/*
** $Id: ltable.c,v 2.72.1.1 2013/04/12 18:48:47 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 <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 "lstring.h"
#include "ltable.h"
#include "lvm.h"

/*
** max size of array part is 2^MAXBITS
*/
#if LUAI_BITSINT >= 32
#define MAXBITS 30
#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))

#define dummynode (&dummynode_)

#define isdummy(n) ((n) == dummynode)

static const Node dummynode_ = {
	{NILCONSTANT},        /* value */
	{{NILCONSTANT, NULL}} /* key */
};

/*
** hash for lua_Numbers
*/
static Node *hashnum(const Table *t, lua_Number n)
{
	int i;
	luai_hashnum(i, n);
	if (i < 0)
	{
		if (cast(unsigned int, i) == 0u - i) /* use unsigned to avoid overflows */
			i = 0;                           /* handle INT_MIN */
		i = -i;                              /* must be a positive value */
	}
	return hashmod(t, i);
}

/*
** 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_TLNGSTR:
		{
			TString *s = rawtsvalue(key);
			if (s->tsv.extra == 0)
			{ /* no hash? */
				s->tsv.hash = luaS_hash(getstr(s), s->tsv.len, s->tsv.hash);
				s->tsv.extra = 1; /* now it has its hash */
			}
			return hashstr(t, rawtsvalue(key));
		}
		case LUA_TSHRSTR:
			return hashstr(t, rawtsvalue(key));
		case LUA_TBOOLEAN:
			return hashboolean(t, bvalue(key));
		case LUA_TLIGHTUSERDATA:
			return hashpointer(t, pvalue(key));
		case LUA_TLCF:
			return hashpointer(t, fvalue(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 signaled 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);
		for (;;)
		{ /* check whether `key' is somewhere in the chain */
			/* key may be dead already, but it is ok to use it in `next' */
			if (luaV_rawequalobj(gkey(n), key) ||
				(ttisdeadkey(gkey(n)) && iscollectable(key) &&
				 deadvalue(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);
			if (n == NULL)
				luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
		}
	}
}

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, gkey(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[luaO_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(gkey(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 = luaO_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 */
}

void luaH_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]))
				luaH_setint(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)))
		{
			/* doesn't need barrier/invalidate cache, as entry was
         already present in the table */
			setobjt2t(L, luaH_set(L, t, gkey(old)), gval(old));
		}
	}
	if (!isdummy(nold))
		luaM_freearray(L, nold, cast(size_t, twoto(oldhsize))); /* free old array */
}

void luaH_resizearray(lua_State *L, Table *t, int nasize)
{
	int nsize = isdummy(t->node) ? 0 : sizenode(t);
	luaH_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 with 2^(i-1) < k <= 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 */
	luaH_resize(L, t, nasize, totaluse - na);
}

/*
** }=============================================================
*/

Table *luaH_new(lua_State *L)
{
	Table *t = &luaC_newobj(L, LUA_TTABLE, sizeof(Table), NULL, 0)->h;
	t->metatable = NULL;
	t->flags = cast_byte(~0);
	t->array = NULL;
	t->sizearray = 0;
	setnodevector(L, t, 0);
	return t;
}

void luaH_free(lua_State *L, Table *t)
{
	if (!isdummy(t->node))
		luaM_freearray(L, t->node, cast(size_t, sizenode(t)));
	luaM_freearray(L, t->array, t->sizearray);
	luaM_free(L, t);
}

static Node *getfreepos(Table *t)
{
	while (t->lastfree > t->node)
	{
		t->lastfree--;
		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.
*/
TValue *luaH_newkey(lua_State *L, Table *t, const TValue *key)
{
	Node *mp;
	if (ttisnil(key))
		luaG_runerror(L, "table index is nil");
	else if (ttisnumber(key) && luai_numisnan(L, nvalue(key)))
		luaG_runerror(L, "table index is NaN");
	mp = mainposition(t, key);
	if (!ttisnil(gval(mp)) || isdummy(mp))
	{ /* main position is taken? */
		Node *othern;
		Node *n = getfreepos(t); /* get a free place */
		if (n == NULL)
		{                      /* cannot find a free place? */
			rehash(L, t, key); /* grow table */
			/* whatever called 'newkey' take care of TM cache and GC barrier */
			return luaH_set(L, t, key); /* insert key into grown table */
		}
		lua_assert(!isdummy(n));
		othern = mainposition(t, gkey(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;
		}
	}
	setobj2t(L, gkey(mp), key);
	luaC_barrierback(L, obj2gco(t), key);
	lua_assert(ttisnil(gval(mp)));
	return gval(mp);
}

/*
** search function for integers
*/
const TValue *luaH_getint(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 short strings
*/
const TValue *luaH_getstr(Table *t, TString *key)
{
	Node *n = hashstr(t, key);
	lua_assert(key->tsv.tt == LUA_TSHRSTR);
	do
	{ /* check whether `key' is somewhere in the chain */
		if (ttisshrstring(gkey(n)) && eqshrstr(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_TSHRSTR:
			return luaH_getstr(t, rawtsvalue(key));
		case LUA_TNIL:
			return luaO_nilobject;
		case LUA_TNUMBER:
		{
			int k;
			lua_Number n = nvalue(key);
			lua_number2int(k, n);
			if (luai_numeq(cast_num(k), n)) /* index is int? */
				return luaH_getint(t, k);   /* use specialized version */
											/* else go through */
		}
		default:
		{
			Node *n = mainposition(t, key);
			do
			{ /* check whether `key' is somewhere in the chain */
				if (luaV_rawequalobj(gkey(n), key))
					return gval(n); /* that's it */
				else
					n = gnext(n);
			} while (n);
			return luaO_nilobject;
		}
	}
}

/*
** beware: when using this function you probably need to check a GC
** barrier and invalidate the TM cache.
*/
TValue *luaH_set(lua_State *L, Table *t, const TValue *key)
{
	const TValue *p = luaH_get(t, key);
	if (p != luaO_nilobject)
		return cast(TValue *, p);
	else
		return luaH_newkey(L, t, key);
}

void luaH_setint(lua_State *L, Table *t, int key, TValue *value)
{
	const TValue *p = luaH_getint(t, key);
	TValue *cell;
	if (p != luaO_nilobject)
		cell = cast(TValue *, p);
	else
	{
		TValue k;
		setnvalue(&k, cast_num(key));
		cell = luaH_newkey(L, t, &k);
	}
	setobj2t(L, cell, value);
}

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_getint(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_getint(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_getint(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 (isdummy(t->node)) /* 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 isdummy(n); }

#endif
