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table sizes don't need to be primes; power of 2 gives the same performance.

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Roberto Ierusalimschy
1999-11-26 16:59:20 -02:00
parent 790690a223
commit d015f1fc02
6 changed files with 37 additions and 40 deletions
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21
lstring.c
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@@ -1,5 +1,5 @@
/*
** $Id: lstring.c,v 1.28 1999/11/22 13:12:07 roberto Exp roberto $
** $Id: lstring.c,v 1.29 1999/11/22 18:24:50 roberto Exp roberto $
** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h
*/
@@ -52,24 +52,25 @@ static unsigned long hash_s (const char *s, long l) {
}
void luaS_grow (lua_State *L, stringtable *tb) {
int ns = luaO_redimension(L, tb->nuse); /* new size */
TaggedString **newhash = luaM_newvector(L, ns, TaggedString *);
void luaS_resize (lua_State *L, stringtable *tb, int newsize) {
TaggedString **newhash = luaM_newvector(L, newsize, TaggedString *);
int i;
for (i=0; i<ns; i++) newhash[i] = NULL;
for (i=0; i<newsize; i++) newhash[i] = NULL;
/* rehash */
for (i=0; i<tb->size; i++) {
TaggedString *p = tb->hash[i];
while (p) { /* for each node in the list */
TaggedString *next = p->nexthash; /* save next */
int h = p->hash%ns; /* new position */
int h = p->hash&(newsize-1); /* new position */
LUA_ASSERT(L, p->hash%newsize == (p->hash&(newsize-1)),
"a&(x-1) == a%x, for x power of 2");
p->nexthash = newhash[h]; /* chain it in new position */
newhash[h] = p;
p = next;
}
}
luaM_free(L, tb->hash);
tb->size = ns;
tb->size = newsize;
tb->hash = newhash;
}
@@ -113,14 +114,14 @@ static void newentry (lua_State *L, stringtable *tb, TaggedString *ts, int h) {
tb->hash[h] = ts;
tb->nuse++;
if (tb->nuse > tb->size) /* too crowded? */
luaS_grow(L, tb);
luaS_resize(L, tb, tb->size*2);
}
TaggedString *luaS_newlstr (lua_State *L, const char *str, long l) {
unsigned long h = hash_s(str, l);
stringtable *tb = &L->string_root[h%NUM_HASHSTR];
int h1 = h%tb->size;
int h1 = h&(tb->size-1);
TaggedString *ts;
for (ts = tb->hash[h1]; ts; ts = ts->nexthash) {
if (ts->u.s.len == l && (memcmp(str, ts->str, l) == 0))
@@ -136,7 +137,7 @@ TaggedString *luaS_newlstr (lua_State *L, const char *str, long l) {
TaggedString *luaS_createudata (lua_State *L, void *udata, int tag) {
unsigned long h = IntPoint(L, udata);
stringtable *tb = &L->string_root[(h%NUM_HASHUDATA)+NUM_HASHSTR];
int h1 = h%tb->size;
int h1 = h&(tb->size-1);
TaggedString *ts;
for (ts = tb->hash[h1]; ts; ts = ts->nexthash) {
if (udata == ts->u.d.value && (tag == ts->u.d.tag || tag == LUA_ANYTAG))