1 /*

     2 ** $Id: ltable.c,v 2.32.1.2 2007/12/28 15:32:23 roberto Exp $

     3 ** Lua tables (hash)

     4 ** See Copyright Notice in lua.h

     5 */

     6 

     7 

     8 /*

     9 ** Implementation of tables (aka arrays, objects, or hash tables).

    10 ** Tables keep its elements in two parts: an array part and a hash part.

    11 ** Non-negative integer keys are all candidates to be kept in the array

    12 ** part. The actual size of the array is the largest `n' such that at

    13 ** least half the slots between 0 and n are in use.

    14 ** Hash uses a mix of chained scatter table with Brent's variation.

    15 ** A main invariant of these tables is that, if an element is not

    16 ** in its main position (i.e. the `original' position that its hash gives

    17 ** to it), then the colliding element is in its own main position.

    18 ** Hence even when the load factor reaches 100%, performance remains good.

    19 */

    20 

    21 #include <math.h>

    22 #include <string.h>

    23 

    24 #define ltable_c

    25 #define LUA_CORE

    26 

    27 #include "lua.h"

    28 

    29 #include "ldebug.h"

    30 #include "ldo.h"

    31 #include "lgc.h"

    32 #include "lmem.h"

    33 #include "lobject.h"

    34 #include "lstate.h"

    35 #include "ltable.h"

    36 

    37 

    38 /*

    39 ** max size of array part is 2^MAXBITS

    40 */

    41 #if LUAI_BITSINT > 26

    42 #define MAXBITS		26

    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 /*

    67 ** number of ints inside a lua_Number

    68 */

    69 #define numints		cast_int(sizeof(lua_Number)/sizeof(int))

    70 

    71 

    72 

    73 #define dummynode		(&dummynode_)

    74 

    75 static const Node dummynode_ = {

    76   {{NULL}, LUA_TNIL},  /* value */

    77   {{{NULL}, LUA_TNIL, NULL}}  /* key */

    78 };

    79 

    80 

    81 /*

    82 ** hash for lua_Numbers

    83 */

    84 static Node *hashnum (const Table *t, lua_Number n) {

    85   unsigned int a[numints];

    86   int i;

    87   if (luai_numeq(n, 0))  /* avoid problems with -0 */

    88     return gnode(t, 0);

    89   memcpy(a, &n, sizeof(a));

    90   for (i = 1; i < numints; i++) a[0] += a[i];

    91   return hashmod(t, a[0]);

    92 }

    93 

    94 

    95 

    96 /*

    97 ** returns the `main' position of an element in a table (that is, the index

    98 ** of its hash value)

    99 */

   100 static Node *mainposition (const Table *t, const TValue *key) {

   101   switch (ttype(key)) {

   102     case LUA_TNUMBER:

   103       return hashnum(t, nvalue(key));

   104     case LUA_TSTRING:

   105       return hashstr(t, rawtsvalue(key));

   106     case LUA_TBOOLEAN:

   107       return hashboolean(t, bvalue(key));

   108     case LUA_TLIGHTUSERDATA:

   109       return hashpointer(t, pvalue(key));

   110     default:

   111       return hashpointer(t, gcvalue(key));

   112   }

   113 }

   114 

   115 

   116 /*

   117 ** returns the index for `key' if `key' is an appropriate key to live in

   118 ** the array part of the table, -1 otherwise.

   119 */

   120 static int arrayindex (const TValue *key) {

   121   if (ttisnumber(key)) {

   122     lua_Number n = nvalue(key);

   123     int k;

   124     lua_number2int(k, n);

   125     if (luai_numeq(cast_num(k), n))

   126       return k;

   127   }

   128   return -1;  /* `key' did not match some condition */

   129 }

   130 

   131 

   132 /*

   133 ** returns the index of a `key' for table traversals. First goes all

   134 ** elements in the array part, then elements in the hash part. The

   135 ** beginning of a traversal is signalled by -1.

   136 */

   137 static int findindex (lua_State *L, Table *t, StkId key) {

   138   int i;

   139   if (ttisnil(key)) return -1;  /* first iteration */

   140   i = arrayindex(key);

   141   if (0 < i && i <= t->sizearray)  /* is `key' inside array part? */

   142     return i-1;  /* yes; that's the index (corrected to C) */

   143   else {

   144     Node *n = mainposition(t, key);

   145     do {  /* check whether `key' is somewhere in the chain */

   146       /* key may be dead already, but it is ok to use it in `next' */

   147       if (luaO_rawequalObj(key2tval(n), key) ||

   148             (ttype(gkey(n)) == LUA_TDEADKEY && iscollectable(key) &&

   149              gcvalue(gkey(n)) == gcvalue(key))) {

   150         i = cast_int(n - gnode(t, 0));  /* key index in hash table */

   151         /* hash elements are numbered after array ones */

   152         return i + t->sizearray;

   153       }

   154       else n = gnext(n);

   155     } while (n);

   156     luaG_runerror(L, "invalid key to " LUA_QL("next"));  /* key not found */

   157     return 0;  /* to avoid warnings */

   158   }

   159 }

   160 

   161 

   162 int luaH_next (lua_State *L, Table *t, StkId key) {

   163   int i = findindex(L, t, key);  /* find original element */

   164   for (i++; i < t->sizearray; i++) {  /* try first array part */

   165     if (!ttisnil(&t->array[i])) {  /* a non-nil value? */

   166       setnvalue(key, cast_num(i+1));

   167       setobj2s(L, key+1, &t->array[i]);

   168       return 1;

   169     }

   170   }

   171   for (i -= t->sizearray; i < sizenode(t); i++) {  /* then hash part */

   172     if (!ttisnil(gval(gnode(t, i)))) {  /* a non-nil value? */

   173       setobj2s(L, key, key2tval(gnode(t, i)));

   174       setobj2s(L, key+1, gval(gnode(t, i)));

   175       return 1;

   176     }

   177   }

   178   return 0;  /* no more elements */

   179 }

   180 

   181 

   182 /*

   183 ** {=============================================================

   184 ** Rehash

   185 ** ==============================================================

   186 */

   187 

   188 

   189 static int computesizes (int nums[], int *narray) {

   190   int i;

   191   int twotoi;  /* 2^i */

   192   int a = 0;  /* number of elements smaller than 2^i */

   193   int na = 0;  /* number of elements to go to array part */

   194   int n = 0;  /* optimal size for array part */

   195   for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {

   196     if (nums[i] > 0) {

   197       a += nums[i];

   198       if (a > twotoi/2) {  /* more than half elements present? */

   199         n = twotoi;  /* optimal size (till now) */

   200         na = a;  /* all elements smaller than n will go to array part */

   201       }

   202     }

   203     if (a == *narray) break;  /* all elements already counted */

   204   }

   205   *narray = n;

   206   lua_assert(*narray/2 <= na && na <= *narray);

   207   return na;

   208 }

   209 

   210 

   211 static int countint (const TValue *key, int *nums) {

   212   int k = arrayindex(key);

   213   if (0 < k && k <= MAXASIZE) {  /* is `key' an appropriate array index? */

   214     nums[ceillog2(k)]++;  /* count as such */

   215     return 1;

   216   }

   217   else

   218     return 0;

   219 }

   220 

   221 

   222 static int numusearray (const Table *t, int *nums) {

   223   int lg;

   224   int ttlg;  /* 2^lg */

   225   int ause = 0;  /* summation of `nums' */

   226   int i = 1;  /* count to traverse all array keys */

   227   for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) {  /* for each slice */

   228     int lc = 0;  /* counter */

   229     int lim = ttlg;

   230     if (lim > t->sizearray) {

   231       lim = t->sizearray;  /* adjust upper limit */

   232       if (i > lim)

   233         break;  /* no more elements to count */

   234     }

   235     /* count elements in range (2^(lg-1), 2^lg] */

   236     for (; i <= lim; i++) {

   237       if (!ttisnil(&t->array[i-1]))

   238         lc++;

   239     }

   240     nums[lg] += lc;

   241     ause += lc;

   242   }

   243   return ause;

   244 }

   245 

   246 

   247 static int numusehash (const Table *t, int *nums, int *pnasize) {

   248   int totaluse = 0;  /* total number of elements */

   249   int ause = 0;  /* summation of `nums' */

   250   int i = sizenode(t);

   251   while (i--) {

   252     Node *n = &t->node[i];

   253     if (!ttisnil(gval(n))) {

   254       ause += countint(key2tval(n), nums);

   255       totaluse++;

   256     }

   257   }

   258   *pnasize += ause;

   259   return totaluse;

   260 }

   261 

   262 

   263 static void setarrayvector (lua_State *L, Table *t, int size) {

   264   int i;

   265   luaM_reallocvector(L, t->array, t->sizearray, size, TValue);

   266   for (i=t->sizearray; i<size; i++)

   267      setnilvalue(&t->array[i]);

   268   t->sizearray = size;

   269 }

   270 

   271 

   272 static void setnodevector (lua_State *L, Table *t, int size) {

   273   int lsize;

   274   if (size == 0) {  /* no elements to hash part? */

   275     t->node = cast(Node *, dummynode);  /* use common `dummynode' */

   276     lsize = 0;

   277   }

   278   else {

   279     int i;

   280     lsize = ceillog2(size);

   281     if (lsize > MAXBITS)

   282       luaG_runerror(L, "table overflow");

   283     size = twoto(lsize);

   284     t->node = luaM_newvector(L, size, Node);

   285     for (i=0; i<size; i++) {

   286       Node *n = gnode(t, i);

   287       gnext(n) = NULL;

   288       setnilvalue(gkey(n));

   289       setnilvalue(gval(n));

   290     }

   291   }

   292   t->lsizenode = cast_byte(lsize);

   293   t->lastfree = gnode(t, size);  /* all positions are free */

   294 }

   295 

   296 

   297 static void resize (lua_State *L, Table *t, int nasize, int nhsize) {

   298   int i;

   299   int oldasize = t->sizearray;

   300   int oldhsize = t->lsizenode;

   301   Node *nold = t->node;  /* save old hash ... */

   302   if (nasize > oldasize)  /* array part must grow? */

   303     setarrayvector(L, t, nasize);

   304   /* create new hash part with appropriate size */

   305   setnodevector(L, t, nhsize);  

   306   if (nasize < oldasize) {  /* array part must shrink? */

   307     t->sizearray = nasize;

   308     /* re-insert elements from vanishing slice */

   309     for (i=nasize; i<oldasize; i++) {

   310       if (!ttisnil(&t->array[i]))

   311         setobjt2t(L, luaH_setnum(L, t, i+1), &t->array[i]);

   312     }

   313     /* shrink array */

   314     luaM_reallocvector(L, t->array, oldasize, nasize, TValue);

   315   }

   316   /* re-insert elements from hash part */

   317   for (i = twoto(oldhsize) - 1; i >= 0; i--) {

   318     Node *old = nold+i;

   319     if (!ttisnil(gval(old)))

   320       setobjt2t(L, luaH_set(L, t, key2tval(old)), gval(old));

   321   }

   322   if (nold != dummynode)

   323     luaM_freearray(L, nold, twoto(oldhsize), Node);  /* free old array */

   324 }

   325 

   326 

   327 void luaH_resizearray (lua_State *L, Table *t, int nasize) {

   328   int nsize = (t->node == dummynode) ? 0 : sizenode(t);

   329   resize(L, t, nasize, nsize);

   330 }

   331 

   332 

   333 static void rehash (lua_State *L, Table *t, const TValue *ek) {

   334   int nasize, na;

   335   int nums[MAXBITS+1];  /* nums[i] = number of keys between 2^(i-1) and 2^i */

   336   int i;

   337   int totaluse;

   338   for (i=0; i<=MAXBITS; i++) nums[i] = 0;  /* reset counts */

   339   nasize = numusearray(t, nums);  /* count keys in array part */

   340   totaluse = nasize;  /* all those keys are integer keys */

   341   totaluse += numusehash(t, nums, &nasize);  /* count keys in hash part */

   342   /* count extra key */

   343   nasize += countint(ek, nums);

   344   totaluse++;

   345   /* compute new size for array part */

   346   na = computesizes(nums, &nasize);

   347   /* resize the table to new computed sizes */

   348   resize(L, t, nasize, totaluse - na);

   349 }

   350 

   351 

   352 

   353 /*

   354 ** }=============================================================

   355 */

   356 

   357 

   358 Table *luaH_new (lua_State *L, int narray, int nhash) {

   359   Table *t = luaM_new(L, Table);

   360   luaC_link(L, obj2gco(t), LUA_TTABLE);

   361   t->metatable = NULL;

   362   t->flags = cast_byte(~0);

   363   /* temporary values (kept only if some malloc fails) */

   364   t->array = NULL;

   365   t->sizearray = 0;

   366   t->lsizenode = 0;

   367   t->node = cast(Node *, dummynode);

   368   setarrayvector(L, t, narray);

   369   setnodevector(L, t, nhash);

   370   return t;

   371 }

   372 

   373 

   374 void luaH_free (lua_State *L, Table *t) {

   375   if (t->node != dummynode)

   376     luaM_freearray(L, t->node, sizenode(t), Node);

   377   luaM_freearray(L, t->array, t->sizearray, TValue);

   378   luaM_free(L, t);

   379 }

   380 

   381 

   382 static Node *getfreepos (Table *t) {

   383   while (t->lastfree-- > t->node) {

   384     if (ttisnil(gkey(t->lastfree)))

   385       return t->lastfree;

   386   }

   387   return NULL;  /* could not find a free place */

   388 }

   389 

   390 

   391 

   392 /*

   393 ** inserts a new key into a hash table; first, check whether key's main 

   394 ** position is free. If not, check whether colliding node is in its main 

   395 ** position or not: if it is not, move colliding node to an empty place and 

   396 ** put new key in its main position; otherwise (colliding node is in its main 

   397 ** position), new key goes to an empty position. 

   398 */

   399 static TValue *newkey (lua_State *L, Table *t, const TValue *key) {

   400   Node *mp = mainposition(t, key);

   401   if (!ttisnil(gval(mp)) || mp == dummynode) {

   402     Node *othern;

   403     Node *n = getfreepos(t);  /* get a free place */

   404     if (n == NULL) {  /* cannot find a free place? */

   405       rehash(L, t, key);  /* grow table */

   406       return luaH_set(L, t, key);  /* re-insert key into grown table */

   407     }

   408     lua_assert(n != dummynode);

   409     othern = mainposition(t, key2tval(mp));

   410     if (othern != mp) {  /* is colliding node out of its main position? */

   411       /* yes; move colliding node into free position */

   412       while (gnext(othern) != mp) othern = gnext(othern);  /* find previous */

   413       gnext(othern) = n;  /* redo the chain with `n' in place of `mp' */

   414       *n = *mp;  /* copy colliding node into free pos. (mp->next also goes) */

   415       gnext(mp) = NULL;  /* now `mp' is free */

   416       setnilvalue(gval(mp));

   417     }

   418     else {  /* colliding node is in its own main position */

   419       /* new node will go into free position */

   420       gnext(n) = gnext(mp);  /* chain new position */

   421       gnext(mp) = n;

   422       mp = n;

   423     }

   424   }

   425   gkey(mp)->value = key->value; gkey(mp)->tt = key->tt;

   426   luaC_barriert(L, t, key);

   427   lua_assert(ttisnil(gval(mp)));

   428   return gval(mp);

   429 }

   430 

   431 

   432 /*

   433 ** search function for integers

   434 */

   435 const TValue *luaH_getnum (Table *t, int key) {

   436   /* (1 <= key && key <= t->sizearray) */

   437   if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))

   438     return &t->array[key-1];

   439   else {

   440     lua_Number nk = cast_num(key);

   441     Node *n = hashnum(t, nk);

   442     do {  /* check whether `key' is somewhere in the chain */

   443       if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))

   444         return gval(n);  /* that's it */

   445       else n = gnext(n);

   446     } while (n);

   447     return luaO_nilobject;

   448   }

   449 }

   450 

   451 

   452 /*

   453 ** search function for strings

   454 */

   455 const TValue *luaH_getstr (Table *t, TString *key) {

   456   Node *n = hashstr(t, key);

   457   do {  /* check whether `key' is somewhere in the chain */

   458     if (ttisstring(gkey(n)) && rawtsvalue(gkey(n)) == key)

   459       return gval(n);  /* that's it */

   460     else n = gnext(n);

   461   } while (n);

   462   return luaO_nilobject;

   463 }

   464 

   465 

   466 /*

   467 ** main search function

   468 */

   469 const TValue *luaH_get (Table *t, const TValue *key) {

   470   switch (ttype(key)) {

   471     case LUA_TNIL: return luaO_nilobject;

   472     case LUA_TSTRING: return luaH_getstr(t, rawtsvalue(key));

   473     case LUA_TNUMBER: {

   474       int k;

   475       lua_Number n = nvalue(key);

   476       lua_number2int(k, n);

   477       if (luai_numeq(cast_num(k), nvalue(key))) /* index is int? */

   478         return luaH_getnum(t, k);  /* use specialized version */

   479       /* else go through */

   480     }

   481     default: {

   482       Node *n = mainposition(t, key);

   483       do {  /* check whether `key' is somewhere in the chain */

   484         if (luaO_rawequalObj(key2tval(n), key))

   485           return gval(n);  /* that's it */

   486         else n = gnext(n);

   487       } while (n);

   488       return luaO_nilobject;

   489     }

   490   }

   491 }

   492 

   493 

   494 TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {

   495   const TValue *p = luaH_get(t, key);

   496   t->flags = 0;

   497   if (p != luaO_nilobject)

   498     return cast(TValue *, p);

   499   else {

   500     if (ttisnil(key)) luaG_runerror(L, "table index is nil");

   501     else if (ttisnumber(key) && luai_numisnan(nvalue(key)))

   502       luaG_runerror(L, "table index is NaN");

   503     return newkey(L, t, key);

   504   }

   505 }

   506 

   507 

   508 TValue *luaH_setnum (lua_State *L, Table *t, int key) {

   509   const TValue *p = luaH_getnum(t, key);

   510   if (p != luaO_nilobject)

   511     return cast(TValue *, p);

   512   else {

   513     TValue k;

   514     setnvalue(&k, cast_num(key));

   515     return newkey(L, t, &k);

   516   }

   517 }

   518 

   519 

   520 TValue *luaH_setstr (lua_State *L, Table *t, TString *key) {

   521   const TValue *p = luaH_getstr(t, key);

   522   if (p != luaO_nilobject)

   523     return cast(TValue *, p);

   524   else {

   525     TValue k;

   526     setsvalue(L, &k, key);

   527     return newkey(L, t, &k);

   528   }

   529 }

   530 

   531 

   532 static int unbound_search (Table *t, unsigned int j) {

   533   unsigned int i = j;  /* i is zero or a present index */

   534   j++;

   535   /* find `i' and `j' such that i is present and j is not */

   536   while (!ttisnil(luaH_getnum(t, j))) {

   537     i = j;

   538     j *= 2;

   539     if (j > cast(unsigned int, MAX_INT)) {  /* overflow? */

   540       /* table was built with bad purposes: resort to linear search */

   541       i = 1;

   542       while (!ttisnil(luaH_getnum(t, i))) i++;

   543       return i - 1;

   544     }

   545   }

   546   /* now do a binary search between them */

   547   while (j - i > 1) {

   548     unsigned int m = (i+j)/2;

   549     if (ttisnil(luaH_getnum(t, m))) j = m;

   550     else i = m;

   551   }

   552   return i;

   553 }

   554 

   555 

   556 /*

   557 ** Try to find a boundary in table `t'. A `boundary' is an integer index

   558 ** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).

   559 */

   560 int luaH_getn (Table *t) {

   561   unsigned int j = t->sizearray;

   562   if (j > 0 && ttisnil(&t->array[j - 1])) {

   563     /* there is a boundary in the array part: (binary) search for it */

   564     unsigned int i = 0;

   565     while (j - i > 1) {

   566       unsigned int m = (i+j)/2;

   567       if (ttisnil(&t->array[m - 1])) j = m;

   568       else i = m;

   569     }

   570     return i;

   571   }

   572   /* else must find a boundary in hash part */

   573   else if (t->node == dummynode)  /* hash part is empty? */

   574     return j;  /* that is easy... */

   575   else return unbound_search(t, j);

   576 }

   577 

   578 

   579 

   580 #if defined(LUA_DEBUG)

   581 

   582 Node *luaH_mainposition (const Table *t, const TValue *key) {

   583   return mainposition(t, key);

   584 }

   585 

   586 int luaH_isdummy (Node *n) { return n == dummynode; }

   587 

   588 #endif