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 #define hashpow2(t,n)		(gnode(t, lmod((n), sizenode(t))))
72 
73 #define hashstr(t,str)		hashpow2(t, (str)->hash)
74 #define hashboolean(t,p)	hashpow2(t, p)
75 #define hashint(t,i)		hashpow2(t, i)
76 
77 
78 /*
79 ** for some types, it is better to avoid modulus by power of 2, as
80 ** they tend to have many 2 factors.
81 */
82 #define hashmod(t,n)	(gnode(t, ((n) % ((sizenode(t)-1)|1))))
83 
84 
85 #define hashpointer(t,p)	hashmod(t, point2uint(p))
86 
87 
88 #define dummynode		(&dummynode_)
89 
90 static const Node dummynode_ = {
91   {{NULL}, LUA_VEMPTY,  /* value's value and type */
92    LUA_VNIL, 0, {NULL}}  /* key type, next, and key value */
93 };
94 
95 
96 static const TValue absentkey = {ABSTKEYCONSTANT};
97 
98 
99 
100 /*
101 ** Hash for floating-point numbers.
102 ** The main computation should be just
103 **     n = frexp(n, &i); return (n * INT_MAX) + i
104 ** but there are some numerical subtleties.
105 ** In a two-complement representation, INT_MAX does not has an exact
106 ** representation as a float, but INT_MIN does; because the absolute
107 ** value of 'frexp' is smaller than 1 (unless 'n' is inf/NaN), the
108 ** absolute value of the product 'frexp * -INT_MIN' is smaller or equal
109 ** to INT_MAX. Next, the use of 'unsigned int' avoids overflows when
110 ** adding 'i'; the use of '~u' (instead of '-u') avoids problems with
111 ** INT_MIN.
112 */
113 #if !defined(l_hashfloat)
l_hashfloat(lua_Number n)114 static int l_hashfloat (lua_Number n) {
115   int i;
116   lua_Integer ni;
117   n = l_mathop(frexp)(n, &i) * -cast_num(INT_MIN);
118   if (!lua_numbertointeger(n, &ni)) {  /* is 'n' inf/-inf/NaN? */
119     lua_assert(luai_numisnan(n) || l_mathop(fabs)(n) == cast_num(HUGE_VAL));
120     return 0;
121   }
122   else {  /* normal case */
123     unsigned int u = cast_uint(i) + cast_uint(ni);
124     return cast_int(u <= cast_uint(INT_MAX) ? u : ~u);
125   }
126 }
127 #endif
128 
129 
130 /*
131 ** returns the 'main' position of an element in a table (that is,
132 ** the index of its hash value). The key comes broken (tag in 'ktt'
133 ** and value in 'vkl') so that we can call it on keys inserted into
134 ** nodes.
135 */
mainposition(const Table * t,int ktt,const Value * kvl)136 static Node *mainposition (const Table *t, int ktt, const Value *kvl) {
137   switch (withvariant(ktt)) {
138     case LUA_VNUMINT:
139       return hashint(t, ivalueraw(*kvl));
140     case LUA_VNUMFLT:
141       return hashmod(t, l_hashfloat(fltvalueraw(*kvl)));
142     case LUA_VSHRSTR:
143       return hashstr(t, tsvalueraw(*kvl));
144     case LUA_VLNGSTR:
145       return hashpow2(t, luaS_hashlongstr(tsvalueraw(*kvl)));
146     case LUA_VFALSE:
147       return hashboolean(t, 0);
148     case LUA_VTRUE:
149       return hashboolean(t, 1);
150     case LUA_VLIGHTUSERDATA:
151       return hashpointer(t, pvalueraw(*kvl));
152     case LUA_VLCF:
153       return hashpointer(t, fvalueraw(*kvl));
154     default:
155       return hashpointer(t, gcvalueraw(*kvl));
156   }
157 }
158 
159 
160 /*
161 ** Returns the main position of an element given as a 'TValue'
162 */
mainpositionTV(const Table * t,const TValue * key)163 static Node *mainpositionTV (const Table *t, const TValue *key) {
164   return mainposition(t, rawtt(key), valraw(key));
165 }
166 
167 
168 /*
169 ** Check whether key 'k1' is equal to the key in node 'n2'.
170 ** This equality is raw, so there are no metamethods. Floats
171 ** with integer values have been normalized, so integers cannot
172 ** be equal to floats. It is assumed that 'eqshrstr' is simply
173 ** pointer equality, so that short strings are handled in the
174 ** default case.
175 */
equalkey(const TValue * k1,const Node * n2)176 static int equalkey (const TValue *k1, const Node *n2) {
177   if (rawtt(k1) != keytt(n2))  /* not the same variants? */
178    return 0;  /* cannot be same key */
179   switch (ttypetag(k1)) {
180     case LUA_VNIL: case LUA_VFALSE: case LUA_VTRUE:
181       return 1;
182     case LUA_VNUMINT:
183       return (ivalue(k1) == keyival(n2));
184     case LUA_VNUMFLT:
185       return luai_numeq(fltvalue(k1), fltvalueraw(keyval(n2)));
186     case LUA_VLIGHTUSERDATA:
187       return pvalue(k1) == pvalueraw(keyval(n2));
188     case LUA_VLCF:
189       return fvalue(k1) == fvalueraw(keyval(n2));
190     case LUA_VLNGSTR:
191       return luaS_eqlngstr(tsvalue(k1), keystrval(n2));
192     default:
193       return gcvalue(k1) == gcvalueraw(keyval(n2));
194   }
195 }
196 
197 
198 /*
199 ** True if value of 'alimit' is equal to the real size of the array
200 ** part of table 't'. (Otherwise, the array part must be larger than
201 ** 'alimit'.)
202 */
203 #define limitequalsasize(t)	(isrealasize(t) || ispow2((t)->alimit))
204 
205 
206 /*
207 ** Returns the real size of the 'array' array
208 */
luaH_realasize(const Table * t)209 LUAI_FUNC unsigned int luaH_realasize (const Table *t) {
210   if (limitequalsasize(t))
211     return t->alimit;  /* this is the size */
212   else {
213     unsigned int size = t->alimit;
214     /* compute the smallest power of 2 not smaller than 'n' */
215     size |= (size >> 1);
216     size |= (size >> 2);
217     size |= (size >> 4);
218     size |= (size >> 8);
219     size |= (size >> 16);
220 #if (UINT_MAX >> 30) > 3
221     size |= (size >> 32);  /* unsigned int has more than 32 bits */
222 #endif
223     size++;
224     lua_assert(ispow2(size) && size/2 < t->alimit && t->alimit < size);
225     return size;
226   }
227 }
228 
229 
230 /*
231 ** Check whether real size of the array is a power of 2.
232 ** (If it is not, 'alimit' cannot be changed to any other value
233 ** without changing the real size.)
234 */
ispow2realasize(const Table * t)235 static int ispow2realasize (const Table *t) {
236   return (!isrealasize(t) || ispow2(t->alimit));
237 }
238 
239 
setlimittosize(Table * t)240 static unsigned int setlimittosize (Table *t) {
241   t->alimit = luaH_realasize(t);
242   setrealasize(t);
243   return t->alimit;
244 }
245 
246 
247 #define limitasasize(t)	check_exp(isrealasize(t), t->alimit)
248 
249 
250 
251 /*
252 ** "Generic" get version. (Not that generic: not valid for integers,
253 ** which may be in array part, nor for floats with integral values.)
254 */
getgeneric(Table * t,const TValue * key)255 static const TValue *getgeneric (Table *t, const TValue *key) {
256   Node *n = mainpositionTV(t, key);
257   for (;;) {  /* check whether 'key' is somewhere in the chain */
258     if (equalkey(key, n))
259       return gval(n);  /* that's it */
260     else {
261       int nx = gnext(n);
262       if (nx == 0)
263         return &absentkey;  /* not found */
264       n += nx;
265     }
266   }
267 }
268 
269 
270 /*
271 ** returns the index for 'k' if 'k' is an appropriate key to live in
272 ** the array part of a table, 0 otherwise.
273 */
arrayindex(lua_Integer k)274 static unsigned int arrayindex (lua_Integer k) {
275   if (l_castS2U(k) - 1u < MAXASIZE)  /* 'k' in [1, MAXASIZE]? */
276     return cast_uint(k);  /* 'key' is an appropriate array index */
277   else
278     return 0;
279 }
280 
281 
282 /*
283 ** returns the index of a 'key' for table traversals. First goes all
284 ** elements in the array part, then elements in the hash part. The
285 ** beginning of a traversal is signaled by 0.
286 */
findindex(lua_State * L,Table * t,TValue * key,unsigned int asize)287 static unsigned int findindex (lua_State *L, Table *t, TValue *key,
288                                unsigned int asize) {
289   unsigned int i;
290   if (ttisnil(key)) return 0;  /* first iteration */
291   i = ttisinteger(key) ? arrayindex(ivalue(key)) : 0;
292   if (i - 1u < asize)  /* is 'key' inside array part? */
293     return i;  /* yes; that's the index */
294   else {
295     const TValue *n = getgeneric(t, key);
296     if (unlikely(isabstkey(n)))
297       luaG_runerror(L, "invalid key to 'next'");  /* key not found */
298     i = cast_int(nodefromval(n) - gnode(t, 0));  /* key index in hash table */
299     /* hash elements are numbered after array ones */
300     return (i + 1) + asize;
301   }
302 }
303 
304 
luaH_next(lua_State * L,Table * t,StkId key)305 int luaH_next (lua_State *L, Table *t, StkId key) {
306   unsigned int asize = luaH_realasize(t);
307   unsigned int i = findindex(L, t, s2v(key), asize);  /* find original key */
308   for (; i < asize; i++) {  /* try first array part */
309     if (!isempty(&t->array[i])) {  /* a non-empty entry? */
310       setivalue(s2v(key), i + 1);
311       setobj2s(L, key + 1, &t->array[i]);
312       return 1;
313     }
314   }
315   for (i -= asize; cast_int(i) < sizenode(t); i++) {  /* hash part */
316     if (!isempty(gval(gnode(t, i)))) {  /* a non-empty entry? */
317       Node *n = gnode(t, i);
318       getnodekey(L, s2v(key), n);
319       setobj2s(L, key + 1, gval(n));
320       return 1;
321     }
322   }
323   return 0;  /* no more elements */
324 }
325 
326 
freehash(lua_State * L,Table * t)327 static void freehash (lua_State *L, Table *t) {
328   if (!isdummy(t))
329     luaM_freearray(L, t->node, cast_sizet(sizenode(t)));
330 }
331 
332 
333 /*
334 ** {=============================================================
335 ** Rehash
336 ** ==============================================================
337 */
338 
339 /*
340 ** Compute the optimal size for the array part of table 't'. 'nums' is a
341 ** "count array" where 'nums[i]' is the number of integers in the table
342 ** between 2^(i - 1) + 1 and 2^i. 'pna' enters with the total number of
343 ** integer keys in the table and leaves with the number of keys that
344 ** will go to the array part; return the optimal size.  (The condition
345 ** 'twotoi > 0' in the for loop stops the loop if 'twotoi' overflows.)
346 */
computesizes(unsigned int nums[],unsigned int * pna)347 static unsigned int computesizes (unsigned int nums[], unsigned int *pna) {
348   int i;
349   unsigned int twotoi;  /* 2^i (candidate for optimal size) */
350   unsigned int a = 0;  /* number of elements smaller than 2^i */
351   unsigned int na = 0;  /* number of elements to go to array part */
352   unsigned int optimal = 0;  /* optimal size for array part */
353   /* loop while keys can fill more than half of total size */
354   for (i = 0, twotoi = 1;
355        twotoi > 0 && *pna > twotoi / 2;
356        i++, twotoi *= 2) {
357     a += nums[i];
358     if (a > twotoi/2) {  /* more than half elements present? */
359       optimal = twotoi;  /* optimal size (till now) */
360       na = a;  /* all elements up to 'optimal' will go to array part */
361     }
362   }
363   lua_assert((optimal == 0 || optimal / 2 < na) && na <= optimal);
364   *pna = na;
365   return optimal;
366 }
367 
368 
countint(lua_Integer key,unsigned int * nums)369 static int countint (lua_Integer key, unsigned int *nums) {
370   unsigned int k = arrayindex(key);
371   if (k != 0) {  /* is 'key' an appropriate array index? */
372     nums[luaO_ceillog2(k)]++;  /* count as such */
373     return 1;
374   }
375   else
376     return 0;
377 }
378 
379 
380 /*
381 ** Count keys in array part of table 't': Fill 'nums[i]' with
382 ** number of keys that will go into corresponding slice and return
383 ** total number of non-nil keys.
384 */
numusearray(const Table * t,unsigned int * nums)385 static unsigned int numusearray (const Table *t, unsigned int *nums) {
386   int lg;
387   unsigned int ttlg;  /* 2^lg */
388   unsigned int ause = 0;  /* summation of 'nums' */
389   unsigned int i = 1;  /* count to traverse all array keys */
390   unsigned int asize = limitasasize(t);  /* real array size */
391   /* traverse each slice */
392   for (lg = 0, ttlg = 1; lg <= MAXABITS; lg++, ttlg *= 2) {
393     unsigned int lc = 0;  /* counter */
394     unsigned int lim = ttlg;
395     if (lim > asize) {
396       lim = asize;  /* adjust upper limit */
397       if (i > lim)
398         break;  /* no more elements to count */
399     }
400     /* count elements in range (2^(lg - 1), 2^lg] */
401     for (; i <= lim; i++) {
402       if (!isempty(&t->array[i-1]))
403         lc++;
404     }
405     nums[lg] += lc;
406     ause += lc;
407   }
408   return ause;
409 }
410 
411 
numusehash(const Table * t,unsigned int * nums,unsigned int * pna)412 static int numusehash (const Table *t, unsigned int *nums, unsigned int *pna) {
413   int totaluse = 0;  /* total number of elements */
414   int ause = 0;  /* elements added to 'nums' (can go to array part) */
415   int i = sizenode(t);
416   while (i--) {
417     Node *n = &t->node[i];
418     if (!isempty(gval(n))) {
419       if (keyisinteger(n))
420         ause += countint(keyival(n), nums);
421       totaluse++;
422     }
423   }
424   *pna += ause;
425   return totaluse;
426 }
427 
428 
429 /*
430 ** Creates an array for the hash part of a table with the given
431 ** size, or reuses the dummy node if size is zero.
432 ** The computation for size overflow is in two steps: the first
433 ** comparison ensures that the shift in the second one does not
434 ** overflow.
435 */
setnodevector(lua_State * L,Table * t,unsigned int size)436 static void setnodevector (lua_State *L, Table *t, unsigned int size) {
437   if (size == 0) {  /* no elements to hash part? */
438     t->node = cast(Node *, dummynode);  /* use common 'dummynode' */
439     t->lsizenode = 0;
440     t->lastfree = NULL;  /* signal that it is using dummy node */
441   }
442   else {
443     int i;
444     int lsize = luaO_ceillog2(size);
445     if (lsize > MAXHBITS || (1u << lsize) > MAXHSIZE)
446       luaG_runerror(L, "table overflow");
447     size = twoto(lsize);
448     t->node = luaM_newvector(L, size, Node);
449     for (i = 0; i < (int)size; i++) {
450       Node *n = gnode(t, i);
451       gnext(n) = 0;
452       setnilkey(n);
453       setempty(gval(n));
454     }
455     t->lsizenode = cast_byte(lsize);
456     t->lastfree = gnode(t, size);  /* all positions are free */
457   }
458 }
459 
460 
461 /*
462 ** (Re)insert all elements from the hash part of 'ot' into table 't'.
463 */
reinsert(lua_State * L,Table * ot,Table * t)464 static void reinsert (lua_State *L, Table *ot, Table *t) {
465   int j;
466   int size = sizenode(ot);
467   for (j = 0; j < size; j++) {
468     Node *old = gnode(ot, j);
469     if (!isempty(gval(old))) {
470       /* doesn't need barrier/invalidate cache, as entry was
471          already present in the table */
472       TValue k;
473       getnodekey(L, &k, old);
474       setobjt2t(L, luaH_set(L, t, &k), gval(old));
475     }
476   }
477 }
478 
479 
480 /*
481 ** Exchange the hash part of 't1' and 't2'.
482 */
exchangehashpart(Table * t1,Table * t2)483 static void exchangehashpart (Table *t1, Table *t2) {
484   lu_byte lsizenode = t1->lsizenode;
485   Node *node = t1->node;
486   Node *lastfree = t1->lastfree;
487   t1->lsizenode = t2->lsizenode;
488   t1->node = t2->node;
489   t1->lastfree = t2->lastfree;
490   t2->lsizenode = lsizenode;
491   t2->node = node;
492   t2->lastfree = lastfree;
493 }
494 
495 
496 /*
497 ** Resize table 't' for the new given sizes. Both allocations (for
498 ** the hash part and for the array part) can fail, which creates some
499 ** subtleties. If the first allocation, for the hash part, fails, an
500 ** error is raised and that is it. Otherwise, it copies the elements from
501 ** the shrinking part of the array (if it is shrinking) into the new
502 ** hash. Then it reallocates the array part.  If that fails, the table
503 ** is in its original state; the function frees the new hash part and then
504 ** raises the allocation error. Otherwise, it sets the new hash part
505 ** into the table, initializes the new part of the array (if any) with
506 ** nils and reinserts the elements of the old hash back into the new
507 ** parts of the table.
508 */
luaH_resize(lua_State * L,Table * t,unsigned int newasize,unsigned int nhsize)509 void luaH_resize (lua_State *L, Table *t, unsigned int newasize,
510                                           unsigned int nhsize) {
511   unsigned int i;
512   Table newt;  /* to keep the new hash part */
513   unsigned int oldasize = setlimittosize(t);
514   TValue *newarray;
515   /* create new hash part with appropriate size into 'newt' */
516   setnodevector(L, &newt, nhsize);
517   if (newasize < oldasize) {  /* will array shrink? */
518     t->alimit = newasize;  /* pretend array has new size... */
519     exchangehashpart(t, &newt);  /* and new hash */
520     /* re-insert into the new hash the elements from vanishing slice */
521     for (i = newasize; i < oldasize; i++) {
522       if (!isempty(&t->array[i]))
523         luaH_setint(L, t, i + 1, &t->array[i]);
524     }
525     t->alimit = oldasize;  /* restore current size... */
526     exchangehashpart(t, &newt);  /* and hash (in case of errors) */
527   }
528   /* allocate new array */
529   newarray = luaM_reallocvector(L, t->array, oldasize, newasize, TValue);
530   if (unlikely(newarray == NULL && newasize > 0)) {  /* allocation failed? */
531     freehash(L, &newt);  /* release new hash part */
532     luaM_error(L);  /* raise error (with array unchanged) */
533   }
534   /* allocation ok; initialize new part of the array */
535   exchangehashpart(t, &newt);  /* 't' has the new hash ('newt' has the old) */
536   t->array = newarray;  /* set new array part */
537   t->alimit = newasize;
538   for (i = oldasize; i < newasize; i++)  /* clear new slice of the array */
539      setempty(&t->array[i]);
540   /* re-insert elements from old hash part into new parts */
541   reinsert(L, &newt, t);  /* 'newt' now has the old hash */
542   freehash(L, &newt);  /* free old hash part */
543 }
544 
545 
luaH_resizearray(lua_State * L,Table * t,unsigned int nasize)546 void luaH_resizearray (lua_State *L, Table *t, unsigned int nasize) {
547   int nsize = allocsizenode(t);
548   luaH_resize(L, t, nasize, nsize);
549 }
550 
551 /*
552 ** nums[i] = number of keys 'k' where 2^(i - 1) < k <= 2^i
553 */
rehash(lua_State * L,Table * t,const TValue * ek)554 static void rehash (lua_State *L, Table *t, const TValue *ek) {
555   unsigned int asize;  /* optimal size for array part */
556   unsigned int na;  /* number of keys in the array part */
557   unsigned int nums[MAXABITS + 1];
558   int i;
559   int totaluse;
560   for (i = 0; i <= MAXABITS; i++) nums[i] = 0;  /* reset counts */
561   setlimittosize(t);
562   na = numusearray(t, nums);  /* count keys in array part */
563   totaluse = na;  /* all those keys are integer keys */
564   totaluse += numusehash(t, nums, &na);  /* count keys in hash part */
565   /* count extra key */
566   if (ttisinteger(ek))
567     na += countint(ivalue(ek), nums);
568   totaluse++;
569   /* compute new size for array part */
570   asize = computesizes(nums, &na);
571   /* resize the table to new computed sizes */
572   luaH_resize(L, t, asize, totaluse - na);
573 }
574 
575 
576 
577 /*
578 ** }=============================================================
579 */
580 
581 
luaH_new(lua_State * L)582 Table *luaH_new (lua_State *L) {
583   GCObject *o = luaC_newobj(L, LUA_VTABLE, sizeof(Table));
584   Table *t = gco2t(o);
585   t->metatable = NULL;
586   t->flags = cast_byte(maskflags);  /* table has no metamethod fields */
587   t->array = NULL;
588   t->alimit = 0;
589   setnodevector(L, t, 0);
590   return t;
591 }
592 
593 
luaH_free(lua_State * L,Table * t)594 void luaH_free (lua_State *L, Table *t) {
595   freehash(L, t);
596   luaM_freearray(L, t->array, luaH_realasize(t));
597   luaM_free(L, t);
598 }
599 
600 
getfreepos(Table * t)601 static Node *getfreepos (Table *t) {
602   if (!isdummy(t)) {
603     while (t->lastfree > t->node) {
604       t->lastfree--;
605       if (keyisnil(t->lastfree))
606         return t->lastfree;
607     }
608   }
609   return NULL;  /* could not find a free place */
610 }
611 
612 
613 
614 /*
615 ** inserts a new key into a hash table; first, check whether key's main
616 ** position is free. If not, check whether colliding node is in its main
617 ** position or not: if it is not, move colliding node to an empty place and
618 ** put new key in its main position; otherwise (colliding node is in its main
619 ** position), new key goes to an empty position.
620 */
luaH_newkey(lua_State * L,Table * t,const TValue * key)621 TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
622   Node *mp;
623   TValue aux;
624   if (unlikely(ttisnil(key)))
625     luaG_runerror(L, "table index is nil");
626   else if (ttisfloat(key)) {
627     lua_Number f = fltvalue(key);
628     lua_Integer k;
629     if (luaV_flttointeger(f, &k, F2Ieq)) {  /* does key fit in an integer? */
630       setivalue(&aux, k);
631       key = &aux;  /* insert it as an integer */
632     }
633     else if (unlikely(luai_numisnan(f)))
634       luaG_runerror(L, "table index is NaN");
635   }
636   mp = mainpositionTV(t, key);
637   if (!isempty(gval(mp)) || isdummy(t)) {  /* main position is taken? */
638     Node *othern;
639     Node *f = getfreepos(t);  /* get a free place */
640     if (f == NULL) {  /* cannot find a free place? */
641       rehash(L, t, key);  /* grow table */
642       /* whatever called 'newkey' takes care of TM cache */
643       return luaH_set(L, t, key);  /* insert key into grown table */
644     }
645     lua_assert(!isdummy(t));
646     othern = mainposition(t, keytt(mp), &keyval(mp));
647     if (othern != mp) {  /* is colliding node out of its main position? */
648       /* yes; move colliding node into free position */
649       while (othern + gnext(othern) != mp)  /* find previous */
650         othern += gnext(othern);
651       gnext(othern) = cast_int(f - othern);  /* rechain to point to 'f' */
652       *f = *mp;  /* copy colliding node into free pos. (mp->next also goes) */
653       if (gnext(mp) != 0) {
654         gnext(f) += cast_int(mp - f);  /* correct 'next' */
655         gnext(mp) = 0;  /* now 'mp' is free */
656       }
657       setempty(gval(mp));
658     }
659     else {  /* colliding node is in its own main position */
660       /* new node will go into free position */
661       if (gnext(mp) != 0)
662         gnext(f) = cast_int((mp + gnext(mp)) - f);  /* chain new position */
663       else lua_assert(gnext(f) == 0);
664       gnext(mp) = cast_int(f - mp);
665       mp = f;
666     }
667   }
668   setnodekey(L, mp, key);
669   luaC_barrierback(L, obj2gco(t), key);
670   lua_assert(isempty(gval(mp)));
671   return gval(mp);
672 }
673 
674 
675 /*
676 ** Search function for integers. If integer is inside 'alimit', get it
677 ** directly from the array part. Otherwise, if 'alimit' is not equal to
678 ** the real size of the array, key still can be in the array part. In
679 ** this case, try to avoid a call to 'luaH_realasize' when key is just
680 ** one more than the limit (so that it can be incremented without
681 ** changing the real size of the array).
682 */
luaH_getint(Table * t,lua_Integer key)683 const TValue *luaH_getint (Table *t, lua_Integer key) {
684   if (l_castS2U(key) - 1u < t->alimit)  /* 'key' in [1, t->alimit]? */
685     return &t->array[key - 1];
686   else if (!limitequalsasize(t) &&  /* key still may be in the array part? */
687            (l_castS2U(key) == t->alimit + 1 ||
688             l_castS2U(key) - 1u < luaH_realasize(t))) {
689     t->alimit = cast_uint(key);  /* probably '#t' is here now */
690     return &t->array[key - 1];
691   }
692   else {
693     Node *n = hashint(t, key);
694     for (;;) {  /* check whether 'key' is somewhere in the chain */
695       if (keyisinteger(n) && keyival(n) == key)
696         return gval(n);  /* that's it */
697       else {
698         int nx = gnext(n);
699         if (nx == 0) break;
700         n += nx;
701       }
702     }
703     return &absentkey;
704   }
705 }
706 
707 
708 /*
709 ** search function for short strings
710 */
luaH_getshortstr(Table * t,TString * key)711 const TValue *luaH_getshortstr (Table *t, TString *key) {
712   Node *n = hashstr(t, key);
713   lua_assert(key->tt == LUA_VSHRSTR);
714   for (;;) {  /* check whether 'key' is somewhere in the chain */
715     if (keyisshrstr(n) && eqshrstr(keystrval(n), key))
716       return gval(n);  /* that's it */
717     else {
718       int nx = gnext(n);
719       if (nx == 0)
720         return &absentkey;  /* not found */
721       n += nx;
722     }
723   }
724 }
725 
726 
luaH_getstr(Table * t,TString * key)727 const TValue *luaH_getstr (Table *t, TString *key) {
728   if (key->tt == LUA_VSHRSTR)
729     return luaH_getshortstr(t, key);
730   else {  /* for long strings, use generic case */
731     TValue ko;
732     setsvalue(cast(lua_State *, NULL), &ko, key);
733     return getgeneric(t, &ko);
734   }
735 }
736 
737 
738 /*
739 ** main search function
740 */
luaH_get(Table * t,const TValue * key)741 const TValue *luaH_get (Table *t, const TValue *key) {
742   switch (ttypetag(key)) {
743     case LUA_VSHRSTR: return luaH_getshortstr(t, tsvalue(key));
744     case LUA_VNUMINT: return luaH_getint(t, ivalue(key));
745     case LUA_VNIL: return &absentkey;
746     case LUA_VNUMFLT: {
747       lua_Integer k;
748       if (luaV_flttointeger(fltvalue(key), &k, F2Ieq)) /* integral index? */
749         return luaH_getint(t, k);  /* use specialized version */
750       /* else... */
751     }  /* FALLTHROUGH */
752     default:
753       return getgeneric(t, key);
754   }
755 }
756 
757 
758 /*
759 ** beware: when using this function you probably need to check a GC
760 ** barrier and invalidate the TM cache.
761 */
luaH_set(lua_State * L,Table * t,const TValue * key)762 TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
763   const TValue *p = luaH_get(t, key);
764   if (!isabstkey(p))
765     return cast(TValue *, p);
766   else return luaH_newkey(L, t, key);
767 }
768 
769 
luaH_setint(lua_State * L,Table * t,lua_Integer key,TValue * value)770 void luaH_setint (lua_State *L, Table *t, lua_Integer key, TValue *value) {
771   const TValue *p = luaH_getint(t, key);
772   TValue *cell;
773   if (!isabstkey(p))
774     cell = cast(TValue *, p);
775   else {
776     TValue k;
777     setivalue(&k, key);
778     cell = luaH_newkey(L, t, &k);
779   }
780   setobj2t(L, cell, value);
781 }
782 
783 
784 /*
785 ** Try to find a boundary in the hash part of table 't'. From the
786 ** caller, we know that 'j' is zero or present and that 'j + 1' is
787 ** present. We want to find a larger key that is absent from the
788 ** table, so that we can do a binary search between the two keys to
789 ** find a boundary. We keep doubling 'j' until we get an absent index.
790 ** If the doubling would overflow, we try LUA_MAXINTEGER. If it is
791 ** absent, we are ready for the binary search. ('j', being max integer,
792 ** is larger or equal to 'i', but it cannot be equal because it is
793 ** absent while 'i' is present; so 'j > i'.) Otherwise, 'j' is a
794 ** boundary. ('j + 1' cannot be a present integer key because it is
795 ** not a valid integer in Lua.)
796 */
hash_search(Table * t,lua_Unsigned j)797 static lua_Unsigned hash_search (Table *t, lua_Unsigned j) {
798   lua_Unsigned i;
799   if (j == 0) j++;  /* the caller ensures 'j + 1' is present */
800   do {
801     i = j;  /* 'i' is a present index */
802     if (j <= l_castS2U(LUA_MAXINTEGER) / 2)
803       j *= 2;
804     else {
805       j = LUA_MAXINTEGER;
806       if (isempty(luaH_getint(t, j)))  /* t[j] not present? */
807         break;  /* 'j' now is an absent index */
808       else  /* weird case */
809         return j;  /* well, max integer is a boundary... */
810     }
811   } while (!isempty(luaH_getint(t, j)));  /* repeat until an absent t[j] */
812   /* i < j  &&  t[i] present  &&  t[j] absent */
813   while (j - i > 1u) {  /* do a binary search between them */
814     lua_Unsigned m = (i + j) / 2;
815     if (isempty(luaH_getint(t, m))) j = m;
816     else i = m;
817   }
818   return i;
819 }
820 
821 
binsearch(const TValue * array,unsigned int i,unsigned int j)822 static unsigned int binsearch (const TValue *array, unsigned int i,
823                                                     unsigned int j) {
824   while (j - i > 1u) {  /* binary search */
825     unsigned int m = (i + j) / 2;
826     if (isempty(&array[m - 1])) j = m;
827     else i = m;
828   }
829   return i;
830 }
831 
832 
833 /*
834 ** Try to find a boundary in table 't'. (A 'boundary' is an integer index
835 ** such that t[i] is present and t[i+1] is absent, or 0 if t[1] is absent
836 ** and 'maxinteger' if t[maxinteger] is present.)
837 ** (In the next explanation, we use Lua indices, that is, with base 1.
838 ** The code itself uses base 0 when indexing the array part of the table.)
839 ** The code starts with 'limit = t->alimit', a position in the array
840 ** part that may be a boundary.
841 **
842 ** (1) If 't[limit]' is empty, there must be a boundary before it.
843 ** As a common case (e.g., after 't[#t]=nil'), check whether 'limit-1'
844 ** is present. If so, it is a boundary. Otherwise, do a binary search
845 ** between 0 and limit to find a boundary. In both cases, try to
846 ** use this boundary as the new 'alimit', as a hint for the next call.
847 **
848 ** (2) If 't[limit]' is not empty and the array has more elements
849 ** after 'limit', try to find a boundary there. Again, try first
850 ** the special case (which should be quite frequent) where 'limit+1'
851 ** is empty, so that 'limit' is a boundary. Otherwise, check the
852 ** last element of the array part. If it is empty, there must be a
853 ** boundary between the old limit (present) and the last element
854 ** (absent), which is found with a binary search. (This boundary always
855 ** can be a new limit.)
856 **
857 ** (3) The last case is when there are no elements in the array part
858 ** (limit == 0) or its last element (the new limit) is present.
859 ** In this case, must check the hash part. If there is no hash part
860 ** or 'limit+1' is absent, 'limit' is a boundary.  Otherwise, call
861 ** 'hash_search' to find a boundary in the hash part of the table.
862 ** (In those cases, the boundary is not inside the array part, and
863 ** therefore cannot be used as a new limit.)
864 */
luaH_getn(Table * t)865 lua_Unsigned luaH_getn (Table *t) {
866   unsigned int limit = t->alimit;
867   if (limit > 0 && isempty(&t->array[limit - 1])) {  /* (1)? */
868     /* there must be a boundary before 'limit' */
869     if (limit >= 2 && !isempty(&t->array[limit - 2])) {
870       /* 'limit - 1' is a boundary; can it be a new limit? */
871       if (ispow2realasize(t) && !ispow2(limit - 1)) {
872         t->alimit = limit - 1;
873         setnorealasize(t);  /* now 'alimit' is not the real size */
874       }
875       return limit - 1;
876     }
877     else {  /* must search for a boundary in [0, limit] */
878       unsigned int boundary = binsearch(t->array, 0, limit);
879       /* can this boundary represent the real size of the array? */
880       if (ispow2realasize(t) && boundary > luaH_realasize(t) / 2) {
881         t->alimit = boundary;  /* use it as the new limit */
882         setnorealasize(t);
883       }
884       return boundary;
885     }
886   }
887   /* 'limit' is zero or present in table */
888   if (!limitequalsasize(t)) {  /* (2)? */
889     /* 'limit' > 0 and array has more elements after 'limit' */
890     if (isempty(&t->array[limit]))  /* 'limit + 1' is empty? */
891       return limit;  /* this is the boundary */
892     /* else, try last element in the array */
893     limit = luaH_realasize(t);
894     if (isempty(&t->array[limit - 1])) {  /* empty? */
895       /* there must be a boundary in the array after old limit,
896          and it must be a valid new limit */
897       unsigned int boundary = binsearch(t->array, t->alimit, limit);
898       t->alimit = boundary;
899       return boundary;
900     }
901     /* else, new limit is present in the table; check the hash part */
902   }
903   /* (3) 'limit' is the last element and either is zero or present in table */
904   lua_assert(limit == luaH_realasize(t) &&
905              (limit == 0 || !isempty(&t->array[limit - 1])));
906   if (isdummy(t) || isempty(luaH_getint(t, cast(lua_Integer, limit + 1))))
907     return limit;  /* 'limit + 1' is absent */
908   else  /* 'limit + 1' is also present */
909     return hash_search(t, limit);
910 }
911 
912 
913 
914 #if defined(LUA_DEBUG)
915 
916 /* export these functions for the test library */
917 
luaH_mainposition(const Table * t,const TValue * key)918 Node *luaH_mainposition (const Table *t, const TValue *key) {
919   return mainpositionTV(t, key);
920 }
921 
luaH_isdummy(const Table * t)922 int luaH_isdummy (const Table *t) { return isdummy(t); }
923 
924 #endif
925