lua/ltable.c

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/*
** $Id: ltable.c,v 2.2 2004/03/26 14:02:41 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 24
#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))
/*
** 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.
*/
static int arrayindex (const TValue *key, lua_Number lim) {
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if (ttisnumber(key)) {
lua_Number n = nvalue(key);
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int k;
if (n <= 0 || n > lim) return -1; /* out of range? */
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 and end of a traversal are signalled by -1.
*/
static int luaH_index (lua_State *L, Table *t, StkId key) {
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int i;
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if (ttisnil(key)) return -1; /* first iteration */
i = arrayindex(key, t->sizearray);
if (0 <= i) { /* is `key' inside array part? */
return i-1; /* yes; that's the index (corrected to C) */
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}
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else {
const TValue *v = luaH_get(t, key);
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if (v == &luaO_nilobject)
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luaG_runerror(L, "invalid key for `next'");
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i = cast(int, (cast(const lu_byte *, v) -
cast(const lu_byte *, gval(gnode(t, 0)))) / sizeof(Node));
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return i + t->sizearray; /* hash elements are numbered after array ones */
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}
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}
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int luaH_next (lua_State *L, Table *t, StkId key) {
int i = luaH_index(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, gkey(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 void computesizes (int nums[], int ntotal, int *narray, int *nhash) {
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int i;
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int a = nums[0]; /* number of elements smaller than 2^i */
int na = a; /* number of elements to go to array part */
int n = (na == 0) ? -1 : 0; /* (log of) optimal size for array part */
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for (i = 1; a < *narray && *narray >= twoto(i-1); i++) {
if (nums[i] > 0) {
a += nums[i];
if (a >= twoto(i-1)) { /* more than half elements in use? */
n = i;
na = a;
}
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}
}
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lua_assert(na <= *narray && *narray <= ntotal);
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*nhash = ntotal - na;
*narray = (n == -1) ? 0 : twoto(n);
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lua_assert(na <= *narray && na >= *narray/2);
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}
static void numuse (const Table *t, int *narray, int *nhash) {
int nums[MAXBITS+1];
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int i, lg;
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int totaluse = 0;
lua_Number sizelimit; /* an upper bound for the array size */
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/* count elements in array part */
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for (i=0, lg=0; lg<=MAXBITS; lg++) { /* for each slice [2^(lg-1) to 2^lg) */
int ttlg = twoto(lg); /* 2^lg */
if (ttlg > t->sizearray) {
ttlg = t->sizearray;
if (i >= ttlg) break;
}
nums[lg] = 0;
for (; i<ttlg; i++) {
if (!ttisnil(&t->array[i])) {
nums[lg]++;
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totaluse++;
}
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}
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}
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for (; lg<=MAXBITS; lg++) nums[lg] = 0; /* reset other counts */
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*narray = totaluse; /* all previous uses were in array part */
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/* count elements in hash part */
i = sizenode(t);
/* array part cannot be larger than twice the maximum number of elements */
sizelimit = cast(lua_Number, totaluse + i) * 2;
if (sizelimit >= MAXASIZE) sizelimit = MAXASIZE;
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while (i--) {
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Node *n = &t->node[i];
if (!ttisnil(gval(n))) {
int k = arrayindex(gkey(n), sizelimit);
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if (k >= 0) { /* is `key' an appropriate array index? */
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nums[luaO_log2(k-1)+1]++; /* count as such */
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(*narray)++;
}
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totaluse++;
}
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}
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computesizes(nums, totaluse, narray, nhash);
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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 lsize) {
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int i;
int size = twoto(lsize);
if (lsize > MAXBITS)
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luaG_runerror(L, "table overflow");
if (lsize == 0) { /* no elements to hash part? */
t->node = G(L)->dummynode; /* use common `dummynode' */
lua_assert(ttisnil(gkey(t->node))); /* assert invariants: */
lua_assert(ttisnil(gval(t->node)));
lua_assert(t->node->next == NULL); /* (`dummynode' must be empty) */
}
else {
t->node = luaM_newvector(L, size, Node);
for (i=0; i<size; i++) {
t->node[i].next = 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->firstfree = gnode(t, size-1); /* first free position to be used */
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}
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void luaH_resize (lua_State *L, Table *t, int nasize, int nhsize) {
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int i;
int oldasize = t->sizearray;
int oldhsize = t->lsizenode;
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Node *nold;
Node temp[1];
if (oldhsize)
nold = t->node; /* save old hash ... */
else { /* old hash is `dummynode' */
lua_assert(t->node == G(L)->dummynode);
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temp[0] = t->node[0]; /* copy it to `temp' */
nold = temp;
setnilvalue(gkey(G(L)->dummynode)); /* restate invariant */
setnilvalue(gval(G(L)->dummynode));
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lua_assert(G(L)->dummynode->next == NULL);
}
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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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/* re-insert elements */
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 in 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, gkey(old)), gval(old));
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}
if (oldhsize)
luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
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}
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static void rehash (lua_State *L, Table *t) {
int nasize, nhsize;
numuse(t, &nasize, &nhsize); /* compute new sizes for array and hash parts */
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luaH_resize(L, t, nasize, luaO_log2(nhsize)+1);
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}
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/*
** }=============================================================
*/
Table *luaH_new (lua_State *L, int narray, int lnhash) {
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 = NULL;
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setarrayvector(L, t, narray);
setnodevector(L, t, lnhash);
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return t;
}
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void luaH_free (lua_State *L, Table *t) {
if (t->lsizenode)
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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_freelem(L, t);
}
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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) {
TValue *val;
Node *mp = luaH_mainposition(t, key);
if (!ttisnil(gval(mp))) { /* main position is not free? */
Node *othern = luaH_mainposition(t, gkey(mp)); /* `mp' of colliding node */
Node *n = t->firstfree; /* get a free place */
if (othern != mp) { /* is colliding node out of its main position? */
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/* yes; move colliding node into free position */
while (othern->next != mp) othern = othern->next; /* find previous */
othern->next = n; /* redo the chain with `n' in place of `mp' */
*n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
mp->next = 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 */
n->next = mp->next; /* chain new position */
mp->next = n;
mp = n;
}
}
setobj2t(L, gkey(mp), key);
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luaC_barrier(L, t, key);
lua_assert(ttisnil(gval(mp)));
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for (;;) { /* correct `firstfree' */
if (ttisnil(gkey(t->firstfree)))
return gval(mp); /* OK; table still has a free place */
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else if (t->firstfree == t->node) break; /* cannot decrement from here */
else (t->firstfree)--;
}
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/* no more free places; must create one */
setbvalue(gval(mp), 0); /* avoid new key being removed */
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rehash(L, t); /* grow table */
val = cast(TValue *, luaH_get(t, key)); /* get new position */
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lua_assert(ttisboolean(val));
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setnilvalue(val);
return val;
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}
/*
** generic search function
*/
static const TValue *luaH_getany (Table *t, const TValue *key) {
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if (!ttisnil(key)) {
Node *n = luaH_mainposition(t, key);
do { /* check whether `key' is somewhere in the chain */
if (luaO_rawequalObj(gkey(n), key)) return gval(n); /* that's it */
else n = n->next;
} while (n);
}
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return &luaO_nilobject;
}
/*
** search function for integers
*/
const TValue *luaH_getnum (Table *t, int key) {
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if (1 <= key && key <= t->sizearray)
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 */
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else n = n->next;
} 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 = n->next;
} while (n);
return &luaO_nilobject;
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}
/*
** main search function
*/
const TValue *luaH_get (Table *t, const TValue *key) {
switch (ttype(key)) {
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 */
}
default: return luaH_getany(t, key);
}
}
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);
}
}