ return cache[pos] = value;
+ }
+
+ /**
+ * Provides a target method handle with one or more <em>bound arguments</em>
+ * in advance of the method handle's invocation.
+ * The formal parameters to the target corresponding to the bound
+ * arguments are called <em>bound parameters</em>.
+ * Returns a new method handle which saves away the bound arguments.
+ * When it is invoked, it receives arguments for any non-bound parameters,
+ * binds the saved arguments to their corresponding parameters,
+ * and calls the original target.
+ * <p>
+ * The type of the new method handle will drop the types for the bound
+ * parameters from the original target type, since the new method handle
+ * will no longer require those arguments to be supplied by its callers.
+ * <p>
+ * Each given argument object must match the corresponding bound parameter type.
+ * If a bound parameter type is a primitive, the argument object
+ * must be a wrapper, and will be unboxed to produce the primitive value.
+ * <p>
+ * The {@code pos} argument selects which parameters are to be bound.
+ * It may range between zero and <i>N-L</i> (inclusively),
+ * where <i>N</i> is the arity of the target method handle
+ * and <i>L</i> is the length of the values array.
+ * @param target the method handle to invoke after the argument is inserted
+ * @param pos where to insert the argument (zero for the first)
+ * @param values the series of arguments to insert
+ * @return a method handle which inserts an additional argument,
+ * before calling the original method handle
+ * @throws NullPointerException if the target or the {@code values} array is null
+ * @see MethodHandle#bindTo
+ */
+ public static
+ MethodHandle insertArguments(MethodHandle target, int pos, Object... values) {
+ int insCount = values.length;
+ Class<?>[] ptypes = insertArgumentsChecks(target, insCount, pos);
+ if (insCount == 0) return target;
+
+ // BoundMethodHandle result = target.rebind();
+ // for (int i = 0; i < insCount; i++) {
+ // Object value = values[i];
+ // Class<?> ptype = ptypes[pos+i];
+ // if (ptype.isPrimitive()) {
+ // result = insertArgumentPrimitive(result, pos, ptype, value);
+ // } else {
+ // value = ptype.cast(value); // throw CCE if needed
+ // result = result.bindArgumentL(pos, value);
+ // }
+ // }
+ // return result;
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.insertArguments is not implemented");
+ }
+
+ // Android-changed: insertArgumentPrimitive is unused.
+ //
+ // private static BoundMethodHandle insertArgumentPrimitive(BoundMethodHandle result, int pos,
+ // Class<?> ptype, Object value) {
+ // Wrapper w = Wrapper.forPrimitiveType(ptype);
+ // // perform unboxing and/or primitive conversion
+ // value = w.convert(value, ptype);
+ // switch (w) {
+ // case INT: return result.bindArgumentI(pos, (int)value);
+ // case LONG: return result.bindArgumentJ(pos, (long)value);
+ // case FLOAT: return result.bindArgumentF(pos, (float)value);
+ // case DOUBLE: return result.bindArgumentD(pos, (double)value);
+ // default: return result.bindArgumentI(pos, ValueConversions.widenSubword(value));
+ // }
+ // }
+
+ private static Class<?>[] insertArgumentsChecks(MethodHandle target, int insCount, int pos) throws RuntimeException {
+ MethodType oldType = target.type();
+ int outargs = oldType.parameterCount();
+ int inargs = outargs - insCount;
+ if (inargs < 0)
+ throw newIllegalArgumentException("too many values to insert");
+ if (pos < 0 || pos > inargs)
+ throw newIllegalArgumentException("no argument type to append");
+ return oldType.ptypes();
+ }
+
+ /**
+ * Produces a method handle which will discard some dummy arguments
+ * before calling some other specified <i>target</i> method handle.
+ * The type of the new method handle will be the same as the target's type,
+ * except it will also include the dummy argument types,
+ * at some given position.
+ * <p>
+ * The {@code pos} argument may range between zero and <i>N</i>,
+ * where <i>N</i> is the arity of the target.
+ * If {@code pos} is zero, the dummy arguments will precede
+ * the target's real arguments; if {@code pos} is <i>N</i>
+ * they will come after.
+ * <p>
+ * <b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle cat = lookup().findVirtual(String.class,
+ "concat", methodType(String.class, String.class));
+assertEquals("xy", (String) cat.invokeExact("x", "y"));
+MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class);
+MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2));
+assertEquals(bigType, d0.type());
+assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z"));
+ * }</pre></blockquote>
+ * <p>
+ * This method is also equivalent to the following code:
+ * <blockquote><pre>
+ * {@link #dropArguments(MethodHandle,int,Class...) dropArguments}{@code (target, pos, valueTypes.toArray(new Class[0]))}
+ * </pre></blockquote>
+ * @param target the method handle to invoke after the arguments are dropped
+ * @param valueTypes the type(s) of the argument(s) to drop
+ * @param pos position of first argument to drop (zero for the leftmost)
+ * @return a method handle which drops arguments of the given types,
+ * before calling the original method handle
+ * @throws NullPointerException if the target is null,
+ * or if the {@code valueTypes} list or any of its elements is null
+ * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
+ * or if {@code pos} is negative or greater than the arity of the target,
+ * or if the new method handle's type would have too many parameters
+ */
+ public static
+ MethodHandle dropArguments(MethodHandle target, int pos, List<Class<?>> valueTypes) {
+ MethodType oldType = target.type(); // get NPE
+ int dropped = dropArgumentChecks(oldType, pos, valueTypes);
+
+ MethodType newType = oldType.insertParameterTypes(pos, valueTypes);
+ // if (dropped == 0) return target;
+ // BoundMethodHandle result = target.rebind();
+ // LambdaForm lform = result.form;
+ // int insertFormArg = 1 + pos;
+ // for (Class<?> ptype : valueTypes) {
+ // lform = lform.editor().addArgumentForm(insertFormArg++, BasicType.basicType(ptype));
+ // }
+ // result = result.copyWith(newType, lform);
+ // return result;
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.dropArguments is not implemented");
+ }
+
+ private static int dropArgumentChecks(MethodType oldType, int pos, List<Class<?>> valueTypes) {
+ int dropped = valueTypes.size();
+ MethodType.checkSlotCount(dropped);
+ int outargs = oldType.parameterCount();
+ int inargs = outargs + dropped;
+ if (pos < 0 || pos > outargs)
+ throw newIllegalArgumentException("no argument type to remove"
+ + Arrays.asList(oldType, pos, valueTypes, inargs, outargs)
+ );
+ return dropped;
+ }
+
+ /**
+ * Produces a method handle which will discard some dummy arguments
+ * before calling some other specified <i>target</i> method handle.
+ * The type of the new method handle will be the same as the target's type,
+ * except it will also include the dummy argument types,
+ * at some given position.
+ * <p>
+ * The {@code pos} argument may range between zero and <i>N</i>,
+ * where <i>N</i> is the arity of the target.
+ * If {@code pos} is zero, the dummy arguments will precede
+ * the target's real arguments; if {@code pos} is <i>N</i>
+ * they will come after.
+ * <p>
+ * <b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle cat = lookup().findVirtual(String.class,
+ "concat", methodType(String.class, String.class));
+assertEquals("xy", (String) cat.invokeExact("x", "y"));
+MethodHandle d0 = dropArguments(cat, 0, String.class);
+assertEquals("yz", (String) d0.invokeExact("x", "y", "z"));
+MethodHandle d1 = dropArguments(cat, 1, String.class);
+assertEquals("xz", (String) d1.invokeExact("x", "y", "z"));
+MethodHandle d2 = dropArguments(cat, 2, String.class);
+assertEquals("xy", (String) d2.invokeExact("x", "y", "z"));
+MethodHandle d12 = dropArguments(cat, 1, int.class, boolean.class);
+assertEquals("xz", (String) d12.invokeExact("x", 12, true, "z"));
+ * }</pre></blockquote>
+ * <p>
+ * This method is also equivalent to the following code:
+ * <blockquote><pre>
+ * {@link #dropArguments(MethodHandle,int,List) dropArguments}{@code (target, pos, Arrays.asList(valueTypes))}
+ * </pre></blockquote>
+ * @param target the method handle to invoke after the arguments are dropped
+ * @param valueTypes the type(s) of the argument(s) to drop
+ * @param pos position of first argument to drop (zero for the leftmost)
+ * @return a method handle which drops arguments of the given types,
+ * before calling the original method handle
+ * @throws NullPointerException if the target is null,
+ * or if the {@code valueTypes} array or any of its elements is null
+ * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
+ * or if {@code pos} is negative or greater than the arity of the target,
+ * or if the new method handle's type would have
+ * <a href="MethodHandle.html#maxarity">too many parameters</a>
+ */
+ public static
+ MethodHandle dropArguments(MethodHandle target, int pos, Class<?>... valueTypes) {
+ return dropArguments(target, pos, Arrays.asList(valueTypes));
+ }
+
+ /**
+ * Adapts a target method handle by pre-processing
+ * one or more of its arguments, each with its own unary filter function,
+ * and then calling the target with each pre-processed argument
+ * replaced by the result of its corresponding filter function.
+ * <p>
+ * The pre-processing is performed by one or more method handles,
+ * specified in the elements of the {@code filters} array.
+ * The first element of the filter array corresponds to the {@code pos}
+ * argument of the target, and so on in sequence.
+ * <p>
+ * Null arguments in the array are treated as identity functions,
+ * and the corresponding arguments left unchanged.
+ * (If there are no non-null elements in the array, the original target is returned.)
+ * Each filter is applied to the corresponding argument of the adapter.
+ * <p>
+ * If a filter {@code F} applies to the {@code N}th argument of
+ * the target, then {@code F} must be a method handle which
+ * takes exactly one argument. The type of {@code F}'s sole argument
+ * replaces the corresponding argument type of the target
+ * in the resulting adapted method handle.
+ * The return type of {@code F} must be identical to the corresponding
+ * parameter type of the target.
+ * <p>
+ * It is an error if there are elements of {@code filters}
+ * (null or not)
+ * which do not correspond to argument positions in the target.
+ * <p><b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle cat = lookup().findVirtual(String.class,
+ "concat", methodType(String.class, String.class));
+MethodHandle upcase = lookup().findVirtual(String.class,
+ "toUpperCase", methodType(String.class));
+assertEquals("xy", (String) cat.invokeExact("x", "y"));
+MethodHandle f0 = filterArguments(cat, 0, upcase);
+assertEquals("Xy", (String) f0.invokeExact("x", "y")); // Xy
+MethodHandle f1 = filterArguments(cat, 1, upcase);
+assertEquals("xY", (String) f1.invokeExact("x", "y")); // xY
+MethodHandle f2 = filterArguments(cat, 0, upcase, upcase);
+assertEquals("XY", (String) f2.invokeExact("x", "y")); // XY
+ * }</pre></blockquote>
+ * <p> Here is pseudocode for the resulting adapter:
+ * <blockquote><pre>{@code
+ * V target(P... p, A[i]... a[i], B... b);
+ * A[i] filter[i](V[i]);
+ * T adapter(P... p, V[i]... v[i], B... b) {
+ * return target(p..., f[i](v[i])..., b...);
+ * }
+ * }</pre></blockquote>
+ *
+ * @param target the method handle to invoke after arguments are filtered
+ * @param pos the position of the first argument to filter
+ * @param filters method handles to call initially on filtered arguments
+ * @return method handle which incorporates the specified argument filtering logic
+ * @throws NullPointerException if the target is null
+ * or if the {@code filters} array is null
+ * @throws IllegalArgumentException if a non-null element of {@code filters}
+ * does not match a corresponding argument type of target as described above,
+ * or if the {@code pos+filters.length} is greater than {@code target.type().parameterCount()},
+ * or if the resulting method handle's type would have
+ * <a href="MethodHandle.html#maxarity">too many parameters</a>
+ */
+ public static
+ MethodHandle filterArguments(MethodHandle target, int pos, MethodHandle... filters) {
+ filterArgumentsCheckArity(target, pos, filters);
+ MethodHandle adapter = target;
+ int curPos = pos-1; // pre-incremented
+ for (MethodHandle filter : filters) {
+ curPos += 1;
+ if (filter == null) continue; // ignore null elements of filters
+ adapter = filterArgument(adapter, curPos, filter);
+ }
+ return adapter;
+ }
+
+ /*non-public*/ static
+ MethodHandle filterArgument(MethodHandle target, int pos, MethodHandle filter) {
+ filterArgumentChecks(target, pos, filter);
+ // MethodType targetType = target.type();
+ // MethodType filterType = filter.type();
+ // BoundMethodHandle result = target.rebind();
+ // Class<?> newParamType = filterType.parameterType(0);
+ // LambdaForm lform = result.editor().filterArgumentForm(1 + pos, BasicType.basicType(newParamType));
+ // MethodType newType = targetType.changeParameterType(pos, newParamType);
+ // result = result.copyWithExtendL(newType, lform, filter);
+ // return result;
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.filterArgument is not implemented");
+ }
+
+ private static void filterArgumentsCheckArity(MethodHandle target, int pos, MethodHandle[] filters) {
+ MethodType targetType = target.type();
+ int maxPos = targetType.parameterCount();
+ if (pos + filters.length > maxPos)
+ throw newIllegalArgumentException("too many filters");
+ }
+
+ private static void filterArgumentChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
+ MethodType targetType = target.type();
+ MethodType filterType = filter.type();
+ if (filterType.parameterCount() != 1
+ || filterType.returnType() != targetType.parameterType(pos))
+ throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
+ }
+
+ /**
+ * Adapts a target method handle by pre-processing
+ * a sub-sequence of its arguments with a filter (another method handle).
+ * The pre-processed arguments are replaced by the result (if any) of the
+ * filter function.
+ * The target is then called on the modified (usually shortened) argument list.
+ * <p>
+ * If the filter returns a value, the target must accept that value as
+ * its argument in position {@code pos}, preceded and/or followed by
+ * any arguments not passed to the filter.
+ * If the filter returns void, the target must accept all arguments
+ * not passed to the filter.
+ * No arguments are reordered, and a result returned from the filter
+ * replaces (in order) the whole subsequence of arguments originally
+ * passed to the adapter.
+ * <p>
+ * The argument types (if any) of the filter
+ * replace zero or one argument types of the target, at position {@code pos},
+ * in the resulting adapted method handle.
+ * The return type of the filter (if any) must be identical to the
+ * argument type of the target at position {@code pos}, and that target argument
+ * is supplied by the return value of the filter.
+ * <p>
+ * In all cases, {@code pos} must be greater than or equal to zero, and
+ * {@code pos} must also be less than or equal to the target's arity.
+ * <p><b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle deepToString = publicLookup()
+ .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
+
+MethodHandle ts1 = deepToString.asCollector(String[].class, 1);
+assertEquals("[strange]", (String) ts1.invokeExact("strange"));
+
+MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
+assertEquals("[up, down]", (String) ts2.invokeExact("up", "down"));
+
+MethodHandle ts3 = deepToString.asCollector(String[].class, 3);
+MethodHandle ts3_ts2 = collectArguments(ts3, 1, ts2);
+assertEquals("[top, [up, down], strange]",
+ (String) ts3_ts2.invokeExact("top", "up", "down", "strange"));
+
+MethodHandle ts3_ts2_ts1 = collectArguments(ts3_ts2, 3, ts1);
+assertEquals("[top, [up, down], [strange]]",
+ (String) ts3_ts2_ts1.invokeExact("top", "up", "down", "strange"));
+
+MethodHandle ts3_ts2_ts3 = collectArguments(ts3_ts2, 1, ts3);
+assertEquals("[top, [[up, down, strange], charm], bottom]",
+ (String) ts3_ts2_ts3.invokeExact("top", "up", "down", "strange", "charm", "bottom"));
+ * }</pre></blockquote>
+ * <p> Here is pseudocode for the resulting adapter:
+ * <blockquote><pre>{@code
+ * T target(A...,V,C...);
+ * V filter(B...);
+ * T adapter(A... a,B... b,C... c) {
+ * V v = filter(b...);
+ * return target(a...,v,c...);
+ * }
+ * // and if the filter has no arguments:
+ * T target2(A...,V,C...);
+ * V filter2();
+ * T adapter2(A... a,C... c) {
+ * V v = filter2();
+ * return target2(a...,v,c...);
+ * }
+ * // and if the filter has a void return:
+ * T target3(A...,C...);
+ * void filter3(B...);
+ * void adapter3(A... a,B... b,C... c) {
+ * filter3(b...);
+ * return target3(a...,c...);
+ * }
+ * }</pre></blockquote>
+ * <p>
+ * A collection adapter {@code collectArguments(mh, 0, coll)} is equivalent to
+ * one which first "folds" the affected arguments, and then drops them, in separate
+ * steps as follows:
+ * <blockquote><pre>{@code
+ * mh = MethodHandles.dropArguments(mh, 1, coll.type().parameterList()); //step 2
+ * mh = MethodHandles.foldArguments(mh, coll); //step 1
+ * }</pre></blockquote>
+ * If the target method handle consumes no arguments besides than the result
+ * (if any) of the filter {@code coll}, then {@code collectArguments(mh, 0, coll)}
+ * is equivalent to {@code filterReturnValue(coll, mh)}.
+ * If the filter method handle {@code coll} consumes one argument and produces
+ * a non-void result, then {@code collectArguments(mh, N, coll)}
+ * is equivalent to {@code filterArguments(mh, N, coll)}.
+ * Other equivalences are possible but would require argument permutation.
+ *
+ * @param target the method handle to invoke after filtering the subsequence of arguments
+ * @param pos the position of the first adapter argument to pass to the filter,
+ * and/or the target argument which receives the result of the filter
+ * @param filter method handle to call on the subsequence of arguments
+ * @return method handle which incorporates the specified argument subsequence filtering logic
+ * @throws NullPointerException if either argument is null
+ * @throws IllegalArgumentException if the return type of {@code filter}
+ * is non-void and is not the same as the {@code pos} argument of the target,
+ * or if {@code pos} is not between 0 and the target's arity, inclusive,
+ * or if the resulting method handle's type would have
+ * <a href="MethodHandle.html#maxarity">too many parameters</a>
+ * @see MethodHandles#foldArguments
+ * @see MethodHandles#filterArguments
+ * @see MethodHandles#filterReturnValue
+ */
+ public static
+ MethodHandle collectArguments(MethodHandle target, int pos, MethodHandle filter) {
+ MethodType newType = collectArgumentsChecks(target, pos, filter);
+ MethodType collectorType = filter.type();
+
+ // BoundMethodHandle result = target.rebind();
+ // LambdaForm lform;
+ // if (collectorType.returnType().isArray() && filter.intrinsicName() == Intrinsic.NEW_ARRAY) {
+ // lform = result.editor().collectArgumentArrayForm(1 + pos, filter);
+ // if (lform != null) {
+ // return result.copyWith(newType, lform);
+ // }
+ // }
+ // lform = result.editor().collectArgumentsForm(1 + pos, collectorType.basicType());
+ // return result.copyWithExtendL(newType, lform, filter);
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.collectArguments is not implemented");
+ }
+
+ private static MethodType collectArgumentsChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
+ MethodType targetType = target.type();
+ MethodType filterType = filter.type();
+ Class<?> rtype = filterType.returnType();
+ List<Class<?>> filterArgs = filterType.parameterList();
+ if (rtype == void.class) {
+ return targetType.insertParameterTypes(pos, filterArgs);
+ }
+ if (rtype != targetType.parameterType(pos)) {
+ throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
+ }
+ return targetType.dropParameterTypes(pos, pos+1).insertParameterTypes(pos, filterArgs);
+ }
+
+ /**
+ * Adapts a target method handle by post-processing
+ * its return value (if any) with a filter (another method handle).
+ * The result of the filter is returned from the adapter.
+ * <p>
+ * If the target returns a value, the filter must accept that value as
+ * its only argument.
+ * If the target returns void, the filter must accept no arguments.
+ * <p>
+ * The return type of the filter
+ * replaces the return type of the target
+ * in the resulting adapted method handle.
+ * The argument type of the filter (if any) must be identical to the
+ * return type of the target.
+ * <p><b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle cat = lookup().findVirtual(String.class,
+ "concat", methodType(String.class, String.class));
+MethodHandle length = lookup().findVirtual(String.class,
+ "length", methodType(int.class));
+System.out.println((String) cat.invokeExact("x", "y")); // xy
+MethodHandle f0 = filterReturnValue(cat, length);
+System.out.println((int) f0.invokeExact("x", "y")); // 2
+ * }</pre></blockquote>
+ * <p> Here is pseudocode for the resulting adapter:
+ * <blockquote><pre>{@code
+ * V target(A...);
+ * T filter(V);
+ * T adapter(A... a) {
+ * V v = target(a...);
+ * return filter(v);
+ * }
+ * // and if the target has a void return:
+ * void target2(A...);
+ * T filter2();
+ * T adapter2(A... a) {
+ * target2(a...);
+ * return filter2();
+ * }
+ * // and if the filter has a void return:
+ * V target3(A...);
+ * void filter3(V);
+ * void adapter3(A... a) {
+ * V v = target3(a...);
+ * filter3(v);
+ * }
+ * }</pre></blockquote>
+ * @param target the method handle to invoke before filtering the return value
+ * @param filter method handle to call on the return value
+ * @return method handle which incorporates the specified return value filtering logic
+ * @throws NullPointerException if either argument is null
+ * @throws IllegalArgumentException if the argument list of {@code filter}
+ * does not match the return type of target as described above
+ */
+ public static
+ MethodHandle filterReturnValue(MethodHandle target, MethodHandle filter) {
+ MethodType targetType = target.type();
+ MethodType filterType = filter.type();
+ filterReturnValueChecks(targetType, filterType);
+
+ // BoundMethodHandle result = target.rebind();
+ // BasicType rtype = BasicType.basicType(filterType.returnType());
+ // LambdaForm lform = result.editor().filterReturnForm(rtype, false);
+ // MethodType newType = targetType.changeReturnType(filterType.returnType());
+ // result = result.copyWithExtendL(newType, lform, filter);
+ // return result;
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.filterReturnValue is not implemented");
+ }
+
+ private static void filterReturnValueChecks(MethodType targetType, MethodType filterType) throws RuntimeException {
+ Class<?> rtype = targetType.returnType();
+ int filterValues = filterType.parameterCount();
+ if (filterValues == 0
+ ? (rtype != void.class)
+ : (rtype != filterType.parameterType(0)))
+ throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
+ }
+
+ /**
+ * Adapts a target method handle by pre-processing
+ * some of its arguments, and then calling the target with
+ * the result of the pre-processing, inserted into the original
+ * sequence of arguments.
+ * <p>
+ * The pre-processing is performed by {@code combiner}, a second method handle.
+ * Of the arguments passed to the adapter, the first {@code N} arguments
+ * are copied to the combiner, which is then called.
+ * (Here, {@code N} is defined as the parameter count of the combiner.)
+ * After this, control passes to the target, with any result
+ * from the combiner inserted before the original {@code N} incoming
+ * arguments.
+ * <p>
+ * If the combiner returns a value, the first parameter type of the target
+ * must be identical with the return type of the combiner, and the next
+ * {@code N} parameter types of the target must exactly match the parameters
+ * of the combiner.
+ * <p>
+ * If the combiner has a void return, no result will be inserted,
+ * and the first {@code N} parameter types of the target
+ * must exactly match the parameters of the combiner.
+ * <p>
+ * The resulting adapter is the same type as the target, except that the
+ * first parameter type is dropped,
+ * if it corresponds to the result of the combiner.
+ * <p>
+ * (Note that {@link #dropArguments(MethodHandle,int,List) dropArguments} can be used to remove any arguments
+ * that either the combiner or the target does not wish to receive.
+ * If some of the incoming arguments are destined only for the combiner,
+ * consider using {@link MethodHandle#asCollector asCollector} instead, since those
+ * arguments will not need to be live on the stack on entry to the
+ * target.)
+ * <p><b>Example:</b>
+ * <blockquote><pre>{@code
+import static java.lang.invoke.MethodHandles.*;
+import static java.lang.invoke.MethodType.*;
+...
+MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class,
+ "println", methodType(void.class, String.class))
+ .bindTo(System.out);
+MethodHandle cat = lookup().findVirtual(String.class,
+ "concat", methodType(String.class, String.class));
+assertEquals("boojum", (String) cat.invokeExact("boo", "jum"));
+MethodHandle catTrace = foldArguments(cat, trace);
+// also prints "boo":
+assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
+ * }</pre></blockquote>
+ * <p> Here is pseudocode for the resulting adapter:
+ * <blockquote><pre>{@code
+ * // there are N arguments in A...
+ * T target(V, A[N]..., B...);
+ * V combiner(A...);
+ * T adapter(A... a, B... b) {
+ * V v = combiner(a...);
+ * return target(v, a..., b...);
+ * }
+ * // and if the combiner has a void return:
+ * T target2(A[N]..., B...);
+ * void combiner2(A...);
+ * T adapter2(A... a, B... b) {
+ * combiner2(a...);
+ * return target2(a..., b...);
+ * }
+ * }</pre></blockquote>
+ * @param target the method handle to invoke after arguments are combined
+ * @param combiner method handle to call initially on the incoming arguments
+ * @return method handle which incorporates the specified argument folding logic
+ * @throws NullPointerException if either argument is null
+ * @throws IllegalArgumentException if {@code combiner}'s return type
+ * is non-void and not the same as the first argument type of
+ * the target, or if the initial {@code N} argument types
+ * of the target
+ * (skipping one matching the {@code combiner}'s return type)
+ * are not identical with the argument types of {@code combiner}
+ */
+ public static
+ MethodHandle foldArguments(MethodHandle target, MethodHandle combiner) {
+ int foldPos = 0;
+ MethodType targetType = target.type();
+ MethodType combinerType = combiner.type();
+ Class<?> rtype = foldArgumentChecks(foldPos, targetType, combinerType);
+
+ // BoundMethodHandle result = target.rebind();
+ // boolean dropResult = (rtype == void.class);
+ // // Note: This may cache too many distinct LFs. Consider backing off to varargs code.
+ // LambdaForm lform = result.editor().foldArgumentsForm(1 + foldPos, dropResult, combinerType.basicType());
+ // MethodType newType = targetType;
+ // if (!dropResult)
+ // newType = newType.dropParameterTypes(foldPos, foldPos + 1);
+ // result = result.copyWithExtendL(newType, lform, combiner);
+ // return result;
+
+ // TODO(narayan): Implement this method.
+ throw new UnsupportedOperationException("MethodHandles.foldArguments is not implemented");
+ }
+
+ private static Class<?> foldArgumentChecks(int foldPos, MethodType targetType, MethodType combinerType) {
+ int foldArgs = combinerType.parameterCount();
+ Class<?> rtype = combinerType.returnType();
+ int foldVals = rtype == void.class ? 0 : 1;
+ int afterInsertPos = foldPos + foldVals;
+ boolean ok = (targetType.parameterCount() >= afterInsertPos + foldArgs);
+ if (ok && !(combinerType.parameterList()
+ .equals(targetType.parameterList().subList(afterInsertPos,
+ afterInsertPos + foldArgs))))
+ ok = false;
+ if (ok && foldVals != 0 && combinerType.returnType() != targetType.parameterType(0))
+ ok = false;
+ if (!ok)
+ throw misMatchedTypes("target and combiner types", targetType, combinerType);
+ return rtype;
+ }
+
+ /**
+ * Makes a method handle which adapts a target method handle,
+ * by guarding it with a test, a boolean-valued method handle.
+ * If the guard fails, a fallback handle is called instead.
+ * All three method handles must have the same corresponding
+ * argument and return types, except that the return type
+ * of the test must be boolean, and the test is allowed
+ * to have fewer arguments than the other two method handles.
+ * <p> Here is pseudocode for the resulting adapter:
+ * <blockquote><pre>{@code
+ * boolean test(A...);
+ * T target(A...,B...);
+ * T fallback(A...,B...);
+ * T adapter(A... a,B... b) {
+ * if (test(a...))
+ * return target(a..., b...);
+ * else
+ * return fallback(a..., b...);
+ * }
+ * }</pre></blockquote>
+ * Note that the test arguments ({@code a...} in the pseudocode) cannot
+ * be modified by execution of the test, and so are passed unchanged
+ * from the caller to the target or fallback as appropriate.
+ * @param test method handle used for test, must return boolean
+ * @param target method handle to call if test passes
+ * @param fallback method handle to call if test fails
+ * @return method handle which incorporates the specified if/then/else logic
+ * @throws NullPointerException if any argument is null
+ * @throws IllegalArgumentException if {@code test} does not return boolean,
+ * or if all three method types do not match (with the return
+ * type of {@code test} changed to match that of the target).
+ */
+ public static
+ MethodHandle guardWithTest(MethodHandle test,
+ MethodHandle target,
+ MethodHandle fallback) {
+ MethodType gtype = test.type();
+ MethodType ttype = target.type();
+ MethodType ftype = fallback.type();
+ if (!ttype.equals(ftype))
+ throw misMatchedTypes("target and fallback types", ttype, ftype);
+ if (gtype.returnType() != boolean.class)
+ throw newIllegalArgumentException("guard type is not a predicate "+gtype);
+ List<Class<?>> targs = ttype.parameterList();
+ List<Class<?>> gargs = gtype.parameterList();
+ if (!targs.equals(gargs)) {
+ int gpc = gargs.size(), tpc = targs.size();
+ if (gpc >= tpc || !targs.subList(0, gpc).equals(gargs))
+ throw misMatchedTypes("target and test types", ttype, gtype);
+ test = dropArguments(test, gpc, targs.subList(gpc, tpc));
+ gtype = test.type();
+ }
+
+ // TODO(narayan): Implement this method.
+ // return MethodHandleImpl.makeGuardWithTest(test, target, fallback);
+ throw new UnsupportedOperationException("MethodHandles.guardWithTest is not implemented");
+ }
+
+ static RuntimeException misMatchedTypes(String what, MethodType t1, MethodType t2) {
+ return newIllegalArgumentException(what + " must match: " + t1 + " != " + t2);
+ }
+
+ /**
+ * Makes a method handle which adapts a target method handle,
+ * by running it inside an exception handler.
+ * If the target returns normally, the adapter returns that value.
+ * If an exception matching the specified type is thrown, the fallback
+ * handle is called instead on the exception, plus the original arguments.
+ * <p>
+ * The target and handler must have the same corresponding
+ * argument and return types, except that handler may omit trailing arguments
+ * (similarly to the predicate in {@link #guardWithTest guardWithTest}).
+ * Also, the handler must have an extra leading parameter of {@code exType} or a supertype.
+ * <p> Here is pseudocode for the resulting adapter:
+ * <blockquote><pre>{@code
+ * T target(A..., B...);
+ * T handler(ExType, A...);
+ * T adapter(A... a, B... b) {
+ * try {
+ * return target(a..., b...);
+ * } catch (ExType ex) {
+ * return handler(ex, a...);
+ * }
+ * }
+ * }</pre></blockquote>
+ * Note that the saved arguments ({@code a...} in the pseudocode) cannot
+ * be modified by execution of the target, and so are passed unchanged
+ * from the caller to the handler, if the handler is invoked.
+ * <p>
+ * The target and handler must return the same type, even if the handler
+ * always throws. (This might happen, for instance, because the handler
+ * is simulating a {@code finally} clause).
+ * To create such a throwing handler, compose the handler creation logic
+ * with {@link #throwException throwException},
+ * in order to create a method handle of the correct return type.
+ * @param target method handle to call
+ * @param exType the type of exception which the handler will catch
+ * @param handler method handle to call if a matching exception is thrown
+ * @return method handle which incorporates the specified try/catch logic
+ * @throws NullPointerException if any argument is null
+ * @throws IllegalArgumentException if {@code handler} does not accept
+ * the given exception type, or if the method handle types do
+ * not match in their return types and their
+ * corresponding parameters
+ */
+ public static
+ MethodHandle catchException(MethodHandle target,
+ Class<? extends Throwable> exType,
+ MethodHandle handler) {
+ MethodType ttype = target.type();
+ MethodType htype = handler.type();
+ if (htype.parameterCount() < 1 ||
+ !htype.parameterType(0).isAssignableFrom(exType))
+ throw newIllegalArgumentException("handler does not accept exception type "+exType);
+ if (htype.returnType() != ttype.returnType())
+ throw misMatchedTypes("target and handler return types", ttype, htype);
+ List<Class<?>> targs = ttype.parameterList();
+ List<Class<?>> hargs = htype.parameterList();
+ hargs = hargs.subList(1, hargs.size()); // omit leading parameter from handler
+ if (!targs.equals(hargs)) {
+ int hpc = hargs.size(), tpc = targs.size();
+ if (hpc >= tpc || !targs.subList(0, hpc).equals(hargs))
+ throw misMatchedTypes("target and handler types", ttype, htype);
+ handler = dropArguments(handler, 1+hpc, targs.subList(hpc, tpc));
+ htype = handler.type();
+ }
+
+ // TODO(narayan): Implement this method.
+ // return MethodHandleImpl.makeGuardWithCatch(target, exType, handler);
+ throw new UnsupportedOperationException("MethodHandles.catchException is not implemented");
+ }
+
+ /**
+ * Produces a method handle which will throw exceptions of the given {@code exType}.
+ * The method handle will accept a single argument of {@code exType},
+ * and immediately throw it as an exception.
+ * The method type will nominally specify a return of {@code returnType}.
+ * The return type may be anything convenient: It doesn't matter to the
+ * method handle's behavior, since it will never return normally.
+ * @param returnType the return type of the desired method handle
+ * @param exType the parameter type of the desired method handle
+ * @return method handle which can throw the given exceptions
+ * @throws NullPointerException if either argument is null
+ */
+ public static
+ MethodHandle throwException(Class<?> returnType, Class<? extends Throwable> exType) {
+ if (!Throwable.class.isAssignableFrom(exType))
+ throw new ClassCastException(exType.getName());
+
+ // TODO(narayan): Implement this method.
+ // return MethodHandleImpl.throwException(MethodType.methodType(returnType, exType));
+ throw new UnsupportedOperationException("MethodHandles.throwException is not implemented");
+ }
+}
diff --git a/ojluni/src/main/java/sun/invoke/util/VerifyAccess.java b/ojluni/src/main/java/sun/invoke/util/VerifyAccess.java
new file mode 100644
index 0000000..d2e5820
--- /dev/null
+++ b/ojluni/src/main/java/sun/invoke/util/VerifyAccess.java
@@ -0,0 +1,300 @@
+/*
+ * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package sun.invoke.util;
+
+import java.lang.reflect.Modifier;
+import static java.lang.reflect.Modifier.*;
+import sun.reflect.Reflection;
+
+/**
+ * This class centralizes information about the JVM's linkage access control.
+ * @author jrose
+ */
+public class VerifyAccess {
+
+ private VerifyAccess() { } // cannot instantiate
+
+ private static final int PACKAGE_ONLY = 0;
+ private static final int PACKAGE_ALLOWED = java.lang.invoke.MethodHandles.Lookup.PACKAGE;
+ private static final int PROTECTED_OR_PACKAGE_ALLOWED = (PACKAGE_ALLOWED|PROTECTED);
+ private static final int ALL_ACCESS_MODES = (PUBLIC|PRIVATE|PROTECTED|PACKAGE_ONLY);
+ private static final boolean ALLOW_NESTMATE_ACCESS = false;
+
+ /**
+ * Evaluate the JVM linkage rules for access to the given method
+ * on behalf of a caller class which proposes to perform the access.
+ * Return true if the caller class has privileges to invoke a method
+ * or access a field with the given properties.
+ * This requires an accessibility check of the referencing class,
+ * plus an accessibility check of the member within the class,
+ * which depends on the member's modifier flags.
+ * <p>
+ * The relevant properties include the defining class ({@code defc})
+ * of the member, and its modifier flags ({@code mods}).
+ * Also relevant is the class used to make the initial symbolic reference
+ * to the member ({@code refc}). If this latter class is not distinguished,
+ * the defining class should be passed for both arguments ({@code defc == refc}).
+ * <h3>JVM Specification, 5.4.4 "Access Control"</h3>
+ * A field or method R is accessible to a class or interface D if
+ * and only if any of the following conditions is true:<ul>
+ * <li>R is public.
+ * <li>R is protected and is declared in a class C, and D is either
+ * a subclass of C or C itself. Furthermore, if R is not
+ * static, then the symbolic reference to R must contain a
+ * symbolic reference to a class T, such that T is either a
+ * subclass of D, a superclass of D or D itself.
+ * <li>R is either protected or has default access (that is,
+ * neither public nor protected nor private), and is declared
+ * by a class in the same runtime package as D.
+ * <li>R is private and is declared in D.
+ * </ul>
+ * This discussion of access control omits a related restriction
+ * on the target of a protected field access or method invocation
+ * (the target must be of class D or a subtype of D). That
+ * requirement is checked as part of the verification process
+ * (5.4.1); it is not part of link-time access control.
+ * @param refc the class used in the symbolic reference to the proposed member
+ * @param defc the class in which the proposed member is actually defined
+ * @param mods modifier flags for the proposed member
+ * @param lookupClass the class for which the access check is being made
+ * @return true iff the the accessing class can access such a member
+ */
+ public static boolean isMemberAccessible(Class<?> refc, // symbolic ref class
+ Class<?> defc, // actual def class
+ int mods, // actual member mods
+ Class<?> lookupClass,
+ int allowedModes) {
+ if (allowedModes == 0) return false;
+ assert((allowedModes & PUBLIC) != 0 &&
+ (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED)) == 0);
+ // The symbolic reference class (refc) must always be fully verified.
+ if (!isClassAccessible(refc, lookupClass, allowedModes)) {
+ return false;
+ }
+ // Usually refc and defc are the same, but verify defc also in case they differ.
+ if (defc == lookupClass &&
+ (allowedModes & PRIVATE) != 0)
+ return true; // easy check; all self-access is OK
+ switch (mods & ALL_ACCESS_MODES) {
+ case PUBLIC:
+ return true; // already checked above
+ case PROTECTED:
+ assert !defc.isInterface(); // protected members aren't allowed in interfaces
+ if ((allowedModes & PROTECTED_OR_PACKAGE_ALLOWED) != 0 &&
+ isSamePackage(defc, lookupClass))
+ return true;
+ if ((allowedModes & PROTECTED) == 0)
+ return false;
+ // Protected members are accessible by subclasses, which does not include interfaces.
+ // Interfaces are types, not classes. They should not have access to
+ // protected members in j.l.Object, even though it is their superclass.
+ if ((mods & STATIC) != 0 &&
+ !isRelatedClass(refc, lookupClass))
+ return false;
+ if ((allowedModes & PROTECTED) != 0 &&
+ isSubClass(lookupClass, defc))
+ return true;
+ return false;
+ case PACKAGE_ONLY: // That is, zero. Unmarked member is package-only access.
+ assert !defc.isInterface(); // package-private members aren't allowed in interfaces
+ return ((allowedModes & PACKAGE_ALLOWED) != 0 &&
+ isSamePackage(defc, lookupClass));
+ case PRIVATE:
+ // Loosened rules for privates follows access rules for inner classes.
+ return (ALLOW_NESTMATE_ACCESS &&
+ (allowedModes & PRIVATE) != 0 &&
+ isSamePackageMember(defc, lookupClass));
+ default:
+ throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods));
+ }
+ }
+
+ static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) {
+ return (refc == lookupClass ||
+ isSubClass(refc, lookupClass) ||
+ isSubClass(lookupClass, refc));
+ }
+
+ static boolean isSubClass(Class<?> lookupClass, Class<?> defc) {
+ return defc.isAssignableFrom(lookupClass) &&
+ !lookupClass.isInterface(); // interfaces are types, not classes.
+ }
+
+ /**
+ * Evaluate the JVM linkage rules for access to the given class on behalf of caller.
+ * <h3>JVM Specification, 5.4.4 "Access Control"</h3>
+ * A class or interface C is accessible to a class or interface D
+ * if and only if either of the following conditions are true:<ul>
+ * <li>C is public.
+ * <li>C and D are members of the same runtime package.
+ * </ul>
+ * @param refc the symbolic reference class to which access is being checked (C)
+ * @param lookupClass the class performing the lookup (D)
+ */
+ public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass,
+ int allowedModes) {
+ if (allowedModes == 0) return false;
+ // Android-changed: Use public APIs to figure out whether a class
+ // is public or not.
+ if (Modifier.isPublic(refc.getModifiers()))
+ return true;
+ if ((allowedModes & PACKAGE_ALLOWED) != 0 &&
+ isSamePackage(lookupClass, refc))
+ return true;
+ return false;
+ }
+
+ /**
+ * Decide if the given method type, attributed to a member or symbolic
+ * reference of a given reference class, is really visible to that class.
+ * @param type the supposed type of a member or symbolic reference of refc
+ * @param refc the class attempting to make the reference
+ */
+ public static boolean isTypeVisible(Class<?> type, Class<?> refc) {
+ if (type == refc) return true; // easy check
+ while (type.isArray()) type = type.getComponentType();
+ if (type.isPrimitive() || type == Object.class) return true;
+ ClassLoader parent = type.getClassLoader();
+ if (parent == null) return true;
+ ClassLoader child = refc.getClassLoader();
+ if (child == null) return false;
+ if (parent == child || loadersAreRelated(parent, child, true))
+ return true;
+ // Do it the hard way: Look up the type name from the refc loader.
+ try {
+ Class<?> res = child.loadClass(type.getName());
+ return (type == res);
+ } catch (ClassNotFoundException ex) {
+ return false;
+ }
+ }
+
+ /**
+ * Decide if the given method type, attributed to a member or symbolic
+ * reference of a given reference class, is really visible to that class.
+ * @param type the supposed type of a member or symbolic reference of refc
+ * @param refc the class attempting to make the reference
+ */
+ public static boolean isTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) {
+ for (int n = -1, max = type.parameterCount(); n < max; n++) {
+ Class<?> ptype = (n < 0 ? type.returnType() : type.parameterType(n));
+ if (!isTypeVisible(ptype, refc))
+ return false;
+ }
+ return true;
+ }
+
+ /**
+ * Test if two classes have the same class loader and package qualifier.
+ * @param class1 a class
+ * @param class2 another class
+ * @return whether they are in the same package
+ */
+ public static boolean isSamePackage(Class<?> class1, Class<?> class2) {
+ // Android-changed: Throw IAE (instead of asserting) if called with array classes.
+ if (class1.isArray() || class2.isArray()) {
+ throw new IllegalArgumentException();
+ }
+
+ if (class1 == class2)
+ return true;
+ if (class1.getClassLoader() != class2.getClassLoader())
+ return false;
+ String name1 = class1.getName(), name2 = class2.getName();
+ int dot = name1.lastIndexOf('.');
+ if (dot != name2.lastIndexOf('.'))
+ return false;
+ for (int i = 0; i < dot; i++) {
+ if (name1.charAt(i) != name2.charAt(i))
+ return false;
+ }
+ return true;
+ }
+
+ /** Return the package name for this class.
+ */
+ public static String getPackageName(Class<?> cls) {
+ assert(!cls.isArray());
+ String name = cls.getName();
+ int dot = name.lastIndexOf('.');
+ if (dot < 0) return "";
+ return name.substring(0, dot);
+ }
+
+ /**
+ * Test if two classes are defined as part of the same package member (top-level class).
+ * If this is true, they can share private access with each other.
+ * @param class1 a class
+ * @param class2 another class
+ * @return whether they are identical or nested together
+ */
+ public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) {
+ if (class1 == class2)
+ return true;
+ if (!isSamePackage(class1, class2))
+ return false;
+ if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2))
+ return false;
+ return true;
+ }
+
+ private static Class<?> getOutermostEnclosingClass(Class<?> c) {
+ Class<?> pkgmem = c;
+ for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; )
+ pkgmem = enc;
+ return pkgmem;
+ }
+
+ private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2,
+ boolean loader1MustBeParent) {
+ if (loader1 == loader2 || loader1 == null
+ || (loader2 == null && !loader1MustBeParent)) {
+ return true;
+ }
+ for (ClassLoader scan2 = loader2;
+ scan2 != null; scan2 = scan2.getParent()) {
+ if (scan2 == loader1) return true;
+ }
+ if (loader1MustBeParent) return false;
+ // see if loader2 is a parent of loader1:
+ for (ClassLoader scan1 = loader1;
+ scan1 != null; scan1 = scan1.getParent()) {
+ if (scan1 == loader2) return true;
+ }
+ return false;
+ }
+
+ /**
+ * Is the class loader of parentClass identical to, or an ancestor of,
+ * the class loader of childClass?
+ * @param parentClass a class
+ * @param childClass another class, which may be a descendent of the first class
+ * @return whether parentClass precedes or equals childClass in class loader order
+ */
+ public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) {
+ return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true);
+ }
+}
diff --git a/openjdk_java_files.mk b/openjdk_java_files.mk
index bf4126a..9c10a2e 100644
--- a/openjdk_java_files.mk
+++ b/openjdk_java_files.mk
@@ -1163,6 +1163,7 @@
ojluni/src/main/java/sun/misc/FloatingDecimal.java \
ojluni/src/main/java/java/lang/invoke/LambdaConversionException.java \
ojluni/src/main/java/java/lang/invoke/MethodHandle.java \
+ ojluni/src/main/java/java/lang/invoke/MethodHandles.java \
ojluni/src/main/java/java/lang/invoke/MethodHandleImpl.java \
ojluni/src/main/java/java/lang/invoke/MethodHandleInfo.java \
ojluni/src/main/java/java/lang/invoke/MethodHandleStatics.java \
@@ -1187,6 +1188,7 @@
ojluni/src/main/java/sun/invoke/empty/Empty.java \
ojluni/src/main/java/sun/invoke/util/BytecodeDescriptor.java \
ojluni/src/main/java/sun/invoke/util/Wrapper.java \
+ ojluni/src/main/java/sun/invoke/util/VerifyAccess.java \
ojluni/src/main/java/sun/misc/ASCIICaseInsensitiveComparator.java \
ojluni/src/main/java/sun/misc/BASE64Decoder.java \
ojluni/src/main/java/sun/misc/BASE64Encoder.java \
@@ -1625,9 +1627,9 @@
openjdk_lambda_stub_files := \
ojluni/src/lambda/java/java/lang/invoke/CallSite.java \
ojluni/src/lambda/java/java/lang/invoke/LambdaMetafactory.java \
- ojluni/src/lambda/java/java/lang/invoke/MethodHandles.java \
ojluni/src/lambda/java/java/lang/invoke/SerializedLambda.java
openjdk_lambda_duplicate_stub_files := \
+ ojluni/src/lambda/java/java/lang/invoke/MethodHandles.java \
ojluni/src/lambda/java/java/lang/invoke/LambdaConversionException.java \
ojluni/src/lambda/java/java/lang/invoke/MethodHandle.java \
ojluni/src/lambda/java/java/lang/invoke/MethodType.java \