1 | /* |
---|
2 | #ifndef _RpDICT_H |
---|
3 | #include "../include/RpDict.h" |
---|
4 | #endif |
---|
5 | */ |
---|
6 | |
---|
7 | /**************************************************************************/ |
---|
8 | |
---|
9 | |
---|
10 | // public RpDict member functions |
---|
11 | |
---|
12 | |
---|
13 | /************************************************************************** |
---|
14 | * |
---|
15 | * int RpDict::size() |
---|
16 | * retrieve the size of the structure |
---|
17 | * |
---|
18 | * Results: |
---|
19 | * Returns size of the hash table |
---|
20 | * |
---|
21 | * Side Effects: |
---|
22 | * none. |
---|
23 | * |
---|
24 | * |
---|
25 | *************************************************************************/ |
---|
26 | |
---|
27 | template <typename KeyType, typename ValType> |
---|
28 | const int |
---|
29 | RpDict<KeyType,ValType>::size() const |
---|
30 | { |
---|
31 | return numEntries; |
---|
32 | } |
---|
33 | |
---|
34 | |
---|
35 | /************************************************************************** |
---|
36 | * |
---|
37 | * RpDict::set() |
---|
38 | * checks to make sure the table exists. |
---|
39 | * places a key/value pair into the hash table |
---|
40 | * |
---|
41 | * Results: |
---|
42 | * Returns a reference to the RpDict object allowing the user to chain |
---|
43 | * together different commands such as |
---|
44 | * rpdict_obj.set(key).find(a).erase(a); |
---|
45 | * |
---|
46 | * Side Effects: |
---|
47 | * if successful, the hash table will have a new entry |
---|
48 | * |
---|
49 | * |
---|
50 | *************************************************************************/ |
---|
51 | template <typename KeyType, typename ValType> |
---|
52 | RpDict<KeyType,ValType>& |
---|
53 | RpDict<KeyType,ValType>::set( KeyType& key, |
---|
54 | ValType& value, |
---|
55 | int* newPtr) |
---|
56 | { |
---|
57 | RpDictEntry<KeyType,ValType> *hPtr; |
---|
58 | unsigned int hash; |
---|
59 | int index; |
---|
60 | |
---|
61 | assert(&key); |
---|
62 | assert(&value); |
---|
63 | |
---|
64 | // take care of the case where we are creating a NULL key entry. |
---|
65 | if (&key) { |
---|
66 | hash = (unsigned int) hashFxn(&key); |
---|
67 | } |
---|
68 | else { |
---|
69 | hash = 0; |
---|
70 | } |
---|
71 | |
---|
72 | index = randomIndex(hash); |
---|
73 | |
---|
74 | /* |
---|
75 | * Search all of the entries in the appropriate bucket. |
---|
76 | */ |
---|
77 | for (hPtr = buckets[index]; hPtr != NULL; hPtr = hPtr->nextPtr) { |
---|
78 | if (hash != (unsigned int) hPtr->hash) { |
---|
79 | continue; |
---|
80 | } |
---|
81 | // if element already exists in hash, it should not be re-entered |
---|
82 | if (key == *(hPtr->getKey())){ |
---|
83 | |
---|
84 | // adjust the new flag if it was provided |
---|
85 | if (newPtr) { |
---|
86 | *newPtr = 0; |
---|
87 | } |
---|
88 | |
---|
89 | // adjust the value if it was provided |
---|
90 | // memory management is left as an exercize for the caller |
---|
91 | if (&value) { |
---|
92 | hPtr->setValue(value); |
---|
93 | } |
---|
94 | |
---|
95 | // return a reference to the dictionary object |
---|
96 | return *this; |
---|
97 | } |
---|
98 | } |
---|
99 | |
---|
100 | /* |
---|
101 | * Entry not found. Add a new one to the bucket. |
---|
102 | */ |
---|
103 | |
---|
104 | if (newPtr) { |
---|
105 | *newPtr = 1; |
---|
106 | } |
---|
107 | |
---|
108 | hPtr = new RpDictEntry<KeyType,ValType>(key,value); |
---|
109 | // hPtr->setValue(value); |
---|
110 | // |
---|
111 | // this is just a pointer that was allocated on the heap |
---|
112 | // it wont stick with the RpDictEntry after the fxn exits... |
---|
113 | // need to fix still. |
---|
114 | hPtr->tablePtr = this; |
---|
115 | hPtr->hash = hash; |
---|
116 | hPtr->nextPtr = buckets[index]; |
---|
117 | buckets[index] = hPtr; |
---|
118 | numEntries++; |
---|
119 | |
---|
120 | /* |
---|
121 | * If the table has exceeded a decent size, rebuild it with many |
---|
122 | * more buckets. |
---|
123 | */ |
---|
124 | |
---|
125 | if (numEntries >= rebuildSize) { |
---|
126 | RebuildTable(); |
---|
127 | } |
---|
128 | |
---|
129 | // return a reference to the original object |
---|
130 | return *this; |
---|
131 | } |
---|
132 | |
---|
133 | |
---|
134 | /* |
---|
135 | *---------------------------------------------------------------------- |
---|
136 | * |
---|
137 | * RpDict::find(const char *key) |
---|
138 | * |
---|
139 | * Given a hash table find the entry with a matching key. |
---|
140 | * |
---|
141 | * Results: |
---|
142 | * The return value is a token for the matching entry in the |
---|
143 | * hash table, or NULL if there was no matching entry. |
---|
144 | * |
---|
145 | * Side effects: |
---|
146 | * None. |
---|
147 | * |
---|
148 | *---------------------------------------------------------------------- |
---|
149 | */ |
---|
150 | |
---|
151 | template <typename KeyType, typename ValType> |
---|
152 | RpDictEntry<KeyType,ValType>& |
---|
153 | RpDict<KeyType,ValType>::find(KeyType& key) |
---|
154 | { |
---|
155 | RpDictEntry<KeyType,ValType> *hPtr; |
---|
156 | unsigned int hash; |
---|
157 | int index; |
---|
158 | |
---|
159 | assert(&key); |
---|
160 | |
---|
161 | // take care of the case where we are creating a NULL key entry. |
---|
162 | if (&key) { |
---|
163 | hash = (unsigned int) hashFxn(&key); |
---|
164 | } |
---|
165 | else { |
---|
166 | hash = 0; |
---|
167 | } |
---|
168 | |
---|
169 | index = randomIndex(hash); |
---|
170 | |
---|
171 | /* |
---|
172 | * Search all of the entries in the appropriate bucket. |
---|
173 | */ |
---|
174 | |
---|
175 | for (hPtr = buckets[index]; hPtr != NULL; hPtr = hPtr->nextPtr) { |
---|
176 | if (hash != (unsigned int) hPtr->hash) { |
---|
177 | continue; |
---|
178 | } |
---|
179 | if (key == *(hPtr->getKey())) { |
---|
180 | // return a reference to the found object |
---|
181 | return *hPtr; |
---|
182 | } |
---|
183 | } |
---|
184 | |
---|
185 | // return a reference to the null object |
---|
186 | // find is not supposed to return a const, but i dont want the user |
---|
187 | // changing this entry's data members... what to do? |
---|
188 | return *nullEntry; |
---|
189 | |
---|
190 | } |
---|
191 | |
---|
192 | |
---|
193 | |
---|
194 | /************************************************************************** |
---|
195 | * |
---|
196 | * virtual RpDict& RpDictIterator::getTable() |
---|
197 | * send the search iterator to the beginning of the hash table |
---|
198 | * |
---|
199 | * Results: |
---|
200 | * returns pointer to the first hash entry of the hash table. |
---|
201 | * |
---|
202 | * Side Effects: |
---|
203 | * moves iterator to the beginning of the hash table. |
---|
204 | * |
---|
205 | * |
---|
206 | *************************************************************************/ |
---|
207 | /* |
---|
208 | template <typename KeyType,typename ValType> |
---|
209 | RpDict<KeyType,ValType>& |
---|
210 | RpDictIterator<KeyType,ValType>::getTable() |
---|
211 | { |
---|
212 | return tablePtr; |
---|
213 | } |
---|
214 | */ |
---|
215 | |
---|
216 | /************************************************************************** |
---|
217 | * |
---|
218 | * virtual RpDictEntry& RpDict::first() |
---|
219 | * send the search iterator to the beginning of the hash table |
---|
220 | * |
---|
221 | * Results: |
---|
222 | * returns pointer to the first hash entry of the hash table. |
---|
223 | * |
---|
224 | * Side Effects: |
---|
225 | * moves iterator to the beginning of the hash table. |
---|
226 | * |
---|
227 | * |
---|
228 | *************************************************************************/ |
---|
229 | template <typename KeyType,typename ValType> |
---|
230 | RpDictEntry<KeyType,ValType>* |
---|
231 | RpDictIterator<KeyType,ValType>::first() |
---|
232 | { |
---|
233 | srchNextIndex = 0; |
---|
234 | srchNextEntryPtr = NULL; |
---|
235 | return next(); |
---|
236 | } |
---|
237 | |
---|
238 | /************************************************************************** |
---|
239 | * |
---|
240 | * Tcl_HashEntry * RpDict::next() |
---|
241 | * send the search iterator to the next entry of the hash table |
---|
242 | * |
---|
243 | * Results: |
---|
244 | * returns pointer to the next hash entry of the hash table. |
---|
245 | * if iterator is at the end of the hash table, NULL is returned |
---|
246 | * and the iterator is left at the end of the hash table. |
---|
247 | * |
---|
248 | * Side Effects: |
---|
249 | * moves iterator to the next entry of the hash table if it exists. |
---|
250 | * |
---|
251 | * |
---|
252 | *************************************************************************/ |
---|
253 | |
---|
254 | template <typename KeyType,typename ValType> |
---|
255 | RpDictEntry<KeyType,ValType>* |
---|
256 | RpDictIterator<KeyType,ValType>::next() |
---|
257 | { |
---|
258 | RpDictEntry<KeyType,ValType>* hPtr; |
---|
259 | |
---|
260 | while (srchNextEntryPtr == NULL) { |
---|
261 | if (srchNextIndex >= tablePtr.numBuckets) { |
---|
262 | return NULL; |
---|
263 | } |
---|
264 | srchNextEntryPtr = tablePtr.buckets[srchNextIndex]; |
---|
265 | srchNextIndex++; |
---|
266 | } |
---|
267 | hPtr = srchNextEntryPtr; |
---|
268 | srchNextEntryPtr = hPtr->nextPtr; |
---|
269 | |
---|
270 | return hPtr; |
---|
271 | } |
---|
272 | |
---|
273 | /************************************************************************** |
---|
274 | * |
---|
275 | * RpDict & clear() |
---|
276 | * iterate through the table and call erase on each element |
---|
277 | * |
---|
278 | * Results: |
---|
279 | * empty hash table |
---|
280 | * |
---|
281 | * Side Effects: |
---|
282 | * every element of the hash table will be erased. |
---|
283 | * |
---|
284 | * |
---|
285 | *************************************************************************/ |
---|
286 | template <typename KeyType, typename ValType> |
---|
287 | RpDict<KeyType,ValType>& |
---|
288 | RpDict<KeyType,ValType>::clear() |
---|
289 | { |
---|
290 | RpDictEntry<KeyType,ValType> *hPtr; |
---|
291 | RpDictIterator<KeyType,ValType> iter((RpDict&)*this); |
---|
292 | |
---|
293 | hPtr = iter.first(); |
---|
294 | |
---|
295 | while (hPtr) { |
---|
296 | hPtr->erase(); |
---|
297 | hPtr = iter.next(); |
---|
298 | } |
---|
299 | |
---|
300 | return *this; |
---|
301 | } |
---|
302 | |
---|
303 | /************************************************************************** |
---|
304 | * |
---|
305 | * RpDict & getNullEntry() |
---|
306 | * get the nullEntry hash entry for initialization of references |
---|
307 | * |
---|
308 | * |
---|
309 | * Results: |
---|
310 | * nullEntry RpDictEntry related to this dictionary is returned |
---|
311 | * |
---|
312 | * Side Effects: |
---|
313 | * none |
---|
314 | * |
---|
315 | * |
---|
316 | *************************************************************************/ |
---|
317 | template <typename KeyType, typename ValType> |
---|
318 | RpDictEntry<KeyType,ValType>& |
---|
319 | RpDict<KeyType,ValType>::getNullEntry() |
---|
320 | { |
---|
321 | return *nullEntry; |
---|
322 | } |
---|
323 | |
---|
324 | |
---|
325 | /* |
---|
326 | *---------------------------------------------------------------------- |
---|
327 | * |
---|
328 | * void RpDictEntry::erase() |
---|
329 | * |
---|
330 | * Remove a single entry from a hash table. |
---|
331 | * |
---|
332 | * Results: |
---|
333 | * None. |
---|
334 | * |
---|
335 | * Side effects: |
---|
336 | * The entry given by entryPtr is deleted from its table and |
---|
337 | * should never again be used by the caller. It is up to the |
---|
338 | * caller to free the clientData field of the entry, if that |
---|
339 | * is relevant. |
---|
340 | * |
---|
341 | *---------------------------------------------------------------------- |
---|
342 | */ |
---|
343 | |
---|
344 | template <typename KeyType, typename ValType> |
---|
345 | void |
---|
346 | RpDictEntry<KeyType,ValType>::erase() |
---|
347 | { |
---|
348 | RpDictEntry<KeyType,ValType> *prevPtr; |
---|
349 | RpDictEntry<KeyType,ValType> **bucketPtr; |
---|
350 | int index = 0; |
---|
351 | |
---|
352 | // check to see if the object is associated with a table |
---|
353 | // if object is not associated with a table, there is no |
---|
354 | // need to try to remove it from the table. |
---|
355 | if (tablePtr) { |
---|
356 | |
---|
357 | index = tablePtr->randomIndex(hash); |
---|
358 | |
---|
359 | // calculate which bucket the entry should be in. |
---|
360 | bucketPtr = &(tablePtr->buckets[index]); |
---|
361 | |
---|
362 | // remove the entry from the buckets |
---|
363 | // |
---|
364 | // if entry is the first entry in the bucket |
---|
365 | // move the bucket to point to the next entry |
---|
366 | if ((*bucketPtr)->key == this->key) { |
---|
367 | *bucketPtr = nextPtr; |
---|
368 | } |
---|
369 | else { |
---|
370 | // if the entry is not the first entry in the bucket |
---|
371 | // search for the entry |
---|
372 | for (prevPtr = *bucketPtr; ; prevPtr = prevPtr->nextPtr) { |
---|
373 | |
---|
374 | // printf("malformed bucket chain in RpDictEntry::erase()"); |
---|
375 | assert(prevPtr != NULL); |
---|
376 | |
---|
377 | if (prevPtr->nextPtr == this) { |
---|
378 | prevPtr->nextPtr = nextPtr; |
---|
379 | break; |
---|
380 | } |
---|
381 | } // end for loop |
---|
382 | } // end else |
---|
383 | |
---|
384 | // update our table's information |
---|
385 | tablePtr->numEntries--; |
---|
386 | |
---|
387 | } // end if tablePtr |
---|
388 | |
---|
389 | // invalidate the object |
---|
390 | nextPtr = NULL; |
---|
391 | tablePtr = NULL; |
---|
392 | hash = 0; |
---|
393 | // clientData = NULL; |
---|
394 | // key = NULL; |
---|
395 | |
---|
396 | // delete the object. |
---|
397 | // printf("delete %x\n", (unsigned) this); |
---|
398 | delete this; |
---|
399 | |
---|
400 | } |
---|
401 | |
---|
402 | |
---|
403 | /* |
---|
404 | *---------------------------------------------------------------------- |
---|
405 | * |
---|
406 | * const char* RpDictEntry::getKey() const |
---|
407 | * |
---|
408 | * retrieve the key of the current object |
---|
409 | * |
---|
410 | * Results: |
---|
411 | * the key is returned to the caller |
---|
412 | * |
---|
413 | * Side effects: |
---|
414 | * None. |
---|
415 | * |
---|
416 | *---------------------------------------------------------------------- |
---|
417 | */ |
---|
418 | |
---|
419 | template <typename KeyType, typename ValType> |
---|
420 | const KeyType* |
---|
421 | RpDictEntry<KeyType,ValType>::getKey() const |
---|
422 | { |
---|
423 | return (const KeyType*) &key; |
---|
424 | } |
---|
425 | |
---|
426 | /* |
---|
427 | *---------------------------------------------------------------------- |
---|
428 | * |
---|
429 | * const char* RpDictEntry::getValue() const |
---|
430 | * |
---|
431 | * retrieve the value of the current object |
---|
432 | * |
---|
433 | * Results: |
---|
434 | * the value is returned to the caller |
---|
435 | * |
---|
436 | * Side effects: |
---|
437 | * None. |
---|
438 | * |
---|
439 | *---------------------------------------------------------------------- |
---|
440 | */ |
---|
441 | |
---|
442 | template <typename KeyType, typename ValType> |
---|
443 | const ValType* |
---|
444 | RpDictEntry<KeyType,ValType>::getValue() const |
---|
445 | { |
---|
446 | return (const ValType*) &clientData; |
---|
447 | } |
---|
448 | |
---|
449 | /* |
---|
450 | *---------------------------------------------------------------------- |
---|
451 | * |
---|
452 | * const void* RpDictEntry::setValue() |
---|
453 | * |
---|
454 | * retrieve the value of the current object |
---|
455 | * |
---|
456 | * Results: |
---|
457 | * the value is returned to the caller |
---|
458 | * |
---|
459 | * Side effects: |
---|
460 | * None. |
---|
461 | * |
---|
462 | *---------------------------------------------------------------------- |
---|
463 | */ |
---|
464 | |
---|
465 | template <typename KeyType, typename ValType> |
---|
466 | const ValType* |
---|
467 | RpDictEntry<KeyType,ValType>::setValue(const ValType& value) |
---|
468 | { |
---|
469 | clientData = value; |
---|
470 | return (const ValType*) &clientData; |
---|
471 | } |
---|
472 | |
---|
473 | template <typename KeyType, typename ValType> |
---|
474 | RpDictEntry<KeyType,ValType>::operator int() const |
---|
475 | { |
---|
476 | |
---|
477 | if (!tablePtr && hash == 0) |
---|
478 | return 0; |
---|
479 | else |
---|
480 | return 1; |
---|
481 | |
---|
482 | // return (key); |
---|
483 | } |
---|
484 | |
---|
485 | |
---|
486 | /*************************************************************************/ |
---|
487 | /*************************************************************************/ |
---|
488 | |
---|
489 | // private member functions |
---|
490 | |
---|
491 | /* |
---|
492 | *---------------------------------------------------------------------- |
---|
493 | * |
---|
494 | * RebuildTable -- |
---|
495 | * |
---|
496 | * This procedure is invoked when the ratio of entries to hash |
---|
497 | * buckets becomes too large. It creates a new table with a |
---|
498 | * larger bucket array and moves all of the entries into the |
---|
499 | * new table. |
---|
500 | * |
---|
501 | * Results: |
---|
502 | * None. |
---|
503 | * |
---|
504 | * Side effects: |
---|
505 | * Memory gets reallocated and entries get re-hashed to new |
---|
506 | * buckets. |
---|
507 | * |
---|
508 | *---------------------------------------------------------------------- |
---|
509 | */ |
---|
510 | |
---|
511 | template <typename KeyType, typename ValType> |
---|
512 | void |
---|
513 | RpDict<KeyType,ValType>::RebuildTable() |
---|
514 | { |
---|
515 | int oldSize=0, count=0, index=0; |
---|
516 | RpDictEntry<KeyType,ValType> **oldBuckets; |
---|
517 | RpDictEntry<KeyType,ValType> **oldChainPtr, **newChainPtr; |
---|
518 | RpDictEntry<KeyType,ValType> *hPtr; |
---|
519 | |
---|
520 | void *key; |
---|
521 | |
---|
522 | oldSize = numBuckets; |
---|
523 | oldBuckets = buckets; |
---|
524 | |
---|
525 | /* |
---|
526 | * Allocate and initialize the new bucket array, and set up |
---|
527 | * hashing constants for new array size. |
---|
528 | */ |
---|
529 | |
---|
530 | |
---|
531 | numBuckets *= 4; |
---|
532 | |
---|
533 | buckets = (RpDictEntry<KeyType,ValType> **) malloc((unsigned) |
---|
534 | (numBuckets * sizeof(RpDictEntry<KeyType,ValType> *))); |
---|
535 | |
---|
536 | for (count = numBuckets, newChainPtr = buckets; |
---|
537 | count > 0; |
---|
538 | count--, newChainPtr++) { |
---|
539 | |
---|
540 | *newChainPtr = NULL; |
---|
541 | } |
---|
542 | |
---|
543 | rebuildSize *= 4; |
---|
544 | downShift -= 2; |
---|
545 | mask = (mask << 2) + 3; |
---|
546 | |
---|
547 | /* |
---|
548 | * Rehash all of the existing entries into the new bucket array. |
---|
549 | */ |
---|
550 | |
---|
551 | for (oldChainPtr = oldBuckets; oldSize > 0; oldSize--, oldChainPtr++) { |
---|
552 | for (hPtr = *oldChainPtr; hPtr != NULL; hPtr = *oldChainPtr) { |
---|
553 | *oldChainPtr = hPtr->nextPtr; |
---|
554 | |
---|
555 | key = (void *) hPtr->getKey(); |
---|
556 | |
---|
557 | index = randomIndex(hPtr->hash); |
---|
558 | |
---|
559 | hPtr->nextPtr = buckets[index]; |
---|
560 | buckets[index] = hPtr; |
---|
561 | } |
---|
562 | } |
---|
563 | |
---|
564 | /* |
---|
565 | * Free up the old bucket array, if it was dynamically allocated. |
---|
566 | */ |
---|
567 | |
---|
568 | if (oldBuckets != staticBuckets) { |
---|
569 | free((char *) oldBuckets); |
---|
570 | } |
---|
571 | } |
---|
572 | |
---|
573 | /* |
---|
574 | *---------------------------------------------------------------------- |
---|
575 | * |
---|
576 | * hashFxn -- |
---|
577 | * |
---|
578 | * Compute a one-word summary of a text string, which can be |
---|
579 | * used to generate a hash index. |
---|
580 | * |
---|
581 | * Results: |
---|
582 | * The return value is a one-word summary of the information in |
---|
583 | * string. |
---|
584 | * |
---|
585 | * Side effects: |
---|
586 | * None. |
---|
587 | * |
---|
588 | *---------------------------------------------------------------------- |
---|
589 | */ |
---|
590 | |
---|
591 | template <typename KeyType, typename ValType> |
---|
592 | unsigned int |
---|
593 | RpDict<KeyType,ValType>::hashFxn(const void *keyPtr) const |
---|
594 | { |
---|
595 | const char *stopAddr = (const char *) keyPtr + sizeof(&keyPtr) - 1 ; |
---|
596 | const char *str = (const char *) keyPtr; |
---|
597 | unsigned int result; |
---|
598 | int c; |
---|
599 | |
---|
600 | result = 0; |
---|
601 | |
---|
602 | while (str != stopAddr) { |
---|
603 | c = *str; |
---|
604 | result += (result<<3) + c; |
---|
605 | str++; |
---|
606 | } |
---|
607 | |
---|
608 | return result; |
---|
609 | } |
---|
610 | |
---|
611 | /* |
---|
612 | * I tried a zillion different hash functions and asked many other |
---|
613 | * people for advice. Many people had their own favorite functions, |
---|
614 | * all different, but no-one had much idea why they were good ones. |
---|
615 | * I chose the one below (multiply by 9 and add new character) |
---|
616 | * because of the following reasons: |
---|
617 | * |
---|
618 | * 1. Multiplying by 10 is perfect for keys that are decimal strings, |
---|
619 | * and multiplying by 9 is just about as good. |
---|
620 | * 2. Times-9 is (shift-left-3) plus (old). This means that each |
---|
621 | * character's bits hang around in the low-order bits of the |
---|
622 | * hash value for ever, plus they spread fairly rapidly up to |
---|
623 | * the high-order bits to fill out the hash value. This seems |
---|
624 | * works well both for decimal and non-decimal strings. |
---|
625 | */ |
---|
626 | |
---|
627 | |
---|
628 | template <typename KeyType, typename ValType> |
---|
629 | unsigned int |
---|
630 | RpDict<KeyType,ValType>::hashFxn(std::string* keyPtr) const |
---|
631 | { |
---|
632 | const char *str = (const char *) (keyPtr->c_str()); |
---|
633 | unsigned int result; |
---|
634 | int c; |
---|
635 | |
---|
636 | result = 0; |
---|
637 | |
---|
638 | while (1) { |
---|
639 | c = *str; |
---|
640 | if (c == 0) { |
---|
641 | break; |
---|
642 | } |
---|
643 | result += (result<<3) + c; |
---|
644 | str++; |
---|
645 | } |
---|
646 | |
---|
647 | return result; |
---|
648 | } |
---|
649 | |
---|
650 | template <typename KeyType, typename ValType> |
---|
651 | unsigned int |
---|
652 | RpDict<KeyType,ValType>::hashFxn(char* keyPtr) const |
---|
653 | { |
---|
654 | const char *str = (const char *) (keyPtr); |
---|
655 | unsigned int result; |
---|
656 | int c; |
---|
657 | |
---|
658 | result = 0; |
---|
659 | |
---|
660 | while (1) { |
---|
661 | c = *str; |
---|
662 | if (c == 0) { |
---|
663 | break; |
---|
664 | } |
---|
665 | result += (result<<3) + c; |
---|
666 | str++; |
---|
667 | } |
---|
668 | |
---|
669 | return result; |
---|
670 | } |
---|
671 | |
---|
672 | /* |
---|
673 | * --------------------------------------------------------------------- |
---|
674 | * |
---|
675 | * int RpDict::randomIndex(hash) |
---|
676 | * |
---|
677 | * The following macro takes a preliminary integer hash value and |
---|
678 | * produces an index into a hash tables bucket list. The idea is |
---|
679 | * to make it so that preliminary values that are arbitrarily similar |
---|
680 | * will end up in different buckets. The hash function was taken |
---|
681 | * from a random-number generator. |
---|
682 | * |
---|
683 | * --------------------------------------------------------------------- |
---|
684 | */ |
---|
685 | |
---|
686 | template <typename KeyType, typename ValType> |
---|
687 | int |
---|
688 | RpDict<KeyType,ValType>::randomIndex(unsigned int hash) |
---|
689 | { |
---|
690 | return (((((long) (hash))*1103515245) >> downShift) & mask); |
---|
691 | } |
---|
692 | |
---|
693 | |
---|