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/*

** $Id: ltable.c,v 2.32 2006/01/18 11:49:02 roberto Exp $

** Lua tables (hash)

** See Copyright Notice in lua.h

*/

/*

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

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

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

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

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

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

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

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

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

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

*/

#include <math.h>

#include <string.h>

#define ltable_c

#define LUA_CORE

#include "lua.h"

#include "ldebug.h"

#include "ldo.h"

#include "lgc.h"

#include "lmem.h"

#include "lobject.h"

#include "lstate.h"

#include "ltable.h"

/*

** max size of array part is 2^MAXBITS

*/

#if LUAI_BITSINT > 26

#define MAXBITS		26

#else

#define MAXBITS		(LUAI_BITSINT-2)

#endif

#define MAXASIZE	(1 << MAXBITS)

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

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

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

/*

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

** they tend to have many 2 factors.

*/

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

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

/*

** number of ints inside a lua_Number

*/

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

#define dummynode		(&dummynode_)

static const Node dummynode_ = {

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

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

};

/*

** hash for lua_Numbers

*/

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

  unsigned int a[numints];

  int i;

  n += 1;  /* normalize number (avoid -0) */

  lua_assert(sizeof(a) <= sizeof(n));

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

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

  return hashmod(t, a[0]);

}

/*

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

** of its hash value)

*/

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

  switch (ttype(key)) {

    case LUA_TNUMBER:

      return hashnum(t, nvalue(key));

    case LUA_TSTRING:

      return hashstr(t, rawtsvalue(key));

    case LUA_TBOOLEAN:

      return hashboolean(t, bvalue(key));

    case LUA_TLIGHTUSERDATA:

      return hashpointer(t, pvalue(key));

    default:

      return hashpointer(t, gcvalue(key));

  }

}

/*

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

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

*/

static int arrayindex (const TValue *key) {

  if (ttisnumber(key)) {

    lua_Number n = nvalue(key);

    int k;

    lua_number2int(k, n);

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

      return k;

  }

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

}

/*

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

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

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

*/

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

  int i;

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

  i = arrayindex(key);

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

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

  else {

    Node *n = mainposition(t, key);

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

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

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

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

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

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

        /* hash elements are numbered after array ones */

        return i + t->sizearray;

      }

      else n = gnext(n);

    } while (n);

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

    return 0;  /* to avoid warnings */

  }

}

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

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

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

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

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

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

      return 1;

    }

  }

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

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

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

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

      return 1;

    }

  }

  return 0;  /* no more elements */

}

/*

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

** Rehash

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

*/

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

  int i;

  int twotoi;  /* 2^i */

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

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

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

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

    if (nums[i] > 0) {

      a += nums[i];

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

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

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

      }

    }

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

  }

  *narray = n;

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

  return na;

}

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

  int k = arrayindex(key);

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

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

    return 1;

  }

  else

    return 0;

}

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

  int lg;

  int ttlg;  /* 2^lg */

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

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

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

    int lc = 0;  /* counter */

    int lim = ttlg;

    if (lim > t->sizearray) {

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

      if (i > lim)

        break;  /* no more elements to count */

    }

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

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

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

        lc++;

    }

    nums[lg] += lc;

    ause += lc;

  }

  return ause;

}

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

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

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

  int i = sizenode(t);

  while (i--) {

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

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

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

      totaluse++;

    }

  }

  *pnasize += ause;

  return totaluse;

}

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

  int i;

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

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

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

  t->sizearray = size;

}

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

  int lsize;

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

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

    lsize = 0;

  }

  else {

    int i;

    lsize = ceillog2(size);

    if (lsize > MAXBITS)

      luaG_runerror(L, "table overflow");

    size = twoto(lsize);

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

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

      Node *n = gnode(t, i);

      gnext(n) = NULL;

      setnilvalue(gkey(n));

      setnilvalue(gval(n));

    }

  }

  t->lsizenode = cast_byte(lsize);

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

}

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

  int i;

  int oldasize = t->sizearray;

  int oldhsize = t->lsizenode;

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

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

    setarrayvector(L, t, nasize);

  /* create new hash part with appropriate size */

  setnodevector(L, t, nhsize);  

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

    t->sizearray = nasize;

    /* re-insert elements from vanishing slice */

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

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

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

    }

    /* shrink array */

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

  }

  /* re-insert elements from hash part */

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

    Node *old = nold+i;

    if (!ttisnil(gval(old)))

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

  }

  if (nold != dummynode)

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

}

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

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

  resize(L, t, nasize, nsize);

}

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

  int nasize, na;

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

  int i;

  int totaluse;

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

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

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

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

  /* count extra key */

  nasize += countint(ek, nums);

  totaluse++;

  /* compute new size for array part */

  na = computesizes(nums, &nasize);

  /* resize the table to new computed sizes */

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

}

/*

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

*/

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

  Table *t = luaM_new(L, Table);

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

  t->metatable = NULL;

  t->flags = cast_byte(~0);

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

  t->array = NULL;

  t->sizearray = 0;

  t->lsizenode = 0;

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

  setarrayvector(L, t, narray);

  setnodevector(L, t, nhash);

  return t;

}

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

  if (t->node != dummynode)

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

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

  luaM_free(L, t);

}

static Node *getfreepos (Table *t) {

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

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

      return t->lastfree;

  }

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

}

/*

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

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

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

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

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

*/

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

  Node *mp = mainposition(t, key);

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

    Node *othern;

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

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

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

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

    }

    lua_assert(n != dummynode);

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

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

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

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

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

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

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

      setnilvalue(gval(mp));

    }

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

      /* new node will go into free position */

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

      gnext(mp) = n;

      mp = n;

    }

  }

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

  luaC_barriert(L, t, key);

  lua_assert(ttisnil(gval(mp)));

  return gval(mp);

}

/*

** search function for integers

*/

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

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

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

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

  else {

    lua_Number nk = cast_num(key);

    Node *n = hashnum(t, nk);

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

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

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

      else n = gnext(n);

    } while (n);

    return luaO_nilobject;

  }

}

/*

** search function for strings

*/

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

  Node *n = hashstr(t, key);

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

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

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

    else n = gnext(n);

  } while (n);

  return luaO_nilobject;

}

/*

** main search function

*/

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

  switch (ttype(key)) {

    case LUA_TNIL: return luaO_nilobject;

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

    case LUA_TNUMBER: {

      int k;

      lua_Number n = nvalue(key);

      lua_number2int(k, n);

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

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

      /* else go through */

    }

    default: {

      Node *n = mainposition(t, key);

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

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

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

        else n = gnext(n);

      } while (n);

      return luaO_nilobject;

    }

  }

}

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

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

  t->flags = 0;

  if (p != luaO_nilobject)

    return cast(TValue *, p);

  else {

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

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

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

    return newkey(L, t, key);

  }

}

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

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

  if (p != luaO_nilobject)

    return cast(TValue *, p);

  else {

    TValue k;

    setnvalue(&k, cast_num(key));

    return newkey(L, t, &k);

  }

}

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

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

  if (p != luaO_nilobject)

    return cast(TValue *, p);

  else {

    TValue k;

    setsvalue(L, &k, key);

    return newkey(L, t, &k);

  }

}

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

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

  j++;

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

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

    i = j;

    j *= 2;

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

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

      i = 1;

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

      return i - 1;

    }

  }

  /* now do a binary search between them */

  while (j - i > 1) {

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

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

    else i = m;

  }

  return i;

}

/*

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

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

*/

int luaH_getn (Table *t) {

  unsigned int j = t->sizearray;

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

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

    unsigned int i = 0;

    while (j - i > 1) {

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

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

      else i = m;

    }

    return i;

  }

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

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

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

  else return unbound_search(t, j);

}

#if defined(LUA_DEBUG)

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

  return mainposition(t, key);

}

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

#endif