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30 :
31 : // from google3/util/gtl/map_util.h
32 : // Author: Anton Carver
33 :
34 : #ifndef GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
35 : #define GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
36 :
37 : #include <stddef.h>
38 : #include <iterator>
39 : #include <string>
40 : #include <utility>
41 : #include <vector>
42 :
43 : #include <google/protobuf/stubs/common.h>
44 :
45 : namespace google {
46 : namespace protobuf {
47 : namespace internal {
48 : // Local implementation of RemoveConst to avoid including base/type_traits.h.
49 : template <class T> struct RemoveConst { typedef T type; };
50 : template <class T> struct RemoveConst<const T> : RemoveConst<T> {};
51 : } // namespace internal
52 :
53 : //
54 : // Find*()
55 : //
56 :
57 : // Returns a const reference to the value associated with the given key if it
58 : // exists. Crashes otherwise.
59 : //
60 : // This is intended as a replacement for operator[] as an rvalue (for reading)
61 : // when the key is guaranteed to exist.
62 : //
63 : // operator[] for lookup is discouraged for several reasons:
64 : // * It has a side-effect of inserting missing keys
65 : // * It is not thread-safe (even when it is not inserting, it can still
66 : // choose to resize the underlying storage)
67 : // * It invalidates iterators (when it chooses to resize)
68 : // * It default constructs a value object even if it doesn't need to
69 : //
70 : // This version assumes the key is printable, and includes it in the fatal log
71 : // message.
72 : template <class Collection>
73 : const typename Collection::value_type::second_type&
74 : FindOrDie(const Collection& collection,
75 : const typename Collection::value_type::first_type& key) {
76 : typename Collection::const_iterator it = collection.find(key);
77 : GOOGLE_CHECK(it != collection.end()) << "Map key not found: " << key;
78 : return it->second;
79 : }
80 :
81 : // Same as above, but returns a non-const reference.
82 : template <class Collection>
83 : typename Collection::value_type::second_type&
84 : FindOrDie(Collection& collection, // NOLINT
85 : const typename Collection::value_type::first_type& key) {
86 : typename Collection::iterator it = collection.find(key);
87 : GOOGLE_CHECK(it != collection.end()) << "Map key not found: " << key;
88 : return it->second;
89 : }
90 :
91 : // Same as FindOrDie above, but doesn't log the key on failure.
92 : template <class Collection>
93 : const typename Collection::value_type::second_type&
94 : FindOrDieNoPrint(const Collection& collection,
95 : const typename Collection::value_type::first_type& key) {
96 : typename Collection::const_iterator it = collection.find(key);
97 : GOOGLE_CHECK(it != collection.end()) << "Map key not found";
98 : return it->second;
99 : }
100 :
101 : // Same as above, but returns a non-const reference.
102 : template <class Collection>
103 : typename Collection::value_type::second_type&
104 : FindOrDieNoPrint(Collection& collection, // NOLINT
105 : const typename Collection::value_type::first_type& key) {
106 : typename Collection::iterator it = collection.find(key);
107 : GOOGLE_CHECK(it != collection.end()) << "Map key not found";
108 : return it->second;
109 : }
110 :
111 : // Returns a const reference to the value associated with the given key if it
112 : // exists, otherwise returns a const reference to the provided default value.
113 : //
114 : // WARNING: If a temporary object is passed as the default "value,"
115 : // this function will return a reference to that temporary object,
116 : // which will be destroyed at the end of the statement. A common
117 : // example: if you have a map with string values, and you pass a char*
118 : // as the default "value," either use the returned value immediately
119 : // or store it in a string (not string&).
120 : // Details: http://go/findwithdefault
121 : template <class Collection>
122 : const typename Collection::value_type::second_type&
123 : FindWithDefault(const Collection& collection,
124 : const typename Collection::value_type::first_type& key,
125 : const typename Collection::value_type::second_type& value) {
126 1025 : typename Collection::const_iterator it = collection.find(key);
127 1025 : if (it == collection.end()) {
128 : return value;
129 : }
130 5 : return it->second;
131 : }
132 :
133 : // Returns a pointer to the const value associated with the given key if it
134 : // exists, or NULL otherwise.
135 : template <class Collection>
136 : const typename Collection::value_type::second_type*
137 8005 : FindOrNull(const Collection& collection,
138 : const typename Collection::value_type::first_type& key) {
139 24015 : typename Collection::const_iterator it = collection.find(key);
140 32020 : if (it == collection.end()) {
141 : return 0;
142 : }
143 10220 : return &it->second;
144 : }
145 :
146 : // Same as above but returns a pointer to the non-const value.
147 : template <class Collection>
148 : typename Collection::value_type::second_type*
149 0 : FindOrNull(Collection& collection, // NOLINT
150 : const typename Collection::value_type::first_type& key) {
151 17 : typename Collection::iterator it = collection.find(key);
152 17 : if (it == collection.end()) {
153 : return 0;
154 : }
155 9 : return &it->second;
156 : }
157 :
158 : // Returns the pointer value associated with the given key. If none is found,
159 : // NULL is returned. The function is designed to be used with a map of keys to
160 : // pointers.
161 : //
162 : // This function does not distinguish between a missing key and a key mapped
163 : // to a NULL value.
164 : template <class Collection>
165 : typename Collection::value_type::second_type
166 5921 : FindPtrOrNull(const Collection& collection,
167 : const typename Collection::value_type::first_type& key) {
168 17763 : typename Collection::const_iterator it = collection.find(key);
169 23684 : if (it == collection.end()) {
170 : return typename Collection::value_type::second_type();
171 : }
172 11484 : return it->second;
173 : }
174 :
175 : // Same as above, except takes non-const reference to collection.
176 : //
177 : // This function is needed for containers that propagate constness to the
178 : // pointee, such as boost::ptr_map.
179 : template <class Collection>
180 : typename Collection::value_type::second_type
181 277 : FindPtrOrNull(Collection& collection, // NOLINT
182 276 : const typename Collection::value_type::first_type& key) {
183 1107 : typename Collection::iterator it = collection.find(key);
184 1108 : if (it == collection.end()) {
185 : return typename Collection::value_type::second_type();
186 : }
187 550 : return it->second;
188 : }
189 :
190 : // Finds the pointer value associated with the given key in a map whose values
191 : // are linked_ptrs. Returns NULL if key is not found.
192 : template <class Collection>
193 : typename Collection::value_type::second_type::element_type*
194 : FindLinkedPtrOrNull(const Collection& collection,
195 : const typename Collection::value_type::first_type& key) {
196 : typename Collection::const_iterator it = collection.find(key);
197 : if (it == collection.end()) {
198 : return 0;
199 : }
200 : // Since linked_ptr::get() is a const member returning a non const,
201 : // we do not need a version of this function taking a non const collection.
202 : return it->second.get();
203 : }
204 :
205 : // Same as above, but dies if the key is not found.
206 : template <class Collection>
207 : typename Collection::value_type::second_type::element_type&
208 : FindLinkedPtrOrDie(const Collection& collection,
209 : const typename Collection::value_type::first_type& key) {
210 : typename Collection::const_iterator it = collection.find(key);
211 : CHECK(it != collection.end()) << "key not found: " << key;
212 : // Since linked_ptr::operator*() is a const member returning a non const,
213 : // we do not need a version of this function taking a non const collection.
214 : return *it->second;
215 : }
216 :
217 : // Finds the value associated with the given key and copies it to *value (if not
218 : // NULL). Returns false if the key was not found, true otherwise.
219 : template <class Collection, class Key, class Value>
220 : bool FindCopy(const Collection& collection,
221 : const Key& key,
222 : Value* const value) {
223 : typename Collection::const_iterator it = collection.find(key);
224 : if (it == collection.end()) {
225 : return false;
226 : }
227 : if (value) {
228 : *value = it->second;
229 : }
230 : return true;
231 : }
232 :
233 : //
234 : // Contains*()
235 : //
236 :
237 : // Returns true if and only if the given collection contains the given key.
238 : template <class Collection, class Key>
239 : bool ContainsKey(const Collection& collection, const Key& key) {
240 : return collection.find(key) != collection.end();
241 : }
242 :
243 : // Returns true if and only if the given collection contains the given key-value
244 : // pair.
245 : template <class Collection, class Key, class Value>
246 : bool ContainsKeyValuePair(const Collection& collection,
247 : const Key& key,
248 : const Value& value) {
249 : typedef typename Collection::const_iterator const_iterator;
250 : std::pair<const_iterator, const_iterator> range = collection.equal_range(key);
251 : for (const_iterator it = range.first; it != range.second; ++it) {
252 : if (it->second == value) {
253 : return true;
254 : }
255 : }
256 : return false;
257 : }
258 :
259 : //
260 : // Insert*()
261 : //
262 :
263 : // Inserts the given key-value pair into the collection. Returns true if and
264 : // only if the key from the given pair didn't previously exist. Otherwise, the
265 : // value in the map is replaced with the value from the given pair.
266 : template <class Collection>
267 : bool InsertOrUpdate(Collection* const collection,
268 : const typename Collection::value_type& vt) {
269 : std::pair<typename Collection::iterator, bool> ret = collection->insert(vt);
270 : if (!ret.second) {
271 : // update
272 : ret.first->second = vt.second;
273 : return false;
274 : }
275 : return true;
276 : }
277 :
278 : // Same as above, except that the key and value are passed separately.
279 : template <class Collection>
280 : bool InsertOrUpdate(Collection* const collection,
281 : const typename Collection::value_type::first_type& key,
282 : const typename Collection::value_type::second_type& value) {
283 : return InsertOrUpdate(
284 : collection, typename Collection::value_type(key, value));
285 : }
286 :
287 : // Inserts/updates all the key-value pairs from the range defined by the
288 : // iterators "first" and "last" into the given collection.
289 : template <class Collection, class InputIterator>
290 : void InsertOrUpdateMany(Collection* const collection,
291 : InputIterator first, InputIterator last) {
292 : for (; first != last; ++first) {
293 : InsertOrUpdate(collection, *first);
294 : }
295 : }
296 :
297 : // Change the value associated with a particular key in a map or hash_map
298 : // of the form map<Key, Value*> which owns the objects pointed to by the
299 : // value pointers. If there was an existing value for the key, it is deleted.
300 : // True indicates an insert took place, false indicates an update + delete.
301 : template <class Collection>
302 : bool InsertAndDeleteExisting(
303 : Collection* const collection,
304 : const typename Collection::value_type::first_type& key,
305 : const typename Collection::value_type::second_type& value) {
306 : std::pair<typename Collection::iterator, bool> ret =
307 : collection->insert(typename Collection::value_type(key, value));
308 : if (!ret.second) {
309 : delete ret.first->second;
310 : ret.first->second = value;
311 : return false;
312 : }
313 : return true;
314 : }
315 :
316 : // Inserts the given key and value into the given collection if and only if the
317 : // given key did NOT already exist in the collection. If the key previously
318 : // existed in the collection, the value is not changed. Returns true if the
319 : // key-value pair was inserted; returns false if the key was already present.
320 : template <class Collection>
321 : bool InsertIfNotPresent(Collection* const collection,
322 : const typename Collection::value_type& vt) {
323 49066 : return collection->insert(vt).second;
324 : }
325 :
326 : // Same as above except the key and value are passed separately.
327 : template <class Collection>
328 24491 : bool InsertIfNotPresent(
329 : Collection* const collection,
330 : const typename Collection::value_type::first_type& key,
331 : const typename Collection::value_type::second_type& value) {
332 : return InsertIfNotPresent(
333 24815 : collection, typename Collection::value_type(key, value));
334 : }
335 :
336 : // Same as above except dies if the key already exists in the collection.
337 : template <class Collection>
338 : void InsertOrDie(Collection* const collection,
339 : const typename Collection::value_type& value) {
340 : CHECK(InsertIfNotPresent(collection, value)) << "duplicate value: " << value;
341 : }
342 :
343 : // Same as above except doesn't log the value on error.
344 : template <class Collection>
345 : void InsertOrDieNoPrint(Collection* const collection,
346 : const typename Collection::value_type& value) {
347 : CHECK(InsertIfNotPresent(collection, value)) << "duplicate value.";
348 : }
349 :
350 : // Inserts the key-value pair into the collection. Dies if key was already
351 : // present.
352 : template <class Collection>
353 : void InsertOrDie(Collection* const collection,
354 : const typename Collection::value_type::first_type& key,
355 : const typename Collection::value_type::second_type& data) {
356 : GOOGLE_CHECK(InsertIfNotPresent(collection, key, data))
357 : << "duplicate key: " << key;
358 : }
359 :
360 : // Same as above except doesn't log the key on error.
361 : template <class Collection>
362 : void InsertOrDieNoPrint(
363 : Collection* const collection,
364 : const typename Collection::value_type::first_type& key,
365 : const typename Collection::value_type::second_type& data) {
366 : GOOGLE_CHECK(InsertIfNotPresent(collection, key, data)) << "duplicate key.";
367 : }
368 :
369 : // Inserts a new key and default-initialized value. Dies if the key was already
370 : // present. Returns a reference to the value. Example usage:
371 : //
372 : // map<int, SomeProto> m;
373 : // SomeProto& proto = InsertKeyOrDie(&m, 3);
374 : // proto.set_field("foo");
375 : template <class Collection>
376 : typename Collection::value_type::second_type& InsertKeyOrDie(
377 : Collection* const collection,
378 : const typename Collection::value_type::first_type& key) {
379 : typedef typename Collection::value_type value_type;
380 : std::pair<typename Collection::iterator, bool> res =
381 : collection->insert(value_type(key, typename value_type::second_type()));
382 : GOOGLE_CHECK(res.second) << "duplicate key: " << key;
383 : return res.first->second;
384 : }
385 :
386 : //
387 : // Lookup*()
388 : //
389 :
390 : // Looks up a given key and value pair in a collection and inserts the key-value
391 : // pair if it's not already present. Returns a reference to the value associated
392 : // with the key.
393 : template <class Collection>
394 : typename Collection::value_type::second_type&
395 : LookupOrInsert(Collection* const collection,
396 : const typename Collection::value_type& vt) {
397 : return collection->insert(vt).first->second;
398 : }
399 :
400 : // Same as above except the key-value are passed separately.
401 : template <class Collection>
402 : typename Collection::value_type::second_type&
403 : LookupOrInsert(Collection* const collection,
404 : const typename Collection::value_type::first_type& key,
405 : const typename Collection::value_type::second_type& value) {
406 : return LookupOrInsert(
407 : collection, typename Collection::value_type(key, value));
408 : }
409 :
410 : // Counts the number of equivalent elements in the given "sequence", and stores
411 : // the results in "count_map" with element as the key and count as the value.
412 : //
413 : // Example:
414 : // vector<string> v = {"a", "b", "c", "a", "b"};
415 : // map<string, int> m;
416 : // AddTokenCounts(v, 1, &m);
417 : // assert(m["a"] == 2);
418 : // assert(m["b"] == 2);
419 : // assert(m["c"] == 1);
420 : template <typename Sequence, typename Collection>
421 : void AddTokenCounts(
422 : const Sequence& sequence,
423 : const typename Collection::value_type::second_type& increment,
424 : Collection* const count_map) {
425 : for (typename Sequence::const_iterator it = sequence.begin();
426 : it != sequence.end(); ++it) {
427 : typename Collection::value_type::second_type& value =
428 : LookupOrInsert(count_map, *it,
429 : typename Collection::value_type::second_type());
430 : value += increment;
431 : }
432 : }
433 :
434 : // Returns a reference to the value associated with key. If not found, a value
435 : // is default constructed on the heap and added to the map.
436 : //
437 : // This function is useful for containers of the form map<Key, Value*>, where
438 : // inserting a new key, value pair involves constructing a new heap-allocated
439 : // Value, and storing a pointer to that in the collection.
440 : template <class Collection>
441 : typename Collection::value_type::second_type&
442 : LookupOrInsertNew(Collection* const collection,
443 : const typename Collection::value_type::first_type& key) {
444 : typedef typename std::iterator_traits<
445 : typename Collection::value_type::second_type>::value_type Element;
446 : std::pair<typename Collection::iterator, bool> ret =
447 : collection->insert(typename Collection::value_type(
448 : key,
449 : static_cast<typename Collection::value_type::second_type>(NULL)));
450 : if (ret.second) {
451 : ret.first->second = new Element();
452 : }
453 : return ret.first->second;
454 : }
455 :
456 : // Same as above but constructs the value using the single-argument constructor
457 : // and the given "arg".
458 : template <class Collection, class Arg>
459 : typename Collection::value_type::second_type&
460 : LookupOrInsertNew(Collection* const collection,
461 : const typename Collection::value_type::first_type& key,
462 : const Arg& arg) {
463 : typedef typename std::iterator_traits<
464 : typename Collection::value_type::second_type>::value_type Element;
465 : std::pair<typename Collection::iterator, bool> ret =
466 : collection->insert(typename Collection::value_type(
467 : key,
468 : static_cast<typename Collection::value_type::second_type>(NULL)));
469 : if (ret.second) {
470 : ret.first->second = new Element(arg);
471 : }
472 : return ret.first->second;
473 : }
474 :
475 : // Lookup of linked/shared pointers is used in two scenarios:
476 : //
477 : // Use LookupOrInsertNewLinkedPtr if the container owns the elements.
478 : // In this case it is fine working with the raw pointer as long as it is
479 : // guaranteed that no other thread can delete/update an accessed element.
480 : // A mutex will need to lock the container operation as well as the use
481 : // of the returned elements. Finding an element may be performed using
482 : // FindLinkedPtr*().
483 : //
484 : // Use LookupOrInsertNewSharedPtr if the container does not own the elements
485 : // for their whole lifetime. This is typically the case when a reader allows
486 : // parallel updates to the container. In this case a Mutex only needs to lock
487 : // container operations, but all element operations must be performed on the
488 : // shared pointer. Finding an element must be performed using FindPtr*() and
489 : // cannot be done with FindLinkedPtr*() even though it compiles.
490 :
491 : // Lookup a key in a map or hash_map whose values are linked_ptrs. If it is
492 : // missing, set collection[key].reset(new Value::element_type) and return that.
493 : // Value::element_type must be default constructable.
494 : template <class Collection>
495 : typename Collection::value_type::second_type::element_type*
496 : LookupOrInsertNewLinkedPtr(
497 : Collection* const collection,
498 : const typename Collection::value_type::first_type& key) {
499 : typedef typename Collection::value_type::second_type Value;
500 : std::pair<typename Collection::iterator, bool> ret =
501 : collection->insert(typename Collection::value_type(key, Value()));
502 : if (ret.second) {
503 : ret.first->second.reset(new typename Value::element_type);
504 : }
505 : return ret.first->second.get();
506 : }
507 :
508 : // A variant of LookupOrInsertNewLinkedPtr where the value is constructed using
509 : // a single-parameter constructor. Note: the constructor argument is computed
510 : // even if it will not be used, so only values cheap to compute should be passed
511 : // here. On the other hand it does not matter how expensive the construction of
512 : // the actual stored value is, as that only occurs if necessary.
513 : template <class Collection, class Arg>
514 : typename Collection::value_type::second_type::element_type*
515 : LookupOrInsertNewLinkedPtr(
516 : Collection* const collection,
517 : const typename Collection::value_type::first_type& key,
518 : const Arg& arg) {
519 : typedef typename Collection::value_type::second_type Value;
520 : std::pair<typename Collection::iterator, bool> ret =
521 : collection->insert(typename Collection::value_type(key, Value()));
522 : if (ret.second) {
523 : ret.first->second.reset(new typename Value::element_type(arg));
524 : }
525 : return ret.first->second.get();
526 : }
527 :
528 : // Lookup a key in a map or hash_map whose values are shared_ptrs. If it is
529 : // missing, set collection[key].reset(new Value::element_type). Unlike
530 : // LookupOrInsertNewLinkedPtr, this function returns the shared_ptr instead of
531 : // the raw pointer. Value::element_type must be default constructable.
532 : template <class Collection>
533 : typename Collection::value_type::second_type&
534 : LookupOrInsertNewSharedPtr(
535 : Collection* const collection,
536 : const typename Collection::value_type::first_type& key) {
537 : typedef typename Collection::value_type::second_type SharedPtr;
538 : typedef typename Collection::value_type::second_type::element_type Element;
539 : std::pair<typename Collection::iterator, bool> ret =
540 : collection->insert(typename Collection::value_type(key, SharedPtr()));
541 : if (ret.second) {
542 : ret.first->second.reset(new Element());
543 : }
544 : return ret.first->second;
545 : }
546 :
547 : // A variant of LookupOrInsertNewSharedPtr where the value is constructed using
548 : // a single-parameter constructor. Note: the constructor argument is computed
549 : // even if it will not be used, so only values cheap to compute should be passed
550 : // here. On the other hand it does not matter how expensive the construction of
551 : // the actual stored value is, as that only occurs if necessary.
552 : template <class Collection, class Arg>
553 : typename Collection::value_type::second_type&
554 : LookupOrInsertNewSharedPtr(
555 : Collection* const collection,
556 : const typename Collection::value_type::first_type& key,
557 : const Arg& arg) {
558 : typedef typename Collection::value_type::second_type SharedPtr;
559 : typedef typename Collection::value_type::second_type::element_type Element;
560 : std::pair<typename Collection::iterator, bool> ret =
561 : collection->insert(typename Collection::value_type(key, SharedPtr()));
562 : if (ret.second) {
563 : ret.first->second.reset(new Element(arg));
564 : }
565 : return ret.first->second;
566 : }
567 :
568 : //
569 : // Misc Utility Functions
570 : //
571 :
572 : // Updates the value associated with the given key. If the key was not already
573 : // present, then the key-value pair are inserted and "previous" is unchanged. If
574 : // the key was already present, the value is updated and "*previous" will
575 : // contain a copy of the old value.
576 : //
577 : // InsertOrReturnExisting has complementary behavior that returns the
578 : // address of an already existing value, rather than updating it.
579 : template <class Collection>
580 : bool UpdateReturnCopy(Collection* const collection,
581 : const typename Collection::value_type::first_type& key,
582 : const typename Collection::value_type::second_type& value,
583 : typename Collection::value_type::second_type* previous) {
584 : std::pair<typename Collection::iterator, bool> ret =
585 : collection->insert(typename Collection::value_type(key, value));
586 : if (!ret.second) {
587 : // update
588 : if (previous) {
589 : *previous = ret.first->second;
590 : }
591 : ret.first->second = value;
592 : return true;
593 : }
594 : return false;
595 : }
596 :
597 : // Same as above except that the key and value are passed as a pair.
598 : template <class Collection>
599 : bool UpdateReturnCopy(Collection* const collection,
600 : const typename Collection::value_type& vt,
601 : typename Collection::value_type::second_type* previous) {
602 : std::pair<typename Collection::iterator, bool> ret = collection->insert(vt);
603 : if (!ret.second) {
604 : // update
605 : if (previous) {
606 : *previous = ret.first->second;
607 : }
608 : ret.first->second = vt.second;
609 : return true;
610 : }
611 : return false;
612 : }
613 :
614 : // Tries to insert the given key-value pair into the collection. Returns NULL if
615 : // the insert succeeds. Otherwise, returns a pointer to the existing value.
616 : //
617 : // This complements UpdateReturnCopy in that it allows to update only after
618 : // verifying the old value and still insert quickly without having to look up
619 : // twice. Unlike UpdateReturnCopy this also does not come with the issue of an
620 : // undefined previous* in case new data was inserted.
621 : template <class Collection>
622 : typename Collection::value_type::second_type* const
623 : InsertOrReturnExisting(Collection* const collection,
624 : const typename Collection::value_type& vt) {
625 : std::pair<typename Collection::iterator, bool> ret = collection->insert(vt);
626 : if (ret.second) {
627 : return NULL; // Inserted, no existing previous value.
628 : } else {
629 : return &ret.first->second; // Return address of already existing value.
630 : }
631 : }
632 :
633 : // Same as above, except for explicit key and data.
634 : template <class Collection>
635 : typename Collection::value_type::second_type* const
636 : InsertOrReturnExisting(
637 : Collection* const collection,
638 : const typename Collection::value_type::first_type& key,
639 : const typename Collection::value_type::second_type& data) {
640 : return InsertOrReturnExisting(collection,
641 : typename Collection::value_type(key, data));
642 : }
643 :
644 : // Erases the collection item identified by the given key, and returns the value
645 : // associated with that key. It is assumed that the value (i.e., the
646 : // mapped_type) is a pointer. Returns NULL if the key was not found in the
647 : // collection.
648 : //
649 : // Examples:
650 : // map<string, MyType*> my_map;
651 : //
652 : // One line cleanup:
653 : // delete EraseKeyReturnValuePtr(&my_map, "abc");
654 : //
655 : // Use returned value:
656 : // scoped_ptr<MyType> value_ptr(EraseKeyReturnValuePtr(&my_map, "abc"));
657 : // if (value_ptr.get())
658 : // value_ptr->DoSomething();
659 : //
660 : template <class Collection>
661 : typename Collection::value_type::second_type EraseKeyReturnValuePtr(
662 : Collection* const collection,
663 : const typename Collection::value_type::first_type& key) {
664 : typename Collection::iterator it = collection->find(key);
665 : if (it == collection->end()) {
666 : return NULL;
667 : }
668 : typename Collection::value_type::second_type v = it->second;
669 : collection->erase(it);
670 : return v;
671 : }
672 :
673 : // Inserts all the keys from map_container into key_container, which must
674 : // support insert(MapContainer::key_type).
675 : //
676 : // Note: any initial contents of the key_container are not cleared.
677 : template <class MapContainer, class KeyContainer>
678 : void InsertKeysFromMap(const MapContainer& map_container,
679 : KeyContainer* key_container) {
680 : GOOGLE_CHECK(key_container != NULL);
681 : for (typename MapContainer::const_iterator it = map_container.begin();
682 : it != map_container.end(); ++it) {
683 : key_container->insert(it->first);
684 : }
685 : }
686 :
687 : // Appends all the keys from map_container into key_container, which must
688 : // support push_back(MapContainer::key_type).
689 : //
690 : // Note: any initial contents of the key_container are not cleared.
691 : template <class MapContainer, class KeyContainer>
692 : void AppendKeysFromMap(const MapContainer& map_container,
693 : KeyContainer* key_container) {
694 : GOOGLE_CHECK(key_container != NULL);
695 : for (typename MapContainer::const_iterator it = map_container.begin();
696 : it != map_container.end(); ++it) {
697 : key_container->push_back(it->first);
698 : }
699 : }
700 :
701 : // A more specialized overload of AppendKeysFromMap to optimize reallocations
702 : // for the common case in which we're appending keys to a vector and hence can
703 : // (and sometimes should) call reserve() first.
704 : //
705 : // (It would be possible to play SFINAE games to call reserve() for any
706 : // container that supports it, but this seems to get us 99% of what we need
707 : // without the complexity of a SFINAE-based solution.)
708 : template <class MapContainer, class KeyType>
709 : void AppendKeysFromMap(const MapContainer& map_container,
710 : vector<KeyType>* key_container) {
711 : GOOGLE_CHECK(key_container != NULL);
712 : // We now have the opportunity to call reserve(). Calling reserve() every
713 : // time is a bad idea for some use cases: libstdc++'s implementation of
714 : // vector<>::reserve() resizes the vector's backing store to exactly the
715 : // given size (unless it's already at least that big). Because of this,
716 : // the use case that involves appending a lot of small maps (total size
717 : // N) one by one to a vector would be O(N^2). But never calling reserve()
718 : // loses the opportunity to improve the use case of adding from a large
719 : // map to an empty vector (this improves performance by up to 33%). A
720 : // number of heuristics are possible; see the discussion in
721 : // cl/34081696. Here we use the simplest one.
722 : if (key_container->empty()) {
723 : key_container->reserve(map_container.size());
724 : }
725 : for (typename MapContainer::const_iterator it = map_container.begin();
726 : it != map_container.end(); ++it) {
727 : key_container->push_back(it->first);
728 : }
729 : }
730 :
731 : // Inserts all the values from map_container into value_container, which must
732 : // support push_back(MapContainer::mapped_type).
733 : //
734 : // Note: any initial contents of the value_container are not cleared.
735 : template <class MapContainer, class ValueContainer>
736 : void AppendValuesFromMap(const MapContainer& map_container,
737 : ValueContainer* value_container) {
738 : GOOGLE_CHECK(value_container != NULL);
739 : for (typename MapContainer::const_iterator it = map_container.begin();
740 : it != map_container.end(); ++it) {
741 : value_container->push_back(it->second);
742 : }
743 : }
744 :
745 : // A more specialized overload of AppendValuesFromMap to optimize reallocations
746 : // for the common case in which we're appending values to a vector and hence
747 : // can (and sometimes should) call reserve() first.
748 : //
749 : // (It would be possible to play SFINAE games to call reserve() for any
750 : // container that supports it, but this seems to get us 99% of what we need
751 : // without the complexity of a SFINAE-based solution.)
752 : template <class MapContainer, class ValueType>
753 : void AppendValuesFromMap(const MapContainer& map_container,
754 : vector<ValueType>* value_container) {
755 : GOOGLE_CHECK(value_container != NULL);
756 : // See AppendKeysFromMap for why this is done.
757 : if (value_container->empty()) {
758 : value_container->reserve(map_container.size());
759 : }
760 : for (typename MapContainer::const_iterator it = map_container.begin();
761 : it != map_container.end(); ++it) {
762 : value_container->push_back(it->second);
763 : }
764 : }
765 :
766 : } // namespace protobuf
767 : } // namespace google
768 :
769 : #endif // GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
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