/*

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

 ** Lua tables (hash)

 ** See Copyright Notice in lua.h

 */

 

 

 /*

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

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

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

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

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

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

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

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

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

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

 */

 

 #include <math.h>

 #include <string.h>

 

 #define ltable_c

 #define LUA_CORE

 

 #include "lua.h"

 

 #include "ldebug.h"

 #include "ldo.h"

 #include "lgc.h"

 #include "lmem.h"

 #include "lobject.h"

 #include "lstate.h"

 #include "ltable.h"

 

 

 /*

 ** max size of array part is 2^MAXBITS

 */

 #if LUAI_BITSINT > 26

 #define MAXBITS		26

 #else

 #define MAXBITS		(LUAI_BITSINT-2)

 #endif

 

 #define MAXASIZE	(1 << MAXBITS)

 

 

 #define hashpow2(t,n)      (gnode(t, lmod((n), sizenode(t))))

   

 #define hashstr(t,str)  hashpow2(t, (str)->tsv.hash)

 #define hashboolean(t,p)        hashpow2(t, p)

 

 

 /*

 ** for some types, it is better to avoid modulus by power of 2, as

 ** they tend to have many 2 factors.

 */

 #define hashmod(t,n)	(gnode(t, ((n) % ((sizenode(t)-1)|1))))

 

 

 #define hashpointer(t,p)	hashmod(t, IntPoint(p))

 

 

 /*

 ** number of ints inside a lua_Number

 */

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

 

 

 

 #define dummynode		(&dummynode_)

 

 static const Node dummynode_ = {

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

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

 };

 

 

 /*

 ** hash for lua_Numbers

 */

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

   unsigned int a[numints];

   int i;

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

     return gnode(t, 0);

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

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

   return hashmod(t, a[0]);

 }

 

 

 

 /*

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

 ** of its hash value)

 */

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

   switch (ttype(key)) {

     case LUA_TNUMBER:

       return hashnum(t, nvalue(key));

     case LUA_TSTRING:

       return hashstr(t, rawtsvalue(key));

     case LUA_TBOOLEAN:

       return hashboolean(t, bvalue(key));

     case LUA_TLIGHTUSERDATA:

       return hashpointer(t, pvalue(key));

     default:

       return hashpointer(t, gcvalue(key));

   }

 }

 

 

 /*

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

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

 */

 static int arrayindex (const TValue *key) {

   if (ttisnumber(key)) {

     lua_Number n = nvalue(key);

     int k;

     lua_number2int(k, n);

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

       return k;

   }

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

 }

 

 

 /*

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

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

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

 */

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

   int i;

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

   i = arrayindex(key);

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

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

   else {

     Node *n = mainposition(t, key);

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

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

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

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

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

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

         /* hash elements are numbered after array ones */

         return i + t->sizearray;

       }

       else n = gnext(n);

     } while (n);

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

     return 0;  /* to avoid warnings */

   }

 }

 

 

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

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

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

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

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

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

       return 1;

     }

   }

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

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

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

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

       return 1;

     }

   }

   return 0;  /* no more elements */

 }

 

 

 /*

 ** {=============================================================

 ** Rehash

 ** ==============================================================

 */

 

 

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

   int i;

   int twotoi;  /* 2^i */

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

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

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

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

     if (nums[i] > 0) {

       a += nums[i];

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

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

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

       }

     }

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

   }

   *narray = n;

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

   return na;

 }

 

 

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

   int k = arrayindex(key);

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

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

     return 1;

   }

   else

     return 0;

 }

 

 

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

   int lg;

   int ttlg;  /* 2^lg */

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

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

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

     int lc = 0;  /* counter */

     int lim = ttlg;

     if (lim > t->sizearray) {

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

       if (i > lim)

         break;  /* no more elements to count */

     }

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

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

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

         lc++;

     }

     nums[lg] += lc;

     ause += lc;

   }

   return ause;

 }

 

 

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

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

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

   int i = sizenode(t);

   while (i--) {

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

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

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

       totaluse++;

     }

   }

   *pnasize += ause;

   return totaluse;

 }

 

 

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

   int i;

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

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

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

   t->sizearray = size;

 }

 

 

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

   int lsize;

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

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

     lsize = 0;

   }

   else {

     int i;

     lsize = ceillog2(size);

     if (lsize > MAXBITS)

       luaG_runerror(L, "table overflow");

     size = twoto(lsize);

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

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

       Node *n = gnode(t, i);

       gnext(n) = NULL;

       setnilvalue(gkey(n));

       setnilvalue(gval(n));

     }

   }

   t->lsizenode = cast_byte(lsize);

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

 }

 

 

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

   int i;

   int oldasize = t->sizearray;

   int oldhsize = t->lsizenode;

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

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

     setarrayvector(L, t, nasize);

   /* create new hash part with appropriate size */

   setnodevector(L, t, nhsize);  

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

     t->sizearray = nasize;

     /* re-insert elements from vanishing slice */

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

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

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

     }

     /* shrink array */

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

   }

   /* re-insert elements from hash part */

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

     Node *old = nold+i;

     if (!ttisnil(gval(old)))

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

   }

   if (nold != dummynode)

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

 }

 

 

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

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

   resize(L, t, nasize, nsize);

 }

 

 

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

   int nasize, na;

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

   int i;

   int totaluse;

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

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

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

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

   /* count extra key */

   nasize += countint(ek, nums);

   totaluse++;

   /* compute new size for array part */

   na = computesizes(nums, &nasize);

   /* resize the table to new computed sizes */

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

 }

 

 

 

 /*

 ** }=============================================================

 */

 

 

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

   Table *t = luaM_new(L, Table);

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

   t->metatable = NULL;

   t->flags = cast_byte(~0);

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

   t->array = NULL;

   t->sizearray = 0;

   t->lsizenode = 0;

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

   setarrayvector(L, t, narray);

   setnodevector(L, t, nhash);

   return t;

 }

 

 

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

   if (t->node != dummynode)

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

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

   luaM_free(L, t);

 }

 

 

 static Node *getfreepos (Table *t) {

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

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

       return t->lastfree;

   }

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

 }

 

 

 

 /*

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

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

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

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

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

 */

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

   Node *mp = mainposition(t, key);

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

     Node *othern;

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

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

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

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

     }

     lua_assert(n != dummynode);

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

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

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

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

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

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

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

       setnilvalue(gval(mp));

     }

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

       /* new node will go into free position */

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

       gnext(mp) = n;

       mp = n;

     }

   }

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

   luaC_barriert(L, t, key);

   lua_assert(ttisnil(gval(mp)));

   return gval(mp);

 }

 

 

 /*

 ** search function for integers

 */

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

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

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

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

   else {

     lua_Number nk = cast_num(key);

     Node *n = hashnum(t, nk);

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

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

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

       else n = gnext(n);

     } while (n);

     return luaO_nilobject;

   }

 }

 

 

 /*

 ** search function for strings

 */

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

   Node *n = hashstr(t, key);

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

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

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

     else n = gnext(n);

   } while (n);

   return luaO_nilobject;

 }

 

 

 /*

 ** main search function

 */

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

   switch (ttype(key)) {

     case LUA_TNIL: return luaO_nilobject;

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

     case LUA_TNUMBER: {

       int k;

       lua_Number n = nvalue(key);

       lua_number2int(k, n);

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

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

       /* else go through */

     }

     default: {

       Node *n = mainposition(t, key);

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

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

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

         else n = gnext(n);

       } while (n);

       return luaO_nilobject;

     }

   }

 }

 

 

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

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

   t->flags = 0;

   if (p != luaO_nilobject)

     return cast(TValue *, p);

   else {

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

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

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

     return newkey(L, t, key);

   }

 }

 

 

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

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

   if (p != luaO_nilobject)

     return cast(TValue *, p);

   else {

     TValue k;

     setnvalue(&k, cast_num(key));

     return newkey(L, t, &k);

   }

 }

 

 

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

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

   if (p != luaO_nilobject)

     return cast(TValue *, p);

   else {

     TValue k;

     setsvalue(L, &k, key);

     return newkey(L, t, &k);

   }

 }

 

 

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

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

   j++;

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

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

     i = j;

     j *= 2;

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

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

       i = 1;

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

       return i - 1;

     }

   }

   /* now do a binary search between them */

   while (j - i > 1) {

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

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

     else i = m;

   }

   return i;

 }

 

 

 /*

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

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

 */

 int luaH_getn (Table *t) {

   unsigned int j = t->sizearray;

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

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

     unsigned int i = 0;

     while (j - i > 1) {

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

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

       else i = m;

     }

     return i;

   }

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

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

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

   else return unbound_search(t, j);

 }

 

 

 

 #if defined(LUA_DEBUG)

 

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

   return mainposition(t, key);

 }

 

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

 

 #endif