Annotation of embedaddon/coova-chilli/src/lookup3.c, revision 1.1.1.1
1.1 misho 1: /*
2: -------------------------------------------------------------------------------
3: lookup3.c, by Bob Jenkins, May 2006, Public Domain.
4:
5: These are functions for producing 32-bit hashes for hash table lookup.
6: hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
7: are externally useful functions. Routines to test the hash are included
8: if SELF_TEST is defined. You can use this free for any purpose. It's in
9: the public domain. It has no warranty.
10:
11: You probably want to use hashlittle(). hashlittle() and hashbig()
12: hash byte arrays. hashlittle() is is faster than hashbig() on
13: little-endian machines. Intel and AMD are little-endian machines.
14: On second thought, you probably want hashlittle2(), which is identical to
15: hashlittle() except it returns two 32-bit hashes for the price of one.
16: You could implement hashbig2() if you wanted but I haven't bothered here.
17:
18: If you want to find a hash of, say, exactly 7 integers, do
19: a = i1; b = i2; c = i3;
20: mix(a,b,c);
21: a += i4; b += i5; c += i6;
22: mix(a,b,c);
23: a += i7;
24: final(a,b,c);
25: then use c as the hash value. If you have a variable length array of
26: 4-byte integers to hash, use hashword(). If you have a byte array (like
27: a character string), use hashlittle(). If you have several byte arrays, or
28: a mix of things, see the comments above hashlittle().
29:
30: Why is this so big? I read 12 bytes at a time into 3 4-byte integers,
31: then mix those integers. This is fast (you can do a lot more thorough
32: mixing with 12*3 instructions on 3 integers than you can with 3 instructions
33: on 1 byte), but shoehorning those bytes into integers efficiently is messy.
34: -------------------------------------------------------------------------------
35: #define SELF_TEST 1
36: */
37:
38: #include <stdio.h> /* defines printf for tests */
39: #include <time.h> /* defines time_t for timings in the test */
40: #include <stdint.h> /* defines uint32_t etc */
41: #include <sys/param.h> /* attempt to define endianness */
42: #ifdef linux
43: # include <endian.h> /* attempt to define endianness */
44: #endif
45:
46: /*
47: * My best guess at if you are big-endian or little-endian. This may
48: * need adjustment.
49: */
50: #if (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && \
51: __BYTE_ORDER == __LITTLE_ENDIAN) || \
52: (defined(i386) || defined(__i386__) || defined(__i486__) || \
53: defined(__i586__) || defined(__i686__) || defined(vax) || defined(MIPSEL))
54: # define HASH_LITTLE_ENDIAN 1
55: # define HASH_BIG_ENDIAN 0
56: #elif (defined(__BYTE_ORDER) && defined(__BIG_ENDIAN) && \
57: __BYTE_ORDER == __BIG_ENDIAN) || \
58: (defined(sparc) || defined(POWERPC) || defined(mc68000) || defined(sel))
59: # define HASH_LITTLE_ENDIAN 0
60: # define HASH_BIG_ENDIAN 1
61: #else
62: # define HASH_LITTLE_ENDIAN 0
63: # define HASH_BIG_ENDIAN 0
64: #endif
65:
66: #define hashsize(n) ((uint32_t)1<<(n))
67: #define hashmask(n) (hashsize(n)-1)
68: #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
69:
70: /*
71: -------------------------------------------------------------------------------
72: mix -- mix 3 32-bit values reversibly.
73:
74: This is reversible, so any information in (a,b,c) before mix() is
75: still in (a,b,c) after mix().
76:
77: If four pairs of (a,b,c) inputs are run through mix(), or through
78: mix() in reverse, there are at least 32 bits of the output that
79: are sometimes the same for one pair and different for another pair.
80: This was tested for:
81: * pairs that differed by one bit, by two bits, in any combination
82: of top bits of (a,b,c), or in any combination of bottom bits of
83: (a,b,c).
84: * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
85: the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
86: is commonly produced by subtraction) look like a single 1-bit
87: difference.
88: * the base values were pseudorandom, all zero but one bit set, or
89: all zero plus a counter that starts at zero.
90:
91: Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
92: satisfy this are
93: 4 6 8 16 19 4
94: 9 15 3 18 27 15
95: 14 9 3 7 17 3
96: Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
97: for "differ" defined as + with a one-bit base and a two-bit delta. I
98: used http://burtleburtle.net/bob/hash/avalanche.html to choose
99: the operations, constants, and arrangements of the variables.
100:
101: This does not achieve avalanche. There are input bits of (a,b,c)
102: that fail to affect some output bits of (a,b,c), especially of a. The
103: most thoroughly mixed value is c, but it doesn't really even achieve
104: avalanche in c.
105:
106: This allows some parallelism. Read-after-writes are good at doubling
107: the number of bits affected, so the goal of mixing pulls in the opposite
108: direction as the goal of parallelism. I did what I could. Rotates
109: seem to cost as much as shifts on every machine I could lay my hands
110: on, and rotates are much kinder to the top and bottom bits, so I used
111: rotates.
112: -------------------------------------------------------------------------------
113: */
114: #define mix(a,b,c) \
115: { \
116: a -= c; a ^= rot(c, 4); c += b; \
117: b -= a; b ^= rot(a, 6); a += c; \
118: c -= b; c ^= rot(b, 8); b += a; \
119: a -= c; a ^= rot(c,16); c += b; \
120: b -= a; b ^= rot(a,19); a += c; \
121: c -= b; c ^= rot(b, 4); b += a; \
122: }
123:
124: /*
125: -------------------------------------------------------------------------------
126: final -- final mixing of 3 32-bit values (a,b,c) into c
127:
128: Pairs of (a,b,c) values differing in only a few bits will usually
129: produce values of c that look totally different. This was tested for
130: * pairs that differed by one bit, by two bits, in any combination
131: of top bits of (a,b,c), or in any combination of bottom bits of
132: (a,b,c).
133: * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
134: the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
135: is commonly produced by subtraction) look like a single 1-bit
136: difference.
137: * the base values were pseudorandom, all zero but one bit set, or
138: all zero plus a counter that starts at zero.
139:
140: These constants passed:
141: 14 11 25 16 4 14 24
142: 12 14 25 16 4 14 24
143: and these came close:
144: 4 8 15 26 3 22 24
145: 10 8 15 26 3 22 24
146: 11 8 15 26 3 22 24
147: -------------------------------------------------------------------------------
148: */
149: #define final(a,b,c) \
150: { \
151: c ^= b; c -= rot(b,14); \
152: a ^= c; a -= rot(c,11); \
153: b ^= a; b -= rot(a,25); \
154: c ^= b; c -= rot(b,16); \
155: a ^= c; a -= rot(c,4); \
156: b ^= a; b -= rot(a,14); \
157: c ^= b; c -= rot(b,24); \
158: }
159:
160: /*
161: --------------------------------------------------------------------
162: This works on all machines. To be useful, it requires
163: -- that the key be an array of uint32_t's, and
164: -- that the length be the number of uint32_t's in the key
165:
166: The function hashword() is identical to hashlittle() on little-endian
167: machines, and identical to hashbig() on big-endian machines,
168: except that the length has to be measured in uint32_ts rather than in
169: bytes. hashlittle() is more complicated than hashword() only because
170: hashlittle() has to dance around fitting the key bytes into registers.
171: --------------------------------------------------------------------
172: */
173: uint32_t hashword(
174: const uint32_t *k, /* the key, an array of uint32_t values */
175: size_t length, /* the length of the key, in uint32_ts */
176: uint32_t initval) /* the previous hash, or an arbitrary value */
177: {
178: uint32_t a,b,c;
179:
180: /* Set up the internal state */
181: a = b = c = 0xdeadbeef + (((uint32_t)length)<<2) + initval;
182:
183: /*------------------------------------------------- handle most of the key */
184: while (length > 3)
185: {
186: a += k[0];
187: b += k[1];
188: c += k[2];
189: mix(a,b,c);
190: length -= 3;
191: k += 3;
192: }
193:
194: /*------------------------------------------- handle the last 3 uint32_t's */
195: switch(length) /* all the case statements fall through */
196: {
197: case 3 : c+=k[2];
198: case 2 : b+=k[1];
199: case 1 : a+=k[0];
200: final(a,b,c);
201: case 0: /* case 0: nothing left to add */
202: break;
203: }
204: /*------------------------------------------------------ report the result */
205: return c;
206: }
207:
208:
209: /*
210: --------------------------------------------------------------------
211: hashword2() -- same as hashword(), but take two seeds and return two
212: 32-bit values. pc and pb must both be nonnull, and *pc and *pb must
213: both be initialized with seeds. If you pass in (*pb)==0, the output
214: (*pc) will be the same as the return value from hashword().
215: --------------------------------------------------------------------
216: */
217: void hashword2 (
218: const uint32_t *k, /* the key, an array of uint32_t values */
219: size_t length, /* the length of the key, in uint32_ts */
220: uint32_t *pc, /* IN: seed OUT: primary hash value */
221: uint32_t *pb) /* IN: more seed OUT: secondary hash value */
222: {
223: uint32_t a,b,c;
224:
225: /* Set up the internal state */
226: a = b = c = 0xdeadbeef + ((uint32_t)(length<<2)) + *pc;
227: c += *pb;
228:
229: /*------------------------------------------------- handle most of the key */
230: while (length > 3)
231: {
232: a += k[0];
233: b += k[1];
234: c += k[2];
235: mix(a,b,c);
236: length -= 3;
237: k += 3;
238: }
239:
240: /*------------------------------------------- handle the last 3 uint32_t's */
241: switch(length) /* all the case statements fall through */
242: {
243: case 3 : c+=k[2];
244: case 2 : b+=k[1];
245: case 1 : a+=k[0];
246: final(a,b,c);
247: case 0: /* case 0: nothing left to add */
248: break;
249: }
250: /*------------------------------------------------------ report the result */
251: *pc=c; *pb=b;
252: }
253:
254:
255: /*
256: -------------------------------------------------------------------------------
257: hashlittle() -- hash a variable-length key into a 32-bit value
258: k : the key (the unaligned variable-length array of bytes)
259: length : the length of the key, counting by bytes
260: initval : can be any 4-byte value
261: Returns a 32-bit value. Every bit of the key affects every bit of
262: the return value. Two keys differing by one or two bits will have
263: totally different hash values.
264:
265: The best hash table sizes are powers of 2. There is no need to do
266: mod a prime (mod is sooo slow!). If you need less than 32 bits,
267: use a bitmask. For example, if you need only 10 bits, do
268: h = (h & hashmask(10));
269: In which case, the hash table should have hashsize(10) elements.
270:
271: If you are hashing n strings (uint8_t **)k, do it like this:
272: for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);
273:
274: By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this
275: code any way you wish, private, educational, or commercial. It's free.
276:
277: Use for hash table lookup, or anything where one collision in 2^^32 is
278: acceptable. Do NOT use for cryptographic purposes.
279: -------------------------------------------------------------------------------
280: */
281:
282: uint32_t hashlittle( const void *key, size_t length, uint32_t initval)
283: {
284: uint32_t a,b,c; /* internal state */
285: union { const void *ptr; size_t i; } u; /* needed for Mac Powerbook G4 */
286:
287: /* Set up the internal state */
288: a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
289:
290: u.ptr = key;
291: if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
292: const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
293: /*const uint8_t *k8;*/
294:
295: /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
296: while (length > 12)
297: {
298: a += k[0];
299: b += k[1];
300: c += k[2];
301: mix(a,b,c);
302: length -= 12;
303: k += 3;
304: }
305:
306: /*----------------------------- handle the last (probably partial) block */
307: /*
308: * "k[2]&0xffffff" actually reads beyond the end of the string, but
309: * then masks off the part it's not allowed to read. Because the
310: * string is aligned, the masked-off tail is in the same word as the
311: * rest of the string. Every machine with memory protection I've seen
312: * does it on word boundaries, so is OK with this. But VALGRIND will
313: * still catch it and complain. The masking trick does make the hash
314: * noticably faster for short strings (like English words).
315: */
316: #ifndef VALGRIND
317:
318: switch(length)
319: {
320: case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
321: case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
322: case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
323: case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
324: case 8 : b+=k[1]; a+=k[0]; break;
325: case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
326: case 6 : b+=k[1]&0xffff; a+=k[0]; break;
327: case 5 : b+=k[1]&0xff; a+=k[0]; break;
328: case 4 : a+=k[0]; break;
329: case 3 : a+=k[0]&0xffffff; break;
330: case 2 : a+=k[0]&0xffff; break;
331: case 1 : a+=k[0]&0xff; break;
332: case 0 : return c; /* zero length strings require no mixing */
333: }
334:
335: #else /* make valgrind happy */
336:
337: k8 = (const uint8_t *)k;
338: switch(length)
339: {
340: case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
341: case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
342: case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
343: case 9 : c+=k8[8]; /* fall through */
344: case 8 : b+=k[1]; a+=k[0]; break;
345: case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
346: case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
347: case 5 : b+=k8[4]; /* fall through */
348: case 4 : a+=k[0]; break;
349: case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
350: case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
351: case 1 : a+=k8[0]; break;
352: case 0 : return c;
353: }
354:
355: #endif /* !valgrind */
356:
357: } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
358: const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */
359: const uint8_t *k8;
360:
361: /*--------------- all but last block: aligned reads and different mixing */
362: while (length > 12)
363: {
364: a += k[0] + (((uint32_t)k[1])<<16);
365: b += k[2] + (((uint32_t)k[3])<<16);
366: c += k[4] + (((uint32_t)k[5])<<16);
367: mix(a,b,c);
368: length -= 12;
369: k += 6;
370: }
371:
372: /*----------------------------- handle the last (probably partial) block */
373: k8 = (const uint8_t *)k;
374: switch(length)
375: {
376: case 12: c+=k[4]+(((uint32_t)k[5])<<16);
377: b+=k[2]+(((uint32_t)k[3])<<16);
378: a+=k[0]+(((uint32_t)k[1])<<16);
379: break;
380: case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
381: case 10: c+=k[4];
382: b+=k[2]+(((uint32_t)k[3])<<16);
383: a+=k[0]+(((uint32_t)k[1])<<16);
384: break;
385: case 9 : c+=k8[8]; /* fall through */
386: case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
387: a+=k[0]+(((uint32_t)k[1])<<16);
388: break;
389: case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
390: case 6 : b+=k[2];
391: a+=k[0]+(((uint32_t)k[1])<<16);
392: break;
393: case 5 : b+=k8[4]; /* fall through */
394: case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
395: break;
396: case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
397: case 2 : a+=k[0];
398: break;
399: case 1 : a+=k8[0];
400: break;
401: case 0 : return c; /* zero length requires no mixing */
402: }
403:
404: } else { /* need to read the key one byte at a time */
405: const uint8_t *k = (const uint8_t *)key;
406:
407: /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
408: while (length > 12)
409: {
410: a += k[0];
411: a += ((uint32_t)k[1])<<8;
412: a += ((uint32_t)k[2])<<16;
413: a += ((uint32_t)k[3])<<24;
414: b += k[4];
415: b += ((uint32_t)k[5])<<8;
416: b += ((uint32_t)k[6])<<16;
417: b += ((uint32_t)k[7])<<24;
418: c += k[8];
419: c += ((uint32_t)k[9])<<8;
420: c += ((uint32_t)k[10])<<16;
421: c += ((uint32_t)k[11])<<24;
422: mix(a,b,c);
423: length -= 12;
424: k += 12;
425: }
426:
427: /*-------------------------------- last block: affect all 32 bits of (c) */
428: switch(length) /* all the case statements fall through */
429: {
430: case 12: c+=((uint32_t)k[11])<<24;
431: case 11: c+=((uint32_t)k[10])<<16;
432: case 10: c+=((uint32_t)k[9])<<8;
433: case 9 : c+=k[8];
434: case 8 : b+=((uint32_t)k[7])<<24;
435: case 7 : b+=((uint32_t)k[6])<<16;
436: case 6 : b+=((uint32_t)k[5])<<8;
437: case 5 : b+=k[4];
438: case 4 : a+=((uint32_t)k[3])<<24;
439: case 3 : a+=((uint32_t)k[2])<<16;
440: case 2 : a+=((uint32_t)k[1])<<8;
441: case 1 : a+=k[0];
442: break;
443: case 0 : return c;
444: }
445: }
446:
447: final(a,b,c);
448: return c;
449: }
450:
451:
452: /*
453: * hashlittle2: return 2 32-bit hash values
454: *
455: * This is identical to hashlittle(), except it returns two 32-bit hash
456: * values instead of just one. This is good enough for hash table
457: * lookup with 2^^64 buckets, or if you want a second hash if you're not
458: * happy with the first, or if you want a probably-unique 64-bit ID for
459: * the key. *pc is better mixed than *pb, so use *pc first. If you want
460: * a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
461: */
462: void hashlittle2(
463: const void *key, /* the key to hash */
464: size_t length, /* length of the key */
465: uint32_t *pc, /* IN: primary initval, OUT: primary hash */
466: uint32_t *pb) /* IN: secondary initval, OUT: secondary hash */
467: {
468: uint32_t a,b,c; /* internal state */
469: union { const void *ptr; size_t i; } u; /* needed for Mac Powerbook G4 */
470:
471: /* Set up the internal state */
472: a = b = c = 0xdeadbeef + ((uint32_t)length) + *pc;
473: c += *pb;
474:
475: u.ptr = key;
476: if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
477: const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
478: /*const uint8_t *k8;*/
479:
480: /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
481: while (length > 12)
482: {
483: a += k[0];
484: b += k[1];
485: c += k[2];
486: mix(a,b,c);
487: length -= 12;
488: k += 3;
489: }
490:
491: /*----------------------------- handle the last (probably partial) block */
492: /*
493: * "k[2]&0xffffff" actually reads beyond the end of the string, but
494: * then masks off the part it's not allowed to read. Because the
495: * string is aligned, the masked-off tail is in the same word as the
496: * rest of the string. Every machine with memory protection I've seen
497: * does it on word boundaries, so is OK with this. But VALGRIND will
498: * still catch it and complain. The masking trick does make the hash
499: * noticably faster for short strings (like English words).
500: */
501: #ifndef VALGRIND
502:
503: switch(length)
504: {
505: case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
506: case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
507: case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
508: case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
509: case 8 : b+=k[1]; a+=k[0]; break;
510: case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
511: case 6 : b+=k[1]&0xffff; a+=k[0]; break;
512: case 5 : b+=k[1]&0xff; a+=k[0]; break;
513: case 4 : a+=k[0]; break;
514: case 3 : a+=k[0]&0xffffff; break;
515: case 2 : a+=k[0]&0xffff; break;
516: case 1 : a+=k[0]&0xff; break;
517: case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
518: }
519:
520: #else /* make valgrind happy */
521:
522: k8 = (const uint8_t *)k;
523: switch(length)
524: {
525: case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
526: case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
527: case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
528: case 9 : c+=k8[8]; /* fall through */
529: case 8 : b+=k[1]; a+=k[0]; break;
530: case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
531: case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
532: case 5 : b+=k8[4]; /* fall through */
533: case 4 : a+=k[0]; break;
534: case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
535: case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
536: case 1 : a+=k8[0]; break;
537: case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
538: }
539:
540: #endif /* !valgrind */
541:
542: } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
543: const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */
544: const uint8_t *k8;
545:
546: /*--------------- all but last block: aligned reads and different mixing */
547: while (length > 12)
548: {
549: a += k[0] + (((uint32_t)k[1])<<16);
550: b += k[2] + (((uint32_t)k[3])<<16);
551: c += k[4] + (((uint32_t)k[5])<<16);
552: mix(a,b,c);
553: length -= 12;
554: k += 6;
555: }
556:
557: /*----------------------------- handle the last (probably partial) block */
558: k8 = (const uint8_t *)k;
559: switch(length)
560: {
561: case 12: c+=k[4]+(((uint32_t)k[5])<<16);
562: b+=k[2]+(((uint32_t)k[3])<<16);
563: a+=k[0]+(((uint32_t)k[1])<<16);
564: break;
565: case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
566: case 10: c+=k[4];
567: b+=k[2]+(((uint32_t)k[3])<<16);
568: a+=k[0]+(((uint32_t)k[1])<<16);
569: break;
570: case 9 : c+=k8[8]; /* fall through */
571: case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
572: a+=k[0]+(((uint32_t)k[1])<<16);
573: break;
574: case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
575: case 6 : b+=k[2];
576: a+=k[0]+(((uint32_t)k[1])<<16);
577: break;
578: case 5 : b+=k8[4]; /* fall through */
579: case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
580: break;
581: case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
582: case 2 : a+=k[0];
583: break;
584: case 1 : a+=k8[0];
585: break;
586: case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
587: }
588:
589: } else { /* need to read the key one byte at a time */
590: const uint8_t *k = (const uint8_t *)key;
591:
592: /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
593: while (length > 12)
594: {
595: a += k[0];
596: a += ((uint32_t)k[1])<<8;
597: a += ((uint32_t)k[2])<<16;
598: a += ((uint32_t)k[3])<<24;
599: b += k[4];
600: b += ((uint32_t)k[5])<<8;
601: b += ((uint32_t)k[6])<<16;
602: b += ((uint32_t)k[7])<<24;
603: c += k[8];
604: c += ((uint32_t)k[9])<<8;
605: c += ((uint32_t)k[10])<<16;
606: c += ((uint32_t)k[11])<<24;
607: mix(a,b,c);
608: length -= 12;
609: k += 12;
610: }
611:
612: /*-------------------------------- last block: affect all 32 bits of (c) */
613: switch(length) /* all the case statements fall through */
614: {
615: case 12: c+=((uint32_t)k[11])<<24;
616: case 11: c+=((uint32_t)k[10])<<16;
617: case 10: c+=((uint32_t)k[9])<<8;
618: case 9 : c+=k[8];
619: case 8 : b+=((uint32_t)k[7])<<24;
620: case 7 : b+=((uint32_t)k[6])<<16;
621: case 6 : b+=((uint32_t)k[5])<<8;
622: case 5 : b+=k[4];
623: case 4 : a+=((uint32_t)k[3])<<24;
624: case 3 : a+=((uint32_t)k[2])<<16;
625: case 2 : a+=((uint32_t)k[1])<<8;
626: case 1 : a+=k[0];
627: break;
628: case 0 : *pc=c; *pb=b; return; /* zero length strings require no mixing */
629: }
630: }
631:
632: final(a,b,c);
633: *pc=c; *pb=b;
634: }
635:
636:
637:
638: /*
639: * hashbig():
640: * This is the same as hashword() on big-endian machines. It is different
641: * from hashlittle() on all machines. hashbig() takes advantage of
642: * big-endian byte ordering.
643: */
644: uint32_t hashbig( const void *key, size_t length, uint32_t initval)
645: {
646: uint32_t a,b,c;
647: union { const void *ptr; size_t i; } u; /* to cast key to (size_t) happily */
648:
649: /* Set up the internal state */
650: a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
651:
652: u.ptr = key;
653: if (HASH_BIG_ENDIAN && ((u.i & 0x3) == 0)) {
654: const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
655: /*const uint8_t *k8;*/
656:
657: /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
658: while (length > 12)
659: {
660: a += k[0];
661: b += k[1];
662: c += k[2];
663: mix(a,b,c);
664: length -= 12;
665: k += 3;
666: }
667:
668: /*----------------------------- handle the last (probably partial) block */
669: /*
670: * "k[2]<<8" actually reads beyond the end of the string, but
671: * then shifts out the part it's not allowed to read. Because the
672: * string is aligned, the illegal read is in the same word as the
673: * rest of the string. Every machine with memory protection I've seen
674: * does it on word boundaries, so is OK with this. But VALGRIND will
675: * still catch it and complain. The masking trick does make the hash
676: * noticably faster for short strings (like English words).
677: */
678: #ifndef VALGRIND
679:
680: switch(length)
681: {
682: case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
683: case 11: c+=k[2]&0xffffff00; b+=k[1]; a+=k[0]; break;
684: case 10: c+=k[2]&0xffff0000; b+=k[1]; a+=k[0]; break;
685: case 9 : c+=k[2]&0xff000000; b+=k[1]; a+=k[0]; break;
686: case 8 : b+=k[1]; a+=k[0]; break;
687: case 7 : b+=k[1]&0xffffff00; a+=k[0]; break;
688: case 6 : b+=k[1]&0xffff0000; a+=k[0]; break;
689: case 5 : b+=k[1]&0xff000000; a+=k[0]; break;
690: case 4 : a+=k[0]; break;
691: case 3 : a+=k[0]&0xffffff00; break;
692: case 2 : a+=k[0]&0xffff0000; break;
693: case 1 : a+=k[0]&0xff000000; break;
694: case 0 : return c; /* zero length strings require no mixing */
695: }
696:
697: #else /* make valgrind happy */
698:
699: k8 = (const uint8_t *)k;
700: switch(length) /* all the case statements fall through */
701: {
702: case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
703: case 11: c+=((uint32_t)k8[10])<<8; /* fall through */
704: case 10: c+=((uint32_t)k8[9])<<16; /* fall through */
705: case 9 : c+=((uint32_t)k8[8])<<24; /* fall through */
706: case 8 : b+=k[1]; a+=k[0]; break;
707: case 7 : b+=((uint32_t)k8[6])<<8; /* fall through */
708: case 6 : b+=((uint32_t)k8[5])<<16; /* fall through */
709: case 5 : b+=((uint32_t)k8[4])<<24; /* fall through */
710: case 4 : a+=k[0]; break;
711: case 3 : a+=((uint32_t)k8[2])<<8; /* fall through */
712: case 2 : a+=((uint32_t)k8[1])<<16; /* fall through */
713: case 1 : a+=((uint32_t)k8[0])<<24; break;
714: case 0 : return c;
715: }
716:
717: #endif /* !VALGRIND */
718:
719: } else { /* need to read the key one byte at a time */
720: const uint8_t *k = (const uint8_t *)key;
721:
722: /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
723: while (length > 12)
724: {
725: a += ((uint32_t)k[0])<<24;
726: a += ((uint32_t)k[1])<<16;
727: a += ((uint32_t)k[2])<<8;
728: a += ((uint32_t)k[3]);
729: b += ((uint32_t)k[4])<<24;
730: b += ((uint32_t)k[5])<<16;
731: b += ((uint32_t)k[6])<<8;
732: b += ((uint32_t)k[7]);
733: c += ((uint32_t)k[8])<<24;
734: c += ((uint32_t)k[9])<<16;
735: c += ((uint32_t)k[10])<<8;
736: c += ((uint32_t)k[11]);
737: mix(a,b,c);
738: length -= 12;
739: k += 12;
740: }
741:
742: /*-------------------------------- last block: affect all 32 bits of (c) */
743: switch(length) /* all the case statements fall through */
744: {
745: case 12: c+=k[11];
746: case 11: c+=((uint32_t)k[10])<<8;
747: case 10: c+=((uint32_t)k[9])<<16;
748: case 9 : c+=((uint32_t)k[8])<<24;
749: case 8 : b+=k[7];
750: case 7 : b+=((uint32_t)k[6])<<8;
751: case 6 : b+=((uint32_t)k[5])<<16;
752: case 5 : b+=((uint32_t)k[4])<<24;
753: case 4 : a+=k[3];
754: case 3 : a+=((uint32_t)k[2])<<8;
755: case 2 : a+=((uint32_t)k[1])<<16;
756: case 1 : a+=((uint32_t)k[0])<<24;
757: break;
758: case 0 : return c;
759: }
760: }
761:
762: final(a,b,c);
763: return c;
764: }
765:
766:
767: #ifdef SELF_TEST
768:
769: /* used for timings */
770: void driver1()
771: {
772: uint8_t buf[256];
773: uint32_t i;
774: uint32_t h=0;
775: time_t a,z;
776:
777: time(&a);
778: for (i=0; i<256; ++i) buf[i] = 'x';
779: for (i=0; i<1; ++i)
780: {
781: h = hashlittle(&buf[0],1,h);
782: }
783: time(&z);
784: if (z-a > 0) printf("time %d %.8x\n", z-a, h);
785: }
786:
787: /* check that every input bit changes every output bit half the time */
788: #define HASHSTATE 1
789: #define HASHLEN 1
790: #define MAXPAIR 60
791: #define MAXLEN 70
792: void driver2()
793: {
794: uint8_t qa[MAXLEN+1], qb[MAXLEN+2], *a = &qa[0], *b = &qb[1];
795: uint32_t c[HASHSTATE], d[HASHSTATE], i=0, j=0, k, l, m=0, z;
796: uint32_t e[HASHSTATE],f[HASHSTATE],g[HASHSTATE],h[HASHSTATE];
797: uint32_t x[HASHSTATE],y[HASHSTATE];
798: uint32_t hlen;
799:
800: printf("No more than %d trials should ever be needed \n",MAXPAIR/2);
801: for (hlen=0; hlen < MAXLEN; ++hlen)
802: {
803: z=0;
804: for (i=0; i<hlen; ++i) /*----------------------- for each input byte, */
805: {
806: for (j=0; j<8; ++j) /*------------------------ for each input bit, */
807: {
808: for (m=1; m<8; ++m) /*------------ for serveral possible initvals, */
809: {
810: for (l=0; l<HASHSTATE; ++l)
811: e[l]=f[l]=g[l]=h[l]=x[l]=y[l]=~((uint32_t)0);
812:
813: /*---- check that every output bit is affected by that input bit */
814: for (k=0; k<MAXPAIR; k+=2)
815: {
816: uint32_t finished=1;
817: /* keys have one bit different */
818: for (l=0; l<hlen+1; ++l) {a[l] = b[l] = (uint8_t)0;}
819: /* have a and b be two keys differing in only one bit */
820: a[i] ^= (k<<j);
821: a[i] ^= (k>>(8-j));
822: c[0] = hashlittle(a, hlen, m);
823: b[i] ^= ((k+1)<<j);
824: b[i] ^= ((k+1)>>(8-j));
825: d[0] = hashlittle(b, hlen, m);
826: /* check every bit is 1, 0, set, and not set at least once */
827: for (l=0; l<HASHSTATE; ++l)
828: {
829: e[l] &= (c[l]^d[l]);
830: f[l] &= ~(c[l]^d[l]);
831: g[l] &= c[l];
832: h[l] &= ~c[l];
833: x[l] &= d[l];
834: y[l] &= ~d[l];
835: if (e[l]|f[l]|g[l]|h[l]|x[l]|y[l]) finished=0;
836: }
837: if (finished) break;
838: }
839: if (k>z) z=k;
840: if (k==MAXPAIR)
841: {
842: printf("Some bit didn't change: ");
843: printf("%.8x %.8x %.8x %.8x %.8x %.8x ",
844: e[0],f[0],g[0],h[0],x[0],y[0]);
845: printf("i %d j %d m %d len %d\n", i, j, m, hlen);
846: }
847: if (z==MAXPAIR) goto done;
848: }
849: }
850: }
851: done:
852: if (z < MAXPAIR)
853: {
854: printf("Mix success %2d bytes %2d initvals ",i,m);
855: printf("required %d trials\n", z/2);
856: }
857: }
858: printf("\n");
859: }
860:
861: /* Check for reading beyond the end of the buffer and alignment problems */
862: void driver3()
863: {
864: uint8_t buf[MAXLEN+20], *b;
865: uint32_t len;
866: uint8_t q[] = "This is the time for all good men to come to the aid of their country...";
867: uint32_t h;
868: uint8_t qq[] = "xThis is the time for all good men to come to the aid of their country...";
869: uint32_t i;
870: uint8_t qqq[] = "xxThis is the time for all good men to come to the aid of their country...";
871: uint32_t j;
872: uint8_t qqqq[] = "xxxThis is the time for all good men to come to the aid of their country...";
873: uint32_t ref,x,y;
874: uint8_t *p;
875:
876: printf("Endianness. These lines should all be the same (for values filled in):\n");
877: printf("%.8x %.8x %.8x\n",
878: hashword((const uint32_t *)q, (sizeof(q)-1)/4, 13),
879: hashword((const uint32_t *)q, (sizeof(q)-5)/4, 13),
880: hashword((const uint32_t *)q, (sizeof(q)-9)/4, 13));
881: p = q;
882: printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
883: hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
884: hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
885: hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
886: hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
887: hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
888: hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
889: p = &qq[1];
890: printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
891: hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
892: hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
893: hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
894: hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
895: hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
896: hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
897: p = &qqq[2];
898: printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
899: hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
900: hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
901: hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
902: hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
903: hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
904: hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
905: p = &qqqq[3];
906: printf("%.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
907: hashlittle(p, sizeof(q)-1, 13), hashlittle(p, sizeof(q)-2, 13),
908: hashlittle(p, sizeof(q)-3, 13), hashlittle(p, sizeof(q)-4, 13),
909: hashlittle(p, sizeof(q)-5, 13), hashlittle(p, sizeof(q)-6, 13),
910: hashlittle(p, sizeof(q)-7, 13), hashlittle(p, sizeof(q)-8, 13),
911: hashlittle(p, sizeof(q)-9, 13), hashlittle(p, sizeof(q)-10, 13),
912: hashlittle(p, sizeof(q)-11, 13), hashlittle(p, sizeof(q)-12, 13));
913: printf("\n");
914:
915: /* check that hashlittle2 and hashlittle produce the same results */
916: i=47; j=0;
917: hashlittle2(q, sizeof(q), &i, &j);
918: if (hashlittle(q, sizeof(q), 47) != i)
919: printf("hashlittle2 and hashlittle mismatch\n");
920:
921: /* check that hashword2 and hashword produce the same results */
922: len = 0xdeadbeef;
923: i=47, j=0;
924: hashword2(&len, 1, &i, &j);
925: if (hashword(&len, 1, 47) != i)
926: printf("hashword2 and hashword mismatch %x %x\n",
927: i, hashword(&len, 1, 47));
928:
929: /* check hashlittle doesn't read before or after the ends of the string */
930: for (h=0, b=buf+1; h<8; ++h, ++b)
931: {
932: for (i=0; i<MAXLEN; ++i)
933: {
934: len = i;
935: for (j=0; j<i; ++j) *(b+j)=0;
936:
937: /* these should all be equal */
938: ref = hashlittle(b, len, (uint32_t)1);
939: *(b+i)=(uint8_t)~0;
940: *(b-1)=(uint8_t)~0;
941: x = hashlittle(b, len, (uint32_t)1);
942: y = hashlittle(b, len, (uint32_t)1);
943: if ((ref != x) || (ref != y))
944: {
945: printf("alignment error: %.8x %.8x %.8x %d %d\n",ref,x,y,
946: h, i);
947: }
948: }
949: }
950: }
951:
952: /* check for problems with nulls */
953: void driver4()
954: {
955: uint8_t buf[1];
956: uint32_t h,i,state[HASHSTATE];
957:
958:
959: buf[0] = ~0;
960: for (i=0; i<HASHSTATE; ++i) state[i] = 1;
961: printf("These should all be different\n");
962: for (i=0, h=0; i<8; ++i)
963: {
964: h = hashlittle(buf, 0, h);
965: printf("%2ld 0-byte strings, hash is %.8x\n", i, h);
966: }
967: }
968:
969:
970: int main()
971: {
972: driver1(); /* test that the key is hashed: used for timings */
973: driver2(); /* test that whole key is hashed thoroughly */
974: driver3(); /* test that nothing but the key is hashed */
975: driver4(); /* test hashing multiple buffers (all buffers are null) */
976: return 1;
977: }
978:
979: #endif /* SELF_TEST */
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>
![[BACK]](/icons/cvsweb/back.gif){kind=icon}
Return to lookup3.c CVS log ![[TXT]](/icons/cvsweb/text.gif){kind=icon}
![[DIR]](/icons/cvsweb/dir.gif){kind=icon}
Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / coova-chilli / src