From a00247f57a1b263d6eace43f36547766566c1de1 Mon Sep 17 00:00:00 2001
From: akr <akr@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Wed, 12 May 2010 13:23:20 +0000
Subject: [PATCH] * 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              | 10 +++++++++
 configure.in           |  2 +-
 include/ruby/missing.h |  4 ++++
 missing/ffs.c          | 47 ++++++++++++++++++++++++++++++++++++++++++
 time.c                 |  2 +-
 5 files changed, 63 insertions(+), 2 deletions(-)
 create mode 100644 missing/ffs.c

diff --git a/ChangeLog b/ChangeLog
index bdd3a79e46..d927f3688f 100644
--- a/ChangeLog
+++ b/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.
diff --git a/configure.in b/configure.in
index 98633bb526..9717f4731f 100644
--- a/configure.in
+++ b/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>
diff --git a/include/ruby/missing.h b/include/ruby/missing.h
index e4ac07018f..18dabaa5b3 100644
--- a/include/ruby/missing.h
+++ b/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 */
diff --git a/missing/ffs.c b/missing/ffs.c
new file mode 100644
index 0000000000..9bbb707959
--- /dev/null
+++ b/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;
+}
diff --git a/time.c b/time.c
index 1b461bbb34..9355c87ec9 100644
--- a/time.c
+++ b/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;
 }