SDL_log10

src/libm/e_log10.c

@@ -0,0 +1,106 @@
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+#if defined(_MSC_VER)           /* Handle Microsoft VC++ compiler specifics. */
+/* C4723: potential divide by zero. */
+#pragma warning ( disable : 4723 )
+#endif
+
+/* __ieee754_log10(x)
+ * Return the base 10 logarithm of x
+ *
+ * Method :
+ *	Let log10_2hi = leading 40 bits of log10(2) and
+ *	    log10_2lo = log10(2) - log10_2hi,
+ *	    ivln10   = 1/log(10) rounded.
+ *	Then
+ *		n = ilogb(x),
+ *		if(n<0)  n = n+1;
+ *		x = scalbn(x,-n);
+ *		log10(x) := n*log10_2hi + (n*log10_2lo + ivln10*log(x))
+ *
+ * Note 1:
+ *	To guarantee log10(10**n)=n, where 10**n is normal, the rounding
+ *	mode must set to Round-to-Nearest.
+ * Note 2:
+ *	[1/log(10)] rounded to 53 bits has error  .198   ulps;
+ *	log10 is monotonic at all binary break points.
+ *
+ * Special cases:
+ *	log10(x) is NaN with signal if x < 0;
+ *	log10(+INF) is +INF with no signal; log10(0) is -INF with signal;
+ *	log10(NaN) is that NaN with no signal;
+ *	log10(10**N) = N  for N=0,1,...,22.
+ *
+ * Constants:
+ * The hexadecimal values are the intended ones for the following constants.
+ * The decimal values may be used, provided that the compiler will convert
+ * from decimal to binary accurately enough to produce the hexadecimal values
+ * shown.
+ */
+
+#include "math_libm.h"
+#include "math_private.h"
+
+static const double
+two54      =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+ivln10     =  4.34294481903251816668e-01, /* 0x3FDBCB7B, 0x1526E50E */
+log10_2hi  =  3.01029995663611771306e-01, /* 0x3FD34413, 0x509F6000 */
+log10_2lo  =  3.69423907715893078616e-13; /* 0x3D59FEF3, 0x11F12B36 */
+
+static const double zero = 0.0;
+
+double attribute_hidden __ieee754_log10(double x)
+{
+	double y,z;
+	int32_t i,k,hx;
+	u_int32_t lx;
+
+	EXTRACT_WORDS(hx,lx,x);
+
+        k=0;
+        if (hx < 0x00100000) {                  /* x < 2**-1022  */
+            if (((hx&0x7fffffff)|lx)==0)
+                return -two54/zero;             /* log(+-0)=-inf */
+            if (hx<0) return (x-x)/zero;        /* log(-#) = NaN */
+            k -= 54; x *= two54; /* subnormal number, scale up x */
+	    GET_HIGH_WORD(hx,x);
+        }
+	if (hx >= 0x7ff00000) return x+x;
+	k += (hx>>20)-1023;
+	i  = ((u_int32_t)k&0x80000000)>>31;
+        hx = (hx&0x000fffff)|((0x3ff-i)<<20);
+        y  = (double)(k+i);
+	SET_HIGH_WORD(x,hx);
+	z  = y*log10_2lo + ivln10*__ieee754_log(x);
+	return  z+y*log10_2hi;
+}
+
+/*
+ * wrapper log10(X)
+ */
+#ifndef _IEEE_LIBM
+double log10(double x)
+{
+	double z = __ieee754_log10(x);
+	if (_LIB_VERSION == _IEEE_ || isnan(x))
+		return z;
+	if (x <= 0.0) {
+		if(x == 0.0)
+			return __kernel_standard(x, x, 18); /* log10(0) */
+		return __kernel_standard(x, x, 19); /* log10(x<0) */
+	}
+	return z;
+}
+#else
+strong_alias(__ieee754_log10, log10)
+#endif
+libm_hidden_def(log10)

src/libm/math_libm.h

@@ -30,6 +30,7 @@ double SDL_uclibc_fabs(double x);
 double SDL_uclibc_floor(double x);
 double SDL_uclibc_fmod(double x, double y);
 double SDL_uclibc_log(double x);
+double SDL_uclibc_log10(double x);
 double SDL_uclibc_pow(double x, double y);    
 double SDL_uclibc_scalbn(double x, int n);
 double SDL_uclibc_sin(double x);

src/libm/math_private.h

@@ -39,6 +39,7 @@ typedef unsigned int u_int32_t;
 #define floor           SDL_uclibc_floor
 #define __ieee754_fmod  SDL_uclibc_fmod
 #define __ieee754_log   SDL_uclibc_log
+#define __ieee754_log10 SDL_uclibc_log10
 #define __ieee754_pow   SDL_uclibc_pow
 #define scalbln         SDL_uclibc_scalbln
 #define scalbn          SDL_uclibc_scalbn