Age Owner TLA Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * hashfn.c
4 : * Generic hashing functions, and hash functions for use in dynahash.c
5 : * hashtables
6 : *
7 : *
8 : * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
9 : * Portions Copyright (c) 1994, Regents of the University of California
10 : *
11 : *
12 : * IDENTIFICATION
13 : * src/common/hashfn.c
14 : *
15 : * NOTES
16 : * It is expected that every bit of a hash function's 32-bit result is
17 : * as random as every other; failure to ensure this is likely to lead
18 : * to poor performance of hash tables. In most cases a hash
19 : * function should use hash_bytes() or its variant hash_bytes_uint32(),
20 : * or the wrappers hash_any() and hash_uint32 defined in hashfn.h.
21 : *
22 : *-------------------------------------------------------------------------
23 : */
24 : #include "postgres.h"
25 :
26 : #include "common/hashfn.h"
27 : #include "port/pg_bitutils.h"
28 :
29 :
30 : /*
31 : * This hash function was written by Bob Jenkins
32 : * (bob_jenkins@burtleburtle.net), and superficially adapted
33 : * for PostgreSQL by Neil Conway. For more information on this
34 : * hash function, see http://burtleburtle.net/bob/hash/doobs.html,
35 : * or Bob's article in Dr. Dobb's Journal, Sept. 1997.
36 : *
37 : * In the current code, we have adopted Bob's 2006 update of his hash
38 : * function to fetch the data a word at a time when it is suitably aligned.
39 : * This makes for a useful speedup, at the cost of having to maintain
40 : * four code paths (aligned vs unaligned, and little-endian vs big-endian).
41 : * It also uses two separate mixing functions mix() and final(), instead
42 : * of a slower multi-purpose function.
43 : */
44 :
45 : /* Get a bit mask of the bits set in non-uint32 aligned addresses */
46 : #define UINT32_ALIGN_MASK (sizeof(uint32) - 1)
47 :
48 : #define rot(x,k) pg_rotate_left32(x, k)
49 :
50 : /*----------
51 : * mix -- mix 3 32-bit values reversibly.
52 : *
53 : * This is reversible, so any information in (a,b,c) before mix() is
54 : * still in (a,b,c) after mix().
55 : *
56 : * If four pairs of (a,b,c) inputs are run through mix(), or through
57 : * mix() in reverse, there are at least 32 bits of the output that
58 : * are sometimes the same for one pair and different for another pair.
59 : * This was tested for:
60 : * * pairs that differed by one bit, by two bits, in any combination
61 : * of top bits of (a,b,c), or in any combination of bottom bits of
62 : * (a,b,c).
63 : * * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
64 : * the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
65 : * is commonly produced by subtraction) look like a single 1-bit
66 : * difference.
67 : * * the base values were pseudorandom, all zero but one bit set, or
68 : * all zero plus a counter that starts at zero.
69 : *
70 : * This does not achieve avalanche. There are input bits of (a,b,c)
71 : * that fail to affect some output bits of (a,b,c), especially of a. The
72 : * most thoroughly mixed value is c, but it doesn't really even achieve
73 : * avalanche in c.
74 : *
75 : * This allows some parallelism. Read-after-writes are good at doubling
76 : * the number of bits affected, so the goal of mixing pulls in the opposite
77 : * direction from the goal of parallelism. I did what I could. Rotates
78 : * seem to cost as much as shifts on every machine I could lay my hands on,
79 : * and rotates are much kinder to the top and bottom bits, so I used rotates.
80 : *----------
81 : */
82 : #define mix(a,b,c) \
83 : { \
84 : a -= c; a ^= rot(c, 4); c += b; \
85 : b -= a; b ^= rot(a, 6); a += c; \
86 : c -= b; c ^= rot(b, 8); b += a; \
87 : a -= c; a ^= rot(c,16); c += b; \
88 : b -= a; b ^= rot(a,19); a += c; \
89 : c -= b; c ^= rot(b, 4); b += a; \
90 : }
91 :
92 : /*----------
93 : * final -- final mixing of 3 32-bit values (a,b,c) into c
94 : *
95 : * Pairs of (a,b,c) values differing in only a few bits will usually
96 : * produce values of c that look totally different. This was tested for
97 : * * pairs that differed by one bit, by two bits, in any combination
98 : * of top bits of (a,b,c), or in any combination of bottom bits of
99 : * (a,b,c).
100 : * * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
101 : * the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
102 : * is commonly produced by subtraction) look like a single 1-bit
103 : * difference.
104 : * * the base values were pseudorandom, all zero but one bit set, or
105 : * all zero plus a counter that starts at zero.
106 : *
107 : * The use of separate functions for mix() and final() allow for a
108 : * substantial performance increase since final() does not need to
109 : * do well in reverse, but is does need to affect all output bits.
110 : * mix(), on the other hand, does not need to affect all output
111 : * bits (affecting 32 bits is enough). The original hash function had
112 : * a single mixing operation that had to satisfy both sets of requirements
113 : * and was slower as a result.
114 : *----------
115 : */
116 : #define final(a,b,c) \
117 : { \
118 : c ^= b; c -= rot(b,14); \
119 : a ^= c; a -= rot(c,11); \
120 : b ^= a; b -= rot(a,25); \
121 : c ^= b; c -= rot(b,16); \
122 : a ^= c; a -= rot(c, 4); \
123 : b ^= a; b -= rot(a,14); \
124 : c ^= b; c -= rot(b,24); \
125 : }
126 :
127 : /*
128 : * hash_bytes() -- hash a variable-length key into a 32-bit value
129 : * k : the key (the unaligned variable-length array of bytes)
130 : * len : the length of the key, counting by bytes
131 : *
132 : * Returns a uint32 value. Every bit of the key affects every bit of
133 : * the return value. Every 1-bit and 2-bit delta achieves avalanche.
134 : * About 6*len+35 instructions. The best hash table sizes are powers
135 : * of 2. There is no need to do mod a prime (mod is sooo slow!).
136 : * If you need less than 32 bits, use a bitmask.
137 : *
138 : * This procedure must never throw elog(ERROR); the ResourceOwner code
139 : * relies on this not to fail.
140 : *
141 : * Note: we could easily change this function to return a 64-bit hash value
142 : * by using the final values of both b and c. b is perhaps a little less
143 : * well mixed than c, however.
144 : */
145 : uint32
1140 rhaas 146 CBC 217938592 : hash_bytes(const unsigned char *k, int keylen)
147 : {
148 : uint32 a,
149 : b,
150 : c,
151 : len;
152 :
153 : /* Set up the internal state */
1490 alvherre 154 217938592 : len = keylen;
155 217938592 : a = b = c = 0x9e3779b9 + len + 3923095;
156 :
157 : /* If the source pointer is word-aligned, we use word-wide fetches */
158 217938592 : if (((uintptr_t) k & UINT32_ALIGN_MASK) == 0)
159 : {
160 : /* Code path for aligned source data */
1330 tgl 161 215280067 : const uint32 *ka = (const uint32 *) k;
162 :
163 : /* handle most of the key */
1490 alvherre 164 426142784 : while (len >= 12)
165 : {
166 210862717 : a += ka[0];
167 210862717 : b += ka[1];
168 210862717 : c += ka[2];
169 210862717 : mix(a, b, c);
170 210862717 : ka += 3;
171 210862717 : len -= 12;
172 : }
173 :
174 : /* handle the last 11 bytes */
175 215280067 : k = (const unsigned char *) ka;
176 : #ifdef WORDS_BIGENDIAN
177 : switch (len)
178 : {
179 : case 11:
180 : c += ((uint32) k[10] << 8);
181 : /* fall through */
182 : case 10:
183 : c += ((uint32) k[9] << 16);
184 : /* fall through */
185 : case 9:
186 : c += ((uint32) k[8] << 24);
187 : /* fall through */
188 : case 8:
189 : /* the lowest byte of c is reserved for the length */
190 : b += ka[1];
191 : a += ka[0];
192 : break;
193 : case 7:
194 : b += ((uint32) k[6] << 8);
195 : /* fall through */
196 : case 6:
197 : b += ((uint32) k[5] << 16);
198 : /* fall through */
199 : case 5:
200 : b += ((uint32) k[4] << 24);
201 : /* fall through */
202 : case 4:
203 : a += ka[0];
204 : break;
205 : case 3:
206 : a += ((uint32) k[2] << 8);
207 : /* fall through */
208 : case 2:
209 : a += ((uint32) k[1] << 16);
210 : /* fall through */
211 : case 1:
212 : a += ((uint32) k[0] << 24);
213 : /* case 0: nothing left to add */
214 : }
215 : #else /* !WORDS_BIGENDIAN */
216 215280067 : switch (len)
217 : {
218 877750 : case 11:
219 877750 : c += ((uint32) k[10] << 24);
220 : /* fall through */
221 1583251 : case 10:
222 1583251 : c += ((uint32) k[9] << 16);
223 : /* fall through */
224 2090577 : case 9:
225 2090577 : c += ((uint32) k[8] << 8);
226 : /* fall through */
227 169156848 : case 8:
228 : /* the lowest byte of c is reserved for the length */
229 169156848 : b += ka[1];
230 169156848 : a += ka[0];
231 169156848 : break;
232 576012 : case 7:
233 576012 : b += ((uint32) k[6] << 16);
234 : /* fall through */
235 1258161 : case 6:
236 1258161 : b += ((uint32) k[5] << 8);
237 : /* fall through */
238 2033300 : case 5:
239 2033300 : b += k[4];
240 : /* fall through */
241 40472873 : case 4:
242 40472873 : a += ka[0];
243 40472873 : break;
244 577858 : case 3:
245 577858 : a += ((uint32) k[2] << 16);
246 : /* fall through */
247 1422020 : case 2:
248 1422020 : a += ((uint32) k[1] << 8);
249 : /* fall through */
250 2124076 : case 1:
251 2124076 : a += k[0];
252 : /* case 0: nothing left to add */
253 : }
254 : #endif /* WORDS_BIGENDIAN */
255 : }
256 : else
257 : {
258 : /* Code path for non-aligned source data */
259 :
260 : /* handle most of the key */
261 3030847 : while (len >= 12)
262 : {
263 : #ifdef WORDS_BIGENDIAN
264 : a += (k[3] + ((uint32) k[2] << 8) + ((uint32) k[1] << 16) + ((uint32) k[0] << 24));
265 : b += (k[7] + ((uint32) k[6] << 8) + ((uint32) k[5] << 16) + ((uint32) k[4] << 24));
266 : c += (k[11] + ((uint32) k[10] << 8) + ((uint32) k[9] << 16) + ((uint32) k[8] << 24));
267 : #else /* !WORDS_BIGENDIAN */
268 372322 : a += (k[0] + ((uint32) k[1] << 8) + ((uint32) k[2] << 16) + ((uint32) k[3] << 24));
269 372322 : b += (k[4] + ((uint32) k[5] << 8) + ((uint32) k[6] << 16) + ((uint32) k[7] << 24));
270 372322 : c += (k[8] + ((uint32) k[9] << 8) + ((uint32) k[10] << 16) + ((uint32) k[11] << 24));
271 : #endif /* WORDS_BIGENDIAN */
272 372322 : mix(a, b, c);
273 372322 : k += 12;
274 372322 : len -= 12;
275 : }
276 :
277 : /* handle the last 11 bytes */
278 : #ifdef WORDS_BIGENDIAN
279 : switch (len)
280 : {
281 : case 11:
282 : c += ((uint32) k[10] << 8);
283 : /* fall through */
284 : case 10:
285 : c += ((uint32) k[9] << 16);
286 : /* fall through */
287 : case 9:
288 : c += ((uint32) k[8] << 24);
289 : /* fall through */
290 : case 8:
291 : /* the lowest byte of c is reserved for the length */
292 : b += k[7];
293 : /* fall through */
294 : case 7:
295 : b += ((uint32) k[6] << 8);
296 : /* fall through */
297 : case 6:
298 : b += ((uint32) k[5] << 16);
299 : /* fall through */
300 : case 5:
301 : b += ((uint32) k[4] << 24);
302 : /* fall through */
303 : case 4:
304 : a += k[3];
305 : /* fall through */
306 : case 3:
307 : a += ((uint32) k[2] << 8);
308 : /* fall through */
309 : case 2:
310 : a += ((uint32) k[1] << 16);
311 : /* fall through */
312 : case 1:
313 : a += ((uint32) k[0] << 24);
314 : /* case 0: nothing left to add */
315 : }
316 : #else /* !WORDS_BIGENDIAN */
317 2658525 : switch (len)
318 : {
319 27840 : case 11:
320 27840 : c += ((uint32) k[10] << 24);
321 : /* fall through */
322 221568 : case 10:
323 221568 : c += ((uint32) k[9] << 16);
324 : /* fall through */
325 273589 : case 9:
326 273589 : c += ((uint32) k[8] << 8);
327 : /* fall through */
328 318930 : case 8:
329 : /* the lowest byte of c is reserved for the length */
330 318930 : b += ((uint32) k[7] << 24);
331 : /* fall through */
332 360665 : case 7:
333 360665 : b += ((uint32) k[6] << 16);
334 : /* fall through */
335 467077 : case 6:
336 467077 : b += ((uint32) k[5] << 8);
337 : /* fall through */
338 551103 : case 5:
339 551103 : b += k[4];
340 : /* fall through */
341 1001192 : case 4:
342 1001192 : a += ((uint32) k[3] << 24);
343 : /* fall through */
344 1094620 : case 3:
345 1094620 : a += ((uint32) k[2] << 16);
346 : /* fall through */
347 1347285 : case 2:
348 1347285 : a += ((uint32) k[1] << 8);
349 : /* fall through */
350 1657964 : case 1:
351 1657964 : a += k[0];
352 : /* case 0: nothing left to add */
353 : }
354 : #endif /* WORDS_BIGENDIAN */
355 : }
356 :
357 217938592 : final(a, b, c);
358 :
359 : /* report the result */
1140 rhaas 360 217938592 : return c;
361 : }
362 :
363 : /*
364 : * hash_bytes_extended() -- hash into a 64-bit value, using an optional seed
365 : * k : the key (the unaligned variable-length array of bytes)
366 : * len : the length of the key, counting by bytes
367 : * seed : a 64-bit seed (0 means no seed)
368 : *
369 : * Returns a uint64 value. Otherwise similar to hash_bytes.
370 : */
371 : uint64
372 2563029 : hash_bytes_extended(const unsigned char *k, int keylen, uint64 seed)
373 : {
374 : uint32 a,
375 : b,
376 : c,
377 : len;
378 :
379 : /* Set up the internal state */
1490 alvherre 380 2563029 : len = keylen;
381 2563029 : a = b = c = 0x9e3779b9 + len + 3923095;
382 :
383 : /* If the seed is non-zero, use it to perturb the internal state. */
384 2563029 : if (seed != 0)
385 : {
386 : /*
387 : * In essence, the seed is treated as part of the data being hashed,
388 : * but for simplicity, we pretend that it's padded with four bytes of
389 : * zeroes so that the seed constitutes a 12-byte chunk.
390 : */
391 2501227 : a += (uint32) (seed >> 32);
392 2501227 : b += (uint32) seed;
393 2501227 : mix(a, b, c);
394 : }
395 :
396 : /* If the source pointer is word-aligned, we use word-wide fetches */
397 2563029 : if (((uintptr_t) k & UINT32_ALIGN_MASK) == 0)
398 : {
399 : /* Code path for aligned source data */
1330 tgl 400 2562939 : const uint32 *ka = (const uint32 *) k;
401 :
402 : /* handle most of the key */
1490 alvherre 403 4640968 : while (len >= 12)
404 : {
405 2078029 : a += ka[0];
406 2078029 : b += ka[1];
407 2078029 : c += ka[2];
408 2078029 : mix(a, b, c);
409 2078029 : ka += 3;
410 2078029 : len -= 12;
411 : }
412 :
413 : /* handle the last 11 bytes */
414 2562939 : k = (const unsigned char *) ka;
415 : #ifdef WORDS_BIGENDIAN
416 : switch (len)
417 : {
418 : case 11:
419 : c += ((uint32) k[10] << 8);
420 : /* fall through */
421 : case 10:
422 : c += ((uint32) k[9] << 16);
423 : /* fall through */
424 : case 9:
425 : c += ((uint32) k[8] << 24);
426 : /* fall through */
427 : case 8:
428 : /* the lowest byte of c is reserved for the length */
429 : b += ka[1];
430 : a += ka[0];
431 : break;
432 : case 7:
433 : b += ((uint32) k[6] << 8);
434 : /* fall through */
435 : case 6:
436 : b += ((uint32) k[5] << 16);
437 : /* fall through */
438 : case 5:
439 : b += ((uint32) k[4] << 24);
440 : /* fall through */
441 : case 4:
442 : a += ka[0];
443 : break;
444 : case 3:
445 : a += ((uint32) k[2] << 8);
446 : /* fall through */
447 : case 2:
448 : a += ((uint32) k[1] << 16);
449 : /* fall through */
450 : case 1:
451 : a += ((uint32) k[0] << 24);
452 : /* case 0: nothing left to add */
453 : }
454 : #else /* !WORDS_BIGENDIAN */
455 2562939 : switch (len)
456 : {
457 7374 : case 11:
458 7374 : c += ((uint32) k[10] << 24);
459 : /* fall through */
460 13595 : case 10:
461 13595 : c += ((uint32) k[9] << 16);
462 : /* fall through */
463 17517 : case 9:
464 17517 : c += ((uint32) k[8] << 8);
465 : /* fall through */
466 22097 : case 8:
467 : /* the lowest byte of c is reserved for the length */
468 22097 : b += ka[1];
469 22097 : a += ka[0];
470 22097 : break;
471 1482202 : case 7:
472 1482202 : b += ((uint32) k[6] << 16);
473 : /* fall through */
474 1666032 : case 6:
475 1666032 : b += ((uint32) k[5] << 8);
476 : /* fall through */
477 1686972 : case 5:
478 1686972 : b += k[4];
479 : /* fall through */
480 2117254 : case 4:
481 2117254 : a += ka[0];
482 2117254 : break;
483 9493 : case 3:
484 9493 : a += ((uint32) k[2] << 16);
485 : /* fall through */
486 16299 : case 2:
487 16299 : a += ((uint32) k[1] << 8);
488 : /* fall through */
489 19846 : case 1:
490 19846 : a += k[0];
491 : /* case 0: nothing left to add */
492 : }
493 : #endif /* WORDS_BIGENDIAN */
494 : }
495 : else
496 : {
497 : /* Code path for non-aligned source data */
498 :
499 : /* handle most of the key */
500 96 : while (len >= 12)
501 : {
502 : #ifdef WORDS_BIGENDIAN
503 : a += (k[3] + ((uint32) k[2] << 8) + ((uint32) k[1] << 16) + ((uint32) k[0] << 24));
504 : b += (k[7] + ((uint32) k[6] << 8) + ((uint32) k[5] << 16) + ((uint32) k[4] << 24));
505 : c += (k[11] + ((uint32) k[10] << 8) + ((uint32) k[9] << 16) + ((uint32) k[8] << 24));
506 : #else /* !WORDS_BIGENDIAN */
507 6 : a += (k[0] + ((uint32) k[1] << 8) + ((uint32) k[2] << 16) + ((uint32) k[3] << 24));
508 6 : b += (k[4] + ((uint32) k[5] << 8) + ((uint32) k[6] << 16) + ((uint32) k[7] << 24));
509 6 : c += (k[8] + ((uint32) k[9] << 8) + ((uint32) k[10] << 16) + ((uint32) k[11] << 24));
510 : #endif /* WORDS_BIGENDIAN */
511 6 : mix(a, b, c);
512 6 : k += 12;
513 6 : len -= 12;
514 : }
515 :
516 : /* handle the last 11 bytes */
517 : #ifdef WORDS_BIGENDIAN
518 : switch (len)
519 : {
520 : case 11:
521 : c += ((uint32) k[10] << 8);
522 : /* fall through */
523 : case 10:
524 : c += ((uint32) k[9] << 16);
525 : /* fall through */
526 : case 9:
527 : c += ((uint32) k[8] << 24);
528 : /* fall through */
529 : case 8:
530 : /* the lowest byte of c is reserved for the length */
531 : b += k[7];
532 : /* fall through */
533 : case 7:
534 : b += ((uint32) k[6] << 8);
535 : /* fall through */
536 : case 6:
537 : b += ((uint32) k[5] << 16);
538 : /* fall through */
539 : case 5:
540 : b += ((uint32) k[4] << 24);
541 : /* fall through */
542 : case 4:
543 : a += k[3];
544 : /* fall through */
545 : case 3:
546 : a += ((uint32) k[2] << 8);
547 : /* fall through */
548 : case 2:
549 : a += ((uint32) k[1] << 16);
550 : /* fall through */
551 : case 1:
552 : a += ((uint32) k[0] << 24);
553 : /* case 0: nothing left to add */
554 : }
555 : #else /* !WORDS_BIGENDIAN */
556 90 : switch (len)
557 : {
1490 alvherre 558 UBC 0 : case 11:
559 0 : c += ((uint32) k[10] << 24);
560 : /* fall through */
1490 alvherre 561 CBC 6 : case 10:
562 6 : c += ((uint32) k[9] << 16);
563 : /* fall through */
564 6 : case 9:
565 6 : c += ((uint32) k[8] << 8);
566 : /* fall through */
567 30 : case 8:
568 : /* the lowest byte of c is reserved for the length */
569 30 : b += ((uint32) k[7] << 24);
570 : /* fall through */
571 36 : case 7:
572 36 : b += ((uint32) k[6] << 16);
573 : /* fall through */
574 36 : case 6:
575 36 : b += ((uint32) k[5] << 8);
576 : /* fall through */
577 42 : case 5:
578 42 : b += k[4];
579 : /* fall through */
580 48 : case 4:
581 48 : a += ((uint32) k[3] << 24);
582 : /* fall through */
583 66 : case 3:
584 66 : a += ((uint32) k[2] << 16);
585 : /* fall through */
586 72 : case 2:
587 72 : a += ((uint32) k[1] << 8);
588 : /* fall through */
589 90 : case 1:
590 90 : a += k[0];
591 : /* case 0: nothing left to add */
592 : }
593 : #endif /* WORDS_BIGENDIAN */
594 : }
595 :
596 2563029 : final(a, b, c);
597 :
598 : /* report the result */
1140 rhaas 599 2563029 : return ((uint64) b << 32) | c;
600 : }
601 :
602 : /*
603 : * hash_bytes_uint32() -- hash a 32-bit value to a 32-bit value
604 : *
605 : * This has the same result as
606 : * hash_bytes(&k, sizeof(uint32))
607 : * but is faster and doesn't force the caller to store k into memory.
608 : */
609 : uint32
610 66772276 : hash_bytes_uint32(uint32 k)
611 : {
612 : uint32 a,
613 : b,
614 : c;
615 :
1490 alvherre 616 66772276 : a = b = c = 0x9e3779b9 + (uint32) sizeof(uint32) + 3923095;
617 66772276 : a += k;
618 :
619 66772276 : final(a, b, c);
620 :
621 : /* report the result */
1140 rhaas 622 66772276 : return c;
623 : }
624 :
625 : /*
626 : * hash_bytes_uint32_extended() -- hash 32-bit value to 64-bit value, with seed
627 : *
628 : * Like hash_bytes_uint32, this is a convenience function.
629 : */
630 : uint64
631 159201 : hash_bytes_uint32_extended(uint32 k, uint64 seed)
632 : {
633 : uint32 a,
634 : b,
635 : c;
636 :
1490 alvherre 637 159201 : a = b = c = 0x9e3779b9 + (uint32) sizeof(uint32) + 3923095;
638 :
639 159201 : if (seed != 0)
640 : {
641 158868 : a += (uint32) (seed >> 32);
642 158868 : b += (uint32) seed;
643 158868 : mix(a, b, c);
644 : }
645 :
646 159201 : a += k;
647 :
648 159201 : final(a, b, c);
649 :
650 : /* report the result */
1140 rhaas 651 159201 : return ((uint64) b << 32) | c;
652 : }
653 :
654 : /*
655 : * string_hash: hash function for keys that are NUL-terminated strings.
656 : *
657 : * NOTE: this is the default hash function if none is specified.
658 : */
659 : uint32
7173 tgl 660 1761563 : string_hash(const void *key, Size keysize)
661 : {
662 : /*
663 : * If the string exceeds keysize-1 bytes, we want to hash only that many,
664 : * because when it is copied into the hash table it will be truncated at
665 : * that length.
666 : */
6031 bruce 667 1761563 : Size s_len = strlen((const char *) key);
668 :
669 1761563 : s_len = Min(s_len, keysize - 1);
1140 rhaas 670 1761563 : return hash_bytes((const unsigned char *) key, (int) s_len);
671 : }
672 :
673 : /*
674 : * tag_hash: hash function for fixed-size tag values
675 : */
676 : uint32
7173 tgl 677 201188770 : tag_hash(const void *key, Size keysize)
678 : {
1140 rhaas 679 201188770 : return hash_bytes((const unsigned char *) key, (int) keysize);
680 : }
681 :
682 : /*
683 : * uint32_hash: hash function for keys that are uint32 or int32
684 : *
685 : * (tag_hash works for this case too, but is slower)
686 : */
687 : uint32
3034 tgl 688 38743604 : uint32_hash(const void *key, Size keysize)
689 : {
690 38743604 : Assert(keysize == sizeof(uint32));
1140 rhaas 691 38743604 : return hash_bytes_uint32(*((const uint32 *) key));
692 : }
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