20060303a

1 files changed, 42 insertions, 0 deletions

diff --git a/libmath/fdlibm/s_ilogb.c b/libmath/fdlibm/s_ilogb.c
new file mode 100644
index 00000000..97e7b09a
--- /dev/null
+++ b/libmath/fdlibm/s_ilogb.c
@@ -0,0 +1,42 @@
+/* derived from /netlib/fdlibm */
+
+/* @(#)s_ilogb.c 1.3 95/01/18 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+/* 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"
+
+	int ilogb(double x)
+{
+	int hx,lx,ix;
+
+	hx  = (__HI(x))&0x7fffffff;	/* high word of x */
+	if(hx<0x00100000) {
+	    lx = __LO(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;
+}