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  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
  589.