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lua/ltable.c

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/*
** $Id: ltable.c,v 1.108 2002/05/15 18:57:44 roberto Exp roberto $
** 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.
** In other words, there are collisions only when two elements have the
** same main position (i.e. the same hash values for that table size).
** Because of that, the load factor of these tables can be 100% without
** performance penalties.
*/
#include "lua.h"
#include "ldebug.h"
#include "ldo.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "ltable.h"
/*
** max size of array part is 2^MAXBITS
*/
#if BITS_INT > 26
#define MAXBITS 24
#else
#define MAXBITS (BITS_INT-2)
#endif
/* check whether `x' < 2^MAXBITS */
#define toobig(x) ((((x)-1) >> MAXBITS) != 0)
#define TagDefault LUA_TTABLE
#define hashnum(t,n) \
(node(t, lmod(cast(lu_hash, cast(ls_hash, n)), sizenode(t))))
#define hashstr(t,str) (node(t, lmod((str)->tsv.hash, sizenode(t))))
#define hashboolean(t,p) (node(t, lmod(p, sizenode(t))))
/*
** avoid modulus by power of 2 for pointers, as they tend to have many
** 2 factors.
*/
#define hashpointer(t,p) (node(t, (IntPoint(p) % ((sizenode(t)-1)|1))))
/*
** 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 TObject *key) {
switch (ttype(key)) {
case LUA_TNUMBER:
return hashnum(t, nvalue(key));
case LUA_TSTRING:
return hashstr(t, tsvalue(key));
case LUA_TBOOLEAN:
return hashboolean(t, bvalue(key));
case LUA_TUDATAVAL:
return hashpointer(t, pvalue(key));
default: /* other types are hashed as (struct *) */
return hashpointer(t, tsvalue(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 TObject *key) {
if (ttype(key) == LUA_TNUMBER) {
int k;
lua_number2int(k, (nvalue(key)));
if (cast(lua_Number, k) == nvalue(key) && k >= 1 && !toobig(k))
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, const TObject *key) {
int i;
if (ttype(key) == LUA_TNIL) 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 {
const TObject *v = luaH_get(t, key);
if (v == &luaO_nilobject)
luaG_runerror(L, "invalid key for `next'");
i = cast(int, (cast(const lu_byte *, v) -
cast(const lu_byte *, val(node(t, 0)))) / sizeof(Node));
return i + t->sizearray; /* hash elements are numbered after array ones */
}
}
int luaH_next (lua_State *L, Table *t, TObject *key) {
int i = luaH_index(L, t, key); /* find original element */
for (i++; i < t->sizearray; i++) { /* try first array part */
if (ttype(&t->array[i]) != LUA_TNIL) { /* a non-nil value? */
setnvalue(key, i+1);
setobj(key+1, &t->array[i]);
return 1;
}
}
for (i -= t->sizearray; i < sizenode(t); i++) { /* then hash part */
if (ttype(val(node(t, i))) != LUA_TNIL) { /* a non-nil value? */
setobj(key, key(node(t, i)));
setobj(key+1, val(node(t, i)));
return 1;
}
}
return 0; /* no more elements */
}
/*
** {=============================================================
** Rehash
** ==============================================================
*/
static void computesizes (int nums[], int ntotal, int *narray, int *nhash) {
int i;
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 */
for (i = 1; i <= MAXBITS && *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;
}
}
}
lua_assert(na <= *narray && *narray <= ntotal);
*nhash = ntotal - na;
*narray = (n == -1) ? 0 : twoto(n);
lua_assert(na <= *narray && na >= *narray/2);
}
static void numuse (const Table *t, int *narray, int *nhash) {
int nums[MAXBITS+1];
int i;
int totaluse = 0;
for (i=0; i<=MAXBITS; i++) nums[i] = 0; /* init `nums' */
/* count elements in array part */
i = luaO_log2(t->sizearray) + 1; /* number of `slices' */
while (i--) { /* for each slice [2^(i-1) to 2^i) */
int to = twoto(i);
int from = to/2;
if (to > t->sizearray) to = t->sizearray;
for (; from < to; from++)
if (ttype(&t->array[from]) != LUA_TNIL) {
nums[i]++;
totaluse++;
}
}
*narray = totaluse; /* all previous uses were in array part */
/* count elements in hash part */
i = sizenode(t);
while (i--) {
if (ttype(val(&t->node[i])) != LUA_TNIL) {
int k = arrayindex(key(&t->node[i]));
if (k >= 0) { /* is `key' an appropriate array index? */
nums[luaO_log2(k-1)+1]++; /* count as such */
(*narray)++;
}
totaluse++;
}
}
computesizes(nums, totaluse, narray, nhash);
}
static void setarrayvector (lua_State *L, Table *t, int size) {
int i;
luaM_reallocvector(L, t->array, t->sizearray, size, TObject);
for (i=t->sizearray; i<size; i++)
setnilvalue(&t->array[i]);
t->sizearray = size;
}
static void setnodevector (lua_State *L, Table *t, int lsize) {
int i;
int size = twoto(lsize);
if (lsize > MAXBITS)
luaG_runerror(L, "table overflow");
if (lsize == 0) { /* no elements to hash part? */
t->node = G(L)->dummynode; /* use common `dummynode' */
lua_assert(ttype(key(t->node)) == LUA_TNIL); /* assert invariants: */
lua_assert(ttype(val(t->node)) == LUA_TNIL);
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(key(node(t, i)));
setnilvalue(val(node(t, i)));
}
}
t->lsizenode = cast(lu_byte, lsize);
t->firstfree = node(t, size-1); /* first free position to be used */
}
static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
int i;
int oldasize = t->sizearray;
int oldhsize = t->lsizenode;
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);
temp[0] = t->node[0]; /* copy it to `temp' */
nold = temp;
setnilvalue(key(G(L)->dummynode)); /* restate invariant */
setnilvalue(val(G(L)->dummynode));
lua_assert(G(L)->dummynode->next == NULL);
}
if (nasize > oldasize) /* array part must grow? */
setarrayvector(L, t, nasize);
/* create new hash part with appropriate size */
setnodevector(L, t, nhsize);
/* 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++) {
if (ttype(&t->array[i]) != LUA_TNIL)
setobj(luaH_setnum(L, t, i+1), &t->array[i]);
}
/* shrink array */
luaM_reallocvector(L, t->array, oldasize, nasize, TObject);
}
/* re-insert elements in hash part */
for (i = twoto(oldhsize) - 1; i >= 0; i--) {
Node *old = nold+i;
if (ttype(val(old)) != LUA_TNIL)
setobj(luaH_set(L, t, key(old)), val(old));
}
if (oldhsize)
luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
}
static void rehash (lua_State *L, Table *t) {
int nasize, nhsize;
numuse(t, &nasize, &nhsize); /* compute new sizes for array and hash parts */
resize(L, t, nasize, luaO_log2(nhsize)+1);
}
/*
** }=============================================================
*/
Table *luaH_new (lua_State *L, int narray, int lnhash) {
Table *t = luaM_new(L, Table);
t->metatable = hvalue(defaultmeta(L));
t->next = G(L)->roottable;
G(L)->roottable = t;
t->mark = t;
t->flags = cast(unsigned short, ~0);
/* temporary values (kept only if some malloc fails) */
t->array = NULL;
t->sizearray = 0;
t->lsizenode = 0;
t->node = NULL;
setarrayvector(L, t, narray);
setnodevector(L, t, lnhash);
return t;
}
void luaH_free (lua_State *L, Table *t) {
if (t->lsizenode)
luaM_freearray(L, t->node, sizenode(t), Node);
luaM_freearray(L, t->array, t->sizearray, TObject);
luaM_freelem(L, t);
}
#if 0
/*
** try to remove an element from a hash table; cannot move any element
** (because gc can call `remove' during a table traversal)
*/
void luaH_remove (Table *t, Node *e) {
Node *mp = luaH_mainposition(t, key(e));
if (e != mp) { /* element not in its main position? */
while (mp->next != e) mp = mp->next; /* find previous */
mp->next = e->next; /* remove `e' from its list */
}
else {
if (e->next != NULL) ??
}
lua_assert(ttype(val(node)) == LUA_TNIL);
setnilvalue(key(e)); /* clear node `e' */
e->next = NULL;
}
#endif
/*
** 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 TObject *newkey (lua_State *L, Table *t, const TObject *key) {
TObject *val;
Node *mp = luaH_mainposition(t, key);
if (ttype(val(mp)) != LUA_TNIL) { /* main position is not free? */
Node *othern = luaH_mainposition(t, key(mp)); /* `mp' of colliding node */
Node *n = t->firstfree; /* get a free place */
if (othern != mp) { /* is colliding node out of its main position? */
/* 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(val(mp));
}
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;
}
}
setobj(key(mp), key);
lua_assert(ttype(val(mp)) == LUA_TNIL);
for (;;) { /* correct `firstfree' */
if (ttype(key(t->firstfree)) == LUA_TNIL)
return val(mp); /* OK; table still has a free place */
else if (t->firstfree == t->node) break; /* cannot decrement from here */
else (t->firstfree)--;
}
/* no more free places; must create one */
setbvalue(val(mp), 0); /* avoid new key being removed */
rehash(L, t); /* grow table */
val = cast(TObject *, luaH_get(t, key)); /* get new position */
lua_assert(ttype(val) == LUA_TBOOLEAN);
setnilvalue(val);
return val;
}
/*
** generic search function
*/
static const TObject *luaH_getany (Table *t, const TObject *key) {
if (ttype(key) == LUA_TNIL) return &luaO_nilobject;
else {
Node *n = luaH_mainposition(t, key);
do { /* check whether `key' is somewhere in the chain */
if (luaO_equalObj(key(n), key)) return val(n); /* that's it */
else n = n->next;
} while (n);
return &luaO_nilobject;
}
}
/*
** search function for integers
*/
const TObject *luaH_getnum (Table *t, int key) {
if (1 <= key && key <= t->sizearray)
return &t->array[key-1];
else {
Node *n = hashnum(t, key);
do { /* check whether `key' is somewhere in the chain */
if (ttype(key(n)) == LUA_TNUMBER && nvalue(key(n)) == (lua_Number)key)
return val(n); /* that's it */
else n = n->next;
} while (n);
return &luaO_nilobject;
}
}
/*
** search function for strings
*/
const TObject *luaH_getstr (Table *t, TString *key) {
Node *n = hashstr(t, key);
do { /* check whether `key' is somewhere in the chain */
if (ttype(key(n)) == LUA_TSTRING && tsvalue(key(n)) == key)
return val(n); /* that's it */
else n = n->next;
} while (n);
return &luaO_nilobject;
}
/*
** main search function
*/
const TObject *luaH_get (Table *t, const TObject *key) {
switch (ttype(key)) {
case LUA_TSTRING: return luaH_getstr(t, tsvalue(key));
case LUA_TNUMBER: {
int k;
lua_number2int(k, (nvalue(key)));
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);
}
}
TObject *luaH_set (lua_State *L, Table *t, const TObject *key) {
const TObject *p = luaH_get(t, key);
t->flags = 0;
if (p != &luaO_nilobject)
return cast(TObject *, p);
else {
if (ttype(key) == LUA_TNIL) luaG_runerror(L, "table index is nil");
return newkey(L, t, key);
}
}
TObject *luaH_setnum (lua_State *L, Table *t, int key) {
const TObject *p = luaH_getnum(t, key);
if (p != &luaO_nilobject)
return cast(TObject *, p);
else {
TObject k;
setnvalue(&k, key);
return newkey(L, t, &k);
}
}
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