1/*
2** $Id: ltable.c $
3** Lua tables (hash)
4** See Copyright Notice in lua.h
5*/
6
7#define ltable_c
8#define LUA_CORE
9
10#include "lprefix.h"
11
12
13/*
14** Implementation of tables (aka arrays, objects, or hash tables).
15** Tables keep its elements in two parts: an array part and a hash part.
16** Non-negative integer keys are all candidates to be kept in the array
17** part. The actual size of the array is the largest 'n' such that
18** more than half the slots between 1 and n are in use.
19** Hash uses a mix of chained scatter table with Brent's variation.
20** A main invariant of these tables is that, if an element is not
21** in its main position (i.e. the 'original' position that its hash gives
22** to it), then the colliding element is in its own main position.
23** Hence even when the load factor reaches 100%, performance remains good.
24*/
25
26#include <math.h>
27#include <limits.h>
28
29#include "lua.h"
30
31#include "ldebug.h"
32#include "ldo.h"
33#include "lgc.h"
34#include "lmem.h"
35#include "lobject.h"
36#include "lstate.h"
37#include "lstring.h"
38#include "ltable.h"
39#include "lvm.h"
40
41
42/*
43** MAXABITS is the largest integer such that MAXASIZE fits in an
44** unsigned int.
45*/
46#define MAXABITS cast_int(sizeof(int) * CHAR_BIT - 1)
47
48
49/*
50** MAXASIZE is the maximum size of the array part. It is the minimum
51** between 2^MAXABITS and the maximum size that, measured in bytes,
52** fits in a 'size_t'.
53*/
54#define MAXASIZE luaM_limitN(1u << MAXABITS, TValue)
55
56/*
57** MAXHBITS is the largest integer such that 2^MAXHBITS fits in a
58** signed int.
59*/
60#define MAXHBITS (MAXABITS - 1)
61
62
63/*
64** MAXHSIZE is the maximum size of the hash part. It is the minimum
65** between 2^MAXHBITS and the maximum size such that, measured in bytes,
66** it fits in a 'size_t'.
67*/
68#define MAXHSIZE luaM_limitN(1u << MAXHBITS, Node)
69
70
71/*
72** When the original hash value is good, hashing by a power of 2
73** avoids the cost of '%'.
74*/
75#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
76
77/*
78** for other types, it is better to avoid modulo by power of 2, as
79** they can have many 2 factors.
80*/
81#define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
82
83
84#define hashstr(t,str) hashpow2(t, (str)->hash)
85#define hashboolean(t,p) hashpow2(t, p)
86
87
88#define hashpointer(t,p) hashmod(t, point2uint(p))
89
90
91#define dummynode (&dummynode_)
92
93static const Node dummynode_ = {
94 {{NULL}, LUA_VEMPTY, /* value's value and type */
95 LUA_VNIL, 0, {NULL}} /* key type, next, and key value */
96};
97
98
99static const TValue absentkey = {ABSTKEYCONSTANT};
100
101
102/*
103** Hash for integers. To allow a good hash, use the remainder operator
104** ('%'). If integer fits as a non-negative int, compute an int
105** remainder, which is faster. Otherwise, use an unsigned-integer
106** remainder, which uses all bits and ensures a non-negative result.
107*/
108static Node *hashint (const Table *t, lua_Integer i) {
109 lua_Unsigned ui = l_castS2U(i);
110 if (ui <= (unsigned int)INT_MAX)
111 return hashmod(t, cast_int(ui));
112 else
113 return hashmod(t, ui);
114}
115
116
117/*
118** Hash for floating-point numbers.
119** The main computation should be just
120** n = frexp(n, &i); return (n * INT_MAX) + i
121** but there are some numerical subtleties.
122** In a two-complement representation, INT_MAX does not has an exact
123** representation as a float, but INT_MIN does; because the absolute
124** value of 'frexp' is smaller than 1 (unless 'n' is inf/NaN), the
125** absolute value of the product 'frexp * -INT_MIN' is smaller or equal
126** to INT_MAX. Next, the use of 'unsigned int' avoids overflows when
127** adding 'i'; the use of '~u' (instead of '-u') avoids problems with
128** INT_MIN.
129*/
130#if !defined(l_hashfloat)
131static int l_hashfloat (lua_Number n) {
132 int i;
133 lua_Integer ni;
134 n = l_mathop(frexp)(n, &i) * -cast_num(INT_MIN);
135 if (!lua_numbertointeger(n, &ni)) { /* is 'n' inf/-inf/NaN? */
136 lua_assert(luai_numisnan(n) || l_mathop(fabs)(n) == cast_num(HUGE_VAL));
137 return 0;
138 }
139 else { /* normal case */
140 unsigned int u = cast_uint(i) + cast_uint(ni);
141 return cast_int(u <= cast_uint(INT_MAX) ? u : ~u);
142 }
143}
144#endif
145
146
147/*
148** returns the 'main' position of an element in a table (that is,
149** the index of its hash value).
150*/
151static Node *mainpositionTV (const Table *t, const TValue *key) {
152 switch (ttypetag(key)) {
153 case LUA_VNUMINT: {
154 lua_Integer i = ivalue(key);
155 return hashint(t, i);
156 }
157 case LUA_VNUMFLT: {
158 lua_Number n = fltvalue(key);
159 return hashmod(t, l_hashfloat(n));
160 }
161 case LUA_VSHRSTR: {
162 TString *ts = tsvalue(key);
163 return hashstr(t, ts);
164 }
165 case LUA_VLNGSTR: {
166 TString *ts = tsvalue(key);
167 return hashpow2(t, luaS_hashlongstr(ts));
168 }
169 case LUA_VFALSE:
170 return hashboolean(t, 0);
171 case LUA_VTRUE:
172 return hashboolean(t, 1);
173 case LUA_VLIGHTUSERDATA: {
174 void *p = pvalue(key);
175 return hashpointer(t, p);
176 }
177 case LUA_VLCF: {
178 lua_CFunction f = fvalue(key);
179 return hashpointer(t, f);
180 }
181 default: {
182 GCObject *o = gcvalue(key);
183 return hashpointer(t, o);
184 }
185 }
186}
187
188
189l_sinline Node *mainpositionfromnode (const Table *t, Node *nd) {
190 TValue key;
191 getnodekey(cast(lua_State *, NULL), &key, nd);
192 return mainpositionTV(t, &key);
193}
194
195
196/*
197** Check whether key 'k1' is equal to the key in node 'n2'. This
198** equality is raw, so there are no metamethods. Floats with integer
199** values have been normalized, so integers cannot be equal to
200** floats. It is assumed that 'eqshrstr' is simply pointer equality, so
201** that short strings are handled in the default case.
202** A true 'deadok' means to accept dead keys as equal to their original
203** values. All dead keys are compared in the default case, by pointer
204** identity. (Only collectable objects can produce dead keys.) Note that
205** dead long strings are also compared by identity.
206** Once a key is dead, its corresponding value may be collected, and
207** then another value can be created with the same address. If this
208** other value is given to 'next', 'equalkey' will signal a false
209** positive. In a regular traversal, this situation should never happen,
210** as all keys given to 'next' came from the table itself, and therefore
211** could not have been collected. Outside a regular traversal, we
212** have garbage in, garbage out. What is relevant is that this false
213** positive does not break anything. (In particular, 'next' will return
214** some other valid item on the table or nil.)
215*/
216static int equalkey (const TValue *k1, const Node *n2, int deadok) {
217 if ((rawtt(k1) != keytt(n2)) && /* not the same variants? */
218 !(deadok && keyisdead(n2) && iscollectable(k1)))
219 return 0; /* cannot be same key */
220 switch (keytt(n2)) {
221 case LUA_VNIL: case LUA_VFALSE: case LUA_VTRUE:
222 return 1;
223 case LUA_VNUMINT:
224 return (ivalue(k1) == keyival(n2));
225 case LUA_VNUMFLT:
226 return luai_numeq(fltvalue(k1), fltvalueraw(keyval(n2)));
227 case LUA_VLIGHTUSERDATA:
228 return pvalue(k1) == pvalueraw(keyval(n2));
229 case LUA_VLCF:
230 return fvalue(k1) == fvalueraw(keyval(n2));
231 case ctb(LUA_VLNGSTR):
232 return luaS_eqlngstr(tsvalue(k1), keystrval(n2));
233 default:
234 return gcvalue(k1) == gcvalueraw(keyval(n2));
235 }
236}
237
238
239/*
240** True if value of 'alimit' is equal to the real size of the array
241** part of table 't'. (Otherwise, the array part must be larger than
242** 'alimit'.)
243*/
244#define limitequalsasize(t) (isrealasize(t) || ispow2((t)->alimit))
245
246
247/*
248** Returns the real size of the 'array' array
249*/
250LUAI_FUNC unsigned int luaH_realasize (const Table *t) {
251 if (limitequalsasize(t))
252 return t->alimit; /* this is the size */
253 else {
254 unsigned int size = t->alimit;
255 /* compute the smallest power of 2 not smaller than 'n' */
256 size |= (size >> 1);
257 size |= (size >> 2);
258 size |= (size >> 4);
259 size |= (size >> 8);
260 size |= (size >> 16);
261#if (UINT_MAX >> 30) > 3
262 size |= (size >> 32); /* unsigned int has more than 32 bits */
263#endif
264 size++;
265 lua_assert(ispow2(size) && size/2 < t->alimit && t->alimit < size);
266 return size;
267 }
268}
269
270
271/*
272** Check whether real size of the array is a power of 2.
273** (If it is not, 'alimit' cannot be changed to any other value
274** without changing the real size.)
275*/
276static int ispow2realasize (const Table *t) {
277 return (!isrealasize(t) || ispow2(t->alimit));
278}
279
280
281static unsigned int setlimittosize (Table *t) {
282 t->alimit = luaH_realasize(t);
283 setrealasize(t);
284 return t->alimit;
285}
286
287
288#define limitasasize(t) check_exp(isrealasize(t), t->alimit)
289
290
291
292/*
293** "Generic" get version. (Not that generic: not valid for integers,
294** which may be in array part, nor for floats with integral values.)
295** See explanation about 'deadok' in function 'equalkey'.
296*/
297static const TValue *getgeneric (Table *t, const TValue *key, int deadok) {
298 Node *n = mainpositionTV(t, key);
299 for (;;) { /* check whether 'key' is somewhere in the chain */
300 if (equalkey(key, n, deadok))
301 return gval(n); /* that's it */
302 else {
303 int nx = gnext(n);
304 if (nx == 0)
305 return &absentkey; /* not found */
306 n += nx;
307 }
308 }
309}
310
311
312/*
313** returns the index for 'k' if 'k' is an appropriate key to live in
314** the array part of a table, 0 otherwise.
315*/
316static unsigned int arrayindex (lua_Integer k) {
317 if (l_castS2U(k) - 1u < MAXASIZE) /* 'k' in [1, MAXASIZE]? */
318 return cast_uint(k); /* 'key' is an appropriate array index */
319 else
320 return 0;
321}
322
323
324/*
325** returns the index of a 'key' for table traversals. First goes all
326** elements in the array part, then elements in the hash part. The
327** beginning of a traversal is signaled by 0.
328*/
329static unsigned int findindex (lua_State *L, Table *t, TValue *key,
330 unsigned int asize) {
331 unsigned int i;
332 if (ttisnil(key)) return 0; /* first iteration */
333 i = ttisinteger(key) ? arrayindex(ivalue(key)) : 0;
334 if (i - 1u < asize) /* is 'key' inside array part? */
335 return i; /* yes; that's the index */
336 else {
337 const TValue *n = getgeneric(t, key, 1);
338 if (l_unlikely(isabstkey(n)))
339 luaG_runerror(L, "invalid key to 'next'"); /* key not found */
340 i = cast_int(nodefromval(n) - gnode(t, 0)); /* key index in hash table */
341 /* hash elements are numbered after array ones */
342 return (i + 1) + asize;
343 }
344}
345
346
347int luaH_next (lua_State *L, Table *t, StkId key) {
348 unsigned int asize = luaH_realasize(t);
349 unsigned int i = findindex(L, t, s2v(key), asize); /* find original key */
350 for (; i < asize; i++) { /* try first array part */
351 if (!isempty(&t->array[i])) { /* a non-empty entry? */
352 setivalue(s2v(key), i + 1);
353 setobj2s(L, key + 1, &t->array[i]);
354 return 1;
355 }
356 }
357 for (i -= asize; cast_int(i) < sizenode(t); i++) { /* hash part */
358 if (!isempty(gval(gnode(t, i)))) { /* a non-empty entry? */
359 Node *n = gnode(t, i);
360 getnodekey(L, s2v(key), n);
361 setobj2s(L, key + 1, gval(n));
362 return 1;
363 }
364 }
365 return 0; /* no more elements */
366}
367
368
369static void freehash (lua_State *L, Table *t) {
370 if (!isdummy(t))
371 luaM_freearray(L, t->node, cast_sizet(sizenode(t)));
372}
373
374
375/*
376** {=============================================================
377** Rehash
378** ==============================================================
379*/
380
381/*
382** Compute the optimal size for the array part of table 't'. 'nums' is a
383** "count array" where 'nums[i]' is the number of integers in the table
384** between 2^(i - 1) + 1 and 2^i. 'pna' enters with the total number of
385** integer keys in the table and leaves with the number of keys that
386** will go to the array part; return the optimal size. (The condition
387** 'twotoi > 0' in the for loop stops the loop if 'twotoi' overflows.)
388*/
389static unsigned int computesizes (unsigned int nums[], unsigned int *pna) {
390 int i;
391 unsigned int twotoi; /* 2^i (candidate for optimal size) */
392 unsigned int a = 0; /* number of elements smaller than 2^i */
393 unsigned int na = 0; /* number of elements to go to array part */
394 unsigned int optimal = 0; /* optimal size for array part */
395 /* loop while keys can fill more than half of total size */
396 for (i = 0, twotoi = 1;
397 twotoi > 0 && *pna > twotoi / 2;
398 i++, twotoi *= 2) {
399 a += nums[i];
400 if (a > twotoi/2) { /* more than half elements present? */
401 optimal = twotoi; /* optimal size (till now) */
402 na = a; /* all elements up to 'optimal' will go to array part */
403 }
404 }
405 lua_assert((optimal == 0 || optimal / 2 < na) && na <= optimal);
406 *pna = na;
407 return optimal;
408}
409
410
411static int countint (lua_Integer key, unsigned int *nums) {
412 unsigned int k = arrayindex(key);
413 if (k != 0) { /* is 'key' an appropriate array index? */
414 nums[luaO_ceillog2(k)]++; /* count as such */
415 return 1;
416 }
417 else
418 return 0;
419}
420
421
422/*
423** Count keys in array part of table 't': Fill 'nums[i]' with
424** number of keys that will go into corresponding slice and return
425** total number of non-nil keys.
426*/
427static unsigned int numusearray (const Table *t, unsigned int *nums) {
428 int lg;
429 unsigned int ttlg; /* 2^lg */
430 unsigned int ause = 0; /* summation of 'nums' */
431 unsigned int i = 1; /* count to traverse all array keys */
432 unsigned int asize = limitasasize(t); /* real array size */
433 /* traverse each slice */
434 for (lg = 0, ttlg = 1; lg <= MAXABITS; lg++, ttlg *= 2) {
435 unsigned int lc = 0; /* counter */
436 unsigned int lim = ttlg;
437 if (lim > asize) {
438 lim = asize; /* adjust upper limit */
439 if (i > lim)
440 break; /* no more elements to count */
441 }
442 /* count elements in range (2^(lg - 1), 2^lg] */
443 for (; i <= lim; i++) {
444 if (!isempty(&t->array[i-1]))
445 lc++;
446 }
447 nums[lg] += lc;
448 ause += lc;
449 }
450 return ause;
451}
452
453
454static int numusehash (const Table *t, unsigned int *nums, unsigned int *pna) {
455 int totaluse = 0; /* total number of elements */
456 int ause = 0; /* elements added to 'nums' (can go to array part) */
457 int i = sizenode(t);
458 while (i--) {
459 Node *n = &t->node[i];
460 if (!isempty(gval(n))) {
461 if (keyisinteger(n))
462 ause += countint(keyival(n), nums);
463 totaluse++;
464 }
465 }
466 *pna += ause;
467 return totaluse;
468}
469
470
471/*
472** Creates an array for the hash part of a table with the given
473** size, or reuses the dummy node if size is zero.
474** The computation for size overflow is in two steps: the first
475** comparison ensures that the shift in the second one does not
476** overflow.
477*/
478static void setnodevector (lua_State *L, Table *t, unsigned int size) {
479 if (size == 0) { /* no elements to hash part? */
480 t->node = cast(Node *, dummynode); /* use common 'dummynode' */
481 t->lsizenode = 0;
482 t->lastfree = NULL; /* signal that it is using dummy node */
483 }
484 else {
485 int i;
486 int lsize = luaO_ceillog2(size);
487 if (lsize > MAXHBITS || (1u << lsize) > MAXHSIZE)
488 luaG_runerror(L, "table overflow");
489 size = twoto(lsize);
490 t->node = luaM_newvector(L, size, Node);
491 for (i = 0; i < (int)size; i++) {
492 Node *n = gnode(t, i);
493 gnext(n) = 0;
494 setnilkey(n);
495 setempty(gval(n));
496 }
497 t->lsizenode = cast_byte(lsize);
498 t->lastfree = gnode(t, size); /* all positions are free */
499 }
500}
501
502
503/*
504** (Re)insert all elements from the hash part of 'ot' into table 't'.
505*/
506static void reinsert (lua_State *L, Table *ot, Table *t) {
507 int j;
508 int size = sizenode(ot);
509 for (j = 0; j < size; j++) {
510 Node *old = gnode(ot, j);
511 if (!isempty(gval(old))) {
512 /* doesn't need barrier/invalidate cache, as entry was
513 already present in the table */
514 TValue k;
515 getnodekey(L, &k, old);
516 luaH_set(L, t, &k, gval(old));
517 }
518 }
519}
520
521
522/*
523** Exchange the hash part of 't1' and 't2'.
524*/
525static void exchangehashpart (Table *t1, Table *t2) {
526 lu_byte lsizenode = t1->lsizenode;
527 Node *node = t1->node;
528 Node *lastfree = t1->lastfree;
529 t1->lsizenode = t2->lsizenode;
530 t1->node = t2->node;
531 t1->lastfree = t2->lastfree;
532 t2->lsizenode = lsizenode;
533 t2->node = node;
534 t2->lastfree = lastfree;
535}
536
537
538/*
539** Resize table 't' for the new given sizes. Both allocations (for
540** the hash part and for the array part) can fail, which creates some
541** subtleties. If the first allocation, for the hash part, fails, an
542** error is raised and that is it. Otherwise, it copies the elements from
543** the shrinking part of the array (if it is shrinking) into the new
544** hash. Then it reallocates the array part. If that fails, the table
545** is in its original state; the function frees the new hash part and then
546** raises the allocation error. Otherwise, it sets the new hash part
547** into the table, initializes the new part of the array (if any) with
548** nils and reinserts the elements of the old hash back into the new
549** parts of the table.
550*/
551void luaH_resize (lua_State *L, Table *t, unsigned int newasize,
552 unsigned int nhsize) {
553 unsigned int i;
554 Table newt; /* to keep the new hash part */
555 unsigned int oldasize = setlimittosize(t);
556 TValue *newarray;
557 /* create new hash part with appropriate size into 'newt' */
558 setnodevector(L, &newt, nhsize);
559 if (newasize < oldasize) { /* will array shrink? */
560 t->alimit = newasize; /* pretend array has new size... */
561 exchangehashpart(t, &newt); /* and new hash */
562 /* re-insert into the new hash the elements from vanishing slice */
563 for (i = newasize; i < oldasize; i++) {
564 if (!isempty(&t->array[i]))
565 luaH_setint(L, t, i + 1, &t->array[i]);
566 }
567 t->alimit = oldasize; /* restore current size... */
568 exchangehashpart(t, &newt); /* and hash (in case of errors) */
569 }
570 /* allocate new array */
571 newarray = luaM_reallocvector(L, t->array, oldasize, newasize, TValue);
572 if (l_unlikely(newarray == NULL && newasize > 0)) { /* allocation failed? */
573 freehash(L, &newt); /* release new hash part */
574 luaM_error(L); /* raise error (with array unchanged) */
575 }
576 /* allocation ok; initialize new part of the array */
577 exchangehashpart(t, &newt); /* 't' has the new hash ('newt' has the old) */
578 t->array = newarray; /* set new array part */
579 t->alimit = newasize;
580 for (i = oldasize; i < newasize; i++) /* clear new slice of the array */
581 setempty(&t->array[i]);
582 /* re-insert elements from old hash part into new parts */
583 reinsert(L, &newt, t); /* 'newt' now has the old hash */
584 freehash(L, &newt); /* free old hash part */
585}
586
587
588void luaH_resizearray (lua_State *L, Table *t, unsigned int nasize) {
589 int nsize = allocsizenode(t);
590 luaH_resize(L, t, nasize, nsize);
591}
592
593/*
594** nums[i] = number of keys 'k' where 2^(i - 1) < k <= 2^i
595*/
596static void rehash (lua_State *L, Table *t, const TValue *ek) {
597 unsigned int asize; /* optimal size for array part */
598 unsigned int na; /* number of keys in the array part */
599 unsigned int nums[MAXABITS + 1];
600 int i;
601 int totaluse;
602 for (i = 0; i <= MAXABITS; i++) nums[i] = 0; /* reset counts */
603 setlimittosize(t);
604 na = numusearray(t, nums); /* count keys in array part */
605 totaluse = na; /* all those keys are integer keys */
606 totaluse += numusehash(t, nums, &na); /* count keys in hash part */
607 /* count extra key */
608 if (ttisinteger(ek))
609 na += countint(ivalue(ek), nums);
610 totaluse++;
611 /* compute new size for array part */
612 asize = computesizes(nums, &na);
613 /* resize the table to new computed sizes */
614 luaH_resize(L, t, asize, totaluse - na);
615}
616
617
618
619/*
620** }=============================================================
621*/
622
623
624Table *luaH_new (lua_State *L) {
625 GCObject *o = luaC_newobj(L, LUA_VTABLE, sizeof(Table));
626 Table *t = gco2t(o);
627 t->metatable = NULL;
628 t->flags = cast_byte(maskflags); /* table has no metamethod fields */
629 t->array = NULL;
630 t->alimit = 0;
631 setnodevector(L, t, 0);
632 return t;
633}
634
635
636void luaH_free (lua_State *L, Table *t) {
637 freehash(L, t);
638 luaM_freearray(L, t->array, luaH_realasize(t));
639 luaM_free(L, t);
640}
641
642
643static Node *getfreepos (Table *t) {
644 if (!isdummy(t)) {
645 while (t->lastfree > t->node) {
646 t->lastfree--;
647 if (keyisnil(t->lastfree))
648 return t->lastfree;
649 }
650 }
651 return NULL; /* could not find a free place */
652}
653
654
655
656/*
657** inserts a new key into a hash table; first, check whether key's main
658** position is free. If not, check whether colliding node is in its main
659** position or not: if it is not, move colliding node to an empty place and
660** put new key in its main position; otherwise (colliding node is in its main
661** position), new key goes to an empty position.
662*/
663void luaH_newkey (lua_State *L, Table *t, const TValue *key, TValue *value) {
664 Node *mp;
665 TValue aux;
666 if (l_unlikely(ttisnil(key)))
667 luaG_runerror(L, "table index is nil");
668 else if (ttisfloat(key)) {
669 lua_Number f = fltvalue(key);
670 lua_Integer k;
671 if (luaV_flttointeger(f, &k, F2Ieq)) { /* does key fit in an integer? */
672 setivalue(&aux, k);
673 key = &aux; /* insert it as an integer */
674 }
675 else if (l_unlikely(luai_numisnan(f)))
676 luaG_runerror(L, "table index is NaN");
677 }
678 if (ttisnil(value))
679 return; /* do not insert nil values */
680 mp = mainpositionTV(t, key);
681 if (!isempty(gval(mp)) || isdummy(t)) { /* main position is taken? */
682 Node *othern;
683 Node *f = getfreepos(t); /* get a free place */
684 if (f == NULL) { /* cannot find a free place? */
685 rehash(L, t, key); /* grow table */
686 /* whatever called 'newkey' takes care of TM cache */
687 luaH_set(L, t, key, value); /* insert key into grown table */
688 return;
689 }
690 lua_assert(!isdummy(t));
691 othern = mainpositionfromnode(t, mp);
692 if (othern != mp) { /* is colliding node out of its main position? */
693 /* yes; move colliding node into free position */
694 while (othern + gnext(othern) != mp) /* find previous */
695 othern += gnext(othern);
696 gnext(othern) = cast_int(f - othern); /* rechain to point to 'f' */
697 *f = *mp; /* copy colliding node into free pos. (mp->next also goes) */
698 if (gnext(mp) != 0) {
699 gnext(f) += cast_int(mp - f); /* correct 'next' */
700 gnext(mp) = 0; /* now 'mp' is free */
701 }
702 setempty(gval(mp));
703 }
704 else { /* colliding node is in its own main position */
705 /* new node will go into free position */
706 if (gnext(mp) != 0)
707 gnext(f) = cast_int((mp + gnext(mp)) - f); /* chain new position */
708 else lua_assert(gnext(f) == 0);
709 gnext(mp) = cast_int(f - mp);
710 mp = f;
711 }
712 }
713 setnodekey(L, mp, key);
714 luaC_barrierback(L, obj2gco(t), key);
715 lua_assert(isempty(gval(mp)));
716 setobj2t(L, gval(mp), value);
717}
718
719
720/*
721** Search function for integers. If integer is inside 'alimit', get it
722** directly from the array part. Otherwise, if 'alimit' is not equal to
723** the real size of the array, key still can be in the array part. In
724** this case, try to avoid a call to 'luaH_realasize' when key is just
725** one more than the limit (so that it can be incremented without
726** changing the real size of the array).
727*/
728const TValue *luaH_getint (Table *t, lua_Integer key) {
729 if (l_castS2U(key) - 1u < t->alimit) /* 'key' in [1, t->alimit]? */
730 return &t->array[key - 1];
731 else if (!limitequalsasize(t) && /* key still may be in the array part? */
732 (l_castS2U(key) == t->alimit + 1 ||
733 l_castS2U(key) - 1u < luaH_realasize(t))) {
734 t->alimit = cast_uint(key); /* probably '#t' is here now */
735 return &t->array[key - 1];
736 }
737 else {
738 Node *n = hashint(t, key);
739 for (;;) { /* check whether 'key' is somewhere in the chain */
740 if (keyisinteger(n) && keyival(n) == key)
741 return gval(n); /* that's it */
742 else {
743 int nx = gnext(n);
744 if (nx == 0) break;
745 n += nx;
746 }
747 }
748 return &absentkey;
749 }
750}
751
752
753/*
754** search function for short strings
755*/
756const TValue *luaH_getshortstr (Table *t, TString *key) {
757 Node *n = hashstr(t, key);
758 lua_assert(key->tt == LUA_VSHRSTR);
759 for (;;) { /* check whether 'key' is somewhere in the chain */
760 if (keyisshrstr(n) && eqshrstr(keystrval(n), key))
761 return gval(n); /* that's it */
762 else {
763 int nx = gnext(n);
764 if (nx == 0)
765 return &absentkey; /* not found */
766 n += nx;
767 }
768 }
769}
770
771
772const TValue *luaH_getstr (Table *t, TString *key) {
773 if (key->tt == LUA_VSHRSTR)
774 return luaH_getshortstr(t, key);
775 else { /* for long strings, use generic case */
776 TValue ko;
777 setsvalue(cast(lua_State *, NULL), &ko, key);
778 return getgeneric(t, &ko, 0);
779 }
780}
781
782
783/*
784** main search function
785*/
786const TValue *luaH_get (Table *t, const TValue *key) {
787 switch (ttypetag(key)) {
788 case LUA_VSHRSTR: return luaH_getshortstr(t, tsvalue(key));
789 case LUA_VNUMINT: return luaH_getint(t, ivalue(key));
790 case LUA_VNIL: return &absentkey;
791 case LUA_VNUMFLT: {
792 lua_Integer k;
793 if (luaV_flttointeger(fltvalue(key), &k, F2Ieq)) /* integral index? */
794 return luaH_getint(t, k); /* use specialized version */
795 /* else... */
796 } /* FALLTHROUGH */
797 default:
798 return getgeneric(t, key, 0);
799 }
800}
801
802
803/*
804** Finish a raw "set table" operation, where 'slot' is where the value
805** should have been (the result of a previous "get table").
806** Beware: when using this function you probably need to check a GC
807** barrier and invalidate the TM cache.
808*/
809void luaH_finishset (lua_State *L, Table *t, const TValue *key,
810 const TValue *slot, TValue *value) {
811 if (isabstkey(slot))
812 luaH_newkey(L, t, key, value);
813 else
814 setobj2t(L, cast(TValue *, slot), value);
815}
816
817
818/*
819** beware: when using this function you probably need to check a GC
820** barrier and invalidate the TM cache.
821*/
822void luaH_set (lua_State *L, Table *t, const TValue *key, TValue *value) {
823 const TValue *slot = luaH_get(t, key);
824 luaH_finishset(L, t, key, slot, value);
825}
826
827
828void luaH_setint (lua_State *L, Table *t, lua_Integer key, TValue *value) {
829 const TValue *p = luaH_getint(t, key);
830 if (isabstkey(p)) {
831 TValue k;
832 setivalue(&k, key);
833 luaH_newkey(L, t, &k, value);
834 }
835 else
836 setobj2t(L, cast(TValue *, p), value);
837}
838
839
840/*
841** Try to find a boundary in the hash part of table 't'. From the
842** caller, we know that 'j' is zero or present and that 'j + 1' is
843** present. We want to find a larger key that is absent from the
844** table, so that we can do a binary search between the two keys to
845** find a boundary. We keep doubling 'j' until we get an absent index.
846** If the doubling would overflow, we try LUA_MAXINTEGER. If it is
847** absent, we are ready for the binary search. ('j', being max integer,
848** is larger or equal to 'i', but it cannot be equal because it is
849** absent while 'i' is present; so 'j > i'.) Otherwise, 'j' is a
850** boundary. ('j + 1' cannot be a present integer key because it is
851** not a valid integer in Lua.)
852*/
853static lua_Unsigned hash_search (Table *t, lua_Unsigned j) {
854 lua_Unsigned i;
855 if (j == 0) j++; /* the caller ensures 'j + 1' is present */
856 do {
857 i = j; /* 'i' is a present index */
858 if (j <= l_castS2U(LUA_MAXINTEGER) / 2)
859 j *= 2;
860 else {
861 j = LUA_MAXINTEGER;
862 if (isempty(luaH_getint(t, j))) /* t[j] not present? */
863 break; /* 'j' now is an absent index */
864 else /* weird case */
865 return j; /* well, max integer is a boundary... */
866 }
867 } while (!isempty(luaH_getint(t, j))); /* repeat until an absent t[j] */
868 /* i < j && t[i] present && t[j] absent */
869 while (j - i > 1u) { /* do a binary search between them */
870 lua_Unsigned m = (i + j) / 2;
871 if (isempty(luaH_getint(t, m))) j = m;
872 else i = m;
873 }
874 return i;
875}
876
877
878static unsigned int binsearch (const TValue *array, unsigned int i,
879 unsigned int j) {
880 while (j - i > 1u) { /* binary search */
881 unsigned int m = (i + j) / 2;
882 if (isempty(&array[m - 1])) j = m;
883 else i = m;
884 }
885 return i;
886}
887
888
889/*
890** Try to find a boundary in table 't'. (A 'boundary' is an integer index
891** such that t[i] is present and t[i+1] is absent, or 0 if t[1] is absent
892** and 'maxinteger' if t[maxinteger] is present.)
893** (In the next explanation, we use Lua indices, that is, with base 1.
894** The code itself uses base 0 when indexing the array part of the table.)
895** The code starts with 'limit = t->alimit', a position in the array
896** part that may be a boundary.
897**
898** (1) If 't[limit]' is empty, there must be a boundary before it.
899** As a common case (e.g., after 't[#t]=nil'), check whether 'limit-1'
900** is present. If so, it is a boundary. Otherwise, do a binary search
901** between 0 and limit to find a boundary. In both cases, try to
902** use this boundary as the new 'alimit', as a hint for the next call.
903**
904** (2) If 't[limit]' is not empty and the array has more elements
905** after 'limit', try to find a boundary there. Again, try first
906** the special case (which should be quite frequent) where 'limit+1'
907** is empty, so that 'limit' is a boundary. Otherwise, check the
908** last element of the array part. If it is empty, there must be a
909** boundary between the old limit (present) and the last element
910** (absent), which is found with a binary search. (This boundary always
911** can be a new limit.)
912**
913** (3) The last case is when there are no elements in the array part
914** (limit == 0) or its last element (the new limit) is present.
915** In this case, must check the hash part. If there is no hash part
916** or 'limit+1' is absent, 'limit' is a boundary. Otherwise, call
917** 'hash_search' to find a boundary in the hash part of the table.
918** (In those cases, the boundary is not inside the array part, and
919** therefore cannot be used as a new limit.)
920*/
921lua_Unsigned luaH_getn (Table *t) {
922 unsigned int limit = t->alimit;
923 if (limit > 0 && isempty(&t->array[limit - 1])) { /* (1)? */
924 /* there must be a boundary before 'limit' */
925 if (limit >= 2 && !isempty(&t->array[limit - 2])) {
926 /* 'limit - 1' is a boundary; can it be a new limit? */
927 if (ispow2realasize(t) && !ispow2(limit - 1)) {
928 t->alimit = limit - 1;
929 setnorealasize(t); /* now 'alimit' is not the real size */
930 }
931 return limit - 1;
932 }
933 else { /* must search for a boundary in [0, limit] */
934 unsigned int boundary = binsearch(t->array, 0, limit);
935 /* can this boundary represent the real size of the array? */
936 if (ispow2realasize(t) && boundary > luaH_realasize(t) / 2) {
937 t->alimit = boundary; /* use it as the new limit */
938 setnorealasize(t);
939 }
940 return boundary;
941 }
942 }
943 /* 'limit' is zero or present in table */
944 if (!limitequalsasize(t)) { /* (2)? */
945 /* 'limit' > 0 and array has more elements after 'limit' */
946 if (isempty(&t->array[limit])) /* 'limit + 1' is empty? */
947 return limit; /* this is the boundary */
948 /* else, try last element in the array */
949 limit = luaH_realasize(t);
950 if (isempty(&t->array[limit - 1])) { /* empty? */
951 /* there must be a boundary in the array after old limit,
952 and it must be a valid new limit */
953 unsigned int boundary = binsearch(t->array, t->alimit, limit);
954 t->alimit = boundary;
955 return boundary;
956 }
957 /* else, new limit is present in the table; check the hash part */
958 }
959 /* (3) 'limit' is the last element and either is zero or present in table */
960 lua_assert(limit == luaH_realasize(t) &&
961 (limit == 0 || !isempty(&t->array[limit - 1])));
962 if (isdummy(t) || isempty(luaH_getint(t, cast(lua_Integer, limit + 1))))
963 return limit; /* 'limit + 1' is absent */
964 else /* 'limit + 1' is also present */
965 return hash_search(t, limit);
966}
967
968
969
970#if defined(LUA_DEBUG)
971
972/* export these functions for the test library */
973
974Node *luaH_mainposition (const Table *t, const TValue *key) {
975 return mainpositionTV(t, key);
976}
977
978int luaH_isdummy (const Table *t) { return isdummy(t); }
979
980#endif
981