com.google.gwt.emul.java.util.InternalJsMapFactory Maven / Gradle / Ivy
/*
* Copyright 2014 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 java.util;
import com.google.gwt.core.client.JavaScriptObject;
/**
* A factory to create JavaScript Map instances.
*/
class InternalJsMapFactory {
private static final JavaScriptObject jsMapCtor = getJsMapConstructor();
private static native JavaScriptObject getJsMapConstructor() /*-{
// Firefox 24 & 25 throws StopIteration to signal the end of iteration.
function isCorrectIterationProtocol() {
try {
return new Map().entries().next().done;
} catch(e) {
return false;
}
}
if (typeof Map === 'function' && Map.prototype.entries && isCorrectIterationProtocol()) {
return Map;
} else {
return @InternalJsMapFactory::getJsMapPolyFill()();
}
}-*/;
public static native InternalJsMap newJsMap() /*-{
return new @InternalJsMapFactory::jsMapCtor;
}-*/;
/**
* Returns a partial polyfill for Map that can handle String keys.
* Implementation notes:
*
String keys are mapped to their values via a JS associative map. String keys could collide
* with intrinsic properties (like watch, constructor). To avoid that; the polyfill uses
* {@code Object.create(null)} so it doesn't inherit any properties.
*
For legacy browsers where {@code Object.create} is not available or handling of
* {@code __proto__} is broken, the polyfill is patched to prepend each key with a ':' while
* storing.
*/
private static native JavaScriptObject getJsMapPolyFill() /*-{
function Stringmap() {
this.obj = this.createObject();
};
Stringmap.prototype.createObject = function(key) {
return Object.create(null);
}
Stringmap.prototype.get = function(key) {
return this.obj[key];
};
Stringmap.prototype.set = function(key, value) {
this.obj[key] = value;
};
Stringmap.prototype['delete'] = function(key) {
delete this.obj[key];
};
Stringmap.prototype.keys = function() {
return Object.getOwnPropertyNames(this.obj);
};
Stringmap.prototype.entries = function() {
var keys = this.keys();
var map = this;
var nextIndex = 0;
return {
next: function() {
if (nextIndex >= keys.length) return {done: true};
var key = keys[nextIndex++];
return {value: [key, map.get(key)], done: false};
}
};
};
if (!@InternalJsMapFactory::canHandleObjectCreateAndProto()()) {
// Patches the polyfill to drop Object.create(null) and prefix each key with ':" so it will
// not interfere with intrinsic fields.
Stringmap.prototype.createObject = function() { return {}; };
Stringmap.prototype.get = function(key) {
return this.obj[':' + key];
};
Stringmap.prototype.set = function(key, value) {
this.obj[':' + key] = value;
};
Stringmap.prototype['delete'] = function(key) {
delete this.obj[':' + key];
};
Stringmap.prototype.keys = function() {
var result = [];
for (var key in this.obj) {
// char code for ':' is 58
if (key.charCodeAt(0) == 58) {
result.push(key.substring(1));
}
}
return result;
};
}
return Stringmap;
}-*/;
/**
* Return {@code true} if the browser is modern enough to handle Object.create and also properly
* handles '__proto__' field with Object.create(null). (Safari 5, Android, old Firefox)
*/
private static native boolean canHandleObjectCreateAndProto() /*-{
if (!Object.create || !Object.getOwnPropertyNames) {
return false;
}
var protoField = "__proto__";
var map = Object.create(null);
if (map[protoField] !== undefined) {
return false;
}
var keys = Object.getOwnPropertyNames(map);
if (keys.length != 0) {
return false;
}
map[protoField] = 42;
if (map[protoField] !== 42) {
return false;
}
// For old Firefox version who doesn't have native Map. See the Firefox bug:
// https://bugzilla.mozilla.org/show_bug.cgi?id=837630
if (Object.getOwnPropertyNames(map).length == 0) {
return false;
}
// Looks like the browser has a workable handling of proto field.
return true;
}-*/;
private InternalJsMapFactory() {
// Hides the constructor.
}
}