initial commit, 4.5 stable

thirdparty/sdl/libm/s_scalbn.c

@@ -0,0 +1,74 @@
+#include "SDL_internal.h"
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+/*
+ * scalbln(double x, long n)
+ * scalbln(x,n) returns x * 2**n computed by exponent
+ * manipulation rather than by actually performing an
+ * exponentiation or a multiplication.
+ */
+
+#include "math_libm.h"
+#include "math_private.h"
+#include <limits.h>
+
+#ifdef __WATCOMC__ /* Watcom defines huge=__huge */
+#undef huge
+#endif
+
+static const double
+two54  = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
+huge   = 1.0e+300,
+tiny   = 1.0e-300;
+
+double scalbln(double x, long n)
+{
+	int32_t k, hx, lx;
+
+	EXTRACT_WORDS(hx, lx, x);
+	k = (hx & 0x7ff00000) >> 20; /* extract exponent */
+	if (k == 0) { /* 0 or subnormal x */
+		if ((lx | (hx & 0x7fffffff)) == 0)
+			return x; /* +-0 */
+		x *= two54;
+		GET_HIGH_WORD(hx, x);
+		k = ((hx & 0x7ff00000) >> 20) - 54;
+	}
+	if (k == 0x7ff)
+		return x + x; /* NaN or Inf */
+	k = (int32_t)(k + n);
+	if (k > 0x7fe)
+		return huge * copysign(huge, x); /* overflow */
+	if (n < -50000)
+		return tiny * copysign(tiny, x); /* underflow */
+	if (k > 0) { /* normal result */
+		SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
+		return x;
+	}
+	if (k <= -54) {
+		if (n > 50000) /* in case integer overflow in n+k */
+			return huge * copysign(huge, x); /* overflow */
+		return tiny * copysign(tiny, x); /* underflow */
+	}
+	k += 54; /* subnormal result */
+	SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
+	return x * twom54;
+}
+libm_hidden_def(scalbln)
+
+
+double scalbn(double x, int n)
+{
+	return scalbln(x, n);
+}
+libm_hidden_def(scalbn)