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keep it simple

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This commit is contained in:
Roberto Ierusalimschy 1999-12-07 10:05:34 -02:00
parent 9c142740c1
commit b3fe203c36
1 changed files with 14 additions and 44 deletions
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58
ltable.c
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@ -1,5 +1,5 @@
/*
** $Id: ltable.c,v 1.30 1999/11/22 13:12:07 roberto Exp roberto $
** $Id: ltable.c,v 1.31 1999/11/26 18:59:20 roberto Exp roberto $
** Lua tables (hash)
** See Copyright Notice in lua.h
*/
@ -40,7 +40,7 @@
** returns the `main' position of an element in a table (that is, the index
** of its hash value)
*/
Node *luaH_mainposition (lua_State *L, const Hash *t, const TObject *key) {
Node *luaH_mainposition (const Hash *t, const TObject *key) {
unsigned long h;
switch (ttype(key)) {
case LUA_T_NUMBER:
@ -62,8 +62,7 @@ Node *luaH_mainposition (lua_State *L, const Hash *t, const TObject *key) {
h = IntPoint(L, clvalue(key));
break;
default:
lua_error(L, "unexpected type to index table");
h = 0; /* to avoid warnings */
return NULL; /* invalid key */
}
LUA_ASSERT(L, h%(unsigned int)t->size == (h&((unsigned int)t->size-1)),
"a&(x-1) == a%x, for x power of 2");
@ -72,13 +71,15 @@ Node *luaH_mainposition (lua_State *L, const Hash *t, const TObject *key) {
const TObject *luaH_get (lua_State *L, const Hash *t, const TObject *key) {
Node *n = luaH_mainposition(L, t, key);
do {
Node *n = luaH_mainposition(t, key);
if (!n)
lua_error(L, "unexpected type to index table");
else do {
if (luaO_equalObj(key, &n->key))
return &n->val;
n = n->next;
} while (n);
return &luaO_nilobject;
return &luaO_nilobject; /* key not found */
}
@ -140,49 +141,16 @@ static int newsize (const Hash *t) {
}
/*
** the rehash is done in two stages: first, we insert only the elements whose
** main position is free, to avoid needless collisions. In the second stage,
** we insert the other elements.
*/
static void rehash (lua_State *L, Hash *t) {
int oldsize = t->size;
Node *nold = t->node;
int i;
L->nblocks -= gcsize(L, oldsize);
setnodevector(L, t, newsize(t)); /* create new array of nodes */
/* first loop; set only elements that can go in their main positions */
for (i=0; i<oldsize; i++) {
Node *old = nold+i;
if (ttype(&old->val) == LUA_T_NIL)
old->next = NULL; /* `remove' it for next loop */
else {
Node *mp = luaH_mainposition(L, t, &old->key); /* new main position */
if (ttype(&mp->key) == LUA_T_NIL) { /* is it empty? */
mp->key = old->key; /* put element there */
mp->val = old->val;
old->next = NULL; /* `remove' it for next loop */
}
else /* it will be copied in next loop */
old->next = mp; /* to be used in next loop */
}
}
/* update `firstfree' */
while (ttype(&t->firstfree->key) != LUA_T_NIL) t->firstfree--;
/* second loop; update elements with colision */
for (i=0; i<oldsize; i++) {
Node *old = nold+i;
if (old->next) { /* wasn't already `removed'? */
Node *mp = old->next; /* main position */
Node *e = t->firstfree; /* actual position */
e->key = old->key; /* put element in the free position */
e->val = old->val;
e->next = mp->next; /* chain actual position in main position's list */
mp->next = e;
do { /* update `firstfree' */
t->firstfree--;
} while (ttype(&t->firstfree->key) != LUA_T_NIL);
}
if (ttype(&old->val) != LUA_T_NIL)
luaH_set(L, t, &old->key, &old->val);
}
luaM_free(L, nold); /* free old array */
}
@ -202,8 +170,10 @@ static void rehash (lua_State *L, Hash *t) {
** (this happens when we use `luaH_move'), there is no problem.
*/
void luaH_set (lua_State *L, Hash *t, const TObject *key, const TObject *val) {
Node *mp = luaH_mainposition(L, t, key);
Node *mp = luaH_mainposition(t, key);
Node *n = mp;
if (!mp)
lua_error(L, "unexpected type to index table");
do { /* check whether `key' is somewhere in the chain */
if (luaO_equalObj(key, &n->key)) {
n->val = *val; /* update value */
@ -217,7 +187,7 @@ void luaH_set (lua_State *L, Hash *t, const TObject *key, const TObject *val) {
n = t->firstfree; /* get a free place */
/* is colliding node out of its main position? (can only happens if
its position if after "firstfree") */
if (mp > n && (othern=luaH_mainposition(L, t, &mp->key)) != mp) {
if (mp > n && (othern=luaH_mainposition(t, &mp->key)) != mp) {
/* 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' */