1: /*
2: * Routines to provide a memory-efficient hashtable.
3: *
4: * Copyright (C) 2007-2020 Wayne Davison
5: *
6: * This program is free software; you can redistribute it and/or modify
7: * it under the terms of the GNU General Public License as published by
8: * the Free Software Foundation; either version 3 of the License, or
9: * (at your option) any later version.
10: *
11: * This program is distributed in the hope that it will be useful,
12: * but WITHOUT ANY WARRANTY; without even the implied warranty of
13: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14: * GNU General Public License for more details.
15: *
16: * You should have received a copy of the GNU General Public License along
17: * with this program; if not, visit the http://fsf.org website.
18: */
19:
20: #include "rsync.h"
21:
22: #define HASH_LOAD_LIMIT(size) ((size)*3/4)
23:
24: struct hashtable *hashtable_create(int size, int key64)
25: {
26: int req = size;
27: struct hashtable *tbl;
28: int node_size = key64 ? sizeof (struct ht_int64_node)
29: : sizeof (struct ht_int32_node);
30:
31: /* Pick a power of 2 that can hold the requested size. */
32: if (size & (size-1) || size < 16) {
33: size = 16;
34: while (size < req)
35: size *= 2;
36: }
37:
38: tbl = new(struct hashtable);
39: tbl->nodes = new_array0(char, size * node_size);
40: tbl->size = size;
41: tbl->entries = 0;
42: tbl->node_size = node_size;
43: tbl->key64 = key64 ? 1 : 0;
44:
45: if (DEBUG_GTE(HASH, 1)) {
46: char buf[32];
47: if (req != size)
48: snprintf(buf, sizeof buf, "req: %d, ", req);
49: else
50: *buf = '\0';
51: rprintf(FINFO, "[%s] created hashtable %lx (%ssize: %d, keys: %d-bit)\n",
52: who_am_i(), (long)tbl, buf, size, key64 ? 64 : 32);
53: }
54:
55: return tbl;
56: }
57:
58: void hashtable_destroy(struct hashtable *tbl)
59: {
60: if (DEBUG_GTE(HASH, 1)) {
61: rprintf(FINFO, "[%s] destroyed hashtable %lx (size: %d, keys: %d-bit)\n",
62: who_am_i(), (long)tbl, tbl->size, tbl->key64 ? 64 : 32);
63: }
64: free(tbl->nodes);
65: free(tbl);
66: }
67:
68: /* Returns the node that holds the indicated key if it exists. When it does not
69: * exist, it returns either NULL (when data_when_new is NULL), or it returns a
70: * new node with its node->data set to the indicated value.
71: *
72: * If your code doesn't know the data value for a new node in advance (usually
73: * because it doesn't know if a node is new or not) you should pass in a unique
74: * (non-0) value that you can use to check if the returned node is new. You can
75: * then overwrite the data with any value you want (even 0) since it only needs
76: * to be different than whatever data_when_new value you use later on.
77: *
78: * This return is a void* just because it might be pointing at a ht_int32_node
79: * or a ht_int64_node, and that makes the caller's assignment a little easier. */
80: void *hashtable_find(struct hashtable *tbl, int64 key, void *data_when_new)
81: {
82: int key64 = tbl->key64;
83: struct ht_int32_node *node;
84: uint32 ndx;
85:
86: if (key64 ? key == 0 : (int32)key == 0) {
87: rprintf(FERROR, "Internal hashtable error: illegal key supplied!\n");
88: exit_cleanup(RERR_MESSAGEIO);
89: }
90:
91: if (data_when_new && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
92: void *old_nodes = tbl->nodes;
93: int size = tbl->size * 2;
94: int i;
95:
96: tbl->nodes = new_array0(char, size * tbl->node_size);
97: tbl->size = size;
98: tbl->entries = 0;
99:
100: if (DEBUG_GTE(HASH, 1)) {
101: rprintf(FINFO, "[%s] growing hashtable %lx (size: %d, keys: %d-bit)\n",
102: who_am_i(), (long)tbl, size, key64 ? 64 : 32);
103: }
104:
105: for (i = size / 2; i-- > 0; ) {
106: struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);
107: int64 move_key = HT_KEY(move_node, key64);
108: if (move_key == 0)
109: continue;
110: if (move_node->data)
111: hashtable_find(tbl, move_key, move_node->data);
112: else {
113: node = hashtable_find(tbl, move_key, "");
114: node->data = 0;
115: }
116: }
117:
118: free(old_nodes);
119: }
120:
121: if (!key64) {
122: /* Based on Jenkins One-at-a-time hash. */
123: uchar buf[4], *keyp = buf;
124: int i;
125:
126: SIVALu(buf, 0, key);
127: for (ndx = 0, i = 0; i < 4; i++) {
128: ndx += keyp[i];
129: ndx += (ndx << 10);
130: ndx ^= (ndx >> 6);
131: }
132: ndx += (ndx << 3);
133: ndx ^= (ndx >> 11);
134: ndx += (ndx << 15);
135: } else {
136: /* Based on Jenkins hashword() from lookup3.c. */
137: uint32 a, b, c;
138:
139: /* Set up the internal state */
140: a = b = c = 0xdeadbeef + (8 << 2);
141:
142: #define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
143: #if SIZEOF_INT64 >= 8
144: b += (uint32)(key >> 32);
145: #endif
146: a += (uint32)key;
147: c ^= b; c -= rot(b, 14);
148: a ^= c; a -= rot(c, 11);
149: b ^= a; b -= rot(a, 25);
150: c ^= b; c -= rot(b, 16);
151: a ^= c; a -= rot(c, 4);
152: b ^= a; b -= rot(a, 14);
153: c ^= b; c -= rot(b, 24);
154: #undef rot
155: ndx = c;
156: }
157:
158: /* If it already exists, return the node. If we're not
159: * allocating, return NULL if the key is not found. */
160: while (1) {
161: int64 nkey;
162:
163: ndx &= tbl->size - 1;
164: node = HT_NODE(tbl, tbl->nodes, ndx);
165: nkey = HT_KEY(node, key64);
166:
167: if (nkey == key)
168: return node;
169: if (nkey == 0) {
170: if (!data_when_new)
171: return NULL;
172: break;
173: }
174: ndx++;
175: }
176:
177: /* Take over this empty spot and then return the node. */
178: if (key64)
179: ((struct ht_int64_node*)node)->key = key;
180: else
181: node->key = (int32)key;
182: node->data = data_when_new;
183: tbl->entries++;
184: return node;
185: }
186:
187: #ifndef WORDS_BIGENDIAN
188: # define HASH_LITTLE_ENDIAN 1
189: # define HASH_BIG_ENDIAN 0
190: #else
191: # define HASH_LITTLE_ENDIAN 0
192: # define HASH_BIG_ENDIAN 1
193: #endif
194:
195: /*
196: -------------------------------------------------------------------------------
197: lookup3.c, by Bob Jenkins, May 2006, Public Domain.
198:
199: These are functions for producing 32-bit hashes for hash table lookup.
200: hash_word(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
201: are externally useful functions. Routines to test the hash are included
202: if SELF_TEST is defined. You can use this free for any purpose. It's in
203: the public domain. It has no warranty.
204:
205: You probably want to use hashlittle(). hashlittle() and hashbig()
206: hash byte arrays. hashlittle() is is faster than hashbig() on
207: little-endian machines. Intel and AMD are little-endian machines.
208: On second thought, you probably want hashlittle2(), which is identical to
209: hashlittle() except it returns two 32-bit hashes for the price of one.
210: You could implement hashbig2() if you wanted but I haven't bothered here.
211:
212: If you want to find a hash of, say, exactly 7 integers, do
213: a = i1; b = i2; c = i3;
214: mix(a,b,c);
215: a += i4; b += i5; c += i6;
216: mix(a,b,c);
217: a += i7;
218: final(a,b,c);
219: then use c as the hash value. If you have a variable length array of
220: 4-byte integers to hash, use hash_word(). If you have a byte array (like
221: a character string), use hashlittle(). If you have several byte arrays, or
222: a mix of things, see the comments above hashlittle().
223:
224: Why is this so big? I read 12 bytes at a time into 3 4-byte integers,
225: then mix those integers. This is fast (you can do a lot more thorough
226: mixing with 12*3 instructions on 3 integers than you can with 3 instructions
227: on 1 byte), but shoehorning those bytes into integers efficiently is messy.
228: */
229:
230: #define hashsize(n) ((uint32_t)1<<(n))
231: #define hashmask(n) (hashsize(n)-1)
232: #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
233:
234: /*
235: -------------------------------------------------------------------------------
236: mix -- mix 3 32-bit values reversibly.
237:
238: This is reversible, so any information in (a,b,c) before mix() is
239: still in (a,b,c) after mix().
240:
241: If four pairs of (a,b,c) inputs are run through mix(), or through
242: mix() in reverse, there are at least 32 bits of the output that
243: are sometimes the same for one pair and different for another pair.
244: This was tested for:
245: * pairs that differed by one bit, by two bits, in any combination
246: of top bits of (a,b,c), or in any combination of bottom bits of
247: (a,b,c).
248: * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
249: the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
250: is commonly produced by subtraction) look like a single 1-bit
251: difference.
252: * the base values were pseudorandom, all zero but one bit set, or
253: all zero plus a counter that starts at zero.
254:
255: Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
256: satisfy this are
257: 4 6 8 16 19 4
258: 9 15 3 18 27 15
259: 14 9 3 7 17 3
260: Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
261: for "differ" defined as + with a one-bit base and a two-bit delta. I
262: used http://burtleburtle.net/bob/hash/avalanche.html to choose
263: the operations, constants, and arrangements of the variables.
264:
265: This does not achieve avalanche. There are input bits of (a,b,c)
266: that fail to affect some output bits of (a,b,c), especially of a. The
267: most thoroughly mixed value is c, but it doesn't really even achieve
268: avalanche in c.
269:
270: This allows some parallelism. Read-after-writes are good at doubling
271: the number of bits affected, so the goal of mixing pulls in the opposite
272: direction as the goal of parallelism. I did what I could. Rotates
273: seem to cost as much as shifts on every machine I could lay my hands
274: on, and rotates are much kinder to the top and bottom bits, so I used
275: rotates.
276: -------------------------------------------------------------------------------
277: */
278: #define mix(a,b,c) \
279: { \
280: a -= c; a ^= rot(c, 4); c += b; \
281: b -= a; b ^= rot(a, 6); a += c; \
282: c -= b; c ^= rot(b, 8); b += a; \
283: a -= c; a ^= rot(c,16); c += b; \
284: b -= a; b ^= rot(a,19); a += c; \
285: c -= b; c ^= rot(b, 4); b += a; \
286: }
287:
288: /*
289: -------------------------------------------------------------------------------
290: final -- final mixing of 3 32-bit values (a,b,c) into c
291:
292: Pairs of (a,b,c) values differing in only a few bits will usually
293: produce values of c that look totally different. This was tested for
294: * pairs that differed by one bit, by two bits, in any combination
295: of top bits of (a,b,c), or in any combination of bottom bits of
296: (a,b,c).
297: * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
298: the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
299: is commonly produced by subtraction) look like a single 1-bit
300: difference.
301: * the base values were pseudorandom, all zero but one bit set, or
302: all zero plus a counter that starts at zero.
303:
304: These constants passed:
305: 14 11 25 16 4 14 24
306: 12 14 25 16 4 14 24
307: and these came close:
308: 4 8 15 26 3 22 24
309: 10 8 15 26 3 22 24
310: 11 8 15 26 3 22 24
311: -------------------------------------------------------------------------------
312: */
313: #define final(a,b,c) \
314: { \
315: c ^= b; c -= rot(b,14); \
316: a ^= c; a -= rot(c,11); \
317: b ^= a; b -= rot(a,25); \
318: c ^= b; c -= rot(b,16); \
319: a ^= c; a -= rot(c,4); \
320: b ^= a; b -= rot(a,14); \
321: c ^= b; c -= rot(b,24); \
322: }
323:
324:
325: /*
326: -------------------------------------------------------------------------------
327: hashlittle() -- hash a variable-length key into a 32-bit value
328: k : the key (the unaligned variable-length array of bytes)
329: length : the length of the key, counting by bytes
330: val2 : IN: can be any 4-byte value OUT: second 32 bit hash.
331: Returns a 32-bit value. Every bit of the key affects every bit of
332: the return value. Two keys differing by one or two bits will have
333: totally different hash values. Note that the return value is better
334: mixed than val2, so use that first.
335:
336: The best hash table sizes are powers of 2. There is no need to do
337: mod a prime (mod is sooo slow!). If you need less than 32 bits,
338: use a bitmask. For example, if you need only 10 bits, do
339: h = (h & hashmask(10));
340: In which case, the hash table should have hashsize(10) elements.
341:
342: If you are hashing n strings (uint8_t **)k, do it like this:
343: for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);
344:
345: By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this
346: code any way you wish, private, educational, or commercial. It's free.
347:
348: Use for hash table lookup, or anything where one collision in 2^^32 is
349: acceptable. Do NOT use for cryptographic purposes.
350: -------------------------------------------------------------------------------
351: */
352:
353: uint32_t hashlittle(const void *key, size_t length)
354: {
355: uint32_t a,b,c; /* internal state */
356: union { const void *ptr; size_t i; } u; /* needed for Mac Powerbook G4 */
357:
358: /* Set up the internal state */
359: a = b = c = 0xdeadbeef + ((uint32_t)length);
360:
361: u.ptr = key;
362: if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
363: const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
364: const uint8_t *k8;
365:
366: /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
367: while (length > 12)
368: {
369: a += k[0];
370: b += k[1];
371: c += k[2];
372: mix(a,b,c);
373: length -= 12;
374: k += 3;
375: }
376:
377: /*----------------------------- handle the last (probably partial) block */
378: k8 = (const uint8_t *)k;
379: switch(length)
380: {
381: case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
382: case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
383: case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
384: case 9 : c+=k8[8]; /* fall through */
385: case 8 : b+=k[1]; a+=k[0]; break;
386: case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
387: case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
388: case 5 : b+=k8[4]; /* fall through */
389: case 4 : a+=k[0]; break;
390: case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
391: case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
392: case 1 : a+=k8[0]; break;
393: case 0 : return c;
394: }
395: } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
396: const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */
397: const uint8_t *k8;
398:
399: /*--------------- all but last block: aligned reads and different mixing */
400: while (length > 12)
401: {
402: a += k[0] + (((uint32_t)k[1])<<16);
403: b += k[2] + (((uint32_t)k[3])<<16);
404: c += k[4] + (((uint32_t)k[5])<<16);
405: mix(a,b,c);
406: length -= 12;
407: k += 6;
408: }
409:
410: /*----------------------------- handle the last (probably partial) block */
411: k8 = (const uint8_t *)k;
412: switch(length)
413: {
414: case 12: c+=k[4]+(((uint32_t)k[5])<<16);
415: b+=k[2]+(((uint32_t)k[3])<<16);
416: a+=k[0]+(((uint32_t)k[1])<<16);
417: break;
418: case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
419: case 10: c+=k[4];
420: b+=k[2]+(((uint32_t)k[3])<<16);
421: a+=k[0]+(((uint32_t)k[1])<<16);
422: break;
423: case 9 : c+=k8[8]; /* fall through */
424: case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
425: a+=k[0]+(((uint32_t)k[1])<<16);
426: break;
427: case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
428: case 6 : b+=k[2];
429: a+=k[0]+(((uint32_t)k[1])<<16);
430: break;
431: case 5 : b+=k8[4]; /* fall through */
432: case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
433: break;
434: case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
435: case 2 : a+=k[0];
436: break;
437: case 1 : a+=k8[0];
438: break;
439: case 0 : return c; /* zero length requires no mixing */
440: }
441:
442: } else { /* need to read the key one byte at a time */
443: const uint8_t *k = (const uint8_t *)key;
444:
445: /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
446: while (length > 12)
447: {
448: a += k[0];
449: a += ((uint32_t)k[1])<<8;
450: a += ((uint32_t)k[2])<<16;
451: a += ((uint32_t)k[3])<<24;
452: b += k[4];
453: b += ((uint32_t)k[5])<<8;
454: b += ((uint32_t)k[6])<<16;
455: b += ((uint32_t)k[7])<<24;
456: c += k[8];
457: c += ((uint32_t)k[9])<<8;
458: c += ((uint32_t)k[10])<<16;
459: c += ((uint32_t)k[11])<<24;
460: mix(a,b,c);
461: length -= 12;
462: k += 12;
463: }
464:
465: /*-------------------------------- last block: affect all 32 bits of (c) */
466: switch(length) /* all the case statements fall through */
467: {
468: case 12: c+=((uint32_t)k[11])<<24;
469: /* FALLTHROUGH */
470: case 11: c+=((uint32_t)k[10])<<16;
471: /* FALLTHROUGH */
472: case 10: c+=((uint32_t)k[9])<<8;
473: /* FALLTHROUGH */
474: case 9 : c+=k[8];
475: /* FALLTHROUGH */
476: case 8 : b+=((uint32_t)k[7])<<24;
477: /* FALLTHROUGH */
478: case 7 : b+=((uint32_t)k[6])<<16;
479: /* FALLTHROUGH */
480: case 6 : b+=((uint32_t)k[5])<<8;
481: /* FALLTHROUGH */
482: case 5 : b+=k[4];
483: /* FALLTHROUGH */
484: case 4 : a+=((uint32_t)k[3])<<24;
485: /* FALLTHROUGH */
486: case 3 : a+=((uint32_t)k[2])<<16;
487: /* FALLTHROUGH */
488: case 2 : a+=((uint32_t)k[1])<<8;
489: /* FALLTHROUGH */
490: case 1 : a+=k[0];
491: break;
492: case 0 : return c;
493: }
494: }
495:
496: final(a,b,c);
497: return c;
498: }
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>
![[BACK]](/icons/cvsweb/back.gif){kind=icon}
Return to hashtable.c CVS log ![[TXT]](/icons/cvsweb/text.gif){kind=icon}
![[DIR]](/icons/cvsweb/dir.gif){kind=icon}
Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / rsync