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Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically embedded into Java applications to provide scripting to end users.
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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.javascript;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.WeakHashMap;

/**
 * This is an implementation of the ES6 WeakSet class. It is very similar to
 * NativeWeakMap, with the exception being that it doesn't store any values.
 * Java will GC the key only when there is no longer any reference to it other
 * than the weak reference. That means that it is important that the "value"
 * that we put in the WeakHashMap here is not one that contains the key.
 */
public class NativeWeakSet extends IdScriptableObject {
    private static final long serialVersionUID = 2065753364224029534L;
    
    private static final Object MAP_TAG = "WeakSet";
    
    private boolean instanceOfWeakSet = false;
    
    private transient WeakHashMap map = new WeakHashMap<>();
    
    static void init(Scriptable scope, boolean sealed) {
        NativeWeakSet m = new NativeWeakSet();
        m.exportAsJSClass(MAX_PROTOTYPE_ID, scope, sealed);
    }

    @Override
    public String getClassName() {
        return "WeakSet";
    }

    @Override
    public Object execIdCall(IdFunctionObject f, Context cx, Scriptable scope,
        Scriptable thisObj, Object[] args) {

        if (!f.hasTag(MAP_TAG)) {
            return super.execIdCall(f, cx, scope, thisObj, args);
        }
        int id = f.methodId();
        switch (id) {
            case Id_constructor:
                if (thisObj == null) {
                    NativeWeakSet ns = new NativeWeakSet();
                    ns.instanceOfWeakSet = true;
                    if (args.length > 0) {
                        NativeSet.loadFromIterable(cx, scope, ns, args[0]);
                    }
                    return ns;
                }
                throw ScriptRuntime.typeError1("msg.no.new", "WeakSet");
            case Id_add:
                return realThis(thisObj, f).js_add(args.length > 0 ? args[0] : Undefined.instance);
            case Id_delete:
                return realThis(thisObj, f).js_delete(args.length > 0 ? args[0] : Undefined.instance);
            case Id_has:
                return realThis(thisObj, f).js_has(args.length > 0 ? args[0] : Undefined.instance);
        }
        throw new IllegalArgumentException("WeakMap.prototype has no method: " + f.getFunctionName());
    }

    private Object js_add(Object key) {
        // As the spec says, only a true "Object" can be the key to a WeakSet.
        // Use the default object equality here. ScriptableObject does not override
        // equals or hashCode, which means that in effect we are only keying on object identity.
        // This is all correct according to the ECMAscript spec.
        if (!ScriptRuntime.isObject(key)) {
            throw ScriptRuntime.typeError1("msg.arg.not.object", ScriptRuntime.typeof(key));
        }
        // Add a value to the map, but don't make it the key -- otherwise the WeakHashMap
        // will never GC anything.
        map.put((Scriptable)key, Boolean.TRUE);
        return this;
    }

    private Object js_delete(Object key) {
        if (!ScriptRuntime.isObject(key)) {
            return false;
        }
        final Object oldVal = map.remove(key);
        return (oldVal != null);
    }

    private Object js_has(Object key) {
        if (!ScriptRuntime.isObject(key)) {
            return false;
        }
        return map.containsKey(key);
    }

    private NativeWeakSet realThis(Scriptable thisObj, IdFunctionObject f) {
        if (thisObj == null) {
            throw incompatibleCallError(f);
        }
        try {
            final NativeWeakSet ns = (NativeWeakSet)thisObj;
            if (!ns.instanceOfWeakSet) {
                // Check for "Set internal data tag"
                throw incompatibleCallError(f);
            }
            return ns;
        } catch (ClassCastException cce) {
            throw incompatibleCallError(f);
        }
    }

    @Override
    protected void initPrototypeId(int id) {
        if (id == SymbolId_toStringTag) {
            initPrototypeValue(SymbolId_toStringTag, SymbolKey.TO_STRING_TAG,
                getClassName(), DONTENUM | READONLY);
            return;
        }

        String s, fnName = null;
        int arity;
        switch (id) {
            case Id_constructor:  arity = 0; s = "constructor"; break;
            case Id_add:          arity = 1; s = "add"; break;
            case Id_delete:       arity = 1; s = "delete"; break;
            case Id_has:          arity = 1; s = "has"; break;
            default: throw new IllegalArgumentException(String.valueOf(id));
        }
        initPrototypeMethod(MAP_TAG, id, s, fnName, arity);
    }

    @Override
    protected int findPrototypeId(Symbol k)
    {
        if (SymbolKey.TO_STRING_TAG.equals(k)) {
            return SymbolId_toStringTag;
        }
        return 0;
    }

// #string_id_map#

    @Override
    protected int findPrototypeId(String s) {
        int id;
// #generated# Last update: 2018-08-27 10:45:54 PDT
        L0: { id = 0; String X = null; int c;
            int s_length = s.length();
            if (s_length==3) {
                c=s.charAt(0);
                if (c=='a') { if (s.charAt(2)=='d' && s.charAt(1)=='d') {id=Id_add; break L0;} }
                else if (c=='h') { if (s.charAt(2)=='s' && s.charAt(1)=='a') {id=Id_has; break L0;} }
            }
            else if (s_length==6) { X="delete";id=Id_delete; }
            else if (s_length==11) { X="constructor";id=Id_constructor; }
            if (X!=null && X!=s && !X.equals(s)) id = 0;
            break L0;
        }
// #/generated#
        return id;
    }

    private static final int
        Id_constructor = 1,
        Id_add = 2,
        Id_delete = 3,
        Id_has = 4,
        SymbolId_toStringTag = 5,
        MAX_PROTOTYPE_ID = SymbolId_toStringTag;

// #/string_id_map#

    private void readObject(ObjectInputStream stream)
        throws IOException, ClassNotFoundException
    {
        stream.defaultReadObject();
        map = new WeakHashMap<>();
    }
}