Commit | Line | Data |
---|---|---|
8befd5cc MG |
1 | /** |
2 | * Seccomp Library hash code | |
3 | * | |
4 | * Release under the Public Domain | |
5 | * Author: Bob Jenkins <bob_jenkins@burtleburtle.net> | |
6 | */ | |
7 | ||
8 | /* | |
9 | * lookup3.c, by Bob Jenkins, May 2006, Public Domain. | |
10 | * | |
11 | * These are functions for producing 32-bit hashes for hash table lookup. | |
12 | * jhash_word(), jhash_le(), jhash_be(), mix(), and final() are externally useful | |
13 | * functions. Routines to test the hash are included if SELF_TEST is defined. | |
14 | * You can use this free for any purpose. It's in the public domain. It has | |
15 | * no warranty. | |
16 | * | |
17 | * You probably want to use jhash_le(). jhash_le() and jhash_be() hash byte | |
18 | * arrays. jhash_le() is is faster than jhash_be() on little-endian machines. | |
19 | * Intel and AMD are little-endian machines. | |
20 | * | |
21 | * If you want to find a hash of, say, exactly 7 integers, do | |
22 | * a = i1; b = i2; c = i3; | |
23 | * mix(a,b,c); | |
24 | * a += i4; b += i5; c += i6; | |
25 | * mix(a,b,c); | |
26 | * a += i7; | |
27 | * final(a,b,c); | |
28 | * | |
29 | * then use c as the hash value. If you have a variable length array of | |
30 | * 4-byte integers to hash, use jhash_word(). If you have a byte array (like | |
31 | * a character string), use jhash_le(). If you have several byte arrays, or | |
32 | * a mix of things, see the comments above jhash_le(). | |
33 | * | |
34 | * Why is this so big? I read 12 bytes at a time into 3 4-byte integers, then | |
35 | * mix those integers. This is fast (you can do a lot more thorough mixing | |
36 | * with 12*3 instructions on 3 integers than you can with 3 instructions on 1 | |
37 | * byte), but shoehorning those bytes into integers efficiently is messy. | |
38 | */ | |
39 | ||
40 | #include <stdint.h> | |
41 | ||
42 | #include "arch.h" | |
43 | #include "hash.h" | |
44 | ||
45 | #define hashsize(n) ((uint32_t)1<<(n)) | |
46 | #define hashmask(n) (hashsize(n)-1) | |
47 | #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k)))) | |
48 | ||
49 | /** | |
50 | * Mix 3 32-bit values reversibly | |
51 | * @param a 32-bit value | |
52 | * @param b 32-bit value | |
53 | * @param c 32-bit value | |
54 | * | |
55 | * This is reversible, so any information in (a,b,c) before mix() is still | |
56 | * in (a,b,c) after mix(). | |
57 | * | |
58 | * If four pairs of (a,b,c) inputs are run through mix(), or through mix() in | |
59 | * reverse, there are at least 32 bits of the output that are sometimes the | |
60 | * same for one pair and different for another pair. | |
61 | * | |
62 | * This was tested for: | |
63 | * - pairs that differed by one bit, by two bits, in any combination of top | |
64 | * bits of (a,b,c), or in any combination of bottom bits of (a,b,c). | |
65 | * - "differ" is defined as +, -, ^, or ~^. For + and -, I transformed the | |
66 | * output delta to a Gray code (a^(a>>1)) so a string of 1's (as is commonly | |
67 | * produced by subtraction) look like a single 1-bit difference. | |
68 | * - the base values were pseudorandom, all zero but one bit set, or all zero | |
69 | * plus a counter that starts at zero. | |
70 | * | |
71 | * Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that | |
72 | * satisfy this are | |
73 | * 4 6 8 16 19 4 | |
74 | * 9 15 3 18 27 15 | |
75 | * 14 9 3 7 17 3 | |
76 | * | |
77 | * Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing for "differ" | |
78 | * defined as + with a one-bit base and a two-bit delta. I used | |
79 | * http://burtleburtle.net/bob/hash/avalanche.html to choose the operations, | |
80 | * constants, and arrangements of the variables. | |
81 | * | |
82 | * This does not achieve avalanche. There are input bits of (a,b,c) that fail | |
83 | * to affect some output bits of (a,b,c), especially of a. The most thoroughly | |
84 | * mixed value is c, but it doesn't really even achieve avalanche in c. | |
85 | * | |
86 | * This allows some parallelism. Read-after-writes are good at doubling the | |
87 | * number of bits affected, so the goal of mixing pulls in the opposite | |
88 | * direction as the goal of parallelism. I did what I could. Rotates seem to | |
89 | * cost as much as shifts on every machine I could lay my hands on, and rotates | |
90 | * are much kinder to the top and bottom bits, so I used rotates. | |
91 | * | |
92 | */ | |
93 | #define mix(a,b,c) \ | |
94 | { \ | |
95 | a -= c; a ^= rot(c, 4); c += b; \ | |
96 | b -= a; b ^= rot(a, 6); a += c; \ | |
97 | c -= b; c ^= rot(b, 8); b += a; \ | |
98 | a -= c; a ^= rot(c,16); c += b; \ | |
99 | b -= a; b ^= rot(a,19); a += c; \ | |
100 | c -= b; c ^= rot(b, 4); b += a; \ | |
101 | } | |
102 | ||
103 | /** | |
104 | * Final mixing of 3 32-bit values (a,b,c) into c | |
105 | * @param a 32-bit value | |
106 | * @param b 32-bit value | |
107 | * @param c 32-bit value | |
108 | * | |
109 | * Pairs of (a,b,c) values differing in only a few bits will usually produce | |
110 | * values of c that look totally different. This was tested for: | |
111 | * - pairs that differed by one bit, by two bits, in any combination of top | |
112 | * bits of (a,b,c), or in any combination of bottom bits of (a,b,c). | |
113 | * - "differ" is defined as +, -, ^, or ~^. For + and -, I transformed the | |
114 | * output delta to a Gray code (a^(a>>1)) so a string of 1's (as is commonly | |
115 | * produced by subtraction) look like a single 1-bit difference. | |
116 | * - the base values were pseudorandom, all zero but one bit set, or all zero | |
117 | * plus a counter that starts at zero. | |
118 | * | |
119 | * These constants passed: | |
120 | * 14 11 25 16 4 14 24 | |
121 | * 12 14 25 16 4 14 24 | |
122 | * and these came close: | |
123 | * 4 8 15 26 3 22 24 | |
124 | * 10 8 15 26 3 22 24 | |
125 | * 11 8 15 26 3 22 24 | |
126 | * | |
127 | */ | |
128 | #define final(a,b,c) \ | |
129 | { \ | |
130 | c ^= b; c -= rot(b,14); \ | |
131 | a ^= c; a -= rot(c,11); \ | |
132 | b ^= a; b -= rot(a,25); \ | |
133 | c ^= b; c -= rot(b,16); \ | |
134 | a ^= c; a -= rot(c,4); \ | |
135 | b ^= a; b -= rot(a,14); \ | |
136 | c ^= b; c -= rot(b,24); \ | |
137 | } | |
138 | ||
139 | /** | |
140 | * Hash an array of 32-bit values | |
141 | * @param k the key, an array of uint32_t values | |
142 | * @param length the number of array elements | |
143 | * @param initval the previous hash, or an arbitrary value | |
144 | * | |
145 | * This works on all machines. To be useful, it requires: | |
146 | * - that the key be an array of uint32_t's, and | |
147 | * - that the length be the number of uint32_t's in the key | |
148 | * | |
149 | * The function jhash_word() is identical to jhash_le() on little-endian | |
150 | * machines, and identical to jhash_be() on big-endian machines, except that | |
151 | * the length has to be measured in uint32_ts rather than in bytes. jhash_le() | |
152 | * is more complicated than jhash_word() only because jhash_le() has to dance | |
153 | * around fitting the key bytes into registers. | |
154 | * | |
155 | */ | |
156 | static uint32_t jhash_word(const uint32_t *k, size_t length, uint32_t initval) | |
157 | { | |
158 | uint32_t a, b, c; | |
159 | ||
160 | /* set up the internal state */ | |
161 | a = b = c = 0xdeadbeef + (((uint32_t)length) << 2) + initval; | |
162 | ||
163 | /* handle most of the key */ | |
164 | while (length > 3) { | |
165 | a += k[0]; | |
166 | b += k[1]; | |
167 | c += k[2]; | |
168 | mix(a, b, c); | |
169 | length -= 3; | |
170 | k += 3; | |
171 | } | |
172 | ||
173 | /* handle the last 3 uint32_t's */ | |
174 | switch(length) { | |
175 | case 3 : | |
176 | c += k[2]; | |
177 | case 2 : | |
178 | b += k[1]; | |
179 | case 1 : | |
180 | a += k[0]; | |
181 | final(a, b, c); | |
182 | case 0: | |
183 | /* nothing left to add */ | |
184 | break; | |
185 | } | |
186 | ||
187 | return c; | |
188 | } | |
189 | ||
190 | /** | |
191 | * Hash a variable-length key into a 32-bit value | |
192 | * @param key the key (the unaligned variable-length array of bytes) | |
193 | * @param length the length of the key, counting by bytes | |
194 | * @param initval can be any 4-byte value | |
195 | * | |
196 | * Returns a 32-bit value. Every bit of the key affects every bit of the | |
197 | * return value. Two keys differing by one or two bits will have totally | |
198 | * different hash values. | |
199 | * | |
200 | * The best hash table sizes are powers of 2. There is no need to do mod a | |
201 | * prime (mod is sooo slow!). If you need less than 32 bits, use a bitmask. | |
202 | * For example, if you need only 10 bits, do: | |
203 | * h = (h & hashmask(10)); | |
204 | * In which case, the hash table should have hashsize(10) elements. | |
205 | * | |
206 | * If you are hashing n strings (uint8_t **)k, do it like this: | |
207 | * for (i=0, h=0; i<n; ++i) h = jhash_le( k[i], len[i], h); | |
208 | * | |
209 | */ | |
210 | static uint32_t jhash_le(const void *key, size_t length, uint32_t initval) | |
211 | { | |
212 | uint32_t a, b, c; | |
213 | union { | |
214 | const void *ptr; | |
215 | size_t i; | |
216 | } u; /* needed for Mac Powerbook G4 */ | |
217 | ||
218 | /* set up the internal state */ | |
219 | a = b = c = 0xdeadbeef + ((uint32_t)length) + initval; | |
220 | ||
221 | u.ptr = key; | |
222 | if ((arch_def_native->endian == ARCH_ENDIAN_LITTLE) && | |
223 | ((u.i & 0x3) == 0)) { | |
224 | /* read 32-bit chunks */ | |
225 | const uint32_t *k = (const uint32_t *)key; | |
226 | ||
227 | while (length > 12) { | |
228 | a += k[0]; | |
229 | b += k[1]; | |
230 | c += k[2]; | |
231 | mix(a, b, c); | |
232 | length -= 12; | |
233 | k += 3; | |
234 | } | |
235 | ||
236 | /* "k[2]&0xffffff" actually reads beyond the end of the string, | |
237 | * but then masks off the part it's not allowed to read. | |
238 | * Because the string is aligned, the masked-off tail is in the | |
239 | * same word as the rest of the string. Every machine with | |
240 | * memory protection I've seen does it on word boundaries, so | |
241 | * is OK with this. But VALGRIND will still catch it and | |
242 | * complain. The masking trick does make the hash noticably | |
243 | * faster for short strings (like English words). */ | |
244 | #ifndef VALGRIND | |
245 | ||
246 | switch(length) { | |
247 | case 12: | |
248 | c += k[2]; | |
249 | b += k[1]; | |
250 | a += k[0]; | |
251 | break; | |
252 | case 11: | |
253 | c += k[2] & 0xffffff; | |
254 | b += k[1]; | |
255 | a += k[0]; | |
256 | break; | |
257 | case 10: | |
258 | c += k[2] & 0xffff; | |
259 | b += k[1]; | |
260 | a += k[0]; | |
261 | break; | |
262 | case 9 : | |
263 | c += k[2] & 0xff; | |
264 | b += k[1]; | |
265 | a += k[0]; | |
266 | break; | |
267 | case 8 : | |
268 | b += k[1]; | |
269 | a += k[0]; | |
270 | break; | |
271 | case 7 : | |
272 | b += k[1] & 0xffffff; | |
273 | a += k[0]; | |
274 | break; | |
275 | case 6 : | |
276 | b += k[1] & 0xffff; | |
277 | a += k[0]; | |
278 | break; | |
279 | case 5 : | |
280 | b += k[1] & 0xff; | |
281 | a += k[0]; | |
282 | break; | |
283 | case 4 : | |
284 | a += k[0]; | |
285 | break; | |
286 | case 3 : | |
287 | a += k[0] & 0xffffff; | |
288 | break; | |
289 | case 2 : | |
290 | a += k[0] & 0xffff; | |
291 | break; | |
292 | case 1 : | |
293 | a += k[0] & 0xff; | |
294 | break; | |
295 | case 0 : | |
296 | /* zero length strings require no mixing */ | |
297 | return c; | |
298 | } | |
299 | ||
300 | #else /* make valgrind happy */ | |
301 | ||
302 | k8 = (const uint8_t *)k; | |
303 | switch(length) { | |
304 | case 12: | |
305 | c += k[2]; | |
306 | b += k[1]; | |
307 | a += k[0]; | |
308 | break; | |
309 | case 11: | |
310 | c += ((uint32_t)k8[10]) << 16; | |
311 | case 10: | |
312 | c += ((uint32_t)k8[9]) << 8; | |
313 | case 9 : | |
314 | c += k8[8]; | |
315 | case 8 : | |
316 | b += k[1]; | |
317 | a += k[0]; | |
318 | break; | |
319 | case 7 : | |
320 | b += ((uint32_t)k8[6]) << 16; | |
321 | case 6 : | |
322 | b += ((uint32_t)k8[5]) << 8; | |
323 | case 5 : | |
324 | b += k8[4]; | |
325 | case 4 : | |
326 | a += k[0]; | |
327 | break; | |
328 | case 3 : | |
329 | a += ((uint32_t)k8[2]) << 16; | |
330 | case 2 : | |
331 | a += ((uint32_t)k8[1]) << 8; | |
332 | case 1 : | |
333 | a += k8[0]; | |
334 | break; | |
335 | case 0 : | |
336 | return c; | |
337 | } | |
338 | ||
339 | #endif /* !valgrind */ | |
340 | ||
341 | } else if ((arch_def_native->endian == ARCH_ENDIAN_LITTLE) && | |
342 | ((u.i & 0x1) == 0)) { | |
343 | /* read 16-bit chunks */ | |
344 | const uint16_t *k = (const uint16_t *)key; | |
345 | const uint8_t *k8; | |
346 | ||
347 | while (length > 12) { | |
348 | a += k[0] + (((uint32_t)k[1]) << 16); | |
349 | b += k[2] + (((uint32_t)k[3]) << 16); | |
350 | c += k[4] + (((uint32_t)k[5]) << 16); | |
351 | mix(a, b, c); | |
352 | length -= 12; | |
353 | k += 6; | |
354 | } | |
355 | ||
356 | k8 = (const uint8_t *)k; | |
357 | switch(length) { | |
358 | case 12: | |
359 | c += k[4] + (((uint32_t)k[5]) << 16); | |
360 | b += k[2] + (((uint32_t)k[3]) << 16); | |
361 | a += k[0] + (((uint32_t)k[1]) << 16); | |
362 | break; | |
363 | case 11: | |
364 | c += ((uint32_t)k8[10]) << 16; | |
365 | case 10: | |
366 | c += k[4]; | |
367 | b += k[2] + (((uint32_t)k[3]) << 16); | |
368 | a += k[0] + (((uint32_t)k[1]) << 16); | |
369 | break; | |
370 | case 9 : | |
371 | c += k8[8]; | |
372 | case 8 : | |
373 | b += k[2] + (((uint32_t)k[3]) << 16); | |
374 | a += k[0] + (((uint32_t)k[1]) << 16); | |
375 | break; | |
376 | case 7 : | |
377 | b += ((uint32_t)k8[6]) << 16; | |
378 | case 6 : | |
379 | b += k[2]; | |
380 | a += k[0] + (((uint32_t)k[1]) << 16); | |
381 | break; | |
382 | case 5 : | |
383 | b += k8[4]; | |
384 | case 4 : | |
385 | a += k[0] + (((uint32_t)k[1]) << 16); | |
386 | break; | |
387 | case 3 : | |
388 | a += ((uint32_t)k8[2]) << 16; | |
389 | case 2 : | |
390 | a += k[0]; | |
391 | break; | |
392 | case 1 : | |
393 | a += k8[0]; | |
394 | break; | |
395 | case 0 : | |
396 | /* zero length requires no mixing */ | |
397 | return c; | |
398 | } | |
399 | ||
400 | } else { | |
401 | /* need to read the key one byte at a time */ | |
402 | const uint8_t *k = (const uint8_t *)key; | |
403 | ||
404 | while (length > 12) { | |
405 | a += k[0]; | |
406 | a += ((uint32_t)k[1]) << 8; | |
407 | a += ((uint32_t)k[2]) << 16; | |
408 | a += ((uint32_t)k[3]) << 24; | |
409 | b += k[4]; | |
410 | b += ((uint32_t)k[5]) << 8; | |
411 | b += ((uint32_t)k[6]) << 16; | |
412 | b += ((uint32_t)k[7]) << 24; | |
413 | c += k[8]; | |
414 | c += ((uint32_t)k[9]) << 8; | |
415 | c += ((uint32_t)k[10]) << 16; | |
416 | c += ((uint32_t)k[11]) << 24; | |
417 | mix(a, b, c); | |
418 | length -= 12; | |
419 | k += 12; | |
420 | } | |
421 | ||
422 | switch(length) { | |
423 | case 12: | |
424 | c += ((uint32_t)k[11]) << 24; | |
425 | case 11: | |
426 | c += ((uint32_t)k[10]) << 16; | |
427 | case 10: | |
428 | c += ((uint32_t)k[9]) << 8; | |
429 | case 9 : | |
430 | c += k[8]; | |
431 | case 8 : | |
432 | b += ((uint32_t)k[7]) << 24; | |
433 | case 7 : | |
434 | b += ((uint32_t)k[6]) << 16; | |
435 | case 6 : | |
436 | b += ((uint32_t)k[5]) << 8; | |
437 | case 5 : | |
438 | b += k[4]; | |
439 | case 4 : | |
440 | a += ((uint32_t)k[3]) << 24; | |
441 | case 3 : | |
442 | a += ((uint32_t)k[2]) << 16; | |
443 | case 2 : | |
444 | a += ((uint32_t)k[1]) << 8; | |
445 | case 1 : | |
446 | a += k[0]; | |
447 | break; | |
448 | case 0 : | |
449 | return c; | |
450 | } | |
451 | } | |
452 | ||
453 | final(a, b, c); | |
454 | return c; | |
455 | } | |
456 | ||
457 | /** | |
458 | * Hash a variable-length key into a 32-bit value | |
459 | * @param key the key (the unaligned variable-length array of bytes) | |
460 | * @param length the length of the key, counting by bytes | |
461 | * @param initval can be any 4-byte value | |
462 | * | |
463 | * This is the same as jhash_word() on big-endian machines. It is different | |
464 | * from jhash_le() on all machines. jhash_be() takes advantage of big-endian | |
465 | * byte ordering. | |
466 | * | |
467 | */ | |
468 | static uint32_t jhash_be( const void *key, size_t length, uint32_t initval) | |
469 | { | |
470 | uint32_t a, b, c; | |
471 | union { | |
472 | const void *ptr; | |
473 | size_t i; | |
474 | } u; /* to cast key to (size_t) happily */ | |
475 | ||
476 | /* set up the internal state */ | |
477 | a = b = c = 0xdeadbeef + ((uint32_t)length) + initval; | |
478 | ||
479 | u.ptr = key; | |
480 | if ((arch_def_native->endian == ARCH_ENDIAN_BIG) && | |
481 | ((u.i & 0x3) == 0)) { | |
482 | /* read 32-bit chunks */ | |
483 | const uint32_t *k = (const uint32_t *)key; | |
484 | ||
485 | while (length > 12) { | |
486 | a += k[0]; | |
487 | b += k[1]; | |
488 | c += k[2]; | |
489 | mix(a, b, c); | |
490 | length -= 12; | |
491 | k += 3; | |
492 | } | |
493 | ||
494 | /* "k[2]<<8" actually reads beyond the end of the string, but | |
495 | * then shifts out the part it's not allowed to read. Because | |
496 | * the string is aligned, the illegal read is in the same word | |
497 | * as the rest of the string. Every machine with memory | |
498 | * protection I've seen does it on word boundaries, so is OK | |
499 | * with this. But VALGRIND will still catch it and complain. | |
500 | * The masking trick does make the hash noticably faster for | |
501 | * short strings (like English words). */ | |
502 | #ifndef VALGRIND | |
503 | ||
504 | switch(length) { | |
505 | case 12: | |
506 | c += k[2]; | |
507 | b += k[1]; | |
508 | a += k[0]; | |
509 | break; | |
510 | case 11: | |
511 | c += k[2] & 0xffffff00; | |
512 | b += k[1]; | |
513 | a += k[0]; | |
514 | break; | |
515 | case 10: | |
516 | c += k[2] & 0xffff0000; | |
517 | b += k[1]; | |
518 | a += k[0]; | |
519 | break; | |
520 | case 9 : | |
521 | c += k[2] & 0xff000000; | |
522 | b += k[1]; | |
523 | a += k[0]; | |
524 | break; | |
525 | case 8 : | |
526 | b += k[1]; | |
527 | a += k[0]; | |
528 | break; | |
529 | case 7 : | |
530 | b += k[1] & 0xffffff00; | |
531 | a += k[0]; | |
532 | break; | |
533 | case 6 : | |
534 | b += k[1] & 0xffff0000; | |
535 | a += k[0]; | |
536 | break; | |
537 | case 5 : | |
538 | b += k[1] & 0xff000000; | |
539 | a += k[0]; | |
540 | break; | |
541 | case 4 : | |
542 | a += k[0]; | |
543 | break; | |
544 | case 3 : | |
545 | a += k[0] & 0xffffff00; | |
546 | break; | |
547 | case 2 : | |
548 | a += k[0] & 0xffff0000; | |
549 | break; | |
550 | case 1 : | |
551 | a += k[0] & 0xff000000; | |
552 | break; | |
553 | case 0 : | |
554 | /* zero length strings require no mixing */ | |
555 | return c; | |
556 | } | |
557 | ||
558 | #else /* make valgrind happy */ | |
559 | ||
560 | k8 = (const uint8_t *)k; | |
561 | switch(length) { | |
562 | case 12: | |
563 | c += k[2]; | |
564 | b += k[1]; | |
565 | a += k[0]; | |
566 | break; | |
567 | case 11: | |
568 | c += ((uint32_t)k8[10]) << 8; | |
569 | case 10: | |
570 | c += ((uint32_t)k8[9]) << 16; | |
571 | case 9 : | |
572 | c += ((uint32_t)k8[8]) << 24; | |
573 | case 8 : | |
574 | b += k[1]; | |
575 | a += k[0]; | |
576 | break; | |
577 | case 7 : | |
578 | b += ((uint32_t)k8[6]) << 8; | |
579 | case 6 : | |
580 | b += ((uint32_t)k8[5]) << 16; | |
581 | case 5 : | |
582 | b += ((uint32_t)k8[4]) << 24; | |
583 | case 4 : | |
584 | a += k[0]; | |
585 | break; | |
586 | case 3 : | |
587 | a += ((uint32_t)k8[2]) << 8; | |
588 | case 2 : | |
589 | a += ((uint32_t)k8[1]) << 16; | |
590 | case 1 : | |
591 | a += ((uint32_t)k8[0]) << 24; | |
592 | break; | |
593 | case 0 : | |
594 | return c; | |
595 | } | |
596 | ||
597 | #endif /* !VALGRIND */ | |
598 | ||
599 | } else { | |
600 | /* need to read the key one byte at a time */ | |
601 | const uint8_t *k = (const uint8_t *)key; | |
602 | ||
603 | while (length > 12) { | |
604 | a += ((uint32_t)k[0]) << 24; | |
605 | a += ((uint32_t)k[1]) << 16; | |
606 | a += ((uint32_t)k[2]) << 8; | |
607 | a += ((uint32_t)k[3]); | |
608 | b += ((uint32_t)k[4]) << 24; | |
609 | b += ((uint32_t)k[5]) << 16; | |
610 | b += ((uint32_t)k[6]) << 8; | |
611 | b += ((uint32_t)k[7]); | |
612 | c += ((uint32_t)k[8]) << 24; | |
613 | c += ((uint32_t)k[9]) << 16; | |
614 | c += ((uint32_t)k[10]) << 8; | |
615 | c += ((uint32_t)k[11]); | |
616 | mix(a, b, c); | |
617 | length -= 12; | |
618 | k += 12; | |
619 | } | |
620 | ||
621 | switch(length) { | |
622 | case 12: | |
623 | c += k[11]; | |
624 | case 11: | |
625 | c += ((uint32_t)k[10]) << 8; | |
626 | case 10: | |
627 | c += ((uint32_t)k[9]) << 16; | |
628 | case 9 : | |
629 | c += ((uint32_t)k[8]) << 24; | |
630 | case 8 : | |
631 | b += k[7]; | |
632 | case 7 : | |
633 | b += ((uint32_t)k[6]) << 8; | |
634 | case 6 : | |
635 | b += ((uint32_t)k[5]) << 16; | |
636 | case 5 : | |
637 | b += ((uint32_t)k[4]) << 24; | |
638 | case 4 : | |
639 | a += k[3]; | |
640 | case 3 : | |
641 | a += ((uint32_t)k[2]) << 8; | |
642 | case 2 : | |
643 | a += ((uint32_t)k[1]) << 16; | |
644 | case 1 : | |
645 | a += ((uint32_t)k[0]) << 24; | |
646 | break; | |
647 | case 0 : | |
648 | return c; | |
649 | } | |
650 | } | |
651 | ||
652 | final(a, b, c); | |
653 | return c; | |
654 | } | |
655 | ||
656 | /** | |
657 | * Hash a variable-length key into a 32-bit value | |
658 | * @param key the key (the unaligned variable-length array of bytes) | |
659 | * @param length the length of the key, counting by bytes | |
660 | * @param initval can be any 4-byte value | |
661 | * | |
662 | * A small wrapper function that selects the proper hash function based on the | |
663 | * native machine's byte-ordering. | |
664 | * | |
665 | */ | |
666 | uint32_t jhash(const void *key, size_t length, uint32_t initval) | |
667 | { | |
668 | if (length % sizeof(uint32_t) == 0) | |
669 | return jhash_word(key, (length / sizeof(uint32_t)), initval); | |
670 | else if (arch_def_native->endian == ARCH_ENDIAN_BIG) | |
671 | return jhash_be(key, length, initval); | |
672 | else | |
673 | return jhash_le(key, length, initval); | |
674 | } |