/*

** $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 hash parts with at least 2^LIMFORLAST have 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    3  /* log2 of real limit (8) */

/*

** 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  (l_numbits(int) - 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(1 << 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)-1u)|1u))))

#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_)

/*

** Common hash part for tables with empty hash parts. That allows all

** tables to have a hash part, avoiding an extra check ("is there a hash

** part?") when indexing. Its sole node has an empty value and a key

** (DEADKEY, NULL) that is different from any valid TValue.

*/

static const Node dummynode_ = {

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

   LUA_TDEADKEY, 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 gnode(t, cast_int(ui) % cast_int((sizenode(t)-1) | 1));

  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 unsigned 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 (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));

  }

}

/*

** "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;

    }

  }

}

/*

** Return the index 'k' (converted to an unsigned) if it is inside

** the range [1, limit].

*/

static unsigned checkrange (lua_Integer k, unsigned limit) {

  return (l_castS2U(k) - 1u < limit) ? cast_uint(k) : 0;

}

/*

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

** array part of a table, 0 otherwise.

*/

#define arrayindex(k) checkrange(k, MAXASIZE)

/*

** Check whether an integer key is in the array part of a table and

** return its index there, or zero.

*/

#define ikeyinarray(t,k)  checkrange(k, t->asize)

/*

** Check whether a key is in the array part of a table and return its

** index there, or zero.

*/

static unsigned keyinarray (Table *t, const TValue *key) {

  return (ttisinteger(key)) ? ikeyinarray(t, ivalue(key)) : 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 = keyinarray(t, key);

  if (i != 0)  /* 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_uint(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 = t->asize;

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

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

    lu_byte tag = *getArrTag(t, i);

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

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

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

      return 1;

    }

  }

  for (i -= asize; 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 */

}

/* Extra space in Node array if it has a lastfree entry */

#define extraLastfree(t)  (haslastfree(t) ? sizeof(Limbox) : 0)

/* 'node' size in bytes */

static size_t sizehash (Table *t) {

  return cast_sizet(sizenode(t)) * sizeof(Node) + extraLastfree(t);

}

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

  if (!isdummy(t)) {

    /* get pointer to the beginning of Node array */

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

    luaM_freearray(L, arr, sizehash(t));

  }

}

/*

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

** Rehash

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

*/

static int insertkey (Table *t, const TValue *key, TValue *value);

static void newcheckedkey (Table *t, const TValue *key, TValue *value);

/*

** Structure to count the keys in a table.

** 'total' is the total number of keys in the table.

** 'na' is the number of *array indices* in the table (see 'arrayindex').

** 'deleted' is true if there are deleted nodes in the hash part.

** 'nums' is a "count array" where 'nums[i]' is the number of integer

** keys between 2^(i - 1) + 1 and 2^i. Note that 'na' is the summation

** of 'nums'.

*/

typedef struct {

  unsigned total;

  unsigned na;

  int deleted;

  unsigned nums[MAXABITS + 1];

} Counters;

/*

** Check whether it is worth to use 'na' array entries instead of 'nh'

** hash nodes. (A hash node uses ~3 times more memory than an array

** entry: Two values plus 'next' versus one value.) Evaluate with size_t

** to avoid overflows.

*/

#define arrayXhash(na,nh) (cast_sizet(na) <= cast_sizet(nh) * 3)

/*

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

** This size maximizes the number of elements going to the array part

** while satisfying the condition 'arrayXhash' with the use of memory if

** all those elements went to the hash part.

** 'ct->na' enters with the total number of array indices in the table

** and leaves with the number of keys that will go to the array part;

** return the optimal size for the array part.

*/

static unsigned computesizes (Counters *ct) {

  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 */

  /* traverse slices while 'twotoi' does not overflow and total of array

     indices still can satisfy 'arrayXhash' against the array size */

  for (i = 0, twotoi = 1;

       twotoi > 0 && arrayXhash(twotoi, ct->na);

       i++, twotoi *= 2) {

    unsigned nums = ct->nums[i];

    a += nums;

    if (nums > 0 &&  /* grows array only if it gets more elements... */

        arrayXhash(twotoi, a)) {  /* ...while using "less memory" */

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

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

    }

  }

  ct->na = na;

  return optimal;

}

static void countint (lua_Integer key, Counters *ct) {

  unsigned int k = arrayindex(key);

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

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

    ct->na++;

  }

}

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

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

  return tagisempty(tag);

}

/*

** Count keys in array part of table 't'.

*/

static void numusearray (const Table *t, Counters *ct) {

  int lg;

  unsigned int ttlg;  /* 2^lg */

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

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

  unsigned int asize = t->asize;

  /* 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++;

    }

    ct->nums[lg] += lc;

    ause += lc;

  }

  ct->total += ause;

  ct->na += ause;

}

/*

** Count keys in hash part of table 't'. As this only happens during

** a rehash, all nodes have been used. A node can have a nil value only

** if it was deleted after being created.

*/

static void numusehash (const Table *t, Counters *ct) {

  unsigned i = sizenode(t);

  unsigned total = 0;

  while (i--) {

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

    if (isempty(gval(n))) {

      lua_assert(!keyisnil(n));  /* entry was deleted; key cannot be nil */

      ct->deleted = 1;

    }

    else {

      total++;

      if (keyisinteger(n))

        countint(keyival(n), ct);

    }

  }

  ct->total += total;

}

/*

** 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) {

  if (size == 0)

    return 0;

  else  /* space for the two arrays plus an unsigned in between */

    return size * (sizeof(Value) + 1) + sizeof(unsigned);

}

/*

** 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 the old array.

** We could reallocate the array, but we still would need to move the

** elements to their new position, so the copy implicit in realloc is a

** waste. Moreover, most allocators will move the array anyway when the

** new size is double the old one (the most common case).

*/

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;

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

    if (oldasize > 0) {

      /* move common elements to new position */

      size_t oldasizeb = concretesize(oldasize);

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

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

      size_t tomoveb = (oldasize < newasize) ? oldasizeb : newasizeb;

      lua_assert(tomoveb > 0);

      memcpy(np - tomove, op - tomove, tomoveb);

      luaM_freemem(L, op - oldasize, oldasizeb);  /* free old block */

    }

    return np;

  }

}

/*

** 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 || (1 << 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 reinserthash (lua_State *L, Table *ot, Table *t) {

  unsigned j;

  unsigned 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);

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

  t2->lsizenode = lsizenode;

  t2->node = node;

  t2->flags = cast_byte((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 (Table *t, unsigned oldasize,

                                        unsigned newasize) {

  unsigned i;

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

    lu_byte tag = *getArrTag(t, i);

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

      TValue key, aux;

      setivalue(&key, l_castU2S(i) + 1);  /* make the key */

      farr2val(t, i, tag, &aux);  /* copy value into 'aux' */

      insertkey(t, &key, &aux);  /* insert entry into the hash part */

    }

  }

}

/*

** 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.

** Note that if the new size for the array part ('newasize') is equal to

** the old one ('oldasize'), this function will do nothing with that

** part.

*/

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

                                          unsigned nhsize) {

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

  unsigned oldasize = t->asize;

  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(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->asize = newasize;

  if (newarray != NULL)

    *lenhint(t) = newasize / 2u;  /* set an initial hint */

  clearNewSlice(t, oldasize, newasize);

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

  reinserthash(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) {

  unsigned nsize = allocsizenode(t);

  luaH_resize(L, t, nasize, nsize);

}

/*

** Rehash a table. First, count its keys. If there are array indices

** outside the array part, compute the new best size for that part.

** Then, resize the table.

*/

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

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

  Counters ct;

  unsigned i;

  unsigned nsize;  /* size for the hash part */

  /* reset counts */

  for (i = 0; i <= MAXABITS; i++) ct.nums[i] = 0;

  ct.na = 0;

  ct.deleted = 0;

  ct.total = 1;  /* count extra key */

  if (ttisinteger(ek))

    countint(ivalue(ek), &ct);  /* extra key may go to array */

  numusehash(t, &ct);  /* count keys in hash part */

  if (ct.na == 0) {

    /* no new keys to enter array part; keep it with the same size */

    asize = t->asize;

  }

  else {  /* compute best size for array part */

    numusearray(t, &ct);  /* count keys in array part */

    asize = computesizes(&ct);  /* compute new size for array part */

  }

  /* all keys not in the array part go to the hash part */

  nsize = ct.total - ct.na;

  if (ct.deleted) {  /* table has deleted entries? */

    /* insertion-deletion-insertion: give hash some extra size to

       avoid repeated resizings */

    nsize += nsize >> 2;

  }

  /* resize the table to new computed sizes */

  luaH_resize(L, t, asize, nsize);

}

/*

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

*/

Table *luaH_new (lua_State *L) {

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

  Table *t = gco2t(o);

  t->metatable = NULL;

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

  t->array = NULL;

  t->asize = 0;

  setnodevector(L, t, 0);

  return t;

}

lu_mem luaH_size (Table *t) {

  lu_mem sz = cast(lu_mem, sizeof(Table)) + concretesize(t->asize);

  if (!isdummy(t))

    sz += sizehash(t);

  return sz;

}

/*

** Frees a table.

*/

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

  freehash(L, t);

  resizearray(L, t, t->asize, 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 */

    unsigned 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. Return 0 if

** could not insert key (could not find a free space).

*/

static int insertkey (Table *t, const TValue *key, TValue *value) {

  Node *mp = mainpositionTV(t, key);

  /* table cannot already contain the key */

  lua_assert(isabstkey(getgeneric(t, key, 0)));

  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? */

      return 0;

    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(mp, key);

  lua_assert(isempty(gval(mp)));

  setobj2t(cast(lua_State *, 0), gval(mp), value);

  return 1;

}

/*

** Insert a key in a table where there is space for that key, the

** key is valid, and the value is not nil.

*/

static void newcheckedkey (Table *t, const TValue *key, TValue *value) {

  unsigned i = keyinarray(t, key);

  if (i > 0)  /* is key in the array part? */

    obj2arr(t, i - 1, value);  /* set value in the array */

  else {

    int done = insertkey(t, key, value);  /* insert key in the hash part */

    lua_assert(done);  /* it cannot fail */

    cast(void, done);  /* to avoid warnings */

  }

}

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

                                                 TValue *value) {

  if (!ttisnil(value)) {  /* do not insert nil values */

    int done = insertkey(t, key, value);

    if (!done) {  /* could not find a free place? */

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

      newcheckedkey(t, key, value);  /* insert key in grown table */

    }

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

    /* for debugging only: any new key may force an emergency collection */

    condchangemem(L, (void)0, (void)0, 1);

  }

}

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

  Node *n = hashint(t, key);

  lua_assert(!ikeyinarray(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;

}

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

  const TValue *val = getintfromhash(t, l_castU2S(key));

  return isempty(val);

}

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

  if (!ttisnil(val)) {

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

  }

  return ttypetag(val);

}

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

  unsigned k = ikeyinarray(t, key);

  if (k > 0) {

    lu_byte tag = *getArrTag(t, k - 1);

    if (!tagisempty(tag))

      farr2val(t, k - 1, 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(strisshr(key));

  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;

    }

  }

}

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

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

}

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

  TValue ko;

  lua_assert(!strisshr(key));

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

  return getgeneric(t, &ko, 0);  /* for long strings, use generic case */

}

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

  if (strisshr(key))

    return luaH_Hgetshortstr(t, key);

  else

    return Hgetlongstr(t, key);

}

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

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

}

/*

** main search function

*/

lu_byte 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);

}