support/fdlibm/s_frexp.c
changeset 2353 fa7400d022a0
child 2380 9195eccdcbd9
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/support/fdlibm/s_frexp.c	Sat Feb 16 19:08:45 2013 +0100
@@ -0,0 +1,56 @@
+
+/* @(#)s_frexp.c 1.4 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.
+ * ====================================================
+ */
+
+/*
+ * for non-zero x 
+ *	x = frexp(arg,&exp);
+ * return a double fp quantity x such that 0.5 <= |x| <1.0
+ * and the corresponding binary exponent "exp". That is
+ *	arg = x*2^exp.
+ * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg 
+ * with *exp=0. 
+ */
+
+#include "fdlibm.h"
+
+#ifdef __STDC__
+static const double
+#else
+static double
+#endif
+two54 =  1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
+
+#ifdef __STDC__
+	double frexp(double x, int *eptr)
+#else
+	double frexp(x, eptr)
+	double x; int *eptr;
+#endif
+{
+	int  hx, ix, lx;
+	hx = __HI(x);
+	ix = 0x7fffffff&hx;
+	lx = __LO(x);
+	*eptr = 0;
+	if(ix>=0x7ff00000||((ix|lx)==0)) return x;	/* 0,inf,nan */
+	if (ix<0x00100000) {		/* subnormal */
+	    x *= two54;
+	    hx = __HI(x);
+	    ix = hx&0x7fffffff;
+	    *eptr = -54;
+	}
+	*eptr += (ix>>20)-1022;
+	hx = (hx&0x800fffff)|0x3fe00000;
+	__HI(x) = hx;
+	return x;
+}