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-rw-r--r--lib/msun/src/s_logb.c48
1 files changed, 48 insertions, 0 deletions
diff --git a/lib/msun/src/s_logb.c b/lib/msun/src/s_logb.c
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+/* @(#)s_logb.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.
+ * ====================================================
+ */
+
+#ifndef lint
+static char rcsid[] = "$Id: s_logb.c,v 1.1.1.1 1994/05/06 00:20:06 gclarkii Exp $";
+#endif
+
+/*
+ * double logb(x)
+ * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
+ * Use ilogb instead.
+ */
+
+#include "math.h"
+#include <machine/endian.h>
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+#define n0 1
+#else
+#define n0 0
+#endif
+
+#ifdef __STDC__
+ double logb(double x)
+#else
+ double logb(x)
+ double x;
+#endif
+{
+ int lx,ix;
+ ix = (*(n0+(int*)&x))&0x7fffffff; /* high |x| */
+ lx = *(1-n0+(int*)&x); /* low x */
+ if((ix|lx)==0) return -1.0/fabs(x);
+ if(ix>=0x7ff00000) return x*x;
+ if((ix>>=20)==0) /* IEEE 754 logb */
+ return -1022.0;
+ else
+ return (double) (ix-1023);
+}