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Optimization: cache the hashed value to avoid negative comparisons.

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With 2^32 possible hash values, this means that collisions no longer
incur supplementary string compares, which was most of the reason for
STREQ in the first place...
This commit is contained in:
espie 1999-11-20 17:48:59 +00:00
parent 7868fed72c
commit 70a009b1b3
4 changed files with 29 additions and 24 deletions
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4
usr.bin/m4/extern.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: extern.h,v 1.11 1999/11/17 15:34:13 espie Exp $ */
/* $OpenBSD: extern.h,v 1.12 1999/11/20 17:48:59 espie Exp $ */
/* $NetBSD: extern.h,v 1.3 1996/01/13 23:25:24 pk Exp $ */
/*-
@ -53,7 +53,7 @@ extern FILE *fopen_trypath __P((const char *filename));
/* look.c */
extern ndptr addent __P((const char *));
extern int hash __P((const char *));
extern unsigned hash __P((const char *));
extern ndptr lookup __P((const char *));
extern void remhash __P((const char *, int));

29
usr.bin/m4/look.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: look.c,v 1.5 1999/11/17 15:34:13 espie Exp $ */
/* $OpenBSD: look.c,v 1.6 1999/11/20 17:48:59 espie Exp $ */
/*
* Copyright (c) 1989, 1993
@ -57,14 +57,14 @@ static char sccsid[] = "@(#)look.c 8.1 (Berkeley) 6/6/93";
static void freent __P((ndptr));
int
unsigned
hash(name)
const char *name;
{
unsigned long h = 0;
unsigned h = 0;
while (*name)
h = (h << 5) + h + *name++;
return (h % HASHSIZE);
return (h);
}
/*
@ -75,9 +75,11 @@ lookup(name)
const char *name;
{
ndptr p;
unsigned h;
for (p = hashtab[hash(name)]; p != nil; p = p->nxtptr)
if (STREQ(name, p->name))
h = hash(name);
for (p = hashtab[h % HASHSIZE]; p != nil; p = p->nxtptr)
if (h == p->hv && STREQ(name, p->name))
break;
return (p);
}
@ -90,14 +92,15 @@ ndptr
addent(name)
const char *name;
{
int h;
unsigned h;
ndptr p;
h = hash(name);
p = (ndptr) xalloc(sizeof(struct ndblock));
p->nxtptr = hashtab[h];
hashtab[h] = p;
p->nxtptr = hashtab[h % HASHSIZE];
hashtab[h % HASHSIZE] = p;
p->name = xstrdup(name);
p->hv = h;
return p;
}
@ -125,14 +128,14 @@ remhash(name, all)
ndptr xp, tp, mp;
h = hash(name);
mp = hashtab[h];
mp = hashtab[h % HASHSIZE];
tp = nil;
while (mp != nil) {
if (STREQ(mp->name, name)) {
if (mp->hv == h && STREQ(mp->name, name)) {
mp = mp->nxtptr;
if (tp == nil) {
freent(hashtab[h]);
hashtab[h] = mp;
freent(hashtab[h % HASHSIZE]);
hashtab[h % HASHSIZE] = mp;
}
else {
xp = tp->nxtptr;

17
usr.bin/m4/main.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: main.c,v 1.18 1999/11/17 15:34:13 espie Exp $ */
/* $OpenBSD: main.c,v 1.19 1999/11/20 17:48:59 espie Exp $ */
/* $NetBSD: main.c,v 1.12 1997/02/08 23:54:49 cgd Exp $ */
/*-
@ -47,7 +47,7 @@ static char copyright[] =
#if 0
static char sccsid[] = "@(#)main.c 8.1 (Berkeley) 6/6/93";
#else
static char rcsid[] = "$OpenBSD: main.c,v 1.18 1999/11/17 15:34:13 espie Exp $";
static char rcsid[] = "$OpenBSD: main.c,v 1.19 1999/11/20 17:48:59 espie Exp $";
#endif
#endif /* not lint */
@ -440,7 +440,7 @@ inspect(tp)
char *name = tp;
char *etp = tp+MAXTOK;
ndptr p;
unsigned long h = 0;
unsigned h = 0;
while ((isalnum(c = gpbc()) || c == '_') && tp < etp)
h = (h << 5) + h + (*tp++ = c);
@ -450,8 +450,8 @@ inspect(tp)
*tp = EOS;
for (p = hashtab[h%HASHSIZE]; p != nil; p = p->nxtptr)
if (STREQ(name, p->name))
for (p = hashtab[h % HASHSIZE]; p != nil; p = p->nxtptr)
if (h == p->hv && STREQ(name, p->name))
break;
return p;
}
@ -467,16 +467,17 @@ static void
initkwds()
{
size_t i;
int h;
unsigned h;
ndptr p;
for (i = 0; i < MAXKEYS; i++) {
h = hash(keywrds[i].knam);
p = (ndptr) xalloc(sizeof(struct ndblock));
p->nxtptr = hashtab[h];
hashtab[h] = p;
p->nxtptr = hashtab[h % HASHSIZE];
hashtab[h % HASHSIZE] = p;
p->name = keywrds[i].knam;
p->defn = null;
p->hv = h;
p->type = keywrds[i].ktyp | STATIC;
}
}

3
usr.bin/m4/mdef.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: mdef.h,v 1.7 1999/09/14 08:35:17 espie Exp $ */
/* $OpenBSD: mdef.h,v 1.8 1999/11/20 17:49:00 espie Exp $ */
/* $NetBSD: mdef.h,v 1.7 1996/01/13 23:25:27 pk Exp $ */
/*
@ -124,6 +124,7 @@ struct ndblock { /* hastable structure */
char *name; /* entry name.. */
char *defn; /* definition.. */
int type; /* type of the entry.. */
unsigned hv;
ndptr nxtptr; /* link to next entry.. */
};