upload sdk

git-svn-id: svn://kolibrios.org@4349 a494cfbc-eb01-0410-851d-a64ba20cac60

contrib/sdk/sources/newlib/math/s_log2.c

@@ -0,0 +1,85 @@
+/* @(#)s_log2.c 5.1 93/09/24 */
+/* Modification from s_exp10.c Yaakov Selkowitz 2009.  */
+
+/*
+ * ====================================================
+ * 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
+	<<log2>>, <<log2f>>--base 2 logarithm
+INDEX
+	log2
+INDEX
+	log2f
+
+ANSI_SYNOPSIS
+	#include <math.h>
+	double log2(double <[x]>);
+	float log2f(float <[x]>);
+
+DESCRIPTION
+The <<log2>> functions compute the base-2 logarithm of <[x]>.  A domain error
+occurs if the argument is less than zero.  A range error occurs if the
+argument is zero.
+
+The Newlib implementations are not full, intrinisic calculations, but
+rather are derivatives based on <<log>>.  (Accuracy might be slightly off from
+a direct calculation.)  In addition to functions, they are also implemented as
+macros defined in math.h:
+. #define log2(x) (log (x) / _M_LN2)
+. #define log2f(x) (logf (x) / (float) _M_LN2)
+To use the functions instead, just undefine the macros first.
+
+You can use the (non-ANSI) function <<matherr>> to specify error
+handling for these functions, indirectly through the respective <<log>>
+function. 
+
+RETURNS
+The <<log2>> functions return
+@ifnottex
+<<log base-2(<[x]>)>>
+@end ifnottex
+@tex
+$log_2(x)$
+@end tex
+on success.
+When <[x]> is zero, the
+returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.
+When <[x]> is negative, the returned value is NaN (not a number) and
+<<errno>> is set to <<EDOM>>.  You can control the error behavior via
+<<matherr>>.
+
+PORTABILITY
+C99, POSIX, System V Interface Definition (Issue 6).
+*/
+
+/*
+ * wrapper log2(x)
+ */
+
+#include "fdlibm.h"
+#include <errno.h>
+#include <math.h>
+#undef log2
+
+#ifndef _DOUBLE_IS_32BITS
+
+#ifdef __STDC__
+	double log2(double x)		/* wrapper log2 */
+#else
+	double log2(x)			/* wrapper log2 */
+	double x;
+#endif
+{
+  return (log(x) / M_LN2);
+}
+
+#endif /* defined(_DOUBLE_IS_32BITS) */