lib/goog/structs/map.js

1// Copyright 2006 The Closure Library Authors. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS-IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15/**
16 * @fileoverview Datastructure: Hash Map.
17 *
18 * @author arv@google.com (Erik Arvidsson)
19 *
20 * This file contains an implementation of a Map structure. It implements a lot
21 * of the methods used in goog.structs so those functions work on hashes. This
22 * is best suited for complex key types. For simple keys such as numbers and
23 * strings consider using the lighter-weight utilities in goog.object.
24 */
25
26
27goog.provide('goog.structs.Map');
28
29goog.require('goog.iter.Iterator');
30goog.require('goog.iter.StopIteration');
31goog.require('goog.object');
32
33
34
35/**
36 * Class for Hash Map datastructure.
37 * @param {*=} opt_map Map or Object to initialize the map with.
38 * @param {...*} var_args If 2 or more arguments are present then they
39 * will be used as key-value pairs.
40 * @constructor
41 * @template K, V
42 */
43goog.structs.Map = function(opt_map, var_args) {
44
45 /**
46 * Underlying JS object used to implement the map.
47 * @private {!Object}
48 */
49 this.map_ = {};
50
51 /**
52 * An array of keys. This is necessary for two reasons:
53 * 1. Iterating the keys using for (var key in this.map_) allocates an
54 * object for every key in IE which is really bad for IE6 GC perf.
55 * 2. Without a side data structure, we would need to escape all the keys
56 * as that would be the only way we could tell during iteration if the
57 * key was an internal key or a property of the object.
58 *
59 * This array can contain deleted keys so it's necessary to check the map
60 * as well to see if the key is still in the map (this doesn't require a
61 * memory allocation in IE).
62 * @private {!Array<string>}
63 */
64 this.keys_ = [];
65
66 /**
67 * The number of key value pairs in the map.
68 * @private {number}
69 */
70 this.count_ = 0;
71
72 /**
73 * Version used to detect changes while iterating.
74 * @private {number}
75 */
76 this.version_ = 0;
77
78 var argLength = arguments.length;
79
80 if (argLength > 1) {
81 if (argLength % 2) {
82 throw Error('Uneven number of arguments');
83 }
84 for (var i = 0; i < argLength; i += 2) {
85 this.set(arguments[i], arguments[i + 1]);
86 }
87 } else if (opt_map) {
88 this.addAll(/** @type {Object} */ (opt_map));
89 }
90};
91
92
93/**
94 * @return {number} The number of key-value pairs in the map.
95 */
96goog.structs.Map.prototype.getCount = function() {
97 return this.count_;
98};
99
100
101/**
102 * Returns the values of the map.
103 * @return {!Array<V>} The values in the map.
104 */
105goog.structs.Map.prototype.getValues = function() {
106 this.cleanupKeysArray_();
107
108 var rv = [];
109 for (var i = 0; i < this.keys_.length; i++) {
110 var key = this.keys_[i];
111 rv.push(this.map_[key]);
112 }
113 return rv;
114};
115
116
117/**
118 * Returns the keys of the map.
119 * @return {!Array<string>} Array of string values.
120 */
121goog.structs.Map.prototype.getKeys = function() {
122 this.cleanupKeysArray_();
123 return /** @type {!Array<string>} */ (this.keys_.concat());
124};
125
126
127/**
128 * Whether the map contains the given key.
129 * @param {*} key The key to check for.
130 * @return {boolean} Whether the map contains the key.
131 */
132goog.structs.Map.prototype.containsKey = function(key) {
133 return goog.structs.Map.hasKey_(this.map_, key);
134};
135
136
137/**
138 * Whether the map contains the given value. This is O(n).
139 * @param {V} val The value to check for.
140 * @return {boolean} Whether the map contains the value.
141 */
142goog.structs.Map.prototype.containsValue = function(val) {
143 for (var i = 0; i < this.keys_.length; i++) {
144 var key = this.keys_[i];
145 if (goog.structs.Map.hasKey_(this.map_, key) && this.map_[key] == val) {
146 return true;
147 }
148 }
149 return false;
150};
151
152
153/**
154 * Whether this map is equal to the argument map.
155 * @param {goog.structs.Map} otherMap The map against which to test equality.
156 * @param {function(V, V): boolean=} opt_equalityFn Optional equality function
157 * to test equality of values. If not specified, this will test whether
158 * the values contained in each map are identical objects.
159 * @return {boolean} Whether the maps are equal.
160 */
161goog.structs.Map.prototype.equals = function(otherMap, opt_equalityFn) {
162 if (this === otherMap) {
163 return true;
164 }
165
166 if (this.count_ != otherMap.getCount()) {
167 return false;
168 }
169
170 var equalityFn = opt_equalityFn || goog.structs.Map.defaultEquals;
171
172 this.cleanupKeysArray_();
173 for (var key, i = 0; key = this.keys_[i]; i++) {
174 if (!equalityFn(this.get(key), otherMap.get(key))) {
175 return false;
176 }
177 }
178
179 return true;
180};
181
182
183/**
184 * Default equality test for values.
185 * @param {*} a The first value.
186 * @param {*} b The second value.
187 * @return {boolean} Whether a and b reference the same object.
188 */
189goog.structs.Map.defaultEquals = function(a, b) {
190 return a === b;
191};
192
193
194/**
195 * @return {boolean} Whether the map is empty.
196 */
197goog.structs.Map.prototype.isEmpty = function() {
198 return this.count_ == 0;
199};
200
201
202/**
203 * Removes all key-value pairs from the map.
204 */
205goog.structs.Map.prototype.clear = function() {
206 this.map_ = {};
207 this.keys_.length = 0;
208 this.count_ = 0;
209 this.version_ = 0;
210};
211
212
213/**
214 * Removes a key-value pair based on the key. This is O(logN) amortized due to
215 * updating the keys array whenever the count becomes half the size of the keys
216 * in the keys array.
217 * @param {*} key The key to remove.
218 * @return {boolean} Whether object was removed.
219 */
220goog.structs.Map.prototype.remove = function(key) {
221 if (goog.structs.Map.hasKey_(this.map_, key)) {
222 delete this.map_[key];
223 this.count_--;
224 this.version_++;
225
226 // clean up the keys array if the threshhold is hit
227 if (this.keys_.length > 2 * this.count_) {
228 this.cleanupKeysArray_();
229 }
230
231 return true;
232 }
233 return false;
234};
235
236
237/**
238 * Cleans up the temp keys array by removing entries that are no longer in the
239 * map.
240 * @private
241 */
242goog.structs.Map.prototype.cleanupKeysArray_ = function() {
243 if (this.count_ != this.keys_.length) {
244 // First remove keys that are no longer in the map.
245 var srcIndex = 0;
246 var destIndex = 0;
247 while (srcIndex < this.keys_.length) {
248 var key = this.keys_[srcIndex];
249 if (goog.structs.Map.hasKey_(this.map_, key)) {
250 this.keys_[destIndex++] = key;
251 }
252 srcIndex++;
253 }
254 this.keys_.length = destIndex;
255 }
256
257 if (this.count_ != this.keys_.length) {
258 // If the count still isn't correct, that means we have duplicates. This can
259 // happen when the same key is added and removed multiple times. Now we have
260 // to allocate one extra Object to remove the duplicates. This could have
261 // been done in the first pass, but in the common case, we can avoid
262 // allocating an extra object by only doing this when necessary.
263 var seen = {};
264 var srcIndex = 0;
265 var destIndex = 0;
266 while (srcIndex < this.keys_.length) {
267 var key = this.keys_[srcIndex];
268 if (!(goog.structs.Map.hasKey_(seen, key))) {
269 this.keys_[destIndex++] = key;
270 seen[key] = 1;
271 }
272 srcIndex++;
273 }
274 this.keys_.length = destIndex;
275 }
276};
277
278
279/**
280 * Returns the value for the given key. If the key is not found and the default
281 * value is not given this will return {@code undefined}.
282 * @param {*} key The key to get the value for.
283 * @param {DEFAULT=} opt_val The value to return if no item is found for the
284 * given key, defaults to undefined.
285 * @return {V|DEFAULT} The value for the given key.
286 * @template DEFAULT
287 */
288goog.structs.Map.prototype.get = function(key, opt_val) {
289 if (goog.structs.Map.hasKey_(this.map_, key)) {
290 return this.map_[key];
291 }
292 return opt_val;
293};
294
295
296/**
297 * Adds a key-value pair to the map.
298 * @param {*} key The key.
299 * @param {V} value The value to add.
300 * @return {*} Some subclasses return a value.
301 */
302goog.structs.Map.prototype.set = function(key, value) {
303 if (!(goog.structs.Map.hasKey_(this.map_, key))) {
304 this.count_++;
305 // TODO(johnlenz): This class lies, it claims to return an array of string
306 // keys, but instead returns the original object used.
307 this.keys_.push(/** @type {?} */ (key));
308 // Only change the version if we add a new key.
309 this.version_++;
310 }
311 this.map_[key] = value;
312};
313
314
315/**
316 * Adds multiple key-value pairs from another goog.structs.Map or Object.
317 * @param {Object} map Object containing the data to add.
318 */
319goog.structs.Map.prototype.addAll = function(map) {
320 var keys, values;
321 if (map instanceof goog.structs.Map) {
322 keys = map.getKeys();
323 values = map.getValues();
324 } else {
325 keys = goog.object.getKeys(map);
326 values = goog.object.getValues(map);
327 }
328 // we could use goog.array.forEach here but I don't want to introduce that
329 // dependency just for this.
330 for (var i = 0; i < keys.length; i++) {
331 this.set(keys[i], values[i]);
332 }
333};
334
335
336/**
337 * Calls the given function on each entry in the map.
338 * @param {function(this:T, V, K, goog.structs.Map<K,V>)} f
339 * @param {T=} opt_obj The value of "this" inside f.
340 * @template T
341 */
342goog.structs.Map.prototype.forEach = function(f, opt_obj) {
343 var keys = this.getKeys();
344 for (var i = 0; i < keys.length; i++) {
345 var key = keys[i];
346 var value = this.get(key);
347 f.call(opt_obj, value, key, this);
348 }
349};
350
351
352/**
353 * Clones a map and returns a new map.
354 * @return {!goog.structs.Map} A new map with the same key-value pairs.
355 */
356goog.structs.Map.prototype.clone = function() {
357 return new goog.structs.Map(this);
358};
359
360
361/**
362 * Returns a new map in which all the keys and values are interchanged
363 * (keys become values and values become keys). If multiple keys map to the
364 * same value, the chosen transposed value is implementation-dependent.
365 *
366 * It acts very similarly to {goog.object.transpose(Object)}.
367 *
368 * @return {!goog.structs.Map} The transposed map.
369 */
370goog.structs.Map.prototype.transpose = function() {
371 var transposed = new goog.structs.Map();
372 for (var i = 0; i < this.keys_.length; i++) {
373 var key = this.keys_[i];
374 var value = this.map_[key];
375 transposed.set(value, key);
376 }
377
378 return transposed;
379};
380
381
382/**
383 * @return {!Object} Object representation of the map.
384 */
385goog.structs.Map.prototype.toObject = function() {
386 this.cleanupKeysArray_();
387 var obj = {};
388 for (var i = 0; i < this.keys_.length; i++) {
389 var key = this.keys_[i];
390 obj[key] = this.map_[key];
391 }
392 return obj;
393};
394
395
396/**
397 * Returns an iterator that iterates over the keys in the map. Removal of keys
398 * while iterating might have undesired side effects.
399 * @return {!goog.iter.Iterator} An iterator over the keys in the map.
400 */
401goog.structs.Map.prototype.getKeyIterator = function() {
402 return this.__iterator__(true);
403};
404
405
406/**
407 * Returns an iterator that iterates over the values in the map. Removal of
408 * keys while iterating might have undesired side effects.
409 * @return {!goog.iter.Iterator} An iterator over the values in the map.
410 */
411goog.structs.Map.prototype.getValueIterator = function() {
412 return this.__iterator__(false);
413};
414
415
416/**
417 * Returns an iterator that iterates over the values or the keys in the map.
418 * This throws an exception if the map was mutated since the iterator was
419 * created.
420 * @param {boolean=} opt_keys True to iterate over the keys. False to iterate
421 * over the values. The default value is false.
422 * @return {!goog.iter.Iterator} An iterator over the values or keys in the map.
423 */
424goog.structs.Map.prototype.__iterator__ = function(opt_keys) {
425 // Clean up keys to minimize the risk of iterating over dead keys.
426 this.cleanupKeysArray_();
427
428 var i = 0;
429 var version = this.version_;
430 var selfObj = this;
431
432 var newIter = new goog.iter.Iterator;
433 newIter.next = function() {
434 if (version != selfObj.version_) {
435 throw Error('The map has changed since the iterator was created');
436 }
437 if (i >= selfObj.keys_.length) {
438 throw goog.iter.StopIteration;
439 }
440 var key = selfObj.keys_[i++];
441 return opt_keys ? key : selfObj.map_[key];
442 };
443 return newIter;
444};
445
446
447/**
448 * Safe way to test for hasOwnProperty. It even allows testing for
449 * 'hasOwnProperty'.
450 * @param {Object} obj The object to test for presence of the given key.
451 * @param {*} key The key to check for.
452 * @return {boolean} Whether the object has the key.
453 * @private
454 */
455goog.structs.Map.hasKey_ = function(obj, key) {
456 return Object.prototype.hasOwnProperty.call(obj, key);
457};