user/super/com/google/gwt/emul/javaemul/internal/HashCodes.java

/*
 * Copyright 2015 Google Inc.
 *
 * 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 javaemul.internal;

import jsinterop.annotations.JsType;

/** Contains logics for calculating hash codes in JavaScript. */
@JsType
public class HashCodes {

  public static int getIdentityHashCode(Object o) {
    switch (JsUtils.typeOf(o)) {
      case "string":
        return JsUtils.<String>uncheckedCast(o).hashCode();
      case "number":
        return JsUtils.<Double>uncheckedCast(o).hashCode();
      case "boolean":
        return JsUtils.<Boolean>uncheckedCast(o).hashCode();
      default:
        return o == null ? 0 : getObjectIdentityHashCode(o);
    }
  }

  private static int nextHash;

  public static native int getObjectIdentityHashCode(Object o) /*-{
    return o.$H || (o.$H = @HashCodes::getNextHash()());
  }-*/;

  public static int getNextHash() {
    return ++nextHash;
  }
}