Mercurial > hg > CbC > CbC_gcc
comparison gcc/objc/objc-map.h @ 111:04ced10e8804
gcc 7
author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |
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1 /* objc-map.h -- Implementation of map data structures for ObjC compiler | |
2 Copyright (C) 2011-2017 Free Software Foundation, Inc. | |
3 Written by Nicola Pero <nicola.pero@meta-innovation.com> | |
4 | |
5 This program is free software; you can redistribute it and/or modify it | |
6 under the terms of the GNU Lesser Public License as published by the | |
7 Free Software Foundation; either version 3, or (at your option) any | |
8 later version. | |
9 | |
10 This program is distributed in the hope that it will be useful, | |
11 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 GNU Lesser Public License for more details. | |
14 | |
15 You should have received a copy of the GNU Lesser Public License | |
16 along with this program; if not, write to the Free Software | |
17 Foundation, 51 Franklin Street - Fifth Floor, | |
18 Boston, MA 02110-1301, USA. */ | |
19 | |
20 #ifndef OBJC_MAP_H | |
21 #define OBJC_MAP_H | |
22 | |
23 /* A map is a data structure that maps a key to a value. In this file | |
24 we currently have maps that can map a GCC identifier (a tree) to | |
25 some other GCC tree. This is what the ObjC frontend mostly needs: | |
26 being able to look up an identifier into an ObjC data structure. A | |
27 typical usage is mapping ObjC class names (as identifiers) to a | |
28 tree representing the class. | |
29 | |
30 This implementation is fast. :-) */ | |
31 | |
32 /** | |
33 ** Private definitions. | |
34 **/ | |
35 | |
36 /* We include private declaration and definitions that are required to | |
37 provide the implementation of inline functions. You should ignore | |
38 these definitions (and the implementation of the inline functions) | |
39 as they are not part of the public API and may change. */ | |
40 typedef unsigned int objc_map_private_hash_t; | |
41 | |
42 /* This is used as sentinel. */ | |
43 #define OBJC_MAP_PRIVATE_EMPTY_SLOT (tree)0 | |
44 | |
45 struct GTY(()) objc_map_private { | |
46 /* Total number of slots. This is the maximum number of elements | |
47 that can be currently stored in the map before resizing. This is | |
48 the number of slots in the C array. Important: this is | |
49 guaranteed to be a power of 2. When we create (or resize) the | |
50 map, we round up the size to the next power of 2. This allows us | |
51 to convert a hash to a position in the hashtable by simply doing | |
52 "position = hash & mask", where mask is number_of_slots - 1 | |
53 instead of using a modulo (which requires a division). */ | |
54 size_t number_of_slots; | |
55 | |
56 /* This is number_of_slots - 1, precomputed. */ | |
57 size_t mask; | |
58 | |
59 /* Number of slots that are not empty (ie, that are active). We | |
60 keep counts using this variable which can easily be checked | |
61 against max_number_of_non_empty_slots. */ | |
62 size_t number_of_non_empty_slots; | |
63 | |
64 /* This is the load factor limit. When the number of non empty | |
65 slots equals this number, we need to resize the array. This is | |
66 calculated once, when the slots are resized, and then kept cached | |
67 so it can be compared quickly when elements are added. */ | |
68 size_t max_number_of_non_empty_slots; | |
69 | |
70 /* The maximum load factor. */ | |
71 int maximum_load_factor; | |
72 | |
73 /* These are the keys. */ | |
74 tree * GTY ((length ("%h.number_of_slots"))) slots; | |
75 | |
76 /* These are the values. values[i] is the value corresponding | |
77 to slots[i]. */ | |
78 tree * GTY ((length ("%h.number_of_slots"))) values; | |
79 }; | |
80 | |
81 /* Private functions used to resize the map. They may be called by | |
82 the inline functions when adding elements. */ | |
83 extern void | |
84 objc_map_private_grow (struct objc_map_private *map); | |
85 | |
86 | |
87 /** | |
88 ** The definition of a map. | |
89 **/ | |
90 typedef struct objc_map_private *objc_map_t; | |
91 | |
92 | |
93 /** | |
94 ** Creating a map. | |
95 **/ | |
96 | |
97 /* objc_map_alloc_ggc() creates a new map which is under GGC. The initial | |
98 capacity must be specified as an argument; this is used to size the map | |
99 when it is created. */ | |
100 objc_map_t objc_map_alloc_ggc (size_t initial_capacity); | |
101 | |
102 /** | |
103 ** Performance tuning. | |
104 **/ | |
105 | |
106 /* Set a maximum load factor for the data structure. This is the main | |
107 tuning parameter to improve performance (at the expense of | |
108 memory). */ | |
109 void objc_map_set_maximum_load_factor (objc_map_t map, int number_between_zero_and_one_hundred); | |
110 | |
111 /* Read the maximum load factor. */ | |
112 int objc_map_maximum_load_factor (objc_map_t map); | |
113 | |
114 | |
115 /** | |
116 ** Getting the value corresponding to a key. | |
117 **/ | |
118 | |
119 /* This is the value returned by objc_map_get() when the value | |
120 corresponding to a key is not found. */ | |
121 #define OBJC_MAP_NOT_FOUND (tree)1 | |
122 | |
123 /* objc_map_get() returns the value associated with a certain key, | |
124 or OBJC_MAP_NOT_FOUND if there is no value associated with that key. | |
125 Note that you can also use it to simply check if the map contains a | |
126 pair with a certain key; just compare the result of calling | |
127 objc_map_get() to OBJC_MAP_NOT_FOUND. | |
128 | |
129 It is essential to always check the results of the call to make | |
130 sure it is not OBJC_MAP_NOT_FOUND. | |
131 | |
132 NULL is a valid value, so a key can be inserted into a map with | |
133 value NULL, and objc_map_get() will return NULL in that case. | |
134 So a result of NULL means that they key *was* found, and the value | |
135 associated with it was NULL. */ | |
136 static inline tree | |
137 objc_map_get (objc_map_t map, /* struct tree_identifier * */tree key) | |
138 { | |
139 /* The inline implementation is private and may change without notice. */ | |
140 objc_map_private_hash_t hash = IDENTIFIER_HASH_VALUE (key); | |
141 size_t i = hash & map->mask; | |
142 size_t j = 1; | |
143 | |
144 if (map->slots[i] == OBJC_MAP_PRIVATE_EMPTY_SLOT) | |
145 return OBJC_MAP_NOT_FOUND; | |
146 | |
147 if (map->slots[i] == key) | |
148 return map->values[i]; | |
149 | |
150 while (1) | |
151 { | |
152 i = (i + j) & map->mask; | |
153 | |
154 if (map->slots[i] == OBJC_MAP_PRIVATE_EMPTY_SLOT) | |
155 return OBJC_MAP_NOT_FOUND; | |
156 | |
157 if (map->slots[i] == key) | |
158 return map->values[i]; | |
159 | |
160 j++; | |
161 } | |
162 } | |
163 | |
164 /* objc_map_put() puts a key/value pair into the map. If the map does | |
165 not contain the key, it is added to it with the specified value. | |
166 If the map already contains the key, the previous value is replaced | |
167 with the new one. | |
168 | |
169 You can use any identifier as key, with the exception of NULL. | |
170 | |
171 You can use any tree as value, including NULL. */ | |
172 static inline | |
173 void objc_map_put (objc_map_t map, /*struct tree_identifier * */tree key, tree value) | |
174 { | |
175 /* The inline implementation is private and may change without notice. */ | |
176 objc_map_private_hash_t hash = IDENTIFIER_HASH_VALUE (key); | |
177 size_t i, j = 0; | |
178 | |
179 if (map->number_of_non_empty_slots == map->max_number_of_non_empty_slots) | |
180 objc_map_private_grow (map); | |
181 | |
182 i = hash & map->mask; | |
183 | |
184 while (1) | |
185 { | |
186 if (map->slots[i] == OBJC_MAP_PRIVATE_EMPTY_SLOT) | |
187 { | |
188 map->number_of_non_empty_slots++; | |
189 map->slots[i] = key; | |
190 map->values[i] = value; | |
191 return; | |
192 } | |
193 if (map->slots[i] == key) | |
194 { | |
195 map->values[i] = value; | |
196 return; | |
197 } | |
198 | |
199 j++; | |
200 i = (i + j) & map->mask; | |
201 } | |
202 } | |
203 | |
204 /** | |
205 ** Iterating over a map using an iterator. | |
206 **/ | |
207 | |
208 /* When using iterators you can iterate directly on the elements in | |
209 the map, and take an action over each one. | |
210 | |
211 Here is how you iterate over a hmap_pointer using iterators: | |
212 | |
213 objc_map_iterator_t i; | |
214 | |
215 objc_map_iterator_initialize (map, &i); | |
216 | |
217 while (objc_map_iterator_move_to_next (map, &i)) | |
218 { | |
219 tree p = objc_map_iterator_current_key (map, i); | |
220 tree q = objc_map_iterator_current_value (map, i); | |
221 | |
222 ... do something with p and q ... | |
223 } | |
224 | |
225 You'll notice that the functions that modify the iterator (to | |
226 initialize it, or move it to the next element) take a pointer to it | |
227 as argument (as in "&i"), while the functions that only read its | |
228 state (to read the current key/value, or remove the current | |
229 key/value from the map) take it as a direct argument (as in "i"). | |
230 | |
231 Note that all the objc_map_iterator_*() functions are inline and if | |
232 you follow the pattern above, the compiler should be able to inline | |
233 everything into a very efficient loop, roughly equivalent to | |
234 hand-writing a C loop that iterates directly onto the hmap_pointer | |
235 internal data structures. */ | |
236 | |
237 /* A objc_map_iterator_t variable encapsulates the state of an | |
238 iteration. The fact that this is actually a size_t (pointing to | |
239 the index of the slot that we return next) is an internal, private | |
240 detail of the implementation and may change without notice. */ | |
241 typedef size_t objc_map_iterator_t; | |
242 | |
243 /* Initialize an iterator to iterate over the specified objc_map. You | |
244 must use this before starting the iteration, to get a working | |
245 iterator. */ | |
246 static inline | |
247 void | |
248 objc_map_iterator_initialize (objc_map_t map ATTRIBUTE_UNUSED, objc_map_iterator_t *i) | |
249 { | |
250 /* The inline implementation is private and may change without notice. */ | |
251 /* This is trivial, but the same API would work to initialize more | |
252 complicated iterators. */ | |
253 *i = 0; | |
254 } | |
255 | |
256 #define OBJC_MAP_FAILURE 0 | |
257 #define OBJC_MAP_SUCCESS 1 | |
258 | |
259 /* Move the iterator to the next key/value pair, and return | |
260 OBJC_MAP_SUCCESS if there is such a key/value pair, and | |
261 OBJC_MAP_FAILURE if there are no more ones. The iterator must have | |
262 been initialized using objc_map_iterator_initialize(). Note that | |
263 because this function is modifying the iterator, you need to pass a | |
264 pointer to it. */ | |
265 static inline | |
266 int | |
267 objc_map_iterator_move_to_next (objc_map_t map, objc_map_iterator_t *i) | |
268 { | |
269 /* The inline implementation is private and may change without notice. */ | |
270 while (1) | |
271 { | |
272 void *slot; | |
273 if (*i == map->number_of_slots) | |
274 return OBJC_MAP_FAILURE; | |
275 | |
276 slot = map->slots[*i]; | |
277 *i = *i + 1; | |
278 if (slot != OBJC_MAP_PRIVATE_EMPTY_SLOT) | |
279 return OBJC_MAP_SUCCESS; | |
280 } | |
281 } | |
282 | |
283 /* Return the current key. You can only call it after you have called | |
284 objc_map_iterator_move_to_next() at least once (to move to the | |
285 first element), and only if the last call returned | |
286 OBJC_MAP_SUCCESS. The behavior is otherwise undefined, probably a | |
287 segmentation fault. */ | |
288 static inline | |
289 tree | |
290 objc_map_iterator_current_key (objc_map_t map, objc_map_iterator_t i) | |
291 { | |
292 /* The inline implementation is private and may change without notice. */ | |
293 return map->slots[i - 1]; | |
294 } | |
295 | |
296 /* Return the current value. You can only call it after you have | |
297 called objc_map_iterator_move_to_next() at least once (to move to | |
298 the first element), and only if the last call returned | |
299 OBJC_MAP_SUCCESS. The behavior is otherwise undefined, probably a | |
300 segmentation fault. */ | |
301 static inline | |
302 tree | |
303 objc_map_iterator_current_value (objc_map_t map, objc_map_iterator_t i) | |
304 { | |
305 /* The inline implementation is private and may change without notice. */ | |
306 return map->values[i - 1]; | |
307 } | |
308 | |
309 #endif /* OBJC_MAP_H */ |