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

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 * 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

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

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package java.lang.invoke;

import jdk.internal.misc.SharedSecrets;

import jdk.internal.module.IllegalAccessLogger;

import jdk.internal.org.objectweb.asm.ClassReader;

import jdk.internal.reflect.CallerSensitive;

import jdk.internal.reflect.Reflection;

import jdk.internal.vm.annotation.ForceInline;

import sun.invoke.util.ValueConversions;

import sun.invoke.util.VerifyAccess;

import sun.invoke.util.Wrapper;

import sun.reflect.misc.ReflectUtil;

import sun.security.util.SecurityConstants;

import java.lang.invoke.LambdaForm.BasicType;

import java.lang.reflect.Constructor;

import java.lang.reflect.Field;

import java.lang.reflect.Member;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;

import java.lang.reflect.ReflectPermission;

import java.nio.ByteOrder;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.security.ProtectionDomain;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.BitSet;

import java.util.Iterator;

import java.util.List;

import java.util.Objects;

import java.util.concurrent.ConcurrentHashMap;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import static java.lang.invoke.MethodHandleImpl.Intrinsic;

import static java.lang.invoke.MethodHandleNatives.Constants.*;

import static java.lang.invoke.MethodHandleStatics.newIllegalArgumentException;

import static java.lang.invoke.MethodType.methodType;

/**

 * 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>

 *

 * @author John Rose, JSR 292 EG

 * @since 1.7

 */

public class MethodHandles {

    private MethodHandles() { }  // do not instantiate

    static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();

    // 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

     */

    @CallerSensitive

    @ForceInline // to ensure Reflection.getCallerClass optimization

    public static Lookup lookup() {

        return new Lookup(Reflection.getCallerClass());

    }

    /**

     * This reflected$lookup method is the alternate implementation of

     * the lookup method when being invoked by reflection.

     */

    @CallerSensitive

    private static Lookup reflected$lookup() {

        Class<?> caller = Reflection.getCallerClass();

        if (caller.getClassLoader() == null) {

            throw newIllegalArgumentException("illegal lookupClass: "+caller);

        }

        return new Lookup(caller);

    }

    /**

     * Returns a {@link Lookup lookup object} which is trusted minimally.

     * The lookup has the {@code PUBLIC} and {@code UNCONDITIONAL} modes.

     * It can only be used to create method handles to public members of

     * public classes in packages that are exported unconditionally.

     * <p>

     * As a matter of pure convention, the {@linkplain Lookup#lookupClass lookup class}

     * of this lookup object will be {@link java.lang.Object}.

     *

     * @apiNote The use of Object is conventional, and because the lookup modes are

     * limited, there is no special access provided to the internals of Object, its package

     * or its module. Consequently, the lookup context of this lookup object will be the

     * bootstrap class loader, which means it cannot find user classes.

     *

     * <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)}.

     * but may change the lookup context by virtue of changing the class loader.

     * 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

     *

     * @revised 9

     * @spec JPMS

     */

    public static Lookup publicLookup() {

        return Lookup.PUBLIC_LOOKUP;

    }

    /**

     * Returns a {@link Lookup lookup object} with full capabilities to emulate all

     * supported bytecode behaviors, including <a href="MethodHandles.Lookup.html#privacc">

     * private access</a>, on a target class.

     * This method checks that a caller, specified as a {@code Lookup} object, is allowed to

     * do <em>deep reflection</em> on the target class. If {@code m1} is the module containing

     * the {@link Lookup#lookupClass() lookup class}, and {@code m2} is the module containing

     * the target class, then this check ensures that

     * <ul>

     *     <li>{@code m1} {@link Module#canRead reads} {@code m2}.</li>

     *     <li>{@code m2} {@link Module#isOpen(String,Module) opens} the package containing

     *     the target class to at least {@code m1}.</li>

     *     <li>The lookup has the {@link Lookup#MODULE MODULE} lookup mode.</li>

     * </ul>

     * <p>

     * If there is a security manager, its {@code checkPermission} method is called to

     * check {@code ReflectPermission("suppressAccessChecks")}.

     * @apiNote The {@code MODULE} lookup mode serves to authenticate that the lookup object

     * was created by code in the caller module (or derived from a lookup object originally

     * created by the caller). A lookup object with the {@code MODULE} lookup mode can be

     * shared with trusted parties without giving away {@code PRIVATE} and {@code PACKAGE}

     * access to the caller.

     * @param targetClass the target class

     * @param lookup the caller lookup object

     * @return a lookup object for the target class, with private access

     * @throws IllegalArgumentException if {@code targetClass} is a primitve type or array class

     * @throws NullPointerException if {@code targetClass} or {@code caller} is {@code null}

     * @throws IllegalAccessException if the access check specified above fails

     * @throws SecurityException if denied by the security manager

     * @since 9

     * @spec JPMS

     * @see Lookup#dropLookupMode

     */

    public static Lookup privateLookupIn(Class<?> targetClass, Lookup lookup) throws IllegalAccessException {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) sm.checkPermission(ACCESS_PERMISSION);

        if (targetClass.isPrimitive())

            throw new IllegalArgumentException(targetClass + " is a primitive class");

        if (targetClass.isArray())

            throw new IllegalArgumentException(targetClass + " is an array class");

        Module targetModule = targetClass.getModule();

        Module callerModule = lookup.lookupClass().getModule();

        if (!callerModule.canRead(targetModule))

            throw new IllegalAccessException(callerModule + " does not read " + targetModule);

        if (targetModule.isNamed()) {

            String pn = targetClass.getPackageName();

            assert pn.length() > 0 : "unnamed package cannot be in named module";

            if (!targetModule.isOpen(pn, callerModule))

                throw new IllegalAccessException(targetModule + " does not open " + pn + " to " + callerModule);

        }

        if ((lookup.lookupModes() & Lookup.MODULE) == 0)

            throw new IllegalAccessException("lookup does not have MODULE lookup mode");

        if (!callerModule.isNamed() && targetModule.isNamed()) {

            IllegalAccessLogger logger = IllegalAccessLogger.illegalAccessLogger();

            if (logger != null) {

                logger.logIfOpenedForIllegalAccess(lookup, targetClass);

            }

        }

        return new Lookup(targetClass);

    }

    /**

     * 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.:

    private static final 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 id="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 of the resulting method handles:

     * <table class="striped">

     * <caption style="display:none">lookup method behaviors</caption>

     * <thead>

     * <tr>

     * </tr>

     * </thead>

     * <tbody>

     * <tr>

     *     <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>

     * </tr>

     * <tr>

     *     <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>

     * </tr>

     * <tr>

     *     <td>{@code FT f;}</td><td>{@code this.f = x;}</td>

     * </tr>

     * <tr>

     *     <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>

     * </tr>

     * <tr>

     *     <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>

     * </tr>

     * <tr>

     *     <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>

     * </tr>

     * <tr>

     *     <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>

     * </tr>

     * <tr>

     *     <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>

     * </tr>

     * <tr>

     *     <td>({@code static})?<br>{@code FT f;}</td><td>{@code (FT) aField.get(thisOrNull);}</td>

     * </tr>

     * <tr>

     *     <td>({@code static})?<br>{@code FT f;}</td><td>{@code aField.set(thisOrNull, arg);}</td>

     * </tr>

     * <tr>

     *     <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>

     * </tr>

     * <tr>

     *     <td>{@code C(A*);}</td><td>{@code (C) aConstructor.newInstance(arg*);}</td>

     * </tr>

     * <tr>

     *     <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>

     * </tr>

     * <tr>

     *     <td>{@code class C { ... }}</td><td>{@code C.class;}</td>

     * </tr>

     * </tbody>

     * </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>

     * The bytecode behavior for a {@code findClass} operation is a load of a constant class,

     * as if by {@code ldc CONSTANT_Class}.

     * The behavior is represented, not as a method handle, but directly as a {@code Class} constant.

     * <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 id="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 &mdash; if a method is requested but does not exist

     * <li>NoSuchFieldException &mdash; if a field is requested but does not exist

     * <li>IllegalAccessException &mdash; 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.