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	/*
	* Copyright (c) 2012, 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
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	*/

	package java.lang.invoke;

	import java.lang.reflect.*;
	import java.util.*;
	import java.lang.invoke.MethodHandleNatives.Constants;
	import java.lang.invoke.MethodHandles.Lookup;
	import static java.lang.invoke.MethodHandleStatics.*;

	/**
	* A symbolic reference obtained by cracking a direct method handle
	* into its consitutent symbolic parts.
	* To crack a direct method handle, call {@link Lookup#revealDirect Lookup.revealDirect}.
	* <h1><a name="directmh"></a>Direct Method Handles</h1>
	* A <em>direct method handle</em> represents a method, constructor, or field without
	* any intervening argument bindings or other transformations.
	* The method, constructor, or field referred to by a direct method handle is called
	* its <em>underlying member</em>.
	* Direct method handles may be obtained in any of these ways:
	* <ul>
	* <li>By executing an {@code ldc} instruction on a {@code CONSTANT_MethodHandle} constant.
	* (See the Java Virtual Machine Specification, sections 4.4.8 and 5.4.3.)
	* <li>By calling one of the <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>,
	* such as {@link Lookup#findVirtual Lookup.findVirtual},
	* to resolve a symbolic reference into a method handle.
	* A symbolic reference consists of a class, name string, and type.
	* <li>By calling the factory method {@link Lookup#unreflect Lookup.unreflect}
	* or {@link Lookup#unreflectSpecial Lookup.unreflectSpecial}
	* to convert a {@link Method} into a method handle.
	* <li>By calling the factory method {@link Lookup#unreflectConstructor Lookup.unreflectConstructor}
	* to convert a {@link Constructor} into a method handle.
	* <li>By calling the factory method {@link Lookup#unreflectGetter Lookup.unreflectGetter}
	* or {@link Lookup#unreflectSetter Lookup.unreflectSetter}
	* to convert a {@link Field} into a method handle.
	* </ul>
	*
	* <h1>Restrictions on Cracking</h1>
	* Given a suitable {@code Lookup} object, it is possible to crack any direct method handle
	* to recover a symbolic reference for the underlying method, constructor, or field.
	* Cracking must be done via a {@code Lookup} object equivalent to that which created
	* the target method handle, or which has enough access permissions to recreate
	* an equivalent method handle.
	* <p>
	* If the underlying method is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a>,
	* the direct method handle will have been "bound" to a particular caller class, the
	* {@linkplain java.lang.invoke.MethodHandles.Lookup#lookupClass() lookup class}
	* of the lookup object used to create it.
	* Cracking this method handle with a different lookup class will fail
	* even if the underlying method is public (like {@code Class.forName}).
	* <p>
	* The requirement of lookup object matching provides a "fast fail" behavior
	* for programs which may otherwise trust erroneous revelation of a method
	* handle with symbolic information (or caller binding) from an unexpected scope.
	* Use {@link java.lang.invoke.MethodHandles#reflectAs} to override this limitation.
	*
	* <h1><a name="refkinds"></a>Reference kinds</h1>
	* The <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>
	* correspond to all major use cases for methods, constructors, and fields.
	* These use cases may be distinguished using small integers as follows:
	* <table border=1 cellpadding=5 summary="reference kinds">
	* <tr><th>reference kind</th><th>descriptive name</th><th>scope</th><th>member</th><th>behavior</th></tr>
	* <tr>
	* <td>{@code 1}</td><td>{@code REF_getField}</td><td>{@code class}</td>
	* <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>
	* </tr>
	* <tr>
	* <td>{@code 2}</td><td>{@code REF_getStatic}</td><td>{@code class} or {@code interface}</td>
	* <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>
	* </tr>
	* <tr>
	* <td>{@code 3}</td><td>{@code REF_putField}</td><td>{@code class}</td>
	* <td>{@code FT f;}</td><td>{@code this.f = x;}</td>
	* </tr>
	* <tr>
	* <td>{@code 4}</td><td>{@code REF_putStatic}</td><td>{@code class}</td>
	* <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>
	* </tr>
	* <tr>
	* <td>{@code 5}</td><td>{@code REF_invokeVirtual}</td><td>{@code class}</td>
	* <td>{@code T m(A);}</td><td>{@code (T) this.m(arg);}</td>
	* </tr>
	* <tr>
	* <td>{@code 6}</td><td>{@code REF_invokeStatic}</td><td>{@code class} or {@code interface}</td>
	* <td>{@code static}<br>{@code T m(A);}</td><td>{@code (T) C.m(arg);}</td>
	* </tr>
	* <tr>
	* <td>{@code 7}</td><td>{@code REF_invokeSpecial}</td><td>{@code class} or {@code interface}</td>
	* <td>{@code T m(A);}</td><td>{@code (T) super.m(arg);}</td>
	* </tr>
	* <tr>
	* <td>{@code 8}</td><td>{@code REF_newInvokeSpecial}</td><td>{@code class}</td>
	* <td>{@code C(A);}</td><td>{@code new C(arg);}</td>
	* </tr>
	* <tr>
	* <td>{@code 9}</td><td>{@code REF_invokeInterface}</td><td>{@code interface}</td>
	* <td>{@code T m(A);}</td><td>{@code (T) this.m(arg);}</td>
	* </tr>
	* </table>
	* @since 1.8
	*/
	public
	interface MethodHandleInfo {
	/**
	* A direct method handle reference kind,
	* as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
	*/
	public static final int
	REF_getField = Constants.REF_getField,
	REF_getStatic = Constants.REF_getStatic,
	REF_putField = Constants.REF_putField,
	REF_putStatic = Constants.REF_putStatic,
	REF_invokeVirtual = Constants.REF_invokeVirtual,
	REF_invokeStatic = Constants.REF_invokeStatic,
	REF_invokeSpecial = Constants.REF_invokeSpecial,
	REF_newInvokeSpecial = Constants.REF_newInvokeSpecial,
	REF_invokeInterface = Constants.REF_invokeInterface;

	/**
	* Returns the reference kind of the cracked method handle, which in turn
	* determines whether the method handle's underlying member was a constructor, method, or field.
	* See the <a href="MethodHandleInfo.html#refkinds">table above</a> for definitions.
	* @return the integer code for the kind of reference used to access the underlying member
	*/
	public int getReferenceKind();

	/**
	* Returns the class in which the cracked method handle's underlying member was defined.
	* @return the declaring class of the underlying member
	*/
	public Class<?> getDeclaringClass();

	/**
	* Returns the name of the cracked method handle's underlying member.
	* This is {@code "<init>"} if the underlying member was a constructor,
	* else it is a simple method name or field name.
	* @return the simple name of the underlying member
	*/
	public String getName();

	/**
	* Returns the nominal type of the cracked symbolic reference, expressed as a method type.
	* If the reference is to a constructor, the return type will be {@code void}.
	* If it is to a non-static method, the method type will not mention the {@code this} parameter.
	* If it is to a field and the requested access is to read the field,
	* the method type will have no parameters and return the field type.
	* If it is to a field and the requested access is to write the field,
	* the method type will have one parameter of the field type and return {@code void}.
	* <p>
	* Note that original direct method handle may include a leading {@code this} parameter,
	* or (in the case of a constructor) will replace the {@code void} return type
	* with the constructed class.
	* The nominal type does not include any {@code this} parameter,
	* and (in the case of a constructor) will return {@code void}.
	* @return the type of the underlying member, expressed as a method type
	*/
	public MethodType getMethodType();

	// Utility methods.
	// NOTE: class/name/type and reference kind constitute a symbolic reference
	// member and modifiers are an add-on, derived from Core Reflection (or the equivalent)

	/**
	* Reflects the underlying member as a method, constructor, or field object.
	* If the underlying member is public, it is reflected as if by
	* {@code getMethod}, {@code getConstructor}, or {@code getField}.
	* Otherwise, it is reflected as if by
	* {@code getDeclaredMethod}, {@code getDeclaredConstructor}, or {@code getDeclaredField}.
	* The underlying member must be accessible to the given lookup object.
	* @param <T> the desired type of the result, either {@link Member} or a subtype
	* @param expected a class object representing the desired result type {@code T}
	* @param lookup the lookup object that created this MethodHandleInfo, or one with equivalent access privileges
	* @return a reference to the method, constructor, or field object
	* @exception ClassCastException if the member is not of the expected type
	* @exception NullPointerException if either argument is {@code null}
	* @exception IllegalArgumentException if the underlying member is not accessible to the given lookup object
	*/
	public <T extends Member> T reflectAs(Class<T> expected, Lookup lookup);

	/**
	* Returns the access modifiers of the underlying member.
	* @return the Java language modifiers for underlying member,
	* or -1 if the member cannot be accessed
	* @see Modifier
	* @see #reflectAs
	*/
	public int getModifiers();

	/**
	* Determines if the underlying member was a variable arity method or constructor.
	* Such members are represented by method handles that are varargs collectors.
	* @implSpec
	* This produces a result equivalent to:
	* <pre>{@code
	* getReferenceKind() >= REF_invokeVirtual && Modifier.isTransient(getModifiers())
	* }</pre>
	*
	*
	* @return {@code true} if and only if the underlying member was declared with variable arity.
	*/
	// spelling derived from java.lang.reflect.Executable, not MethodHandle.isVarargsCollector
	public default boolean isVarArgs() {
	// fields are never varargs:
	if (MethodHandleNatives.refKindIsField((byte) getReferenceKind()))
	return false;
	// not in the public API: Modifier.VARARGS
	final int ACC_VARARGS = 0x00000080; // from JVMS 4.6 (Table 4.20)
	assert(ACC_VARARGS == Modifier.TRANSIENT);
	return Modifier.isTransient(getModifiers());
	}

	/**
	* Returns the descriptive name of the given reference kind,
	* as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
	* The conventional prefix "REF_" is omitted.
	* @param referenceKind an integer code for a kind of reference used to access a class member
	* @return a mixed-case string such as {@code "getField"}
	* @exception IllegalArgumentException if the argument is not a valid
	* <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
	*/
	public static String referenceKindToString(int referenceKind) {
	if (!MethodHandleNatives.refKindIsValid(referenceKind))
	throw newIllegalArgumentException("invalid reference kind", referenceKind);
	return MethodHandleNatives.refKindName((byte)referenceKind);
	}

	/**
	* Returns a string representation for a {@code MethodHandleInfo},
	* given the four parts of its symbolic reference.
	* This is defined to be of the form {@code "RK C.N:MT"}, where {@code RK} is the
	* {@linkplain #referenceKindToString reference kind string} for {@code kind},
	* {@code C} is the {@linkplain java.lang.Class#getName name} of {@code defc}
	* {@code N} is the {@code name}, and
	* {@code MT} is the {@code type}.
	* These four values may be obtained from the
	* {@linkplain #getReferenceKind reference kind},
	* {@linkplain #getDeclaringClass declaring class},
	* {@linkplain #getName member name},
	* and {@linkplain #getMethodType method type}
	* of a {@code MethodHandleInfo} object.
	*
	* @implSpec
	* This produces a result equivalent to:
	* <pre>{@code
	* String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type)
	* }</pre>
	*
	* @param kind the {@linkplain #getReferenceKind reference kind} part of the symbolic reference
	* @param defc the {@linkplain #getDeclaringClass declaring class} part of the symbolic reference
	* @param name the {@linkplain #getName member name} part of the symbolic reference
	* @param type the {@linkplain #getMethodType method type} part of the symbolic reference
	* @return a string of the form {@code "RK C.N:MT"}
	* @exception IllegalArgumentException if the first argument is not a valid
	* <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
	* @exception NullPointerException if any reference argument is {@code null}
	*/
	public static String toString(int kind, Class<?> defc, String name, MethodType type) {
	Objects.requireNonNull(name); Objects.requireNonNull(type);
	return String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type);
	}
	}

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