/*

 * Copyright (c) 2008, 2015, 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 jdk.internal.vm.annotation.Stable;

import sun.invoke.util.Wrapper;

import java.lang.ref.WeakReference;

import java.lang.ref.Reference;

import java.lang.ref.ReferenceQueue;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

import java.util.Objects;

import java.util.StringJoiner;

import java.util.concurrent.ConcurrentMap;

import java.util.concurrent.ConcurrentHashMap;

import sun.invoke.util.BytecodeDescriptor;

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

import sun.invoke.util.VerifyType;

/**

 * A method type represents the arguments and return type accepted and

 * returned by a method handle, or the arguments and return type passed

 * and expected  by a method handle caller.  Method types must be properly

 * matched between a method handle and all its callers,

 * and the JVM's operations enforce this matching at, specifically

 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}

 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution

 * of {@code invokedynamic} instructions.

 * <p>

 * The structure is a return type accompanied by any number of parameter types.

 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.

 * (For ease of exposition, we treat {@code void} as if it were a type.

 * In fact, it denotes the absence of a return type.)

 * <p>

 * All instances of {@code MethodType} are immutable.

 * Two instances are completely interchangeable if they compare equal.

 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.

 * <p>

 * This type can be created only by factory methods.

 * All factory methods may cache values, though caching is not guaranteed.

 * Some factory methods are static, while others are virtual methods which

 * modify precursor method types, e.g., by changing a selected parameter.

 * <p>

 * Factory methods which operate on groups of parameter types

 * are systematically presented in two versions, so that both Java arrays and

 * Java lists can be used to work with groups of parameter types.

 * The query methods {@code parameterArray} and {@code parameterList}

 * also provide a choice between arrays and lists.

 * <p>

 * {@code MethodType} objects are sometimes derived from bytecode instructions

 * such as {@code invokedynamic}, specifically from the type descriptor strings associated

 * with the instructions in a class file's constant pool.

 * <p>

 * Like classes and strings, method types can also be represented directly

 * in a class file's constant pool as constants.

 * A method type may be loaded by an {@code ldc} instruction which refers

 * to a suitable {@code CONSTANT_MethodType} constant pool entry.

 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.

 * (For full details on method type constants,

 * see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)

 * <p>

 * When the JVM materializes a {@code MethodType} from a descriptor string,

 * all classes named in the descriptor must be accessible, and will be loaded.

 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)

 * This loading may occur at any time before the {@code MethodType} object is first derived.

 * @author John Rose, JSR 292 EG

 */

public final

class MethodType implements java.io.Serializable {

    private static final long serialVersionUID = 292L;  // {rtype, {ptype...}}

    // The rtype and ptypes fields define the structural identity of the method type:

    private final Class<?>   rtype;

    // The remaining fields are caches of various sorts:

    private @Stable MethodTypeForm form; // erased form, plus cached data about primitives

    private @Stable MethodType wrapAlt;  // alternative wrapped/unwrapped version

    private @Stable Invokers invokers;   // cache of handy higher-order adapters

    private @Stable String methodDescriptor;  // cache for toMethodDescriptorString

    /**

     * Check the given parameters for validity and store them into the final fields.

     */

    private MethodType(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {

        checkRtype(rtype);

        checkPtypes(ptypes);

        this.rtype = rtype;

        // defensively copy the array passed in by the user

        this.ptypes = trusted ? ptypes : Arrays.copyOf(ptypes, ptypes.length);

    }

    /**

     * Construct a temporary unchecked instance of MethodType for use only as a key to the intern table.

     * Does not check the given parameters for validity, and must be discarded after it is used as a searching key.

     * The parameters are reversed for this constructor, so that it is not accidentally used.

     */

    private MethodType(Class<?>[] ptypes, Class<?> rtype) {

        this.rtype = rtype;

        this.ptypes = ptypes;

    }

    /*trusted*/ MethodTypeForm form() { return form; }

    /*trusted*/ Class<?> rtype() { return rtype; }

    /*trusted*/ Class<?>[] ptypes() { return ptypes; }

    void setForm(MethodTypeForm f) { form = f; }

    /** This number, mandated by the JVM spec as 255,

     *  is the maximum number of <em>slots</em>

     *  that any Java method can receive in its argument list.

     *  It limits both JVM signatures and method type objects.

     *  The longest possible invocation will look like

     *  {@code staticMethod(arg1, arg2, ..., arg255)} or

     *  {@code x.virtualMethod(arg1, arg2, ..., arg254)}.

     */

    /*non-public*/ static final int MAX_JVM_ARITY = 255;  // this is mandated by the JVM spec.

    /** This number is the maximum arity of a method handle, 254.

     *  It is derived from the absolute JVM-imposed arity by subtracting one,

     *  which is the slot occupied by the method handle itself at the

     *  beginning of the argument list used to invoke the method handle.

     *  The longest possible invocation will look like

     *  {@code mh.invoke(arg1, arg2, ..., arg254)}.

     */

    // Issue:  Should we allow MH.invokeWithArguments to go to the full 255?

    /*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY-1;  // deduct one for mh receiver

    /** This number is the maximum arity of a method handle invoker, 253.

     *  It is derived from the absolute JVM-imposed arity by subtracting two,

     *  which are the slots occupied by invoke method handle, and the

     *  target method handle, which are both at the beginning of the argument

     *  list used to invoke the target method handle.

     *  The longest possible invocation will look like

     *  {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.

     */

    /*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1;  // deduct one more for invoker

    private static void checkRtype(Class<?> rtype) {

        Objects.requireNonNull(rtype);

    }

    private static void checkPtype(Class<?> ptype) {

        Objects.requireNonNull(ptype);

        if (ptype == void.class)

            throw newIllegalArgumentException("parameter type cannot be void");

    }

    /** Return number of extra slots (count of long/double args). */

    private static int checkPtypes(Class<?>[] ptypes) {

        int slots = 0;

        for (Class<?> ptype : ptypes) {

            checkPtype(ptype);

            if (ptype == double.class || ptype == long.class) {

                slots++;

            }

        }

        checkSlotCount(ptypes.length + slots);

        return slots;

    }

    static {

        // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:

        assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);

    }

    static void checkSlotCount(int count) {

        if ((count & MAX_JVM_ARITY) != count)

            throw newIllegalArgumentException("bad parameter count "+count);

    }

    private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {

        if (num instanceof Integer)  num = "bad index: "+num;

        return new IndexOutOfBoundsException(num.toString());

    }

    static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();

    static final Class<?>[] NO_PTYPES = {};

    /**

     * Finds or creates an instance of the given method type.

     * @param rtype  the return type

     * @param ptypes the parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null

     * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {

        return makeImpl(rtype, ptypes, false);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param rtype  the return type

     * @param ptypes the parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null

     * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {

        boolean notrust = false;  // random List impl. could return evil ptypes array

        return makeImpl(rtype, listToArray(ptypes), notrust);

    }

    private static Class<?>[] listToArray(List<Class<?>> ptypes) {

        // sanity check the size before the toArray call, since size might be huge

        checkSlotCount(ptypes.size());

        return ptypes.toArray(NO_PTYPES);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The leading parameter type is prepended to the remaining array.

     * @param rtype  the return type

     * @param ptype0 the first parameter type

     * @param ptypes the remaining parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null

     * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {

        Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];

        ptypes1[0] = ptype0;

        System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);

        return makeImpl(rtype, ptypes1, true);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The resulting method has no parameter types.

     * @param rtype  the return type

     * @return a method type with the given return value

     * @throws NullPointerException if {@code rtype} is null

     */

    public static

    MethodType methodType(Class<?> rtype) {

        return makeImpl(rtype, NO_PTYPES, true);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The resulting method has the single given parameter type.

     * @param rtype  the return type

     * @param ptype0 the parameter type

     * @return a method type with the given return value and parameter type

     * @throws NullPointerException if {@code rtype} or {@code ptype0} is null

     * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}

     */

    public static

    MethodType methodType(Class<?> rtype, Class<?> ptype0) {

        return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);

    }

    /**

     * Finds or creates a method type with the given components.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * The resulting method has the same parameter types as {@code ptypes},

     * and the specified return type.

     * @param rtype  the return type

     * @param ptypes the method type which supplies the parameter types

     * @return a method type with the given components

     * @throws NullPointerException if {@code rtype} or {@code ptypes} is null

     */

    public static

    MethodType methodType(Class<?> rtype, MethodType ptypes) {

        return makeImpl(rtype, ptypes.ptypes, true);

    }

    /**

     * Sole factory method to find or create an interned method type.

     * @param rtype desired return type

     * @param ptypes desired parameter types

     * @param trusted whether the ptypes can be used without cloning

     * @return the unique method type of the desired structure

     */

    /*trusted*/ static

    MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {

        MethodType mt = internTable.get(new MethodType(ptypes, rtype));

        if (mt != null)

            return mt;

        if (ptypes.length == 0) {

            ptypes = NO_PTYPES; trusted = true;

        }

        mt = new MethodType(rtype, ptypes, trusted);

        // promote the object to the Real Thing, and reprobe

        mt.form = MethodTypeForm.findForm(mt);

        return internTable.add(mt);

    }

    private static final MethodType[] objectOnlyTypes = new MethodType[20];

    /**

     * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * All parameters and the return type will be {@code Object},

     * except the final array parameter if any, which will be {@code Object[]}.

     * @param objectArgCount number of parameters (excluding the final array parameter if any)

     * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}

     * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments

     * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)

     * @see #genericMethodType(int)

     */

    public static

    MethodType genericMethodType(int objectArgCount, boolean finalArray) {

        MethodType mt;

        checkSlotCount(objectArgCount);

        int ivarargs = (!finalArray ? 0 : 1);

        int ootIndex = objectArgCount*2 + ivarargs;

        if (ootIndex < objectOnlyTypes.length) {

            mt = objectOnlyTypes[ootIndex];

            if (mt != null)  return mt;

        }

        Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];

        Arrays.fill(ptypes, Object.class);

        if (ivarargs != 0)  ptypes[objectArgCount] = Object[].class;

        mt = makeImpl(Object.class, ptypes, true);

        if (ootIndex < objectOnlyTypes.length) {

            objectOnlyTypes[ootIndex] = mt;     // cache it here also!

        }

        return mt;

    }

    /**

     * Finds or creates a method type whose components are all {@code Object}.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * All parameters and the return type will be Object.

     * @param objectArgCount number of parameters

     * @return a generally applicable method type, for all calls of the given argument count

     * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255

     * @see #genericMethodType(int, boolean)

     */

    public static

    MethodType genericMethodType(int objectArgCount) {

        return genericMethodType(objectArgCount, false);

    }

    /**

     * Finds or creates a method type with a single different parameter type.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param num    the index (zero-based) of the parameter type to change

     * @param nptype a new parameter type to replace the old one with

     * @return the same type, except with the selected parameter changed

     * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}

     * @throws IllegalArgumentException if {@code nptype} is {@code void.class}

     * @throws NullPointerException if {@code nptype} is null

     */

    public MethodType changeParameterType(int num, Class<?> nptype) {

        if (parameterType(num) == nptype)  return this;

        checkPtype(nptype);

        Class<?>[] nptypes = ptypes.clone();

        nptypes[num] = nptype;

        return makeImpl(rtype, nptypes, true);

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param num    the position (zero-based) of the inserted parameter type(s)

     * @param ptypesToInsert zero or more new parameter types to insert into the parameter list

     * @return the same type, except with the selected parameter(s) inserted

     * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {

        int len = ptypes.length;

        if (num < 0 || num > len)

            throw newIndexOutOfBoundsException(num);

        int ins = checkPtypes(ptypesToInsert);

        checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);

        int ilen = ptypesToInsert.length;

        if (ilen == 0)  return this;

        Class<?>[] nptypes = Arrays.copyOfRange(ptypes, 0, len+ilen);

        System.arraycopy(nptypes, num, nptypes, num+ilen, len-num);

        System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);

        return makeImpl(rtype, nptypes, true);

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list

     * @return the same type, except with the selected parameter(s) appended

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {

        return insertParameterTypes(parameterCount(), ptypesToInsert);

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param num    the position (zero-based) of the inserted parameter type(s)

     * @param ptypesToInsert zero or more new parameter types to insert into the parameter list

     * @return the same type, except with the selected parameter(s) inserted

     * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {

        return insertParameterTypes(num, listToArray(ptypesToInsert));

    }

    /**

     * Finds or creates a method type with additional parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list

     * @return the same type, except with the selected parameter(s) appended

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {

        return insertParameterTypes(parameterCount(), ptypesToInsert);

    }

     /**

     * Finds or creates a method type with modified parameter types.

     * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.

     * @param start  the position (zero-based) of the first replaced parameter type(s)

     * @param end    the position (zero-based) after the last replaced parameter type(s)

     * @param ptypesToInsert zero or more new parameter types to insert into the parameter list

     * @return the same type, except with the selected parameter(s) replaced

     * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}

     *                                  or if {@code end} is negative or greater than {@code parameterCount()}

     *                                  or if {@code start} is greater than {@code end}

     * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}

     *                                  or if the resulting method type would have more than 255 parameter slots

     * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null

     */

    /*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {

        if (start == end)

            return insertParameterTypes(start, ptypesToInsert);

        int len = ptypes.length;

        if (!(0 <= start && start <= end && end <= len))

            throw newIndexOutOfBoundsException("start="+start+" end="+end);

        int ilen = ptypesToInsert.length;

        if (ilen == 0)

            return dropParameterTypes(start, end);

        return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);

    }

    /** Replace the last arrayLength parameter types with the component type of arrayType.

     * @param arrayType any array type

     * @param pos position at which to spread

     * @param arrayLength the number of parameter types to change

     * @return the resulting type

     */

    /*non-public*/ MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {

        assert(parameterCount() >= arrayLength);

        int spreadPos = pos;

        if (arrayLength == 0)  return this;  // nothing to change

        if (arrayType == Object[].class) {

            if (isGeneric())  return this;  // nothing to change

            if (spreadPos == 0) {

                // no leading arguments to preserve; go generic

                MethodType res = genericMethodType(arrayLength);

                if (rtype != Object.class) {

                    res = res.changeReturnType(rtype);

                }

                return res;

            }