From: Martin Mares <mj@ucw.cz>
Date: Wed, 3 Dec 1997 08:11:25 +0000 (+0000)
Subject: ffs _cannot_ be used as a substitute for log2, because it scans in the
X-Git-Tag: holmes-import~1685
X-Git-Url: http://mj.ucw.cz/gitweb/?a=commitdiff_plain;h=a048770f41b23fdba09e2a70a9711f48152e6778;p=libucw.git

ffs _cannot_ be used as a substitute for log2, because it scans in the
opposite direction :-(

Fixed our own log2 (it hadn't any chance to work before).
---

diff --git a/lib/config.h b/lib/config.h
index 62ef1af3..e9b84fc3 100644
--- a/lib/config.h
+++ b/lib/config.h
@@ -39,7 +39,3 @@ typedef unsigned int uns;		/* at least 32 bits */
 #define NONRET
 
 #endif
-
-#ifdef linux
-#define HAVE_FFS
-#endif
diff --git a/lib/lib.h b/lib/lib.h
index 24d7e352..59cb6621 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -74,11 +74,7 @@ int match_ct_filter(struct ct_filter *, byte *);
 
 /* Binary log */
 
-#ifdef HAVE_FFS
-#define log2(x) (ffs(x) - 1)
-#else
 int log2(ulg);
-#endif
 
 /* obj.c */
 
diff --git a/lib/log2.c b/lib/log2.c
index dc0a9297..3cd98335 100644
--- a/lib/log2.c
+++ b/lib/log2.c
@@ -8,8 +8,10 @@
 
 #include "lib.h"
 
+#undef log2
+
 int
-ffs(ulg x)
+log2(ulg x)
 {
   ulg l;
 
@@ -17,10 +19,10 @@ ffs(ulg x)
 	return 0;
 
   l = 0;
-  if (x & 0xffff0000) l += 16;
-  if (x & 0xff00ff00) l += 8;
-  if (x & 0xf0f0f0f0) l += 4;
-  if (x & 0xcccccccc) l += 2;
+  if (x & 0xffff0000) { l += 16; x &= 0xffff0000; }
+  if (x & 0xff00ff00) { l += 8;  x &= 0xff00ff00; }
+  if (x & 0xf0f0f0f0) { l += 4;  x &= 0xf0f0f0f0; }
+  if (x & 0xcccccccc) { l += 2;  x &= 0xcccccccc; }
   if (x & 0xaaaaaaaa) l++;
   return l;
 }