* time.c (rb_big_abs_find_minbit): use ffs().

* configure.in: check ffs().

* missing/ffs.c: new file.

* include/ruby/missing.h (ffs): declared.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27759 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,13 @@
+Wed May 12 22:22:05 2010  Tanaka Akira  <akr@fsij.org>
+
+	* time.c (rb_big_abs_find_minbit): use ffs().
+
+	* configure.in: check ffs().
+
+	* missing/ffs.c: new file.
+
+	* include/ruby/missing.h (ffs): declared.
+
 Wed May 12 16:43:12 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* numeric.c (flo_to_s): fixed broken output including nuls.

configure.in

@@ -1117,7 +1117,7 @@ AS_CASE([$rb_cv_broken_glibc_ia64_erfc],[yes],[ac_cv_func_erf=no])
 AC_REPLACE_FUNCS(dup2 memmove strerror\
 		 strchr strstr crypt flock\
 		 isnan finite isinf hypot acosh erf tgamma lgamma_r cbrt \
-                 strlcpy strlcat)
+                 strlcpy strlcat ffs)
 AC_CACHE_CHECK(for signbit, rb_cv_have_signbit,
   [AC_TRY_LINK([
 #include <math.h>

include/ruby/missing.h

@@ -159,6 +159,10 @@ RUBY_EXTERN size_t strlcpy(char *, const char*, size_t);
 RUBY_EXTERN size_t strlcat(char *, const char*, size_t);
 #endif
 
+#ifndef HAVE_FFS
+RUBY_EXTERN int ffs(int);
+#endif
+
 #if defined(__cplusplus)
 #if 0
 { /* satisfy cc-mode */

missing/ffs.c

@@ -0,0 +1,47 @@
+/* ffs.c - find first set bit */
+/* ffs() is defined by POSIX. */
+
+#include "ruby.h"
+
+int ffs(int arg)
+{
+    unsigned int x = (unsigned int)arg;
+    int r = 0;
+
+    if (x == 0)
+        return 0;
+
+#if 32 < SIZEOF_INT * CHAR_BIT
+    if ((x & 0xffffffff) == 0) {
+        x >>= 32;
+        r += 32;
+    }
+#endif
+
+    if ((x & 0xffff) == 0) {
+        x >>= 16;
+        r += 16;
+    }
+
+    if ((x & 0xff) == 0) {
+        x >>= 8;
+        r += 8;
+    }
+
+    if ((x & 0xf) == 0) {
+        x >>= 4;
+        r += 4;
+    }
+
+    if ((x & 0x3) == 0) {
+        x >>= 2;
+        r += 2;
+    }
+
+    if ((x & 0x1) == 0) {
+        x >>= 1;
+        r += 1;
+    }
+
+    return r;
+}

time.c

@@ -345,7 +345,7 @@ rb_big_abs_find_minbit(VALUE big)
         return Qnil;
     res = mul(LONG2NUM(i), INT2FIX(SIZEOF_BDIGITS * CHAR_BIT));
     d = ds[i];
-    res = add(res, LONG2FIX(bdigit_find_maxbit(d & (~d+1))));
+    res = add(res, LONG2FIX(ffs(d)-1));
     return res;
 }