/*

** $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 "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"

/*

** MAXABITS is the largest integer such that MAXASIZE fits in an

** unsigned int.

*/

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

/*

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

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

** fits in a 'size_t'.

*/

#define MAXASIZE  luaM_limitN(1u << MAXABITS, TValue)

/*

** 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 'n' */

    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 int findindex (lua_State *L, Table *t, TValue *key,

                               unsigned int 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 */

    if (!isempty(&t->array[i])) {  /* a non-empty entry? */

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

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

      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))

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

}

/*

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

** 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 int computesizes (unsigned int nums[], unsigned int *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;

}

/*

** 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 int numusearray (const Table *t, unsigned int *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 (!isempty(&t->array[i-1]))

        lc++;

    }

    nums[lg] += lc;

    ause += lc;

  }

  return ause;

}

static int numusehash (const Table *t, unsigned int *nums, unsigned int *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;

}

/*

** 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 int size) {

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

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

    t->lsizenode = 0;

    t->lastfree = NULL;  /* 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);

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

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

      Node *n = gnode(t, i);

      gnext(n) = 0;

      setnilkey(n);

      setempty(gval(n));

    }

    t->lsizenode = cast_byte(lsize);

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

  }

}

/*

** (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'.

*/

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

  lu_byte lsizenode = t1->lsizenode;

  Node *node = t1->node;

  Node *lastfree = t1->lastfree;

  t1->lsizenode = t2->lsizenode;

  t1->node = t2->node;

  t1->lastfree = t2->lastfree;

  t2->lsizenode = lsizenode;

  t2->node = node;

  t2->lastfree = lastfree;

}

/*

** 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 int newasize,

                                          unsigned int nhsize) {

  unsigned int i;

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

  unsigned int oldasize = setlimittosize(t);

  TValue *newarray;

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

  setnodevector(L, &newt, nhsize);

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

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

    exchangehashpart(t, &newt);  /* and new hash */

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

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

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

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

    }

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

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

  }

  /* allocate new array */

  newarray = luaM_reallocvector(L, t->array, oldasize, newasize, TValue);

  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;

  for (i = oldasize; i < newasize; i++)  /* clear new slice of the array */

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

  /* 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;

}

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

  freehash(L, t);

  luaM_freearray(L, t->array, luaH_realasize(t));

  luaM_free(L, t);

}

static Node *getfreepos (Table *t) {

  if (!isdummy(t)) {

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

      t->lastfree--;

      if (keyisnil(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 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);

}

/*

** Search function for integers. If integer is inside 'alimit', get it

** directly from the array part. Otherwise, if 'alimit' is not equal to

** the real size of the array, key still can be in the array part. In

** this case, try to avoid a call to 'luaH_realasize' when key is just

** one more than the limit (so that it can be incremented without

** changing the real size of the array).

*/

const TValue *luaH_getint (Table *t, lua_Integer key) {

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

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

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

           (l_castS2U(key) == t->alimit + 1 ||

            l_castS2U(key) - 1u < luaH_realasize(t))) {

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

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

  }

  else {

    Node *n = hashint(t, key);

    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;

  }

}

/*

** search function for short strings

*/

const TValue *luaH_getshortstr (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;

    }

  }

}

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

  if (key->tt == LUA_VSHRSTR)

    return luaH_getshortstr(t, key);

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

    TValue ko;

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

    return getgeneric(t, &ko, 0);

  }

}

/*

** main search function

*/

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

  switch (ttypetag(key)) {

    case LUA_VSHRSTR: return luaH_getshortstr(t, tsvalue(key));

    case LUA_VNUMINT: return luaH_getint(t, ivalue(key));

    case LUA_VNIL: return &absentkey;

    case LUA_VNUMFLT: {

      lua_Integer k;

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

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

      /* else... */

    }  /* FALLTHROUGH */

    default:

      return getgeneric(t, key, 0);

  }

}

/*

** Finish a raw "set table" operation, where 'slot' is where the value

** should have been (the result of a previous "get table").

** Beware: when using this function you probably need to check a GC

** barrier and invalidate the TM cache.

*/

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

                                   const TValue *slot, TValue *value) {

  if (isabstkey(slot))

    luaH_newkey(L, t, key, value);

  else

    setobj2t(L, cast(TValue *, slot), value);

}

/*

** beware: when using this function you probably need to check a GC

** barrier and invalidate the TM cache.

*/

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

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

  luaH_finishset(L, t, key, slot, value);

}

void luaH_setint (lua_State *L, Table *t, lua_Integer key, TValue *value) {

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

  if (isabstkey(p)) {

    TValue k;

    setivalue(&k, key);

    luaH_newkey(L, t, &k, value);

  }

  else

    setobj2t(L, cast(TValue *, p), value);

}

/*

** Try to find a boundary in the hash part of table 't'. From the

** caller, we know that 'j' is zero or present and that 'j + 1' is

** present. We want to find a larger key that is absent from the

** table, so that we can do a binary search between the two keys to

** find a boundary. We keep doubling 'j' until we get an absent index.

** If the doubling would overflow, we try LUA_MAXINTEGER. If it is

** absent, we are ready for the binary search. ('j', being max integer,

** is larger or equal to 'i', but it cannot be equal because it is

** absent while 'i' is present; so 'j > i'.) Otherwise, 'j' is a

** boundary. ('j + 1' cannot be a present integer key because it is

** not a valid integer in Lua.)

*/

static lua_Unsigned hash_search (Table *t, lua_Unsigned j) {

  lua_Unsigned i;

  if (j == 0) j++;  /* the caller ensures 'j + 1' is present */

  do {

    i = j;  /* 'i' is a present index */

    if (j <= l_castS2U(LUA_MAXINTEGER) / 2)

      j *= 2;

    else {

      j = LUA_MAXINTEGER;

      if (isempty(luaH_getint(t, j)))  /* t[j] not present? */

        break;  /* 'j' now is an absent index */

      else  /* weird case */

        return j;  /* well, max integer is a boundary... */

    }

  } while (!isempty(luaH_getint(t, j)));  /* repeat until an absent t[j] */

  /* i < j  &&  t[i] present  &&  t[j] absent */

  while (j - i > 1u) {  /* do a binary search between them */

    lua_Unsigned m = (i + j) / 2;

    if (isempty(luaH_getint(t, m))) j = m;

    else i = m;

  }

  return i;

}

static unsigned int binsearch (const TValue *array, unsigned int i,

                                                    unsigned int j) {

  while (j - i > 1u) {  /* binary search */

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

    if (isempty(&array[m - 1])) 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 present and t[i+1] is absent, or 0 if t[1] is absent

** and 'maxinteger' if t[maxinteger] is present.)

** (In the next explanation, we use Lua indices, that is, with base 1.

** The code itself uses base 0 when indexing the array part of the table.)

** The code starts with 'limit = t->alimit', a position in the array

** part that may be a boundary.

**

** (1) If 't[limit]' is empty, there must be a boundary before it.

** As a common case (e.g., after 't[#t]=nil'), check whether 'limit-1'

** is present. If so, it is a boundary. Otherwise, do a binary search

** between 0 and limit to find a boundary. In both cases, try to

** use this boundary as the new 'alimit', as a hint for the next call.

**

** (2) If 't[limit]' is not empty and the array has more elements

** after 'limit', try to find a boundary there. Again, try first

** the special case (which should be quite frequent) where 'limit+1'

** is empty, so that 'limit' is a boundary. Otherwise, check the

** last element of the array part. If it is empty, there must be a

** boundary between the old limit (present) and the last element

** (absent), which is found with a binary search. (This boundary always

** can be a new limit.)

**

** (3) The last case is when there are no elements in the array part

** (limit == 0) or its last element (the new limit) is present.

** In this case, must check the hash part. If there is no hash part

** or 'limit+1' is absent, 'limit' is a boundary.  Otherwise, call

** 'hash_search' to find a boundary in the hash part of the table.

** (In those cases, the boundary is not inside the array part, and

** therefore cannot be used as a new limit.)

*/

lua_Unsigned luaH_getn (Table *t) {

  unsigned int limit = t->alimit;

  if (limit > 0 && isempty(&t->array[limit - 1])) {  /* (1)? */

    /* there must be a boundary before 'limit' */

    if (limit >= 2 && !isempty(&t->array[limit - 2])) {

      /* 'limit - 1' is a boundary; can it be a new limit? */

      if (ispow2realasize(t) && !ispow2(limit - 1)) {

        t->alimit = limit - 1;

        setnorealasize(t);  /* now 'alimit' is not the real size */

      }

      return limit - 1;

    }

    else {  /* must search for a boundary in [0, limit] */

      unsigned int boundary = binsearch(t->array, 0, limit);

      /* can this boundary represent the real size of the array? */

      if (ispow2realasize(t) && boundary > luaH_realasize(t) / 2) {

        t->alimit = boundary;  /* use it as the new limit */

        setnorealasize(t);

      }

      return boundary;

    }

  }

  /* 'limit' is zero or present in table */

  if (!limitequalsasize(t)) {  /* (2)? */

    /* 'limit' > 0 and array has more elements after 'limit' */

    if (isempty(&t->array[limit]))  /* 'limit + 1' is empty? */

      return limit;  /* this is the boundary */

    /* else, try last element in the array */

    limit = luaH_realasize(t);

    if (isempty(&t->array[limit - 1])) {  /* empty? */

      /* there must be a boundary in the array after old limit,

         and it must be a valid new limit */

      unsigned int boundary = binsearch(t->array, t->alimit, limit);

      t->alimit = boundary;

      return boundary;

    }

    /* else, new limit is present in the table; check the hash part */

  }

  /* (3) 'limit' is the last element and either is zero or present in table */

  lua_assert(limit == luaH_realasize(t) &&

             (limit == 0 || !isempty(&t->array[limit - 1])));

  if (isdummy(t) || isempty(luaH_getint(t, cast(lua_Integer, limit + 1))))

    return limit;  /* 'limit + 1' is absent */

  else  /* 'limit + 1' is also present */

    return hash_search(t, limit);

}

#if defined(LUA_DEBUG)

/* export these functions for the test library */

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

  return mainpositionTV(t, key);

}

#endif