import newlib-2000-02-17 snapshot

1 files changed, 92 insertions, 0 deletions

diff --git a/newlib/libm/common/s_ilogb.c b/newlib/libm/common/s_ilogb.c
new file mode 100644
index 000000000..4e3e69f12
--- /dev/null
+++ b/newlib/libm/common/s_ilogb.c
@@ -0,0 +1,92 @@
+
+/* @(#)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.
+ * ====================================================
+ */
+
+/*
+FUNCTION
+       <<ilogb>>, <<ilogbf>>---get exponent of floating point number
+INDEX
+	ilogb
+INDEX
+	ilogbf
+
+ANSI_SYNOPSIS
+	#include <math.h>
+        int ilogb(double <[val]>);
+        int ilogbf(float <[val]>);
+
+TRAD_SYNOPSIS
+	#include <math.h>
+        int ilogb(<[val]>)
+        double <[val]>;
+
+        int ilogbf(<[val]>)
+        float <[val]>;
+
+
+DESCRIPTION
+
+	All non zero, normal numbers can be described as <[m]> *
+	2**<[p]>.  <<ilogb>> and <<ilogbf>> examine the argument
+	<[val]>, and return <[p]>.  The functions <<frexp>> and
+	<<frexpf>> are similar to <<ilogb>> and <<ilogbf>>, but also
+	return <[m]>.
+
+RETURNS
+
+<<ilogb>> and <<ilogbf>> return the power of two used to form the
+floating point argument.  If <[val]> is <<0>>, they return <<-
+INT_MAX>> (<<INT_MAX>> is defined in limits.h).  If <[val]> is
+infinite, or NaN, they return <<INT_MAX>>.
+
+PORTABILITY
+	Neither <<ilogb>> nor <<ilogbf>> is required by ANSI C or by
+	the System V Interface Definition (Issue 2).  */
+
+/* ilogb(double x)
+ * return the binary exponent of non-zero x
+ * ilogb(0) = 0x80000001
+ * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
+ */
+
+#include "fdlibm.h"
+#include <limits.h>
+
+#ifndef _DOUBLE_IS_32BITS
+
+#ifdef __STDC__
+	int ilogb(double x)
+#else
+	int ilogb(x)
+	double x;
+#endif
+{
+	__int32_t hx,lx,ix;
+
+	EXTRACT_WORDS(hx,lx,x);
+	hx &= 0x7fffffff;
+	if(hx<0x00100000) {
+	    if((hx|lx)==0) 
+		return - INT_MAX;	/* 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 INT_MAX;
+}
+
+#endif /* _DOUBLE_IS_32BITS */