set default newlib dir's structure

git-svn-id: svn://kolibrios.org@4874 a494cfbc-eb01-0410-851d-a64ba20cac60

contrib/sdk/sources/newlib/libc/math/s_logb.c

@@ -0,0 +1,110 @@
+/* 2009 for Newlib:  Sun's s_ilogb.c converted to be s_logb.c.  */
+/* @(#)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
+       <<logb>>, <<logbf>>--get exponent of floating-point number
+INDEX
+	logb
+INDEX
+	logbf
+
+ANSI_SYNOPSIS
+	#include <math.h>
+        double logb(double <[x]>);
+        float logbf(float <[x]>);
+
+DESCRIPTION
+The <<logb>> functions extract the exponent of <[x]>, as a signed integer value
+in floating-point format.  If <[x]> is subnormal it is treated as though it were
+normalized; thus, for positive finite <[x]>,
+@ifnottex
+1 <= (<[x]> * FLT_RADIX to the power (-logb(<[x]>))) < FLT_RADIX.
+@end ifnottex
+@tex
+$1 \leq ( x \cdot FLT\_RADIX ^ {-logb(x)} ) < FLT\_RADIX$.
+@end tex
+A domain error may occur if the argument is zero.
+In this floating-point implementation, FLT_RADIX is 2.  Which also means
+that for finite <[x]>, <<logb>>(<[x]>) = <<floor>>(<<log2>>(<<fabs>>(<[x]>))).
+
+All nonzero, normal numbers can be described as
+@ifnottex
+<[m]> * 2**<[p]>, where 1.0 <= <[m]> < 2.0.
+@end ifnottex
+@tex
+$m \cdot 2^p$, where $1.0 \leq m < 2.0$.
+@end tex
+The <<logb>> functions examine the argument <[x]>, and return <[p]>.
+The <<frexp>> functions are similar to the <<logb>> functions, but
+returning <[m]> adjusted to the interval [.5, 1) or 0, and <[p]>+1.
+
+RETURNS
+@comment Formatting note:  "$@" forces a new line
+When <[x]> is:@*
++inf or -inf, +inf is returned;@*
+NaN, NaN is returned;@*
+0, -inf is returned, and the divide-by-zero exception is raised;@*
+otherwise, the <<logb>> functions return the signed exponent of <[x]>.
+
+PORTABILITY
+ANSI C, POSIX
+
+SEEALSO
+frexp, ilogb
+*/
+
+/* double logb(double x)
+ * return the binary exponent of non-zero x
+ * logb(0) = -inf, raise divide-by-zero floating point exception
+ * logb(+inf|-inf) = +inf (no signal is raised)
+ * logb(NaN) = NaN (no signal is raised)
+ * Per C99 recommendation, a NaN argument is returned unchanged.
+ */
+
+#include "fdlibm.h"
+
+#ifndef _DOUBLE_IS_32BITS
+
+double
+#ifdef __STDC__
+logb(double x)
+#else
+logb(x)
+double x;
+#endif
+{
+	__int32_t hx,lx,ix;
+
+	EXTRACT_WORDS(hx,lx,x);
+	hx &= 0x7fffffff;		/* high |x| */
+	if(hx<0x00100000) {		/* 0 or subnormal */
+	    if((hx|lx)==0)  {
+		double  xx;
+		/* arg==0:  return -inf and raise divide-by-zero exception */
+		INSERT_WORDS(xx,hx,lx);	/* +0.0 */
+		return -1./xx;	/* logb(0) = -inf */
+		}
+	    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 (double) ix;
+	}
+	else if (hx<0x7ff00000) return (hx>>20)-1023;	/* normal # */
+	else if (hx>0x7ff00000 || lx)  return x;	/* x==NaN */
+	else  return HUGE_VAL;	/* x==inf (+ or -) */
+}
+
+#endif /* _DOUBLE_IS_32BITS */