lua/ltable.c

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/*
** $Id: ltable.c,v 2.13 2005/01/04 15:55:12 roberto Exp roberto $
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** Lua tables (hash)
** See Copyright Notice in lua.h
*/
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/*
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** 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.
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** 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.
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** Hence even when the load factor reaches 100%, performance remains good.
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*/
#include <string.h>
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#define ltable_c
#define LUA_CORE
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#include "lua.h"
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#include "ldebug.h"
#include "ldo.h"
#include "lgc.h"
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#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
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#include "ltable.h"
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/*
** max size of array part is 2^MAXBITS
*/
#if LUA_BITSINT > 26
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#define MAXBITS 26
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#else
#define MAXBITS (LUA_BITSINT-2)
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#endif
#define MAXASIZE (1 << MAXBITS)
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#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
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#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))
const Node luaH_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]);
}
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/*
** returns the `main' position of an element in a table (that is, the index
** of its hash value)
*/
Node *luaH_mainposition (const Table *t, const TValue *key) {
switch (ttype(key)) {
case LUA_TNUMBER:
return hashnum(t, nvalue(key));
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case LUA_TSTRING:
return hashstr(t, rawtsvalue(key));
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case LUA_TBOOLEAN:
return hashboolean(t, bvalue(key));
case LUA_TLIGHTUSERDATA:
return hashpointer(t, pvalue(key));
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default:
return hashpointer(t, gcvalue(key));
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}
}
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/*
** returns the index for `key' if `key' is an appropriate key to live in
** the array part of the table, -1 otherwise.
*/
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static int arrayindex (const TValue *key) {
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if (ttisnumber(key)) {
lua_Number n = nvalue(key);
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int k;
lua_number2int(k, n);
if (cast(lua_Number, k) == nvalue(key))
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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.
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*/
static int findindex (lua_State *L, Table *t, StkId key) {
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int i;
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if (ttisnil(key)) return -1; /* first iteration */
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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) */
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else {
Node *n = luaH_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 = 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 for `next'"); /* key not found */
return 0; /* to avoid warnings */
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}
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}
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int luaH_next (lua_State *L, Table *t, StkId key) {
int i = findindex(L, t, key); /* find original element */
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for (i++; i < t->sizearray; i++) { /* try first array part */
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if (!ttisnil(&t->array[i])) { /* a non-nil value? */
setnvalue(key, cast(lua_Number, i+1));
setobj2s(L, key+1, &t->array[i]);
return 1;
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}
}
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;
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}
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}
return 0; /* no more elements */
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}
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/*
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** {=============================================================
** Rehash
** ==============================================================
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*/
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static int computesizes (int nums[], int *narray) {
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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 */
}
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}
if (a == *narray) break; /* all elements already counted */
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}
*narray = n;
lua_assert(*narray/2 <= na && na <= *narray);
return na;
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}
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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 */
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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 */
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}
/* count elements in range (2^(lg-1), 2^lg] */
for (; i <= lim; i++) {
if (!ttisnil(&t->array[i-1]))
lc++;
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}
nums[lg] += lc;
ause += lc;
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}
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);
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while (i--) {
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Node *n = &t->node[i];
if (!ttisnil(gval(n))) {
ause += countint(key2tval(n), nums);
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totaluse++;
}
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}
*pnasize += ause;
return totaluse;
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}
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static void setarrayvector (lua_State *L, Table *t, int size) {
int i;
luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
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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 *, &luaH_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++) {
gnext(&t->node[i]) = NULL;
setnilvalue(gkey(gnode(t, i)));
setnilvalue(gval(gnode(t, i)));
}
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}
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t->lsizenode = cast(lu_byte, lsize);
t->lastfree = gnode(t, size); /* all positions are free */
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}
static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
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int i;
int oldasize = t->sizearray;
int oldhsize = t->lsizenode;
Node *nold = t->node; /* save old hash ... */
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if (nasize > oldasize) /* array part must grow? */
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setarrayvector(L, t, nasize);
/* create new hash part with appropriate size */
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setnodevector(L, t, nhsize);
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if (nasize < oldasize) { /* array part must shrink? */
t->sizearray = nasize;
/* re-insert elements from vanishing slice */
for (i=nasize; i<oldasize; i++) {
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if (!ttisnil(&t->array[i]))
setobjt2t(L, luaH_setnum(L, t, i+1), &t->array[i]);
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}
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/* shrink array */
luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
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}
/* re-insert elements from hash part */
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for (i = twoto(oldhsize) - 1; i >= 0; i--) {
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Node *old = nold+i;
if (!ttisnil(gval(old)))
setobjt2t(L, luaH_set(L, t, key2tval(old)), gval(old));
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}
if (nold != &luaH_dummynode)
luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
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}
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void luaH_resizearray (lua_State *L, Table *t, int nasize) {
int nsize = (t->node == &luaH_dummynode) ? 0 : sizenode(t);
resize(L, t, nasize, nsize);
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}
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);
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/* resize the table to new computed sizes */
resize(L, t, nasize, totaluse - na);
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}
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/*
** }=============================================================
*/
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Table *luaH_new (lua_State *L, int narray, int nhash) {
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Table *t = luaM_new(L, Table);
luaC_link(L, obj2gco(t), LUA_TTABLE);
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t->metatable = NULL;
t->flags = cast(lu_byte, ~0);
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/* temporary values (kept only if some malloc fails) */
t->array = NULL;
t->sizearray = 0;
t->lsizenode = 0;
t->node = cast(Node *, &luaH_dummynode);
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setarrayvector(L, t, narray);
setnodevector(L, t, nhash);
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return t;
}
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void luaH_free (lua_State *L, Table *t) {
if (t->node != &luaH_dummynode)
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luaM_freearray(L, t->node, sizenode(t), Node);
luaM_freearray(L, t->array, t->sizearray, TValue);
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luaM_free(L, t);
}
static Node *getfreepos (lua_State *L, Table *t) {
while (t->lastfree-- > t->node) {
if (ttisnil(gkey(t->lastfree)))
return t->lastfree;
}
return NULL; /* could not find a free place */
}
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/*
** 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.
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*/
static TValue *newkey (lua_State *L, Table *t, const TValue *key) {
Node *mp = luaH_mainposition(t, key);
if (!ttisnil(gval(mp)) || mp == &luaH_dummynode) {
Node *othern;
Node *n = getfreepos(L, 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 != &luaH_dummynode);
othern = luaH_mainposition(t, key2tval(mp));
if (othern != mp) { /* is colliding node out of its main position? */
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/* 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' */
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*n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
gnext(mp) = NULL; /* now `mp' is free */
setnilvalue(gval(mp));
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}
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;
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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);
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}
/*
** search function for integers
*/
const TValue *luaH_getnum (Table *t, int key) {
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/* (1 <= key && key <= t->sizearray) */
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if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
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return &t->array[key-1];
else {
lua_Number nk = cast(lua_Number, key);
Node *n = hashnum(t, nk);
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do { /* check whether `key' is somewhere in the chain */
if (ttisnumber(gkey(n)) && nvalue(gkey(n)) == nk)
return gval(n); /* that's it */
else n = gnext(n);
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} 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;
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}
/*
** main search function
*/
const TValue *luaH_get (Table *t, const TValue *key) {
switch (ttype(key)) {
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case LUA_TNIL: return &luaO_nilobject;
case LUA_TSTRING: return luaH_getstr(t, rawtsvalue(key));
case LUA_TNUMBER: {
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int k;
lua_number2int(k, (nvalue(key)));
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if (cast(lua_Number, k) == nvalue(key)) /* is an integer index? */
return luaH_getnum(t, k); /* use specialized version */
/* else go through */
}
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default: {
Node *n = luaH_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);
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} while (n);
return &luaO_nilobject;
}
}
}
TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
const TValue *p = luaH_get(t, key);
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t->flags = 0;
if (p != &luaO_nilobject)
return cast(TValue *, p);
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else {
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if (ttisnil(key)) luaG_runerror(L, "table index is nil");
else if (ttisnumber(key) && nvalue(key) != nvalue(key))
luaG_runerror(L, "table index is NaN");
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return newkey(L, t, key);
}
}
TValue *luaH_setnum (lua_State *L, Table *t, int key) {
const TValue *p = luaH_getnum(t, key);
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if (p != &luaO_nilobject)
return cast(TValue *, p);
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else {
TValue k;
setnvalue(&k, cast(lua_Number, key));
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return newkey(L, t, &k);
}
}
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TValue *luaH_setstr (lua_State *L, Table *t, TString *key) {
const TValue *p = luaH_getstr(t, key);
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if (p != &luaO_nilobject)
return cast(TValue *, p);
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else {
TValue k;
setsvalue(L, &k, key);
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return newkey(L, t, &k);
}
}