/*

** $Id: ltable.c $

** Lua tables (hash)

** See Copyright Notice in lua.h

*/

#define ltable_c

#define LUA_CORE

#include "lprefix.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

** more than half the slots between 1 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 <limits.h>

#include <string.h>

#include "lua.h"

#include "ldebug.h"

#include "ldo.h"

#include "lgc.h"

#include "lmem.h"

#include "lobject.h"

#include "lstate.h"

#include "lstring.h"

#include "ltable.h"

#include "lvm.h"

/*

** Only tables with hash parts larger than 2^LIMFORLAST has a 'lastfree'

** field that optimizes finding a free slot. That field is stored just

** before the array of nodes, in the same block. Smaller tables do a

** complete search when looking for a free slot.

*/

#define LIMFORLAST    2  /* log2 of real limit */

/*

** The union 'Limbox' stores 'lastfree' and ensures that what follows it

** is properly aligned to store a Node.

*/

typedef struct { Node *dummy; Node follows_pNode; } Limbox_aux;

typedef union {

  Node *lastfree;

  char padding[offsetof(Limbox_aux, follows_pNode)];

} Limbox;

#define haslastfree(t)     ((t)->lsizenode > LIMFORLAST)

#define getlastfree(t)     ((cast(Limbox *, (t)->node) - 1)->lastfree)

/*

** MAXABITS is the largest integer such that 2^MAXABITS fits in an

** unsigned int.

*/

#define MAXABITS  cast_int(sizeof(int) * CHAR_BIT - 1)

/*

** MAXASIZEB is the maximum number of elements in the array part such

** that the size of the array fits in 'size_t'.

*/

#define MAXASIZEB (MAX_SIZET/(sizeof(Value) + 1))

/*

** MAXASIZE is the maximum size of the array part. It is the minimum

** between 2^MAXABITS and MAXASIZEB.

*/

#define MAXASIZE  \

    (((1u << MAXABITS) < MAXASIZEB) ? (1u << MAXABITS) : cast_uint(MAXASIZEB))

/*

** MAXHBITS is the largest integer such that 2^MAXHBITS fits in a

** signed int.

*/

#define MAXHBITS  (MAXABITS - 1)

/*

** MAXHSIZE is the maximum size of the hash part. It is the minimum

** between 2^MAXHBITS and the maximum size such that, measured in bytes,

** it fits in a 'size_t'.

*/

#define MAXHSIZE  luaM_limitN(1u << MAXHBITS, Node)

/*

** When the original hash value is good, hashing by a power of 2

** avoids the cost of '%'.

*/

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

/*

** for other types, it is better to avoid modulo by power of 2, as

** they can have many 2 factors.

*/

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

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

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

#define hashpointer(t,p)  hashmod(t, point2uint(p))

#define dummynode   (&dummynode_)

static const Node dummynode_ = {

  {{NULL}, LUA_VEMPTY,  /* value's value and type */

   LUA_VNIL, 0, {NULL}}  /* key type, next, and key value */

};

static const TValue absentkey = {ABSTKEYCONSTANT};

/*

** Hash for integers. To allow a good hash, use the remainder operator

** ('%'). If integer fits as a non-negative int, compute an int

** remainder, which is faster. Otherwise, use an unsigned-integer

** remainder, which uses all bits and ensures a non-negative result.

*/

static Node *hashint (const Table *t, lua_Integer i) {

  lua_Unsigned ui = l_castS2U(i);

  if (ui <= cast_uint(INT_MAX))

    return hashmod(t, cast_int(ui));

  else

    return hashmod(t, ui);

}

/*

** Hash for floating-point numbers.

** The main computation should be just

**     n = frexp(n, &i); return (n * INT_MAX) + i

** but there are some numerical subtleties.

** In a two-complement representation, INT_MAX does not has an exact

** representation as a float, but INT_MIN does; because the absolute

** value of 'frexp' is smaller than 1 (unless 'n' is inf/NaN), the

** absolute value of the product 'frexp * -INT_MIN' is smaller or equal

** to INT_MAX. Next, the use of 'unsigned int' avoids overflows when

** adding 'i'; the use of '~u' (instead of '-u') avoids problems with

** INT_MIN.

*/

#if !defined(l_hashfloat)

static int l_hashfloat (lua_Number n) {

  int i;

  lua_Integer ni;

  n = l_mathop(frexp)(n, &i) * -cast_num(INT_MIN);

  if (!lua_numbertointeger(n, &ni)) {  /* is 'n' inf/-inf/NaN? */

    lua_assert(luai_numisnan(n) || l_mathop(fabs)(n) == cast_num(HUGE_VAL));

    return 0;

  }

  else {  /* normal case */

    unsigned int u = cast_uint(i) + cast_uint(ni);

    return cast_int(u <= cast_uint(INT_MAX) ? u : ~u);

  }

}

#endif

/*

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

** the index of its hash value).

*/

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

  switch (ttypetag(key)) {

    case LUA_VNUMINT: {

      lua_Integer i = ivalue(key);

      return hashint(t, i);

    }

    case LUA_VNUMFLT: {

      lua_Number n = fltvalue(key);

      return hashmod(t, l_hashfloat(n));

    }

    case LUA_VSHRSTR: {

      TString *ts = tsvalue(key);

      return hashstr(t, ts);

    }

    case LUA_VLNGSTR: {

      TString *ts = tsvalue(key);

      return hashpow2(t, luaS_hashlongstr(ts));

    }

    case LUA_VFALSE:

      return hashboolean(t, 0);

    case LUA_VTRUE:

      return hashboolean(t, 1);

    case LUA_VLIGHTUSERDATA: {

      void *p = pvalue(key);

      return hashpointer(t, p);

    }

    case LUA_VLCF: {

      lua_CFunction f = fvalue(key);

      return hashpointer(t, f);

    }

    default: {

      GCObject *o = gcvalue(key);

      return hashpointer(t, o);

    }

  }

}

l_sinline Node *mainpositionfromnode (const Table *t, Node *nd) {

  TValue key;

  getnodekey(cast(lua_State *, NULL), &key, nd);

  return mainpositionTV(t, &key);

}

/*

** Check whether key 'k1' is equal to the key in node 'n2'. This

** equality is raw, so there are no metamethods. Floats with integer

** values have been normalized, so integers cannot be equal to

** floats. It is assumed that 'eqshrstr' is simply pointer equality, so

** that short strings are handled in the default case.

** A true 'deadok' means to accept dead keys as equal to their original

** values. All dead keys are compared in the default case, by pointer

** identity. (Only collectable objects can produce dead keys.) Note that

** dead long strings are also compared by identity.

** Once a key is dead, its corresponding value may be collected, and

** then another value can be created with the same address. If this

** other value is given to 'next', 'equalkey' will signal a false

** positive. In a regular traversal, this situation should never happen,

** as all keys given to 'next' came from the table itself, and therefore

** could not have been collected. Outside a regular traversal, we

** have garbage in, garbage out. What is relevant is that this false

** positive does not break anything.  (In particular, 'next' will return

** some other valid item on the table or nil.)

*/

static int equalkey (const TValue *k1, const Node *n2, int deadok) {

  if ((rawtt(k1) != keytt(n2)) &&  /* not the same variants? */

       !(deadok && keyisdead(n2) && iscollectable(k1)))

   return 0;  /* cannot be same key */

  switch (keytt(n2)) {

    case LUA_VNIL: case LUA_VFALSE: case LUA_VTRUE:

      return 1;

    case LUA_VNUMINT:

      return (ivalue(k1) == keyival(n2));

    case LUA_VNUMFLT:

      return luai_numeq(fltvalue(k1), fltvalueraw(keyval(n2)));

    case LUA_VLIGHTUSERDATA:

      return pvalue(k1) == pvalueraw(keyval(n2));

    case LUA_VLCF:

      return fvalue(k1) == fvalueraw(keyval(n2));

    case ctb(LUA_VLNGSTR):

      return luaS_eqlngstr(tsvalue(k1), keystrval(n2));

    default:

      return gcvalue(k1) == gcvalueraw(keyval(n2));

  }

}

/*

** True if value of 'alimit' is equal to the real size of the array

** part of table 't'. (Otherwise, the array part must be larger than

** 'alimit'.)

*/

#define limitequalsasize(t) (isrealasize(t) || ispow2((t)->alimit))

/*

** Returns the real size of the 'array' array

*/

LUAI_FUNC unsigned int luaH_realasize (const Table *t) {

  if (limitequalsasize(t))

    return t->alimit;  /* this is the size */

  else {

    unsigned int size = t->alimit;

    /* compute the smallest power of 2 not smaller than 'size' */

    size |= (size >> 1);

    size |= (size >> 2);

    size |= (size >> 4);

    size |= (size >> 8);

#if (UINT_MAX >> 14) > 3  /* unsigned int has more than 16 bits */

    size |= (size >> 16);

#if (UINT_MAX >> 30) > 3

    size |= (size >> 32);  /* unsigned int has more than 32 bits */

#endif

#endif

    size++;

    lua_assert(ispow2(size) && size/2 < t->alimit && t->alimit < size);

    return size;

  }

}

/*

** Check whether real size of the array is a power of 2.

** (If it is not, 'alimit' cannot be changed to any other value

** without changing the real size.)

*/

static int ispow2realasize (const Table *t) {

  return (!isrealasize(t) || ispow2(t->alimit));

}

static unsigned int setlimittosize (Table *t) {

  t->alimit = luaH_realasize(t);

  setrealasize(t);

  return t->alimit;

}

#define limitasasize(t) check_exp(isrealasize(t), t->alimit)

/*

** "Generic" get version. (Not that generic: not valid for integers,

** which may be in array part, nor for floats with integral values.)

** See explanation about 'deadok' in function 'equalkey'.

*/

static const TValue *getgeneric (Table *t, const TValue *key, int deadok) {

  Node *n = mainpositionTV(t, key);

  for (;;) {  /* check whether 'key' is somewhere in the chain */

    if (equalkey(key, n, deadok))

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

    else {

      int nx = gnext(n);

      if (nx == 0)

        return &absentkey;  /* not found */

      n += nx;

    }

  }

}

/*

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

** the array part of a table, 0 otherwise.

*/

static unsigned int arrayindex (lua_Integer k) {

  if (l_castS2U(k) - 1u < MAXASIZE)  /* 'k' in [1, MAXASIZE]? */

    return cast_uint(k);  /* 'key' is an appropriate array index */

  else

    return 0;

}

/*

** 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 signaled by 0.

*/

static unsigned findindex (lua_State *L, Table *t, TValue *key,

                               unsigned asize) {

  unsigned int i;

  if (ttisnil(key)) return 0;  /* first iteration */

  i = ttisinteger(key) ? arrayindex(ivalue(key)) : 0;

  if (i - 1u < asize)  /* is 'key' inside array part? */

    return i;  /* yes; that's the index */

  else {

    const TValue *n = getgeneric(t, key, 1);

    if (l_unlikely(isabstkey(n)))

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

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

    /* hash elements are numbered after array ones */

    return (i + 1) + asize;

  }

}

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

  unsigned int asize = luaH_realasize(t);

  unsigned int i = findindex(L, t, s2v(key), asize);  /* find original key */

  for (; i < asize; i++) {  /* try first array part */

    int tag = *getArrTag(t, i);

    if (!tagisempty(tag)) {  /* a non-empty entry? */

      setivalue(s2v(key), i + 1);

      farr2val(t, i + 1, tag, s2v(key + 1));

      return 1;

    }

  }

  for (i -= asize; cast_int(i) < sizenode(t); i++) {  /* hash part */

    if (!isempty(gval(gnode(t, i)))) {  /* a non-empty entry? */

      Node *n = gnode(t, i);

      getnodekey(L, s2v(key), n);

      setobj2s(L, key + 1, gval(n));

      return 1;

    }

  }

  return 0;  /* no more elements */

}

static void freehash (lua_State *L, Table *t) {

  if (!isdummy(t)) {

    size_t bsize = sizenode(t) * sizeof(Node);  /* 'node' size in bytes */

    char *arr = cast_charp(t->node);

    if (haslastfree(t)) {

      bsize += sizeof(Limbox);

      arr -= sizeof(Limbox);

    }

    luaM_freearray(L, arr, bsize);

  }

}

/*

** Check whether an integer key is in the array part. If 'alimit' is

** not the real size of the array, the key still can be in the array

** part.  In this case, do the "Xmilia trick" to check whether 'key-1'

** is smaller than the real size.

** The trick works as follow: let 'p' be the integer such that

** '2^(p+1) >= alimit > 2^p', or '2^(p+1) > alimit-1 >= 2^p'.  That is,

** 'p' is the highest 1-bit in 'alimit-1', and 2^(p+1) is the real size

** of the array. What we have to check becomes 'key-1 < 2^(p+1)'.  We

** compute '(key-1) & ~(alimit-1)', which we call 'res'; it will have

** the 'p' bit cleared. (It may also clear other bits smaller than 'p',

** but no bit higher than 'p'.) If the key is outside the array, that

** is, 'key-1 >= 2^(p+1)', then 'res' will have some 1-bit higher than

** 'p', therefore it will be larger or equal to 'alimit', and the check

** will fail. If 'key-1 < 2^(p+1)', then 'res' has no 1-bit higher than

** 'p', and as the bit 'p' itself was cleared, 'res' will be smaller

** than 2^p, therefore smaller than 'alimit', and the check succeeds.

** As special cases, when 'alimit' is 0 the condition is trivially false,

** and when 'alimit' is 1 the condition simplifies to 'key-1 < alimit'.

** If key is 0 or negative, 'res' will have its higher bit on, so that

** it cannot be smaller than 'alimit'.

*/

static int keyinarray (Table *t, lua_Integer key) {

  lua_Unsigned alimit = t->alimit;

  if (l_castS2U(key) - 1u < alimit)  /* 'key' in [1, t->alimit]? */

    return 1;

  else if (!isrealasize(t) &&  /* key still may be in the array part? */

           (((l_castS2U(key) - 1u) & ~(alimit - 1u)) < alimit)) {

    t->alimit = cast_uint(key);  /* probably '#t' is here now */

    return 1;

  }

  else

    return 0;

}

/*

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

** Rehash

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

*/

/*

** Compute the optimal size for the array part of table 't'. 'nums' is a

** "count array" where 'nums[i]' is the number of integers in the table

** between 2^(i - 1) + 1 and 2^i. 'pna' enters with the total number of

** integer keys in the table and leaves with the number of keys that

** will go to the array part; return the optimal size.  (The condition

** 'twotoi > 0' in the for loop stops the loop if 'twotoi' overflows.)

*/

static unsigned computesizes (unsigned nums[], unsigned *pna) {

  int i;

  unsigned int twotoi;  /* 2^i (candidate for optimal size) */

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

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

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

  /* loop while keys can fill more than half of total size */

  for (i = 0, twotoi = 1;

       twotoi > 0 && *pna > twotoi / 2;

       i++, twotoi *= 2) {

    a += nums[i];

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

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

      na = a;  /* all elements up to 'optimal' will go to array part */

    }

  }

  lua_assert((optimal == 0 || optimal / 2 < na) && na <= optimal);

  *pna = na;

  return optimal;

}

static int countint (lua_Integer key, unsigned int *nums) {

  unsigned int k = arrayindex(key);

  if (k != 0) {  /* is 'key' an appropriate array index? */

    nums[luaO_ceillog2(k)]++;  /* count as such */

    return 1;

  }

  else

    return 0;

}

l_sinline int arraykeyisempty (const Table *t, lua_Integer key) {

  int tag = *getArrTag(t, key - 1);

  return tagisempty(tag);

}

/*

** Count keys in array part of table 't': Fill 'nums[i]' with

** number of keys that will go into corresponding slice and return

** total number of non-nil keys.

*/

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

  int lg;

  unsigned int ttlg;  /* 2^lg */

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

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

  unsigned int asize = limitasasize(t);  /* real array size */

  /* traverse each slice */

  for (lg = 0, ttlg = 1; lg <= MAXABITS; lg++, ttlg *= 2) {

    unsigned int lc = 0;  /* counter */

    unsigned int lim = ttlg;

    if (lim > asize) {

      lim = asize;  /* 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 (!arraykeyisempty(t, i))

        lc++;

    }

    nums[lg] += lc;

    ause += lc;

  }

  return ause;

}

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

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

  int ause = 0;  /* elements added to 'nums' (can go to array part) */

  int i = sizenode(t);

  while (i--) {

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

    if (!isempty(gval(n))) {

      if (keyisinteger(n))

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

      totaluse++;

    }

  }

  *pna += ause;

  return totaluse;

}

/*

** Convert an "abstract size" (number of slots in an array) to

** "concrete size" (number of bytes in the array).

*/

static size_t concretesize (unsigned int size) {

  return size * sizeof(Value) + size;  /* space for the two arrays */

}

/*

** Resize the array part of a table. If new size is equal to the old,

** do nothing. Else, if new size is zero, free the old array. (It must

** be present, as the sizes are different.) Otherwise, allocate a new

** array, move the common elements to new proper position, and then

** frees old array.

** When array grows, we could reallocate it, but we still would need

** to move the elements to their new position, so the copy implicit

** in realloc is a waste.  When array shrinks, it always erases some

** elements that should still be in the array, so we must reallocate in

** two steps anyway. It is simpler to always reallocate in two steps.

*/

static Value *resizearray (lua_State *L , Table *t,

                               unsigned oldasize,

                               unsigned newasize) {

  if (oldasize == newasize)

    return t->array;  /* nothing to be done */

  else if (newasize == 0) {  /* erasing array? */

    Value *op = t->array - oldasize;  /* original array's real address */

    luaM_freemem(L, op, concretesize(oldasize));  /* free it */

    return NULL;

  }

  else {

    size_t newasizeb = concretesize(newasize);

    Value *np = cast(Value *,

                  luaM_reallocvector(L, NULL, 0, newasizeb, lu_byte));

    if (np == NULL)  /* allocation error? */

      return NULL;

    if (oldasize > 0) {

      Value *op = t->array - oldasize;  /* real original array */

      unsigned tomove = (oldasize < newasize) ? oldasize : newasize;

      lua_assert(tomove > 0);

      /* move common elements to new position */

      memcpy(np + newasize - tomove,

             op + oldasize - tomove,

             concretesize(tomove));

      luaM_freemem(L, op, concretesize(oldasize));

    }

    return np + newasize;  /* shift pointer to the end of value segment */

  }

}

/*

** Creates an array for the hash part of a table with the given

** size, or reuses the dummy node if size is zero.

** The computation for size overflow is in two steps: the first

** comparison ensures that the shift in the second one does not

** overflow.

*/

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

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

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

    t->lsizenode = 0;

    setdummy(t);  /* signal that it is using dummy node */

  }

  else {

    int i;

    int lsize = luaO_ceillog2(size);

    if (lsize > MAXHBITS || (1u << lsize) > MAXHSIZE)

      luaG_runerror(L, "table overflow");

    size = twoto(lsize);

    if (lsize <= LIMFORLAST)  /* no 'lastfree' field? */

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

    else {

      size_t bsize = size * sizeof(Node) + sizeof(Limbox);

      char *node = luaM_newblock(L, bsize);

      t->node = cast(Node *, node + sizeof(Limbox));

      getlastfree(t) = gnode(t, size);  /* all positions are free */

    }

    t->lsizenode = cast_byte(lsize);

    setnodummy(t);

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

      Node *n = gnode(t, i);

      gnext(n) = 0;

      setnilkey(n);

      setempty(gval(n));

    }

  }

}

/*

** (Re)insert all elements from the hash part of 'ot' into table 't'.

*/

static void reinsert (lua_State *L, Table *ot, Table *t) {

  int j;

  int size = sizenode(ot);

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

    Node *old = gnode(ot, j);

    if (!isempty(gval(old))) {

      /* doesn't need barrier/invalidate cache, as entry was

         already present in the table */

      TValue k;

      getnodekey(L, &k, old);

      luaH_set(L, t, &k, gval(old));

    }

  }

}

/*

** Exchange the hash part of 't1' and 't2'. (In 'flags', only the

** dummy bit must be exchanged: The 'isrealasize' is not related

** to the hash part, and the metamethod bits do not change during

** a resize, so the "real" table can keep their values.)

*/

static void exchangehashpart (Table *t1, Table *t2) {

  lu_byte lsizenode = t1->lsizenode;

  Node *node = t1->node;

  int bitdummy1 = t1->flags & BITDUMMY;

  t1->lsizenode = t2->lsizenode;

  t1->node = t2->node;

  t1->flags = (t1->flags & NOTBITDUMMY) | (t2->flags & BITDUMMY);

  t2->lsizenode = lsizenode;

  t2->node = node;

  t2->flags = (t2->flags & NOTBITDUMMY) | bitdummy1;

}

/*

** Re-insert into the new hash part of a table the elements from the

** vanishing slice of the array part.

*/

static void reinsertOldSlice (lua_State *L, Table *t, unsigned oldasize,

                                            unsigned newasize) {

  unsigned i;

  t->alimit = newasize;  /* pretend array has new size... */

  for (i = newasize; i < oldasize; i++) {  /* traverse vanishing slice */

    int tag = *getArrTag(t, i);

    if (!tagisempty(tag)) {  /* a non-empty entry? */

      TValue aux;

      farr2val(t, i + 1, tag, &aux);  /* copy entry into 'aux' */

      luaH_setint(L, t, i + 1, &aux);  /* re-insert it into the table */

    }

  }

  t->alimit = oldasize;  /* restore current size... */

}

/*

** Clear new slice of the array.

*/

static void clearNewSlice (Table *t, unsigned oldasize, unsigned newasize) {

  for (; oldasize < newasize; oldasize++)

    *getArrTag(t, oldasize) = LUA_VEMPTY;

}

/*

** Resize table 't' for the new given sizes. Both allocations (for

** the hash part and for the array part) can fail, which creates some

** subtleties. If the first allocation, for the hash part, fails, an

** error is raised and that is it. Otherwise, it copies the elements from

** the shrinking part of the array (if it is shrinking) into the new

** hash. Then it reallocates the array part.  If that fails, the table

** is in its original state; the function frees the new hash part and then

** raises the allocation error. Otherwise, it sets the new hash part

** into the table, initializes the new part of the array (if any) with

** nils and reinserts the elements of the old hash back into the new

** parts of the table.

*/

void luaH_resize (lua_State *L, Table *t, unsigned newasize,

                                          unsigned nhsize) {

  Table newt;  /* to keep the new hash part */

  unsigned int oldasize = setlimittosize(t);

  Value *newarray;

  if (newasize > MAXASIZE)

    luaG_runerror(L, "table overflow");

  /* create new hash part with appropriate size into 'newt' */

  newt.flags = 0;

  setnodevector(L, &newt, nhsize);

  if (newasize < oldasize) {  /* will array shrink? */

    /* re-insert into the new hash the elements from vanishing slice */

    exchangehashpart(t, &newt);  /* pretend table has new hash */

    reinsertOldSlice(L, t, oldasize, newasize);

    exchangehashpart(t, &newt);  /* restore old hash (in case of errors) */

  }

  /* allocate new array */

  newarray = resizearray(L, t, oldasize, newasize);

  if (l_unlikely(newarray == NULL && newasize > 0)) {  /* allocation failed? */

    freehash(L, &newt);  /* release new hash part */

    luaM_error(L);  /* raise error (with array unchanged) */

  }

  /* allocation ok; initialize new part of the array */

  exchangehashpart(t, &newt);  /* 't' has the new hash ('newt' has the old) */

  t->array = newarray;  /* set new array part */

  t->alimit = newasize;

  clearNewSlice(t, oldasize, newasize);

  /* re-insert elements from old hash part into new parts */

  reinsert(L, &newt, t);  /* 'newt' now has the old hash */

  freehash(L, &newt);  /* free old hash part */

}

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

  int nsize = allocsizenode(t);

  luaH_resize(L, t, nasize, nsize);

}

/*

** nums[i] = number of keys 'k' where 2^(i - 1) < k <= 2^i

*/

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

  unsigned int asize;  /* optimal size for array part */

  unsigned int na;  /* number of keys in the array part */

  unsigned int nums[MAXABITS + 1];

  int i;

  int totaluse;

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

  setlimittosize(t);

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

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

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

  /* count extra key */

  if (ttisinteger(ek))

    na += countint(ivalue(ek), nums);

  totaluse++;

  /* compute new size for array part */

  asize = computesizes(nums, &na);

  /* resize the table to new computed sizes */

  luaH_resize(L, t, asize, totaluse - na);

}

/*

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

*/

Table *luaH_new (lua_State *L) {

  GCObject *o = luaC_newobj(L, LUA_VTABLE, sizeof(Table));

  Table *t = gco2t(o);

  t->metatable = NULL;

  t->flags = cast_byte(maskflags);  /* table has no metamethod fields */

  t->array = NULL;

  t->alimit = 0;

  setnodevector(L, t, 0);

  return t;

}

/*

** Frees a table.

*/

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

  unsigned int realsize = luaH_realasize(t);

  freehash(L, t);

  resizearray(L, t, realsize, 0);

  luaM_free(L, t);

}

static Node *getfreepos (Table *t) {

  if (haslastfree(t)) {  /* does it have 'lastfree' information? */

    /* look for a spot before 'lastfree', updating 'lastfree' */

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

      Node *free = --getlastfree(t);

      if (keyisnil(free))

        return free;

    }

  }

  else {  /* no 'lastfree' information */

    if (!isdummy(t)) {

      int i = sizenode(t);

      while (i--) {  /* do a linear search */

        Node *free = gnode(t, i);

        if (keyisnil(free))

          return free;

      }

    }

  }

  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 void luaH_newkey (lua_State *L, Table *t, const TValue *key,

                                                 TValue *value) {

  Node *mp;

  TValue aux;

  if (l_unlikely(ttisnil(key)))

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

  else if (ttisfloat(key)) {

    lua_Number f = fltvalue(key);

    lua_Integer k;

    if (luaV_flttointeger(f, &k, F2Ieq)) {  /* does key fit in an integer? */

      setivalue(&aux, k);

      key = &aux;  /* insert it as an integer */

    }

    else if (l_unlikely(luai_numisnan(f)))

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

  }

  if (ttisnil(value))

    return;  /* do not insert nil values */

  mp = mainpositionTV(t, key);

  if (!isempty(gval(mp)) || isdummy(t)) {  /* main position is taken? */

    Node *othern;

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

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

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

      /* whatever called 'newkey' takes care of TM cache */

      luaH_set(L, t, key, value);  /* insert key into grown table */

      return;

    }

    lua_assert(!isdummy(t));

    othern = mainpositionfromnode(t, mp);

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

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

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

        othern += gnext(othern);

      gnext(othern) = cast_int(f - othern);  /* rechain to point to 'f' */

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

      if (gnext(mp) != 0) {

        gnext(f) += cast_int(mp - f);  /* correct 'next' */

        gnext(mp) = 0;  /* now 'mp' is free */

      }

      setempty(gval(mp));

    }

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

      /* new node will go into free position */

      if (gnext(mp) != 0)

        gnext(f) = cast_int((mp + gnext(mp)) - f);  /* chain new position */

      else lua_assert(gnext(f) == 0);

      gnext(mp) = cast_int(f - mp);

      mp = f;

    }

  }

  setnodekey(L, mp, key);

  luaC_barrierback(L, obj2gco(t), key);

  lua_assert(isempty(gval(mp)));

  setobj2t(L, gval(mp), value);

}

static const TValue *getintfromhash (Table *t, lua_Integer key) {

  Node *n = hashint(t, key);

  lua_assert(l_castS2U(key) - 1u >= luaH_realasize(t));

  for (;;) {  /* check whether 'key' is somewhere in the chain */

    if (keyisinteger(n) && keyival(n) == key)

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

    else {

      int nx = gnext(n);

      if (nx == 0) break;

      n += nx;

    }

  }

  return &absentkey;

}

static int hashkeyisempty (Table *t, lua_Integer key) {

  const TValue *val = getintfromhash(t, key);

  return isempty(val);

}

static int finishnodeget (const TValue *val, TValue *res) {

  if (!ttisnil(val)) {

    setobj(((lua_State*)NULL), res, val);

  }

  return ttypetag(val);

}

int luaH_getint (Table *t, lua_Integer key, TValue *res) {

  if (keyinarray(t, key)) {

    int tag = *getArrTag(t, key - 1);

    if (!tagisempty(tag))

      farr2val(t, key, tag, res);

    return tag;

  }

  else

    return finishnodeget(getintfromhash(t, key), res);

}

/*

** search function for short strings

*/

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

  Node *n = hashstr(t, key);

  lua_assert(key->tt == LUA_VSHRSTR);

  for (;;) {  /* check whether 'key' is somewhere in the chain */

    if (keyisshrstr(n) && eqshrstr(keystrval(n), key))

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

    else {

      int nx = gnext(n);

      if (nx == 0)

        return &absentkey;  /* not found */

      n += nx;

    }

  }

}

int luaH_getshortstr (Table *t, TString *key, TValue *res) {

  return finishnodeget(luaH_Hgetshortstr(t, key), res);

}

static const TValue *Hgetstr (Table *t, TString *key) {

  if (key->tt == LUA_VSHRSTR)

    return luaH_Hgetshortstr(t, key);

  else {  /* for long strings, use generic case */

    TValue ko;

    setsvalue(cast(lua_State *, NULL), &ko, key);

    return getgeneric(t, &ko, 0);

  }

}

int luaH_getstr (Table *t, TString *key, TValue *res) {

  return finishnodeget(Hgetstr(t, key), res);

}

TString *luaH_getstrkey (Table *t, TString *key) {

  const TValue *o = Hgetstr(t, key);

  if (!isabstkey(o))  /* string already present? */

    return keystrval(nodefromval(o));  /* get saved copy */

  else

    return NULL;

}

/*

** main search function

*/

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

  const TValue *slot;

  switch (ttypetag(key)) {

    case LUA_VSHRSTR:

      slot = luaH_Hgetshortstr(t, tsvalue(key));

      break;

    case LUA_VNUMINT:

      return luaH_getint(t, ivalue(key), res);

    case LUA_VNIL:

      slot = &absentkey;

      break;

    case LUA_VNUMFLT: {

      lua_Integer k;

      if (luaV_flttointeger(fltvalue(key), &k, F2Ieq)) /* integral index? */

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

      /* else... */

    }  /* FALLTHROUGH */

    default:

      slot = getgeneric(t, key, 0);

      break;

  }

  return finishnodeget(slot, res);

}

static int finishnodeset (Table *t, const TValue *slot, TValue *val) {

  if (!ttisnil(slot)) {

    setobj(((lua_State*)NULL), cast(TValue*, slot), val);

    return HOK;  /* success */

  }

  else if (isabstkey(slot))