1 /*
2 ** $Id: ltable.c,v 2.72.1.1 2013/04/12 18:48:47 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
22 #define ltable_c
23 #define LUA_CORE
24
25 #include <sys/lua/lua.h>
26
27 #include "ldebug.h"
28 #include "ldo.h"
29 #include "lgc.h"
30 #include "lmem.h"
31 #include "lobject.h"
32 #include "lstate.h"
33 #include "lstring.h"
34 #include "ltable.h"
35 #include "lvm.h"
36
37
38 /*
39 ** max size of array part is 2^MAXBITS
40 */
41 #if LUAI_BITSINT >= 32
42 #define MAXBITS 30
43 #else
44 #define MAXBITS (LUAI_BITSINT-2)
45 #endif
46
47 #define MAXASIZE (1 << MAXBITS)
48
49
50 #define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
51
52 #define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
53 #define hashboolean(t,p) hashpow2(t, p)
54
55
56 /*
57 ** for some types, it is better to avoid modulus by power of 2, as
58 ** they tend to have many 2 factors.
59 */
60 #define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
61
62
63 #define hashpointer(t,p) hashmod(t, IntPoint(p))
64
65
66 #define dummynode (&dummynode_)
67
68 #define isdummy(n) ((n) == dummynode)
69
70 static const Node dummynode_ = {
71 {NILCONSTANT}, /* value */
72 {{NILCONSTANT, NULL}} /* key */
73 };
74
75
76 /*
77 ** hash for lua_Numbers
78 */
hashnum(const Table * t,lua_Number n)79 static Node *hashnum (const Table *t, lua_Number n) {
80 int i;
81 luai_hashnum(i, n);
82 if (i < 0) {
83 if (cast(unsigned int, i) == 0u - i) /* use unsigned to avoid overflows */
84 i = 0; /* handle INT_MIN */
85 i = -i; /* must be a positive value */
86 }
87 return hashmod(t, i);
88 }
89
90
91
92 /*
93 ** returns the `main' position of an element in a table (that is, the index
94 ** of its hash value)
95 */
mainposition(const Table * t,const TValue * key)96 static Node *mainposition (const Table *t, const TValue *key) {
97 switch (ttype(key)) {
98 case LUA_TNUMBER:
99 return hashnum(t, nvalue(key));
100 case LUA_TLNGSTR: {
101 TString *s = rawtsvalue(key);
102 if (s->tsv.extra == 0) { /* no hash? */
103 s->tsv.hash = luaS_hash(getstr(s), s->tsv.len, s->tsv.hash);
104 s->tsv.extra = 1; /* now it has its hash */
105 }
106 return hashstr(t, rawtsvalue(key));
107 }
108 case LUA_TSHRSTR:
109 return hashstr(t, rawtsvalue(key));
110 case LUA_TBOOLEAN:
111 return hashboolean(t, bvalue(key));
112 case LUA_TLIGHTUSERDATA:
113 return hashpointer(t, pvalue(key));
114 case LUA_TLCF:
115 return hashpointer(t, fvalue(key));
116 default:
117 return hashpointer(t, gcvalue(key));
118 }
119 }
120
121
122 /*
123 ** returns the index for `key' if `key' is an appropriate key to live in
124 ** the array part of the table, -1 otherwise.
125 */
arrayindex(const TValue * key)126 static int arrayindex (const TValue *key) {
127 if (ttisnumber(key)) {
128 lua_Number n = nvalue(key);
129 int k;
130 lua_number2int(k, n);
131 if (luai_numeq(cast_num(k), n))
132 return k;
133 }
134 return -1; /* `key' did not match some condition */
135 }
136
137
138 /*
139 ** returns the index of a `key' for table traversals. First goes all
140 ** elements in the array part, then elements in the hash part. The
141 ** beginning of a traversal is signaled by -1.
142 */
findindex(lua_State * L,Table * t,StkId key)143 static int findindex (lua_State *L, Table *t, StkId key) {
144 int i;
145 if (ttisnil(key)) return -1; /* first iteration */
146 i = arrayindex(key);
147 if (0 < i && i <= t->sizearray) /* is `key' inside array part? */
148 return i-1; /* yes; that's the index (corrected to C) */
149 else {
150 Node *n = mainposition(t, key);
151 for (;;) { /* check whether `key' is somewhere in the chain */
152 /* key may be dead already, but it is ok to use it in `next' */
153 if (luaV_rawequalobj(gkey(n), key) ||
154 (ttisdeadkey(gkey(n)) && iscollectable(key) &&
155 deadvalue(gkey(n)) == gcvalue(key))) {
156 i = cast_int(n - gnode(t, 0)); /* key index in hash table */
157 /* hash elements are numbered after array ones */
158 return i + t->sizearray;
159 }
160 else n = gnext(n);
161 if (n == NULL)
162 luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
163 }
164 }
165 }
166
167
luaH_next(lua_State * L,Table * t,StkId key)168 int luaH_next (lua_State *L, Table *t, StkId key) {
169 int i = findindex(L, t, key); /* find original element */
170 for (i++; i < t->sizearray; i++) { /* try first array part */
171 if (!ttisnil(&t->array[i])) { /* a non-nil value? */
172 setnvalue(key, cast_num(i+1));
173 setobj2s(L, key+1, &t->array[i]);
174 return 1;
175 }
176 }
177 for (i -= t->sizearray; i < sizenode(t); i++) { /* then hash part */
178 if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
179 setobj2s(L, key, gkey(gnode(t, i)));
180 setobj2s(L, key+1, gval(gnode(t, i)));
181 return 1;
182 }
183 }
184 return 0; /* no more elements */
185 }
186
187
188 /*
189 ** {=============================================================
190 ** Rehash
191 ** ==============================================================
192 */
193
194
computesizes(int nums[],int * narray)195 static int computesizes (int nums[], int *narray) {
196 int i;
197 int twotoi; /* 2^i */
198 int a = 0; /* number of elements smaller than 2^i */
199 int na = 0; /* number of elements to go to array part */
200 int n = 0; /* optimal size for array part */
201 for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {
202 if (nums[i] > 0) {
203 a += nums[i];
204 if (a > twotoi/2) { /* more than half elements present? */
205 n = twotoi; /* optimal size (till now) */
206 na = a; /* all elements smaller than n will go to array part */
207 }
208 }
209 if (a == *narray) break; /* all elements already counted */
210 }
211 *narray = n;
212 lua_assert(*narray/2 <= na && na <= *narray);
213 return na;
214 }
215
216
countint(const TValue * key,int * nums)217 static int countint (const TValue *key, int *nums) {
218 int k = arrayindex(key);
219 if (0 < k && k <= MAXASIZE) { /* is `key' an appropriate array index? */
220 nums[luaO_ceillog2(k)]++; /* count as such */
221 return 1;
222 }
223 else
224 return 0;
225 }
226
227
numusearray(const Table * t,int * nums)228 static int numusearray (const Table *t, int *nums) {
229 int lg;
230 int ttlg; /* 2^lg */
231 int ause = 0; /* summation of `nums' */
232 int i = 1; /* count to traverse all array keys */
233 for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) { /* for each slice */
234 int lc = 0; /* counter */
235 int lim = ttlg;
236 if (lim > t->sizearray) {
237 lim = t->sizearray; /* adjust upper limit */
238 if (i > lim)
239 break; /* no more elements to count */
240 }
241 /* count elements in range (2^(lg-1), 2^lg] */
242 for (; i <= lim; i++) {
243 if (!ttisnil(&t->array[i-1]))
244 lc++;
245 }
246 nums[lg] += lc;
247 ause += lc;
248 }
249 return ause;
250 }
251
252
numusehash(const Table * t,int * nums,int * pnasize)253 static int numusehash (const Table *t, int *nums, int *pnasize) {
254 int totaluse = 0; /* total number of elements */
255 int ause = 0; /* summation of `nums' */
256 int i = sizenode(t);
257 while (i--) {
258 Node *n = &t->node[i];
259 if (!ttisnil(gval(n))) {
260 ause += countint(gkey(n), nums);
261 totaluse++;
262 }
263 }
264 *pnasize += ause;
265 return totaluse;
266 }
267
268
setarrayvector(lua_State * L,Table * t,int size)269 static void setarrayvector (lua_State *L, Table *t, int size) {
270 int i;
271 luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
272 for (i=t->sizearray; i<size; i++)
273 setnilvalue(&t->array[i]);
274 t->sizearray = size;
275 }
276
277
setnodevector(lua_State * L,Table * t,int size)278 static void setnodevector (lua_State *L, Table *t, int size) {
279 int lsize;
280 if (size == 0) { /* no elements to hash part? */
281 t->node = cast(Node *, dummynode); /* use common `dummynode' */
282 lsize = 0;
283 }
284 else {
285 int i;
286 lsize = luaO_ceillog2(size);
287 if (lsize > MAXBITS)
288 luaG_runerror(L, "table overflow");
289 size = twoto(lsize);
290 t->node = luaM_newvector(L, size, Node);
291 for (i=0; i<size; i++) {
292 Node *n = gnode(t, i);
293 gnext(n) = NULL;
294 setnilvalue(gkey(n));
295 setnilvalue(gval(n));
296 }
297 }
298 t->lsizenode = cast_byte(lsize);
299 t->lastfree = gnode(t, size); /* all positions are free */
300 }
301
302
luaH_resize(lua_State * L,Table * t,int nasize,int nhsize)303 void luaH_resize (lua_State *L, Table *t, int nasize, int nhsize) {
304 int i;
305 int oldasize = t->sizearray;
306 int oldhsize = t->lsizenode;
307 Node *nold = t->node; /* save old hash ... */
308 if (nasize > oldasize) /* array part must grow? */
309 setarrayvector(L, t, nasize);
310 /* create new hash part with appropriate size */
311 setnodevector(L, t, nhsize);
312 if (nasize < oldasize) { /* array part must shrink? */
313 t->sizearray = nasize;
314 /* re-insert elements from vanishing slice */
315 for (i=nasize; i<oldasize; i++) {
316 if (!ttisnil(&t->array[i]))
317 luaH_setint(L, t, i + 1, &t->array[i]);
318 }
319 /* shrink array */
320 luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
321 }
322 /* re-insert elements from hash part */
323 for (i = twoto(oldhsize) - 1; i >= 0; i--) {
324 Node *old = nold+i;
325 if (!ttisnil(gval(old))) {
326 /* doesn't need barrier/invalidate cache, as entry was
327 already present in the table */
328 setobjt2t(L, luaH_set(L, t, gkey(old)), gval(old));
329 }
330 }
331 if (!isdummy(nold))
332 luaM_freearray(L, nold, cast(size_t, twoto(oldhsize))); /* free old array */
333 }
334
335
luaH_resizearray(lua_State * L,Table * t,int nasize)336 void luaH_resizearray (lua_State *L, Table *t, int nasize) {
337 int nsize = isdummy(t->node) ? 0 : sizenode(t);
338 luaH_resize(L, t, nasize, nsize);
339 }
340
341
rehash(lua_State * L,Table * t,const TValue * ek)342 static void rehash (lua_State *L, Table *t, const TValue *ek) {
343 int nasize, na;
344 int nums[MAXBITS+1]; /* nums[i] = number of keys with 2^(i-1) < k <= 2^i */
345 int i;
346 int totaluse;
347 for (i=0; i<=MAXBITS; i++) nums[i] = 0; /* reset counts */
348 nasize = numusearray(t, nums); /* count keys in array part */
349 totaluse = nasize; /* all those keys are integer keys */
350 totaluse += numusehash(t, nums, &nasize); /* count keys in hash part */
351 /* count extra key */
352 nasize += countint(ek, nums);
353 totaluse++;
354 /* compute new size for array part */
355 na = computesizes(nums, &nasize);
356 /* resize the table to new computed sizes */
357 luaH_resize(L, t, nasize, totaluse - na);
358 }
359
360
361
362 /*
363 ** }=============================================================
364 */
365
366
luaH_new(lua_State * L)367 Table *luaH_new (lua_State *L) {
368 Table *t = &luaC_newobj(L, LUA_TTABLE, sizeof(Table), NULL, 0)->h;
369 t->metatable = NULL;
370 t->flags = cast_byte(~0);
371 t->array = NULL;
372 t->sizearray = 0;
373 setnodevector(L, t, 0);
374 return t;
375 }
376
377
luaH_free(lua_State * L,Table * t)378 void luaH_free (lua_State *L, Table *t) {
379 if (!isdummy(t->node))
380 luaM_freearray(L, t->node, cast(size_t, sizenode(t)));
381 luaM_freearray(L, t->array, t->sizearray);
382 luaM_free(L, t);
383 }
384
385
getfreepos(Table * t)386 static Node *getfreepos (Table *t) {
387 while (t->lastfree > t->node) {
388 t->lastfree--;
389 if (ttisnil(gkey(t->lastfree)))
390 return t->lastfree;
391 }
392 return NULL; /* could not find a free place */
393 }
394
395
396
397 /*
398 ** inserts a new key into a hash table; first, check whether key's main
399 ** position is free. If not, check whether colliding node is in its main
400 ** position or not: if it is not, move colliding node to an empty place and
401 ** put new key in its main position; otherwise (colliding node is in its main
402 ** position), new key goes to an empty position.
403 */
luaH_newkey(lua_State * L,Table * t,const TValue * key)404 TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
405 Node *mp;
406 if (ttisnil(key)) luaG_runerror(L, "table index is nil");
407 #if defined LUA_HAS_FLOAT_NUMBERS
408 else if (ttisnumber(key) && luai_numisnan(L, nvalue(key)))
409 luaG_runerror(L, "table index is NaN");
410 #endif
411 mp = mainposition(t, key);
412 if (!ttisnil(gval(mp)) || isdummy(mp)) { /* main position is taken? */
413 Node *othern;
414 Node *n = getfreepos(t); /* get a free place */
415 if (n == NULL) { /* cannot find a free place? */
416 rehash(L, t, key); /* grow table */
417 /* whatever called 'newkey' take care of TM cache and GC barrier */
418 return luaH_set(L, t, key); /* insert key into grown table */
419 }
420 lua_assert(!isdummy(n));
421 othern = mainposition(t, gkey(mp));
422 if (othern != mp) { /* is colliding node out of its main position? */
423 /* yes; move colliding node into free position */
424 while (gnext(othern) != mp) othern = gnext(othern); /* find previous */
425 gnext(othern) = n; /* redo the chain with `n' in place of `mp' */
426 *n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
427 gnext(mp) = NULL; /* now `mp' is free */
428 setnilvalue(gval(mp));
429 }
430 else { /* colliding node is in its own main position */
431 /* new node will go into free position */
432 gnext(n) = gnext(mp); /* chain new position */
433 gnext(mp) = n;
434 mp = n;
435 }
436 }
437 setobj2t(L, gkey(mp), key);
438 luaC_barrierback(L, obj2gco(t), key);
439 lua_assert(ttisnil(gval(mp)));
440 return gval(mp);
441 }
442
443
444 /*
445 ** search function for integers
446 */
luaH_getint(Table * t,int key)447 const TValue *luaH_getint (Table *t, int key) {
448 /* (1 <= key && key <= t->sizearray) */
449 if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
450 return &t->array[key-1];
451 else {
452 lua_Number nk = cast_num(key);
453 Node *n = hashnum(t, nk);
454 do { /* check whether `key' is somewhere in the chain */
455 if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
456 return gval(n); /* that's it */
457 else n = gnext(n);
458 } while (n);
459 return luaO_nilobject;
460 }
461 }
462
463
464 /*
465 ** search function for short strings
466 */
luaH_getstr(Table * t,TString * key)467 const TValue *luaH_getstr (Table *t, TString *key) {
468 Node *n = hashstr(t, key);
469 lua_assert(key->tsv.tt == LUA_TSHRSTR);
470 do { /* check whether `key' is somewhere in the chain */
471 if (ttisshrstring(gkey(n)) && eqshrstr(rawtsvalue(gkey(n)), key))
472 return gval(n); /* that's it */
473 else n = gnext(n);
474 } while (n);
475 return luaO_nilobject;
476 }
477
478
479 /*
480 ** main search function
481 */
luaH_get(Table * t,const TValue * key)482 const TValue *luaH_get (Table *t, const TValue *key) {
483 switch (ttype(key)) {
484 case LUA_TSHRSTR: return luaH_getstr(t, rawtsvalue(key));
485 case LUA_TNIL: return luaO_nilobject;
486 case LUA_TNUMBER: {
487 int k;
488 lua_Number n = nvalue(key);
489 lua_number2int(k, n);
490 if (luai_numeq(cast_num(k), n)) /* index is int? */
491 return luaH_getint(t, k); /* use specialized version */
492 /* else go through */
493 }
494 zfs_fallthrough;
495 default: {
496 Node *n = mainposition(t, key);
497 do { /* check whether `key' is somewhere in the chain */
498 if (luaV_rawequalobj(gkey(n), key))
499 return gval(n); /* that's it */
500 else n = gnext(n);
501 } while (n);
502 return luaO_nilobject;
503 }
504 }
505 }
506
507
508 /*
509 ** beware: when using this function you probably need to check a GC
510 ** barrier and invalidate the TM cache.
511 */
luaH_set(lua_State * L,Table * t,const TValue * key)512 TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
513 const TValue *p = luaH_get(t, key);
514 if (p != luaO_nilobject)
515 return cast(TValue *, p);
516 else return luaH_newkey(L, t, key);
517 }
518
519
luaH_setint(lua_State * L,Table * t,int key,TValue * value)520 void luaH_setint (lua_State *L, Table *t, int key, TValue *value) {
521 const TValue *p = luaH_getint(t, key);
522 TValue *cell;
523 if (p != luaO_nilobject)
524 cell = cast(TValue *, p);
525 else {
526 TValue k;
527 setnvalue(&k, cast_num(key));
528 cell = luaH_newkey(L, t, &k);
529 }
530 setobj2t(L, cell, value);
531 }
532
533
unbound_search(Table * t,unsigned int j)534 static int unbound_search (Table *t, unsigned int j) {
535 unsigned int i = j; /* i is zero or a present index */
536 j++;
537 /* find `i' and `j' such that i is present and j is not */
538 while (!ttisnil(luaH_getint(t, j))) {
539 i = j;
540 j *= 2;
541 if (j > cast(unsigned int, MAX_INT)) { /* overflow? */
542 /* table was built with bad purposes: resort to linear search */
543 i = 1;
544 while (!ttisnil(luaH_getint(t, i))) i++;
545 return i - 1;
546 }
547 }
548 /* now do a binary search between them */
549 while (j - i > 1) {
550 unsigned int m = (i+j)/2;
551 if (ttisnil(luaH_getint(t, m))) j = m;
552 else i = m;
553 }
554 return i;
555 }
556
557
558 /*
559 ** Try to find a boundary in table `t'. A `boundary' is an integer index
560 ** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
561 */
luaH_getn(Table * t)562 int luaH_getn (Table *t) {
563 unsigned int j = t->sizearray;
564 if (j > 0 && ttisnil(&t->array[j - 1])) {
565 /* there is a boundary in the array part: (binary) search for it */
566 unsigned int i = 0;
567 while (j - i > 1) {
568 unsigned int m = (i+j)/2;
569 if (ttisnil(&t->array[m - 1])) j = m;
570 else i = m;
571 }
572 return i;
573 }
574 /* else must find a boundary in hash part */
575 else if (isdummy(t->node)) /* hash part is empty? */
576 return j; /* that is easy... */
577 else return unbound_search(t, j);
578 }
579
580
581
582 #if defined(LUA_DEBUG)
583
luaH_mainposition(const Table * t,const TValue * key)584 Node *luaH_mainposition (const Table *t, const TValue *key) {
585 return mainposition(t, key);
586 }
587
luaH_isdummy(Node * n)588 int luaH_isdummy (Node *n) { return isdummy(n); }
589
590 #endif
591