/*
** $Id: ltable.c,v 2.72 2012/09/11 19:37:16 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
