/src/abseil-cpp/absl/container/flat_hash_map.h
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1  |  | // Copyright 2018 The Abseil Authors.  | 
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  |  | //      https://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  |  | // File: flat_hash_map.h  | 
17  |  | // -----------------------------------------------------------------------------  | 
18  |  | //  | 
19  |  | // An `absl::flat_hash_map<K, V>` is an unordered associative container of  | 
20  |  | // unique keys and associated values designed to be a more efficient replacement  | 
21  |  | // for `std::unordered_map`. Like `unordered_map`, search, insertion, and  | 
22  |  | // deletion of map elements can be done as an `O(1)` operation. However,  | 
23  |  | // `flat_hash_map` (and other unordered associative containers known as the  | 
24  |  | // collection of Abseil "Swiss tables") contain other optimizations that result  | 
25  |  | // in both memory and computation advantages.  | 
26  |  | //  | 
27  |  | // In most cases, your default choice for a hash map should be a map of type  | 
28  |  | // `flat_hash_map`.  | 
29  |  | //  | 
30  |  | // `flat_hash_map` is not exception-safe.  | 
31  |  |  | 
32  |  | #ifndef ABSL_CONTAINER_FLAT_HASH_MAP_H_  | 
33  |  | #define ABSL_CONTAINER_FLAT_HASH_MAP_H_  | 
34  |  |  | 
35  |  | #include <cstddef>  | 
36  |  | #include <memory>  | 
37  |  | #include <type_traits>  | 
38  |  | #include <utility>  | 
39  |  |  | 
40  |  | #include "absl/algorithm/container.h"  | 
41  |  | #include "absl/base/attributes.h"  | 
42  |  | #include "absl/base/macros.h"  | 
43  |  | #include "absl/container/hash_container_defaults.h"  | 
44  |  | #include "absl/container/internal/container_memory.h"  | 
45  |  | #include "absl/container/internal/raw_hash_map.h"  // IWYU pragma: export  | 
46  |  | #include "absl/meta/type_traits.h"  | 
47  |  |  | 
48  |  | namespace absl { | 
49  |  | ABSL_NAMESPACE_BEGIN  | 
50  |  | namespace container_internal { | 
51  |  | template <class K, class V>  | 
52  |  | struct FlatHashMapPolicy;  | 
53  |  | }  // namespace container_internal  | 
54  |  |  | 
55  |  | // -----------------------------------------------------------------------------  | 
56  |  | // absl::flat_hash_map  | 
57  |  | // -----------------------------------------------------------------------------  | 
58  |  | //  | 
59  |  | // An `absl::flat_hash_map<K, V>` is an unordered associative container which  | 
60  |  | // has been optimized for both speed and memory footprint in most common use  | 
61  |  | // cases. Its interface is similar to that of `std::unordered_map<K, V>` with  | 
62  |  | // the following notable differences:  | 
63  |  | //  | 
64  |  | // * Requires keys that are CopyConstructible  | 
65  |  | // * Requires values that are MoveConstructible  | 
66  |  | // * Supports heterogeneous lookup, through `find()`, `operator[]()` and  | 
67  |  | //   `insert()`, provided that the map is provided a compatible heterogeneous  | 
68  |  | //   hashing function and equality operator. See below for details.  | 
69  |  | // * Invalidates any references and pointers to elements within the table after  | 
70  |  | //   `rehash()` and when the table is moved.  | 
71  |  | // * Contains a `capacity()` member function indicating the number of element  | 
72  |  | //   slots (open, deleted, and empty) within the hash map.  | 
73  |  | // * Returns `void` from the `erase(iterator)` overload.  | 
74  |  | //  | 
75  |  | // By default, `flat_hash_map` uses the `absl::Hash` hashing framework.  | 
76  |  | // All fundamental and Abseil types that support the `absl::Hash` framework have  | 
77  |  | // a compatible equality operator for comparing insertions into `flat_hash_map`.  | 
78  |  | // If your type is not yet supported by the `absl::Hash` framework, see  | 
79  |  | // absl/hash/hash.h for information on extending Abseil hashing to user-defined  | 
80  |  | // types.  | 
81  |  | //  | 
82  |  | // Using `absl::flat_hash_map` at interface boundaries in dynamically loaded  | 
83  |  | // libraries (e.g. .dll, .so) is unsupported due to way `absl::Hash` values may  | 
84  |  | // be randomized across dynamically loaded libraries.  | 
85  |  | //  | 
86  |  | // To achieve heterogeneous lookup for custom types either `Hash` and `Eq` type  | 
87  |  | // parameters can be used or `T` should have public inner types  | 
88  |  | // `absl_container_hash` and (optionally) `absl_container_eq`. In either case,  | 
89  |  | // `typename Hash::is_transparent` and `typename Eq::is_transparent` should be  | 
90  |  | // well-formed. Both types are basically functors:  | 
91  |  | // * `Hash` should support `size_t operator()(U val) const` that returns a hash  | 
92  |  | // for the given `val`.  | 
93  |  | // * `Eq` should support `bool operator()(U lhs, V rhs) const` that returns true  | 
94  |  | // if `lhs` is equal to `rhs`.  | 
95  |  | //  | 
96  |  | // In most cases `T` needs only to provide the `absl_container_hash`. In this  | 
97  |  | // case `std::equal_to<void>` will be used instead of `eq` part.  | 
98  |  | //  | 
99  |  | // NOTE: A `flat_hash_map` stores its value types directly inside its  | 
100  |  | // implementation array to avoid memory indirection. Because a `flat_hash_map`  | 
101  |  | // is designed to move data when rehashed, map values will not retain pointer  | 
102  |  | // stability. If you require pointer stability, or if your values are large,  | 
103  |  | // consider using `absl::flat_hash_map<Key, std::unique_ptr<Value>>` instead.  | 
104  |  | // If your types are not moveable or you require pointer stability for keys,  | 
105  |  | // consider `absl::node_hash_map`.  | 
106  |  | //  | 
107  |  | // PERFORMANCE WARNING: Erasure & sparsity can negatively affect performance:  | 
108  |  | //  * Iteration takes O(capacity) time, not O(size).  | 
109  |  | //  * erase() slows down begin() and ++iterator.  | 
110  |  | //  * Capacity only shrinks on rehash() or clear() -- not on erase().  | 
111  |  | //  | 
112  |  | // Example:  | 
113  |  | //  | 
114  |  | //   // Create a flat hash map of three strings (that map to strings)  | 
115  |  | //   absl::flat_hash_map<std::string, std::string> ducks =  | 
116  |  | //     {{"a", "huey"}, {"b", "dewey"}, {"c", "louie"}}; | 
117  |  | //  | 
118  |  | //   // Insert a new element into the flat hash map  | 
119  |  | //   ducks.insert({"d", "donald"}); | 
120  |  | //  | 
121  |  | //   // Force a rehash of the flat hash map  | 
122  |  | //   ducks.rehash(0);  | 
123  |  | //  | 
124  |  | //   // Find the element with the key "b"  | 
125  |  | //   std::string search_key = "b";  | 
126  |  | //   auto result = ducks.find(search_key);  | 
127  |  | //   if (result != ducks.end()) { | 
128  |  | //     std::cout << "Result: " << result->second << std::endl;  | 
129  |  | //   }  | 
130  |  | template <class K, class V, class Hash = DefaultHashContainerHash<K>,  | 
131  |  |           class Eq = DefaultHashContainerEq<K>,  | 
132  |  |           class Allocator = std::allocator<std::pair<const K, V>>>  | 
133  |  | class ABSL_ATTRIBUTE_OWNER flat_hash_map  | 
134  |  |     : public absl::container_internal::raw_hash_map<  | 
135  |  |           absl::container_internal::FlatHashMapPolicy<K, V>, Hash, Eq,  | 
136  |  |           Allocator> { | 
137  |  |   using Base = typename flat_hash_map::raw_hash_map;  | 
138  |  |  | 
139  |  |  public:  | 
140  |  |   // Constructors and Assignment Operators  | 
141  |  |   //  | 
142  |  |   // A flat_hash_map supports the same overload set as `std::unordered_map`  | 
143  |  |   // for construction and assignment:  | 
144  |  |   //  | 
145  |  |   // *  Default constructor  | 
146  |  |   //  | 
147  |  |   //    // No allocation for the table's elements is made.  | 
148  |  |   //    absl::flat_hash_map<int, std::string> map1;  | 
149  |  |   //  | 
150  |  |   // * Initializer List constructor  | 
151  |  |   //  | 
152  |  |   //   absl::flat_hash_map<int, std::string> map2 =  | 
153  |  |   //       {{1, "huey"}, {2, "dewey"}, {3, "louie"},}; | 
154  |  |   //  | 
155  |  |   // * Copy constructor  | 
156  |  |   //  | 
157  |  |   //   absl::flat_hash_map<int, std::string> map3(map2);  | 
158  |  |   //  | 
159  |  |   // * Copy assignment operator  | 
160  |  |   //  | 
161  |  |   //   // Hash functor and Comparator are copied as well  | 
162  |  |   //   absl::flat_hash_map<int, std::string> map4;  | 
163  |  |   //   map4 = map3;  | 
164  |  |   //  | 
165  |  |   // * Move constructor  | 
166  |  |   //  | 
167  |  |   //   // Move is guaranteed efficient  | 
168  |  |   //   absl::flat_hash_map<int, std::string> map5(std::move(map4));  | 
169  |  |   //  | 
170  |  |   // * Move assignment operator  | 
171  |  |   //  | 
172  |  |   //   // May be efficient if allocators are compatible  | 
173  |  |   //   absl::flat_hash_map<int, std::string> map6;  | 
174  |  |   //   map6 = std::move(map5);  | 
175  |  |   //  | 
176  |  |   // * Range constructor  | 
177  |  |   //  | 
178  |  |   //   std::vector<std::pair<int, std::string>> v = {{1, "a"}, {2, "b"}}; | 
179  |  |   //   absl::flat_hash_map<int, std::string> map7(v.begin(), v.end());  | 
180  | 2  |   flat_hash_map() {} | 
181  |  |   using Base::Base;  | 
182  |  |  | 
183  |  |   // flat_hash_map::begin()  | 
184  |  |   //  | 
185  |  |   // Returns an iterator to the beginning of the `flat_hash_map`.  | 
186  |  |   using Base::begin;  | 
187  |  |  | 
188  |  |   // flat_hash_map::cbegin()  | 
189  |  |   //  | 
190  |  |   // Returns a const iterator to the beginning of the `flat_hash_map`.  | 
191  |  |   using Base::cbegin;  | 
192  |  |  | 
193  |  |   // flat_hash_map::cend()  | 
194  |  |   //  | 
195  |  |   // Returns a const iterator to the end of the `flat_hash_map`.  | 
196  |  |   using Base::cend;  | 
197  |  |  | 
198  |  |   // flat_hash_map::end()  | 
199  |  |   //  | 
200  |  |   // Returns an iterator to the end of the `flat_hash_map`.  | 
201  |  |   using Base::end;  | 
202  |  |  | 
203  |  |   // flat_hash_map::capacity()  | 
204  |  |   //  | 
205  |  |   // Returns the number of element slots (assigned, deleted, and empty)  | 
206  |  |   // available within the `flat_hash_map`.  | 
207  |  |   //  | 
208  |  |   // NOTE: this member function is particular to `absl::flat_hash_map` and is  | 
209  |  |   // not provided in the `std::unordered_map` API.  | 
210  |  |   using Base::capacity;  | 
211  |  |  | 
212  |  |   // flat_hash_map::empty()  | 
213  |  |   //  | 
214  |  |   // Returns whether or not the `flat_hash_map` is empty.  | 
215  |  |   using Base::empty;  | 
216  |  |  | 
217  |  |   // flat_hash_map::max_size()  | 
218  |  |   //  | 
219  |  |   // Returns the largest theoretical possible number of elements within a  | 
220  |  |   // `flat_hash_map` under current memory constraints. This value can be thought  | 
221  |  |   // of the largest value of `std::distance(begin(), end())` for a  | 
222  |  |   // `flat_hash_map<K, V>`.  | 
223  |  |   using Base::max_size;  | 
224  |  |  | 
225  |  |   // flat_hash_map::size()  | 
226  |  |   //  | 
227  |  |   // Returns the number of elements currently within the `flat_hash_map`.  | 
228  |  |   using Base::size;  | 
229  |  |  | 
230  |  |   // flat_hash_map::clear()  | 
231  |  |   //  | 
232  |  |   // Removes all elements from the `flat_hash_map`. Invalidates any references,  | 
233  |  |   // pointers, or iterators referring to contained elements.  | 
234  |  |   //  | 
235  |  |   // NOTE: this operation may shrink the underlying buffer. To avoid shrinking  | 
236  |  |   // the underlying buffer call `erase(begin(), end())`.  | 
237  |  |   using Base::clear;  | 
238  |  |  | 
239  |  |   // flat_hash_map::erase()  | 
240  |  |   //  | 
241  |  |   // Erases elements within the `flat_hash_map`. Erasing does not trigger a  | 
242  |  |   // rehash. Overloads are listed below.  | 
243  |  |   //  | 
244  |  |   // void erase(const_iterator pos):  | 
245  |  |   //  | 
246  |  |   //   Erases the element at `position` of the `flat_hash_map`, returning  | 
247  |  |   //   `void`.  | 
248  |  |   //  | 
249  |  |   //   NOTE: returning `void` in this case is different than that of STL  | 
250  |  |   //   containers in general and `std::unordered_map` in particular (which  | 
251  |  |   //   return an iterator to the element following the erased element). If that  | 
252  |  |   //   iterator is needed, simply post increment the iterator:  | 
253  |  |   //  | 
254  |  |   //     map.erase(it++);  | 
255  |  |   //  | 
256  |  |   // iterator erase(const_iterator first, const_iterator last):  | 
257  |  |   //  | 
258  |  |   //   Erases the elements in the open interval [`first`, `last`), returning an  | 
259  |  |   //   iterator pointing to `last`. The special case of calling  | 
260  |  |   //   `erase(begin(), end())` resets the reserved growth such that if  | 
261  |  |   //   `reserve(N)` has previously been called and there has been no intervening  | 
262  |  |   //   call to `clear()`, then after calling `erase(begin(), end())`, it is safe  | 
263  |  |   //   to assume that inserting N elements will not cause a rehash.  | 
264  |  |   //  | 
265  |  |   // size_type erase(const key_type& key):  | 
266  |  |   //  | 
267  |  |   //   Erases the element with the matching key, if it exists, returning the  | 
268  |  |   //   number of elements erased (0 or 1).  | 
269  |  |   using Base::erase;  | 
270  |  |  | 
271  |  |   // flat_hash_map::insert()  | 
272  |  |   //  | 
273  |  |   // Inserts an element of the specified value into the `flat_hash_map`,  | 
274  |  |   // returning an iterator pointing to the newly inserted element, provided that  | 
275  |  |   // an element with the given key does not already exist. If rehashing occurs  | 
276  |  |   // due to the insertion, all iterators are invalidated. Overloads are listed  | 
277  |  |   // below.  | 
278  |  |   //  | 
279  |  |   // std::pair<iterator,bool> insert(const init_type& value):  | 
280  |  |   //  | 
281  |  |   //   Inserts a value into the `flat_hash_map`. Returns a pair consisting of an  | 
282  |  |   //   iterator to the inserted element (or to the element that prevented the  | 
283  |  |   //   insertion) and a bool denoting whether the insertion took place.  | 
284  |  |   //  | 
285  |  |   // std::pair<iterator,bool> insert(T&& value):  | 
286  |  |   // std::pair<iterator,bool> insert(init_type&& value):  | 
287  |  |   //  | 
288  |  |   //   Inserts a moveable value into the `flat_hash_map`. Returns a pair  | 
289  |  |   //   consisting of an iterator to the inserted element (or to the element that  | 
290  |  |   //   prevented the insertion) and a bool denoting whether the insertion took  | 
291  |  |   //   place.  | 
292  |  |   //  | 
293  |  |   // iterator insert(const_iterator hint, const init_type& value):  | 
294  |  |   // iterator insert(const_iterator hint, T&& value):  | 
295  |  |   // iterator insert(const_iterator hint, init_type&& value);  | 
296  |  |   //  | 
297  |  |   //   Inserts a value, using the position of `hint` as a non-binding suggestion  | 
298  |  |   //   for where to begin the insertion search. Returns an iterator to the  | 
299  |  |   //   inserted element, or to the existing element that prevented the  | 
300  |  |   //   insertion.  | 
301  |  |   //  | 
302  |  |   // void insert(InputIterator first, InputIterator last):  | 
303  |  |   //  | 
304  |  |   //   Inserts a range of values [`first`, `last`).  | 
305  |  |   //  | 
306  |  |   //   NOTE: Although the STL does not specify which element may be inserted if  | 
307  |  |   //   multiple keys compare equivalently, for `flat_hash_map` we guarantee the  | 
308  |  |   //   first match is inserted.  | 
309  |  |   //  | 
310  |  |   // void insert(std::initializer_list<init_type> ilist):  | 
311  |  |   //  | 
312  |  |   //   Inserts the elements within the initializer list `ilist`.  | 
313  |  |   //  | 
314  |  |   //   NOTE: Although the STL does not specify which element may be inserted if  | 
315  |  |   //   multiple keys compare equivalently within the initializer list, for  | 
316  |  |   //   `flat_hash_map` we guarantee the first match is inserted.  | 
317  |  |   using Base::insert;  | 
318  |  |  | 
319  |  |   // flat_hash_map::insert_or_assign()  | 
320  |  |   //  | 
321  |  |   // Inserts an element of the specified value into the `flat_hash_map` provided  | 
322  |  |   // that a value with the given key does not already exist, or replaces it with  | 
323  |  |   // the element value if a key for that value already exists, returning an  | 
324  |  |   // iterator pointing to the newly inserted element.  If rehashing occurs due  | 
325  |  |   // to the insertion, all existing iterators are invalidated. Overloads are  | 
326  |  |   // listed below.  | 
327  |  |   //  | 
328  |  |   // pair<iterator, bool> insert_or_assign(const init_type& k, T&& obj):  | 
329  |  |   // pair<iterator, bool> insert_or_assign(init_type&& k, T&& obj):  | 
330  |  |   //  | 
331  |  |   //   Inserts/Assigns (or moves) the element of the specified key into the  | 
332  |  |   //   `flat_hash_map`.  | 
333  |  |   //  | 
334  |  |   // iterator insert_or_assign(const_iterator hint,  | 
335  |  |   //                           const init_type& k, T&& obj):  | 
336  |  |   // iterator insert_or_assign(const_iterator hint, init_type&& k, T&& obj):  | 
337  |  |   //  | 
338  |  |   //   Inserts/Assigns (or moves) the element of the specified key into the  | 
339  |  |   //   `flat_hash_map` using the position of `hint` as a non-binding suggestion  | 
340  |  |   //   for where to begin the insertion search.  | 
341  |  |   using Base::insert_or_assign;  | 
342  |  |  | 
343  |  |   // flat_hash_map::emplace()  | 
344  |  |   //  | 
345  |  |   // Inserts an element of the specified value by constructing it in-place  | 
346  |  |   // within the `flat_hash_map`, provided that no element with the given key  | 
347  |  |   // already exists.  | 
348  |  |   //  | 
349  |  |   // The element may be constructed even if there already is an element with the  | 
350  |  |   // key in the container, in which case the newly constructed element will be  | 
351  |  |   // destroyed immediately. Prefer `try_emplace()` unless your key is not  | 
352  |  |   // copyable or moveable.  | 
353  |  |   //  | 
354  |  |   // If rehashing occurs due to the insertion, all iterators are invalidated.  | 
355  |  |   using Base::emplace;  | 
356  |  |  | 
357  |  |   // flat_hash_map::emplace_hint()  | 
358  |  |   //  | 
359  |  |   // Inserts an element of the specified value by constructing it in-place  | 
360  |  |   // within the `flat_hash_map`, using the position of `hint` as a non-binding  | 
361  |  |   // suggestion for where to begin the insertion search, and only inserts  | 
362  |  |   // provided that no element with the given key already exists.  | 
363  |  |   //  | 
364  |  |   // The element may be constructed even if there already is an element with the  | 
365  |  |   // key in the container, in which case the newly constructed element will be  | 
366  |  |   // destroyed immediately. Prefer `try_emplace()` unless your key is not  | 
367  |  |   // copyable or moveable.  | 
368  |  |   //  | 
369  |  |   // If rehashing occurs due to the insertion, all iterators are invalidated.  | 
370  |  |   using Base::emplace_hint;  | 
371  |  |  | 
372  |  |   // flat_hash_map::try_emplace()  | 
373  |  |   //  | 
374  |  |   // Inserts an element of the specified value by constructing it in-place  | 
375  |  |   // within the `flat_hash_map`, provided that no element with the given key  | 
376  |  |   // already exists. Unlike `emplace()`, if an element with the given key  | 
377  |  |   // already exists, we guarantee that no element is constructed.  | 
378  |  |   //  | 
379  |  |   // If rehashing occurs due to the insertion, all iterators are invalidated.  | 
380  |  |   // Overloads are listed below.  | 
381  |  |   //  | 
382  |  |   //   pair<iterator, bool> try_emplace(const key_type& k, Args&&... args):  | 
383  |  |   //   pair<iterator, bool> try_emplace(key_type&& k, Args&&... args):  | 
384  |  |   //  | 
385  |  |   // Inserts (via copy or move) the element of the specified key into the  | 
386  |  |   // `flat_hash_map`.  | 
387  |  |   //  | 
388  |  |   //   iterator try_emplace(const_iterator hint,  | 
389  |  |   //                        const key_type& k, Args&&... args):  | 
390  |  |   //   iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args):  | 
391  |  |   //  | 
392  |  |   // Inserts (via copy or move) the element of the specified key into the  | 
393  |  |   // `flat_hash_map` using the position of `hint` as a non-binding suggestion  | 
394  |  |   // for where to begin the insertion search.  | 
395  |  |   //  | 
396  |  |   // All `try_emplace()` overloads make the same guarantees regarding rvalue  | 
397  |  |   // arguments as `std::unordered_map::try_emplace()`, namely that these  | 
398  |  |   // functions will not move from rvalue arguments if insertions do not happen.  | 
399  |  |   using Base::try_emplace;  | 
400  |  |  | 
401  |  |   // flat_hash_map::extract()  | 
402  |  |   //  | 
403  |  |   // Extracts the indicated element, erasing it in the process, and returns it  | 
404  |  |   // as a C++17-compatible node handle. Overloads are listed below.  | 
405  |  |   //  | 
406  |  |   // node_type extract(const_iterator position):  | 
407  |  |   //  | 
408  |  |   //   Extracts the key,value pair of the element at the indicated position and  | 
409  |  |   //   returns a node handle owning that extracted data.  | 
410  |  |   //  | 
411  |  |   // node_type extract(const key_type& x):  | 
412  |  |   //  | 
413  |  |   //   Extracts the key,value pair of the element with a key matching the passed  | 
414  |  |   //   key value and returns a node handle owning that extracted data. If the  | 
415  |  |   //   `flat_hash_map` does not contain an element with a matching key, this  | 
416  |  |   //   function returns an empty node handle.  | 
417  |  |   //  | 
418  |  |   // NOTE: when compiled in an earlier version of C++ than C++17,  | 
419  |  |   // `node_type::key()` returns a const reference to the key instead of a  | 
420  |  |   // mutable reference. We cannot safely return a mutable reference without  | 
421  |  |   // std::launder (which is not available before C++17).  | 
422  |  |   using Base::extract;  | 
423  |  |  | 
424  |  |   // flat_hash_map::merge()  | 
425  |  |   //  | 
426  |  |   // Extracts elements from a given `source` flat hash map into this  | 
427  |  |   // `flat_hash_map`. If the destination `flat_hash_map` already contains an  | 
428  |  |   // element with an equivalent key, that element is not extracted.  | 
429  |  |   using Base::merge;  | 
430  |  |  | 
431  |  |   // flat_hash_map::swap(flat_hash_map& other)  | 
432  |  |   //  | 
433  |  |   // Exchanges the contents of this `flat_hash_map` with those of the `other`  | 
434  |  |   // flat hash map.  | 
435  |  |   //  | 
436  |  |   // All iterators and references on the `flat_hash_map` remain valid, excepting  | 
437  |  |   // for the past-the-end iterator, which is invalidated.  | 
438  |  |   //  | 
439  |  |   // `swap()` requires that the flat hash map's hashing and key equivalence  | 
440  |  |   // functions be Swappable, and are exchanged using unqualified calls to  | 
441  |  |   // non-member `swap()`. If the map's allocator has  | 
442  |  |   // `std::allocator_traits<allocator_type>::propagate_on_container_swap::value`  | 
443  |  |   // set to `true`, the allocators are also exchanged using an unqualified call  | 
444  |  |   // to non-member `swap()`; otherwise, the allocators are not swapped.  | 
445  |  |   using Base::swap;  | 
446  |  |  | 
447  |  |   // flat_hash_map::rehash(count)  | 
448  |  |   //  | 
449  |  |   // Rehashes the `flat_hash_map`, setting the number of slots to be at least  | 
450  |  |   // the passed value. If the new number of slots increases the load factor more  | 
451  |  |   // than the current maximum load factor  | 
452  |  |   // (`count` < `size()` / `max_load_factor()`), then the new number of slots  | 
453  |  |   // will be at least `size()` / `max_load_factor()`.  | 
454  |  |   //  | 
455  |  |   // To force a rehash, pass rehash(0).  | 
456  |  |   //  | 
457  |  |   // NOTE: unlike behavior in `std::unordered_map`, references are also  | 
458  |  |   // invalidated upon a `rehash()`.  | 
459  |  |   using Base::rehash;  | 
460  |  |  | 
461  |  |   // flat_hash_map::reserve(count)  | 
462  |  |   //  | 
463  |  |   // Sets the number of slots in the `flat_hash_map` to the number needed to  | 
464  |  |   // accommodate at least `count` total elements without exceeding the current  | 
465  |  |   // maximum load factor, and may rehash the container if needed. After this  | 
466  |  |   // returns, it is guaranteed that `count - size()` elements can be inserted  | 
467  |  |   // into the `flat_hash_map` without another rehash.  | 
468  |  |   using Base::reserve;  | 
469  |  |  | 
470  |  |   // flat_hash_map::at()  | 
471  |  |   //  | 
472  |  |   // Returns a reference to the mapped value of the element with key equivalent  | 
473  |  |   // to the passed key.  | 
474  |  |   using Base::at;  | 
475  |  |  | 
476  |  |   // flat_hash_map::contains()  | 
477  |  |   //  | 
478  |  |   // Determines whether an element with a key comparing equal to the given `key`  | 
479  |  |   // exists within the `flat_hash_map`, returning `true` if so or `false`  | 
480  |  |   // otherwise.  | 
481  |  |   using Base::contains;  | 
482  |  |  | 
483  |  |   // flat_hash_map::count(const Key& key) const  | 
484  |  |   //  | 
485  |  |   // Returns the number of elements with a key comparing equal to the given  | 
486  |  |   // `key` within the `flat_hash_map`. note that this function will return  | 
487  |  |   // either `1` or `0` since duplicate keys are not allowed within a  | 
488  |  |   // `flat_hash_map`.  | 
489  |  |   using Base::count;  | 
490  |  |  | 
491  |  |   // flat_hash_map::equal_range()  | 
492  |  |   //  | 
493  |  |   // Returns a closed range [first, last], defined by a `std::pair` of two  | 
494  |  |   // iterators, containing all elements with the passed key in the  | 
495  |  |   // `flat_hash_map`.  | 
496  |  |   using Base::equal_range;  | 
497  |  |  | 
498  |  |   // flat_hash_map::find()  | 
499  |  |   //  | 
500  |  |   // Finds an element with the passed `key` within the `flat_hash_map`.  | 
501  |  |   using Base::find;  | 
502  |  |  | 
503  |  |   // flat_hash_map::operator[]()  | 
504  |  |   //  | 
505  |  |   // Returns a reference to the value mapped to the passed key within the  | 
506  |  |   // `flat_hash_map`, performing an `insert()` if the key does not already  | 
507  |  |   // exist.  | 
508  |  |   //  | 
509  |  |   // If an insertion occurs and results in a rehashing of the container, all  | 
510  |  |   // iterators are invalidated. Otherwise iterators are not affected and  | 
511  |  |   // references are not invalidated. Overloads are listed below.  | 
512  |  |   //  | 
513  |  |   // T& operator[](const Key& key):  | 
514  |  |   //  | 
515  |  |   //   Inserts an init_type object constructed in-place if the element with the  | 
516  |  |   //   given key does not exist.  | 
517  |  |   //  | 
518  |  |   // T& operator[](Key&& key):  | 
519  |  |   //  | 
520  |  |   //   Inserts an init_type object constructed in-place provided that an element  | 
521  |  |   //   with the given key does not exist.  | 
522  |  |   using Base::operator[];  | 
523  |  |  | 
524  |  |   // flat_hash_map::bucket_count()  | 
525  |  |   //  | 
526  |  |   // Returns the number of "buckets" within the `flat_hash_map`. Note that  | 
527  |  |   // because a flat hash map contains all elements within its internal storage,  | 
528  |  |   // this value simply equals the current capacity of the `flat_hash_map`.  | 
529  |  |   using Base::bucket_count;  | 
530  |  |  | 
531  |  |   // flat_hash_map::load_factor()  | 
532  |  |   //  | 
533  |  |   // Returns the current load factor of the `flat_hash_map` (the average number  | 
534  |  |   // of slots occupied with a value within the hash map).  | 
535  |  |   using Base::load_factor;  | 
536  |  |  | 
537  |  |   // flat_hash_map::max_load_factor()  | 
538  |  |   //  | 
539  |  |   // Manages the maximum load factor of the `flat_hash_map`. Overloads are  | 
540  |  |   // listed below.  | 
541  |  |   //  | 
542  |  |   // float flat_hash_map::max_load_factor()  | 
543  |  |   //  | 
544  |  |   //   Returns the current maximum load factor of the `flat_hash_map`.  | 
545  |  |   //  | 
546  |  |   // void flat_hash_map::max_load_factor(float ml)  | 
547  |  |   //  | 
548  |  |   //   Sets the maximum load factor of the `flat_hash_map` to the passed value.  | 
549  |  |   //  | 
550  |  |   //   NOTE: This overload is provided only for API compatibility with the STL;  | 
551  |  |   //   `flat_hash_map` will ignore any set load factor and manage its rehashing  | 
552  |  |   //   internally as an implementation detail.  | 
553  |  |   using Base::max_load_factor;  | 
554  |  |  | 
555  |  |   // flat_hash_map::get_allocator()  | 
556  |  |   //  | 
557  |  |   // Returns the allocator function associated with this `flat_hash_map`.  | 
558  |  |   using Base::get_allocator;  | 
559  |  |  | 
560  |  |   // flat_hash_map::hash_function()  | 
561  |  |   //  | 
562  |  |   // Returns the hashing function used to hash the keys within this  | 
563  |  |   // `flat_hash_map`.  | 
564  |  |   using Base::hash_function;  | 
565  |  |  | 
566  |  |   // flat_hash_map::key_eq()  | 
567  |  |   //  | 
568  |  |   // Returns the function used for comparing keys equality.  | 
569  |  |   using Base::key_eq;  | 
570  |  | };  | 
571  |  |  | 
572  |  | // erase_if(flat_hash_map<>, Pred)  | 
573  |  | //  | 
574  |  | // Erases all elements that satisfy the predicate `pred` from the container `c`.  | 
575  |  | // Returns the number of erased elements.  | 
576  |  | template <typename K, typename V, typename H, typename E, typename A,  | 
577  |  |           typename Predicate>  | 
578  |  | typename flat_hash_map<K, V, H, E, A>::size_type erase_if(  | 
579  |  |     flat_hash_map<K, V, H, E, A>& c, Predicate pred) { | 
580  |  |   return container_internal::EraseIf(pred, &c);  | 
581  |  | }  | 
582  |  |  | 
583  |  | // swap(flat_hash_map<>, flat_hash_map<>)  | 
584  |  | //  | 
585  |  | // Swaps the contents of two `flat_hash_map` containers.  | 
586  |  | //  | 
587  |  | // NOTE: we need to define this function template in order for  | 
588  |  | // `flat_hash_set::swap` to be called instead of `std::swap`. Even though we  | 
589  |  | // have `swap(raw_hash_set&, raw_hash_set&)` defined, that function requires a  | 
590  |  | // derived-to-base conversion, whereas `std::swap` is a function template so  | 
591  |  | // `std::swap` will be preferred by compiler.  | 
592  |  | template <typename K, typename V, typename H, typename E, typename A>  | 
593  |  | void swap(flat_hash_map<K, V, H, E, A>& x,  | 
594  |  |           flat_hash_map<K, V, H, E, A>& y) noexcept(noexcept(x.swap(y))) { | 
595  |  |   x.swap(y);  | 
596  |  | }  | 
597  |  |  | 
598  |  | namespace container_internal { | 
599  |  |  | 
600  |  | // c_for_each_fast(flat_hash_map<>, Function)  | 
601  |  | //  | 
602  |  | // Container-based version of the <algorithm> `std::for_each()` function to  | 
603  |  | // apply a function to a container's elements.  | 
604  |  | // There is no guarantees on the order of the function calls.  | 
605  |  | // Erasure and/or insertion of elements in the function is not allowed.  | 
606  |  | template <typename K, typename V, typename H, typename E, typename A,  | 
607  |  |           typename Function>  | 
608  |  | decay_t<Function> c_for_each_fast(const flat_hash_map<K, V, H, E, A>& c,  | 
609  |  |                                   Function&& f) { | 
610  |  |   container_internal::ForEach(f, &c);  | 
611  |  |   return f;  | 
612  |  | }  | 
613  |  | template <typename K, typename V, typename H, typename E, typename A,  | 
614  |  |           typename Function>  | 
615  |  | decay_t<Function> c_for_each_fast(flat_hash_map<K, V, H, E, A>& c,  | 
616  |  |                                   Function&& f) { | 
617  |  |   container_internal::ForEach(f, &c);  | 
618  |  |   return f;  | 
619  |  | }  | 
620  |  | template <typename K, typename V, typename H, typename E, typename A,  | 
621  |  |           typename Function>  | 
622  |  | decay_t<Function> c_for_each_fast(flat_hash_map<K, V, H, E, A>&& c,  | 
623  |  |                                   Function&& f) { | 
624  |  |   container_internal::ForEach(f, &c);  | 
625  |  |   return f;  | 
626  |  | }  | 
627  |  |  | 
628  |  | }  // namespace container_internal  | 
629  |  |  | 
630  |  | namespace container_internal { | 
631  |  |  | 
632  |  | template <class K, class V>  | 
633  |  | struct FlatHashMapPolicy { | 
634  |  |   using slot_policy = container_internal::map_slot_policy<K, V>;  | 
635  |  |   using slot_type = typename slot_policy::slot_type;  | 
636  |  |   using key_type = K;  | 
637  |  |   using mapped_type = V;  | 
638  |  |   using init_type = std::pair</*non const*/ key_type, mapped_type>;  | 
639  |  |  | 
640  |  |   template <class Allocator, class... Args>  | 
641  | 16  |   static void construct(Allocator* alloc, slot_type* slot, Args&&... args) { | 
642  | 16  |     slot_policy::construct(alloc, slot, std::forward<Args>(args)...);  | 
643  | 16  |   } void absl::container_internal::FlatHashMapPolicy<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>::construct<std::__1::allocator<std::__1::pair<std::__1::basic_string_view<char, std::__1::char_traits<char> > const, absl::CommandLineFlag*> >, std::__1::piecewise_construct_t const&, std::__1::tuple<std::__1::basic_string_view<char, std::__1::char_traits<char> > const&&>, std::__1::tuple<absl::CommandLineFlag*&&> >(std::__1::allocator<std::__1::pair<std::__1::basic_string_view<char, std::__1::char_traits<char> > const, absl::CommandLineFlag*> >*, absl::container_internal::map_slot_type<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>*, std::__1::piecewise_construct_t const&, std::__1::tuple<std::__1::basic_string_view<char, std::__1::char_traits<char> > const&&>&&, std::__1::tuple<absl::CommandLineFlag*&&>&&) Line  | Count  | Source  |  641  | 16  |   static void construct(Allocator* alloc, slot_type* slot, Args&&... args) { |  642  | 16  |     slot_policy::construct(alloc, slot, std::forward<Args>(args)...);  |  643  | 16  |   }  |  
 Unexecuted instantiation: void absl::container_internal::FlatHashMapPolicy<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>::construct<std::__1::allocator<std::__1::pair<std::__1::basic_string_view<char, std::__1::char_traits<char> > const, absl::CommandLineFlag*> >, std::__1::piecewise_construct_t const&, std::__1::tuple<std::__1::basic_string_view<char, std::__1::char_traits<char> >&&>, std::__1::tuple<absl::CommandLineFlag*&&> >(std::__1::allocator<std::__1::pair<std::__1::basic_string_view<char, std::__1::char_traits<char> > const, absl::CommandLineFlag*> >*, absl::container_internal::map_slot_type<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>*, std::__1::piecewise_construct_t const&, std::__1::tuple<std::__1::basic_string_view<char, std::__1::char_traits<char> >&&>&&, std::__1::tuple<absl::CommandLineFlag*&&>&&)  | 
644  |  |  | 
645  |  |   // Returns std::true_type in case destroy is trivial.  | 
646  |  |   template <class Allocator>  | 
647  | 0  |   static auto destroy(Allocator* alloc, slot_type* slot) { | 
648  | 0  |     return slot_policy::destroy(alloc, slot);  | 
649  | 0  |   }  | 
650  |  |  | 
651  |  |   template <class Allocator>  | 
652  |  |   static auto transfer(Allocator* alloc, slot_type* new_slot,  | 
653  | 0  |                        slot_type* old_slot) { | 
654  | 0  |     return slot_policy::transfer(alloc, new_slot, old_slot);  | 
655  | 0  |   } Unexecuted instantiation: auto absl::container_internal::FlatHashMapPolicy<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>::transfer<std::__1::allocator<std::__1::pair<std::__1::basic_string_view<char, std::__1::char_traits<char> > const, absl::CommandLineFlag*> > >(std::__1::allocator<std::__1::pair<std::__1::basic_string_view<char, std::__1::char_traits<char> > const, absl::CommandLineFlag*> >*, absl::container_internal::map_slot_type<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>*, absl::container_internal::map_slot_type<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>*) Unexecuted instantiation: auto absl::container_internal::FlatHashMapPolicy<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>::transfer<std::__1::allocator<char> >(std::__1::allocator<char>*, absl::container_internal::map_slot_type<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>*, absl::container_internal::map_slot_type<std::__1::basic_string_view<char, std::__1::char_traits<char> >, absl::CommandLineFlag*>*)  | 
656  |  |  | 
657  |  |   template <class F, class... Args>  | 
658  |  |   static decltype(absl::container_internal::DecomposePair(  | 
659  |  |       std::declval<F>(), std::declval<Args>()...))  | 
660  | 46  |   apply(F&& f, Args&&... args) { | 
661  | 46  |     return absl::container_internal::DecomposePair(std::forward<F>(f),  | 
662  | 46  |                                                    std::forward<Args>(args)...);  | 
663  | 46  |   } _ZN4absl18container_internal17FlatHashMapPolicyINSt3__117basic_string_viewIcNS2_11char_traitsIcEEEEPNS_15CommandLineFlagEE5applyINS0_12EqualElementIS6_NS0_8StringEqEEEJRNS2_4pairIKS6_S8_EEEEEDTclsr4absl18container_internalE13DecomposePairclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOSI_DpOSJ_ Line  | Count  | Source  |  660  | 16  |   apply(F&& f, Args&&... args) { |  661  | 16  |     return absl::container_internal::DecomposePair(std::forward<F>(f),  |  662  | 16  |                                                    std::forward<Args>(args)...);  |  663  | 16  |   }  |  
 _ZN4absl18container_internal17FlatHashMapPolicyINSt3__117basic_string_viewIcNS2_11char_traitsIcEEEEPNS_15CommandLineFlagEE5applyINS0_12raw_hash_setIS9_NS0_10StringHashENS0_8StringEqENS2_9allocatorINS2_4pairIKS6_S8_EEEEE19EmplaceDecomposableEJSH_EEEDTclsr4absl18container_internalE13DecomposePairclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOSL_DpOSM_ Line  | Count  | Source  |  660  | 16  |   apply(F&& f, Args&&... args) { |  661  | 16  |     return absl::container_internal::DecomposePair(std::forward<F>(f),  |  662  | 16  |                                                    std::forward<Args>(args)...);  |  663  | 16  |   }  |  
 Unexecuted instantiation: _ZN4absl18container_internal17FlatHashMapPolicyINSt3__117basic_string_viewIcNS2_11char_traitsIcEEEEPNS_15CommandLineFlagEE5applyINS0_11HashElementINS0_10StringHashELb1EEEJRNS2_4pairIKS6_S8_EEEEEDTclsr4absl18container_internalE13DecomposePairclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOSI_DpOSJ_ _ZN4absl18container_internal17FlatHashMapPolicyINSt3__117basic_string_viewIcNS2_11char_traitsIcEEEEPNS_15CommandLineFlagEE5applyINS0_12raw_hash_setIS9_NS0_10StringHashENS0_8StringEqENS2_9allocatorINS2_4pairIKS6_S8_EEEEE11FindElementEJRSH_EEEDTclsr4absl18container_internalE13DecomposePairclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOSM_DpOSN_ Line  | Count  | Source  |  660  | 14  |   apply(F&& f, Args&&... args) { |  661  | 14  |     return absl::container_internal::DecomposePair(std::forward<F>(f),  |  662  | 14  |                                                    std::forward<Args>(args)...);  |  663  | 14  |   }  |  
 Unexecuted instantiation: _ZN4absl18container_internal17FlatHashMapPolicyINSt3__117basic_string_viewIcNS2_11char_traitsIcEEEEPNS_15CommandLineFlagEE5applyINS0_12raw_hash_setIS9_NS0_10StringHashENS0_8StringEqENS2_9allocatorINS2_4pairIKS6_S8_EEEEE19EmplaceDecomposableEJNSF_IS6_S8_EEEEEDTclsr4absl18container_internalE13DecomposePairclsr3stdE7declvalIT_EEspclsr3stdE7declvalIT0_EEEEOSM_DpOSN_  | 
664  |  |  | 
665  |  |   template <class Hash, bool kIsDefault>  | 
666  | 0  |   static constexpr HashSlotFn get_hash_slot_fn() { | 
667  | 0  |     return memory_internal::IsLayoutCompatible<K, V>::value  | 
668  | 0  |                ? &TypeErasedApplyToSlotFn<Hash, K, kIsDefault>  | 
669  | 0  |                : nullptr;  | 
670  | 0  |   }  | 
671  |  |  | 
672  |  |   static size_t space_used(const slot_type*) { return 0; } | 
673  |  |  | 
674  | 30  |   static std::pair<const K, V>& element(slot_type* slot) { return slot->value; } | 
675  |  |  | 
676  |  |   static V& value(std::pair<const K, V>* kv) { return kv->second; } | 
677  |  |   static const V& value(const std::pair<const K, V>* kv) { return kv->second; } | 
678  |  | };  | 
679  |  |  | 
680  |  | }  // namespace container_internal  | 
681  |  |  | 
682  |  | namespace container_algorithm_internal { | 
683  |  |  | 
684  |  | // Specialization of trait in absl/algorithm/container.h  | 
685  |  | template <class Key, class T, class Hash, class KeyEqual, class Allocator>  | 
686  |  | struct IsUnorderedContainer<  | 
687  |  |     absl::flat_hash_map<Key, T, Hash, KeyEqual, Allocator>> : std::true_type {}; | 
688  |  |  | 
689  |  | }  // namespace container_algorithm_internal  | 
690  |  |  | 
691  |  | ABSL_NAMESPACE_END  | 
692  |  | }  // namespace absl  | 
693  |  |  | 
694  |  | #endif  // ABSL_CONTAINER_FLAT_HASH_MAP_H_  |