From 7ce331c01ce6eb7b3f5c715a38a24359da9c6ee2 Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Thu, 22 Nov 2001 14:04:29 +0000
Subject: Totally rework the math library, this time based on the MacOs X math
 library (which is itself based on the math lib from FreeBSD).  -Erik

---
 libm/s_ilogb.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 libm/s_ilogb.c

(limited to 'libm/s_ilogb.c')

diff --git a/libm/s_ilogb.c b/libm/s_ilogb.c
new file mode 100644
index 000000000..ee81570aa
--- /dev/null
+++ b/libm/s_ilogb.c
@@ -0,0 +1,51 @@
+/* @(#)s_ilogb.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: s_ilogb.c,v 1.9 1995/05/10 20:47:28 jtc Exp $";
+#endif
+
+/* ilogb(double x)
+ * return the binary exponent of non-zero x
+ * ilogb(0) = 0x80000001
+ * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+	int ilogb(double x)
+#else
+	int ilogb(x)
+	double x;
+#endif
+{
+	int32_t hx,lx,ix;
+
+	GET_HIGH_WORD(hx,x);
+	hx &= 0x7fffffff;
+	if(hx<0x00100000) {
+	    GET_LOW_WORD(lx,x);
+	    if((hx|lx)==0) 
+		return 0x80000001;	/* ilogb(0) = 0x80000001 */
+	    else			/* subnormal x */
+		if(hx==0) {
+		    for (ix = -1043; lx>0; lx<<=1) ix -=1;
+		} else {
+		    for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
+		}
+	    return ix;
+	}
+	else if (hx<0x7ff00000) return (hx>>20)-1023;
+	else return 0x7fffffff;
+}
-- 
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