[src/trunk]: src/usr.bin/make make(1): clean up hash function for HashTable

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/ec8cd9389600
branches:  trunk
changeset: 957915:ec8cd9389600
user:      rillig <rillig%NetBSD.org@localhost>
date:      Tue Dec 15 15:20:05 2020 +0000

description:
make(1): clean up hash function for HashTable

Expressing a multiplication as a bit shifts and subtraction is the job
of the compiler.  For humans, a multiplication is easier to read.

diffstat:

 usr.bin/make/hash.c |  15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)

diffs (36 lines):

diff -r 1b4d87686247 -r ec8cd9389600 usr.bin/make/hash.c
--- a/usr.bin/make/hash.c       Tue Dec 15 08:35:52 2020 +0000
+++ b/usr.bin/make/hash.c       Tue Dec 15 15:20:05 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: hash.c,v 1.58 2020/11/23 17:59:21 rillig Exp $ */
+/*     $NetBSD: hash.c,v 1.59 2020/12/15 15:20:05 rillig Exp $ */
 
 /*
  * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
@@ -74,7 +74,7 @@
 #include "make.h"
 
 /*     "@(#)hash.c     8.1 (Berkeley) 6/6/93"  */
-MAKE_RCSID("$NetBSD: hash.c,v 1.58 2020/11/23 17:59:21 rillig Exp $");
+MAKE_RCSID("$NetBSD: hash.c,v 1.59 2020/12/15 15:20:05 rillig Exp $");
 
 /*
  * The ratio of # entries to # buckets at which we rebuild the table to
@@ -86,10 +86,13 @@
 static unsigned int
 hash(const char *key, size_t *out_keylen)
 {
-       unsigned int h = 0;
-       const char *p = key;
-       while (*p != '\0')
-               h = (h << 5) - h + (unsigned char)*p++;
+       unsigned int h;
+       const char *p;
+
+       h = 0;
+       for (p = key; *p != '\0'; p++)
+               h = 31 * h + (unsigned char)*p;
+
        if (out_keylen != NULL)
                *out_keylen = (size_t)(p - key);
        return h;