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comparison lib/lua/lua-5.2.2/ltable.c @ 1866:41cc4dd3c122

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Lua 5.2.2 added.
author Nomad
date Wed, 16 Oct 2013 13:34:26 +0200
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1848:3b39b70e8e93 1866:41cc4dd3c122
1 /*
2 ** $Id: ltable.c,v 2.72 2012/09/11 19:37:16 roberto Exp $
3 ** Lua tables (hash)
4 ** See Copyright Notice in lua.h
5 */
6
7
8 /*
9 ** Implementation of tables (aka arrays, objects, or hash tables).
10 ** Tables keep its elements in two parts: an array part and a hash part.
11 ** Non-negative integer keys are all candidates to be kept in the array
12 ** part. The actual size of the array is the largest `n' such that at
13 ** least half the slots between 0 and n are in use.
14 ** Hash uses a mix of chained scatter table with Brent's variation.
15 ** A main invariant of these tables is that, if an element is not
16 ** in its main position (i.e. the `original' position that its hash gives
17 ** to it), then the colliding element is in its own main position.
18 ** Hence even when the load factor reaches 100%, performance remains good.
19 */
20
21 #include <string.h>
22
23 #define ltable_c
24 #define LUA_CORE
25
26 #include "lua.h"
27
28 #include "ldebug.h"
29 #include "ldo.h"
30 #include "lgc.h"
31 #include "lmem.h"
32 #include "lobject.h"
33 #include "lstate.h"
34 #include "lstring.h"
35 #include "ltable.h"
36 #include "lvm.h"
37
38
39 /*
40 ** max size of array part is 2^MAXBITS
41 */
42 #if LUAI_BITSINT >= 32
43 #define MAXBITS 30
44 #else
45 #define MAXBITS (LUAI_BITSINT-2)
46 #endif
47
48 #define MAXASIZE (1 << MAXBITS)
49
50
51 #define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
52
53 #define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
54 #define hashboolean(t,p) hashpow2(t, p)
55
56
57 /*
58 ** for some types, it is better to avoid modulus by power of 2, as
59 ** they tend to have many 2 factors.
60 */
61 #define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
62
63
64 #define hashpointer(t,p) hashmod(t, IntPoint(p))
65
66
67 #define dummynode (&dummynode_)
68
69 #define isdummy(n) ((n) == dummynode)
70
71 static const Node dummynode_ = {
72 {NILCONSTANT}, /* value */
73 {{NILCONSTANT, NULL}} /* key */
74 };
75
76
77 /*
78 ** hash for lua_Numbers
79 */
80 static Node *hashnum (const Table *t, lua_Number n) {
81 int i;
82 luai_hashnum(i, n);
83 if (i < 0) {
84 if (cast(unsigned int, i) == 0u - i) /* use unsigned to avoid overflows */
85 i = 0; /* handle INT_MIN */
86 i = -i; /* must be a positive value */
87 }
88 return hashmod(t, i);
89 }
90
91
92
93 /*
94 ** returns the `main' position of an element in a table (that is, the index
95 ** of its hash value)
96 */
97 static Node *mainposition (const Table *t, const TValue *key) {
98 switch (ttype(key)) {
99 case LUA_TNUMBER:
100 return hashnum(t, nvalue(key));
101 case LUA_TLNGSTR: {
102 TString *s = rawtsvalue(key);
103 if (s->tsv.extra == 0) { /* no hash? */
104 s->tsv.hash = luaS_hash(getstr(s), s->tsv.len, s->tsv.hash);
105 s->tsv.extra = 1; /* now it has its hash */
106 }
107 return hashstr(t, rawtsvalue(key));
108 }
109 case LUA_TSHRSTR:
110 return hashstr(t, rawtsvalue(key));
111 case LUA_TBOOLEAN:
112 return hashboolean(t, bvalue(key));
113 case LUA_TLIGHTUSERDATA:
114 return hashpointer(t, pvalue(key));
115 case LUA_TLCF:
116 return hashpointer(t, fvalue(key));
117 default:
118 return hashpointer(t, gcvalue(key));
119 }
120 }
121
122
123 /*
124 ** returns the index for `key' if `key' is an appropriate key to live in
125 ** the array part of the table, -1 otherwise.
126 */
127 static int arrayindex (const TValue *key) {
128 if (ttisnumber(key)) {
129 lua_Number n = nvalue(key);
130 int k;
131 lua_number2int(k, n);
132 if (luai_numeq(cast_num(k), n))
133 return k;
134 }
135 return -1; /* `key' did not match some condition */
136 }
137
138
139 /*
140 ** returns the index of a `key' for table traversals. First goes all
141 ** elements in the array part, then elements in the hash part. The
142 ** beginning of a traversal is signaled by -1.
143 */
144 static int findindex (lua_State *L, Table *t, StkId key) {
145 int i;
146 if (ttisnil(key)) return -1; /* first iteration */
147 i = arrayindex(key);
148 if (0 < i && i <= t->sizearray) /* is `key' inside array part? */
149 return i-1; /* yes; that's the index (corrected to C) */
150 else {
151 Node *n = mainposition(t, key);
152 for (;;) { /* check whether `key' is somewhere in the chain */
153 /* key may be dead already, but it is ok to use it in `next' */
154 if (luaV_rawequalobj(gkey(n), key) ||
155 (ttisdeadkey(gkey(n)) && iscollectable(key) &&
156 deadvalue(gkey(n)) == gcvalue(key))) {
157 i = cast_int(n - gnode(t, 0)); /* key index in hash table */
158 /* hash elements are numbered after array ones */
159 return i + t->sizearray;
160 }
161 else n = gnext(n);
162 if (n == NULL)
163 luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
164 }
165 }
166 }
167
168
169 int luaH_next (lua_State *L, Table *t, StkId key) {
170 int i = findindex(L, t, key); /* find original element */
171 for (i++; i < t->sizearray; i++) { /* try first array part */
172 if (!ttisnil(&t->array[i])) { /* a non-nil value? */
173 setnvalue(key, cast_num(i+1));
174 setobj2s(L, key+1, &t->array[i]);
175 return 1;
176 }
177 }
178 for (i -= t->sizearray; i < sizenode(t); i++) { /* then hash part */
179 if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
180 setobj2s(L, key, gkey(gnode(t, i)));
181 setobj2s(L, key+1, gval(gnode(t, i)));
182 return 1;
183 }
184 }
185 return 0; /* no more elements */
186 }
187
188
189 /*
190 ** {=============================================================
191 ** Rehash
192 ** ==============================================================
193 */
194
195
196 static int computesizes (int nums[], int *narray) {
197 int i;
198 int twotoi; /* 2^i */
199 int a = 0; /* number of elements smaller than 2^i */
200 int na = 0; /* number of elements to go to array part */
201 int n = 0; /* optimal size for array part */
202 for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {
203 if (nums[i] > 0) {
204 a += nums[i];
205 if (a > twotoi/2) { /* more than half elements present? */
206 n = twotoi; /* optimal size (till now) */
207 na = a; /* all elements smaller than n will go to array part */
208 }
209 }
210 if (a == *narray) break; /* all elements already counted */
211 }
212 *narray = n;
213 lua_assert(*narray/2 <= na && na <= *narray);
214 return na;
215 }
216
217
218 static int countint (const TValue *key, int *nums) {
219 int k = arrayindex(key);
220 if (0 < k && k <= MAXASIZE) { /* is `key' an appropriate array index? */
221 nums[luaO_ceillog2(k)]++; /* count as such */
222 return 1;
223 }
224 else
225 return 0;
226 }
227
228
229 static int numusearray (const Table *t, int *nums) {
230 int lg;
231 int ttlg; /* 2^lg */
232 int ause = 0; /* summation of `nums' */
233 int i = 1; /* count to traverse all array keys */
234 for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) { /* for each slice */
235 int lc = 0; /* counter */
236 int lim = ttlg;
237 if (lim > t->sizearray) {
238 lim = t->sizearray; /* adjust upper limit */
239 if (i > lim)
240 break; /* no more elements to count */
241 }
242 /* count elements in range (2^(lg-1), 2^lg] */
243 for (; i <= lim; i++) {
244 if (!ttisnil(&t->array[i-1]))
245 lc++;
246 }
247 nums[lg] += lc;
248 ause += lc;
249 }
250 return ause;
251 }
252
253
254 static int numusehash (const Table *t, int *nums, int *pnasize) {
255 int totaluse = 0; /* total number of elements */
256 int ause = 0; /* summation of `nums' */
257 int i = sizenode(t);
258 while (i--) {
259 Node *n = &t->node[i];
260 if (!ttisnil(gval(n))) {
261 ause += countint(gkey(n), nums);
262 totaluse++;
263 }
264 }
265 *pnasize += ause;
266 return totaluse;
267 }
268
269
270 static void setarrayvector (lua_State *L, Table *t, int size) {
271 int i;
272 luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
273 for (i=t->sizearray; i<size; i++)
274 setnilvalue(&t->array[i]);
275 t->sizearray = size;
276 }
277
278
279 static void setnodevector (lua_State *L, Table *t, int size) {
280 int lsize;
281 if (size == 0) { /* no elements to hash part? */
282 t->node = cast(Node *, dummynode); /* use common `dummynode' */
283 lsize = 0;
284 }
285 else {
286 int i;
287 lsize = luaO_ceillog2(size);
288 if (lsize > MAXBITS)
289 luaG_runerror(L, "table overflow");
290 size = twoto(lsize);
291 t->node = luaM_newvector(L, size, Node);
292 for (i=0; i<size; i++) {
293 Node *n = gnode(t, i);
294 gnext(n) = NULL;
295 setnilvalue(gkey(n));
296 setnilvalue(gval(n));
297 }
298 }
299 t->lsizenode = cast_byte(lsize);
300 t->lastfree = gnode(t, size); /* all positions are free */
301 }
302
303
304 void luaH_resize (lua_State *L, Table *t, int nasize, int nhsize) {
305 int i;
306 int oldasize = t->sizearray;
307 int oldhsize = t->lsizenode;
308 Node *nold = t->node; /* save old hash ... */
309 if (nasize > oldasize) /* array part must grow? */
310 setarrayvector(L, t, nasize);
311 /* create new hash part with appropriate size */
312 setnodevector(L, t, nhsize);
313 if (nasize < oldasize) { /* array part must shrink? */
314 t->sizearray = nasize;
315 /* re-insert elements from vanishing slice */
316 for (i=nasize; i<oldasize; i++) {
317 if (!ttisnil(&t->array[i]))
318 luaH_setint(L, t, i + 1, &t->array[i]);
319 }
320 /* shrink array */
321 luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
322 }
323 /* re-insert elements from hash part */
324 for (i = twoto(oldhsize) - 1; i >= 0; i--) {
325 Node *old = nold+i;
326 if (!ttisnil(gval(old))) {
327 /* doesn't need barrier/invalidate cache, as entry was
328 already present in the table */
329 setobjt2t(L, luaH_set(L, t, gkey(old)), gval(old));
330 }
331 }
332 if (!isdummy(nold))
333 luaM_freearray(L, nold, cast(size_t, twoto(oldhsize))); /* free old array */
334 }
335
336
337 void luaH_resizearray (lua_State *L, Table *t, int nasize) {
338 int nsize = isdummy(t->node) ? 0 : sizenode(t);
339 luaH_resize(L, t, nasize, nsize);
340 }
341
342
343 static void rehash (lua_State *L, Table *t, const TValue *ek) {
344 int nasize, na;
345 int nums[MAXBITS+1]; /* nums[i] = number of keys with 2^(i-1) < k <= 2^i */
346 int i;
347 int totaluse;
348 for (i=0; i<=MAXBITS; i++) nums[i] = 0; /* reset counts */
349 nasize = numusearray(t, nums); /* count keys in array part */
350 totaluse = nasize; /* all those keys are integer keys */
351 totaluse += numusehash(t, nums, &nasize); /* count keys in hash part */
352 /* count extra key */
353 nasize += countint(ek, nums);
354 totaluse++;
355 /* compute new size for array part */
356 na = computesizes(nums, &nasize);
357 /* resize the table to new computed sizes */
358 luaH_resize(L, t, nasize, totaluse - na);
359 }
360
361
362
363 /*
364 ** }=============================================================
365 */
366
367
368 Table *luaH_new (lua_State *L) {
369 Table *t = &luaC_newobj(L, LUA_TTABLE, sizeof(Table), NULL, 0)->h;
370 t->metatable = NULL;
371 t->flags = cast_byte(~0);
372 t->array = NULL;
373 t->sizearray = 0;
374 setnodevector(L, t, 0);
375 return t;
376 }
377
378
379 void luaH_free (lua_State *L, Table *t) {
380 if (!isdummy(t->node))
381 luaM_freearray(L, t->node, cast(size_t, sizenode(t)));
382 luaM_freearray(L, t->array, t->sizearray);
383 luaM_free(L, t);
384 }
385
386
387 static Node *getfreepos (Table *t) {
388 while (t->lastfree > t->node) {
389 t->lastfree--;
390 if (ttisnil(gkey(t->lastfree)))
391 return t->lastfree;
392 }
393 return NULL; /* could not find a free place */
394 }
395
396
397
398 /*
399 ** inserts a new key into a hash table; first, check whether key's main
400 ** position is free. If not, check whether colliding node is in its main
401 ** position or not: if it is not, move colliding node to an empty place and
402 ** put new key in its main position; otherwise (colliding node is in its main
403 ** position), new key goes to an empty position.
404 */
405 TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
406 Node *mp;
407 if (ttisnil(key)) luaG_runerror(L, "table index is nil");
408 else if (ttisnumber(key) && luai_numisnan(L, nvalue(key)))
409 luaG_runerror(L, "table index is NaN");
410 mp = mainposition(t, key);
411 if (!ttisnil(gval(mp)) || isdummy(mp)) { /* main position is taken? */
412 Node *othern;
413 Node *n = getfreepos(t); /* get a free place */
414 if (n == NULL) { /* cannot find a free place? */
415 rehash(L, t, key); /* grow table */
416 /* whatever called 'newkey' take care of TM cache and GC barrier */
417 return luaH_set(L, t, key); /* insert key into grown table */
418 }
419 lua_assert(!isdummy(n));
420 othern = mainposition(t, gkey(mp));
421 if (othern != mp) { /* is colliding node out of its main position? */
422 /* yes; move colliding node into free position */
423 while (gnext(othern) != mp) othern = gnext(othern); /* find previous */
424 gnext(othern) = n; /* redo the chain with `n' in place of `mp' */
425 *n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
426 gnext(mp) = NULL; /* now `mp' is free */
427 setnilvalue(gval(mp));
428 }
429 else { /* colliding node is in its own main position */
430 /* new node will go into free position */
431 gnext(n) = gnext(mp); /* chain new position */
432 gnext(mp) = n;
433 mp = n;
434 }
435 }
436 setobj2t(L, gkey(mp), key);
437 luaC_barrierback(L, obj2gco(t), key);
438 lua_assert(ttisnil(gval(mp)));
439 return gval(mp);
440 }
441
442
443 /*
444 ** search function for integers
445 */
446 const TValue *luaH_getint (Table *t, int key) {
447 /* (1 <= key && key <= t->sizearray) */
448 if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
449 return &t->array[key-1];
450 else {
451 lua_Number nk = cast_num(key);
452 Node *n = hashnum(t, nk);
453 do { /* check whether `key' is somewhere in the chain */
454 if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
455 return gval(n); /* that's it */
456 else n = gnext(n);
457 } while (n);
458 return luaO_nilobject;
459 }
460 }
461
462
463 /*
464 ** search function for short strings
465 */
466 const TValue *luaH_getstr (Table *t, TString *key) {
467 Node *n = hashstr(t, key);
468 lua_assert(key->tsv.tt == LUA_TSHRSTR);
469 do { /* check whether `key' is somewhere in the chain */
470 if (ttisshrstring(gkey(n)) && eqshrstr(rawtsvalue(gkey(n)), key))
471 return gval(n); /* that's it */
472 else n = gnext(n);
473 } while (n);
474 return luaO_nilobject;
475 }
476
477
478 /*
479 ** main search function
480 */
481 const TValue *luaH_get (Table *t, const TValue *key) {
482 switch (ttype(key)) {
483 case LUA_TSHRSTR: return luaH_getstr(t, rawtsvalue(key));
484 case LUA_TNIL: return luaO_nilobject;
485 case LUA_TNUMBER: {
486 int k;
487 lua_Number n = nvalue(key);
488 lua_number2int(k, n);
489 if (luai_numeq(cast_num(k), n)) /* index is int? */
490 return luaH_getint(t, k); /* use specialized version */
491 /* else go through */
492 }
493 default: {
494 Node *n = mainposition(t, key);
495 do { /* check whether `key' is somewhere in the chain */
496 if (luaV_rawequalobj(gkey(n), key))
497 return gval(n); /* that's it */
498 else n = gnext(n);
499 } while (n);
500 return luaO_nilobject;
501 }
502 }
503 }
504
505
506 /*
507 ** beware: when using this function you probably need to check a GC
508 ** barrier and invalidate the TM cache.
509 */
510 TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
511 const TValue *p = luaH_get(t, key);
512 if (p != luaO_nilobject)
513 return cast(TValue *, p);
514 else return luaH_newkey(L, t, key);
515 }
516
517
518 void luaH_setint (lua_State *L, Table *t, int key, TValue *value) {
519 const TValue *p = luaH_getint(t, key);
520 TValue *cell;
521 if (p != luaO_nilobject)
522 cell = cast(TValue *, p);
523 else {
524 TValue k;
525 setnvalue(&k, cast_num(key));
526 cell = luaH_newkey(L, t, &k);
527 }
528 setobj2t(L, cell, value);
529 }
530
531
532 static int unbound_search (Table *t, unsigned int j) {
533 unsigned int i = j; /* i is zero or a present index */
534 j++;
535 /* find `i' and `j' such that i is present and j is not */
536 while (!ttisnil(luaH_getint(t, j))) {
537 i = j;
538 j *= 2;
539 if (j > cast(unsigned int, MAX_INT)) { /* overflow? */
540 /* table was built with bad purposes: resort to linear search */
541 i = 1;
542 while (!ttisnil(luaH_getint(t, i))) i++;
543 return i - 1;
544 }
545 }
546 /* now do a binary search between them */
547 while (j - i > 1) {
548 unsigned int m = (i+j)/2;
549 if (ttisnil(luaH_getint(t, m))) j = m;
550 else i = m;
551 }
552 return i;
553 }
554
555
556 /*
557 ** Try to find a boundary in table `t'. A `boundary' is an integer index
558 ** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
559 */
560 int luaH_getn (Table *t) {
561 unsigned int j = t->sizearray;
562 if (j > 0 && ttisnil(&t->array[j - 1])) {
563 /* there is a boundary in the array part: (binary) search for it */
564 unsigned int i = 0;
565 while (j - i > 1) {
566 unsigned int m = (i+j)/2;
567 if (ttisnil(&t->array[m - 1])) j = m;
568 else i = m;
569 }
570 return i;
571 }
572 /* else must find a boundary in hash part */
573 else if (isdummy(t->node)) /* hash part is empty? */
574 return j; /* that is easy... */
575 else return unbound_search(t, j);
576 }
577
578
579
580 #if defined(LUA_DEBUG)
581
582 Node *luaH_mainposition (const Table *t, const TValue *key) {
583 return mainposition(t, key);
584 }
585
586 int luaH_isdummy (Node *n) { return isdummy(n); }
587
588 #endif