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uses the same double hashing that is used for tables

This commit is contained in:
Roberto Ierusalimschy 1999-01-25 15:38:04 -02:00
parent 1b45e967b4
commit 13ad46b67d
1 changed files with 17 additions and 12 deletions
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29
lstring.c
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@ -1,5 +1,5 @@
/* /*
** $Id: lstring.c,v 1.15 1998/08/10 21:36:32 roberto Exp roberto $ ** $Id: lstring.c,v 1.16 1999/01/04 13:37:29 roberto Exp roberto $
** String table (keeps all strings handled by Lua) ** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -51,8 +51,7 @@ static int newsize (stringtable *tb) {
for (i=0; i<size; i++) for (i=0; i<size; i++)
if (tb->hash[i] != NULL && tb->hash[i] != &EMPTY) if (tb->hash[i] != NULL && tb->hash[i] != &EMPTY)
realuse++; realuse++;
return luaO_redimension((realuse+1)*2+6); /* +1 is the new element, +6 to return luaO_redimension((realuse+1)*2); /* +1 is the new element */
ensure minimum size of 8 (for double hashing) */
} }
@ -68,9 +67,10 @@ static void grow (stringtable *tb) {
if (tb->hash[i] != NULL && tb->hash[i] != &EMPTY) { if (tb->hash[i] != NULL && tb->hash[i] != &EMPTY) {
unsigned long h = tb->hash[i]->hash; unsigned long h = tb->hash[i]->hash;
int h1 = h%ns; int h1 = h%ns;
int h2 = 8-(h&7); while (newhash[h1]) {
while (newhash[h1]) h1 += (h&(ns-2)) + 1; /* double hashing */
h1 = (h1+h2)%ns; if (h1 >= ns) h1 -= ns;
}
newhash[h1] = tb->hash[i]; newhash[h1] = tb->hash[i];
tb->nuse++; tb->nuse++;
} }
@ -113,18 +113,20 @@ static TaggedString *insert_s (char *str, long l, stringtable *tb) {
int size = tb->size; int size = tb->size;
int j = -1; int j = -1;
int h1; int h1;
int h2 = 8-(h&7); /* for double hashing */
if ((long)tb->nuse*3 >= (long)size*2) { if ((long)tb->nuse*3 >= (long)size*2) {
grow(tb); grow(tb);
size = tb->size; size = tb->size;
} }
for (h1 = h%size; (ts = tb->hash[h1]) != NULL; h1 = (h1+h2)%size) { h1 = h%size;
while ((ts = tb->hash[h1]) != NULL) {
if (ts == &EMPTY) if (ts == &EMPTY)
j = h1; j = h1;
else if (ts->constindex >= 0 && else if (ts->constindex >= 0 &&
ts->u.s.len == l && ts->u.s.len == l &&
(memcmp(str, ts->str, l) == 0)) (memcmp(str, ts->str, l) == 0))
return ts; return ts;
h1 += (h&(size-2)) + 1; /* double hashing */
if (h1 >= size) h1 -= size;
} }
/* not found */ /* not found */
if (j != -1) /* is there an EMPTY space? */ if (j != -1) /* is there an EMPTY space? */
@ -141,18 +143,20 @@ static TaggedString *insert_u (void *buff, int tag, stringtable *tb) {
int size = tb->size; int size = tb->size;
int j = -1; int j = -1;
int h1; int h1;
int h2 = 8-(h&7); /* for double hashing */
if ((long)tb->nuse*3 >= (long)size*2) { if ((long)tb->nuse*3 >= (long)size*2) {
grow(tb); grow(tb);
size = tb->size; size = tb->size;
} }
for (h1 = h%size; (ts = tb->hash[h1]) != NULL; h1 = (h1+h2)%size) { h1 = h%size;
while ((ts = tb->hash[h1]) != NULL) {
if (ts == &EMPTY) if (ts == &EMPTY)
j = h1; j = h1;
else if (ts->constindex < 0 && /* is a udata? */ else if (ts->constindex < 0 && /* is a udata? */
(tag == ts->u.d.tag || tag == LUA_ANYTAG) && (tag == ts->u.d.tag || tag == LUA_ANYTAG) &&
buff == ts->u.d.v) buff == ts->u.d.v)
return ts; return ts;
h1 += (h&(size-2)) + 1; /* double hashing */
if (h1 >= size) h1 -= size;
} }
/* not found */ /* not found */
if (j != -1) /* is there an EMPTY space? */ if (j != -1) /* is there an EMPTY space? */
@ -163,6 +167,7 @@ static TaggedString *insert_u (void *buff, int tag, stringtable *tb) {
return ts; return ts;
} }
TaggedString *luaS_createudata (void *udata, int tag) { TaggedString *luaS_createudata (void *udata, int tag) {
return insert_u(udata, tag, &L->string_root[(unsigned)udata%NUM_HASHS]); return insert_u(udata, tag, &L->string_root[(unsigned)udata%NUM_HASHS]);
} }