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use of a common `dummynode' for all empty tables

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This commit is contained in:
Roberto Ierusalimschy
2002-04-23 12:04:39 -03:00
parent f1a1bb23fe
commit 383e8b9e77
4 changed files with 46 additions and 35 deletions
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58
ltable.c
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@@ -1,5 +1,5 @@
/*
** $Id: ltable.c,v 1.103 2002/04/05 18:54:31 roberto Exp roberto $
** $Id: ltable.c,v 1.104 2002/04/22 14:40:23 roberto Exp roberto $
** Lua tables (hash)
** See Copyright Notice in lua.h
*/
@@ -52,13 +52,13 @@
#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, p)) /* `p' in [0,1] < minimum table size */
#define hashboolean(t,p) (node(t, lmod(p, sizenode(t))))
/*
** for pointers, avoid modulus by power of 2, as they tend to have many
** 2 factors.
*/
#define hashpointer(t,p) (node(t, (IntPoint(p) % (sizenode(t)-1))))
#define hashpointer(t,p) (node(t, (IntPoint(p) % ((sizenode(t)-1)|1))))
/*
@@ -200,12 +200,6 @@ static void numuse (const Table *t, int *narray, int *nhash) {
}
/*
** (log2 of) minimum size for hash part of a table
*/
#define MINHASHSIZE 1
static void setarrayvector (lua_State *L, Table *t, int size) {
int i;
luaM_reallocvector(L, t->array, t->sizearray, size, TObject);
@@ -217,16 +211,22 @@ static void setarrayvector (lua_State *L, Table *t, int size) {
static void setnodevector (lua_State *L, Table *t, int lsize) {
int i;
int size;
if (lsize < MINHASHSIZE) lsize = MINHASHSIZE;
else if (lsize > MAXBITS)
int size = twoto(lsize);
if (lsize > MAXBITS)
luaD_runerror(L, "table overflow");
size = twoto(lsize);
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)));
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 */
@@ -235,14 +235,22 @@ static void setnodevector (lua_State *L, Table *t, int lsize) {
static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
int i;
int oldasize, oldhsize;
int oldasize = t->sizearray;
int oldhsize = t->lsizenode;
Node *nold;
oldasize = t->sizearray;
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' (in case of errors) */
nold = temp;
setnilvalue(key(G(L)->dummynode)); /* restate invariant */
setnilvalue(val(G(L)->dummynode));
}
if (nasize > oldasize) /* should grow array part? */
setarrayvector(L, t, nasize);
/* create new hash part with appropriate size */
nold = t->node; /* save old hash ... */
oldhsize = t->lsizenode; /* ... and (log of) old size */
setnodevector(L, t, nhsize);
/* re-insert elements */
if (nasize < oldasize) { /* array part must shrink? */
@@ -262,7 +270,8 @@ static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
if (ttype(val(old)) != LUA_TNIL)
luaH_set(L, t, key(old), val(old));
}
luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
if (oldhsize)
luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
}
@@ -299,8 +308,7 @@ Table *luaH_new (lua_State *L, int narray, int lnhash) {
void luaH_free (lua_State *L, Table *t) {
lua_assert(t->lsizenode > 0 || t->node == NULL);
if (t->lsizenode > 0)
if (t->lsizenode)
luaM_freearray(L, t->node, sizenode(t), Node);
luaM_freearray(L, t->array, t->sizearray, TObject);
luaM_freelem(L, t);