module/lua/ltable.c

   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 */
  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 */
  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 */
 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 */
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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
 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 */
 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 */
 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 */
 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 */
 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       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 */
 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
 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
 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 */
 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
 584 Node *luaH_mainposition (const Table *t, const TValue *key) {
 585   return mainposition(t, key);
 586 }
 587
 588 int luaH_isdummy (Node *n) { return isdummy(n); }
 589
 590 #endif