1 files changed, 90 insertions, 0 deletions
diff --git a/src/math/rint.c b/src/math/rint.c
new file mode 100644
index 00000000..775c7b8d
--- /dev/null
+++ b/src/math/rint.c
@@ -0,0 +1,90 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_rint.c */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+/*
+ * rint(x)
+ * Return x rounded to integral value according to the prevailing
+ * rounding mode.
+ * Method:
+ *      Using floating addition.
+ * Exception:
+ *      Inexact flag raised if x not equal to rint(x).
+ */
+
+#include "libm.h"
+
+static const double
+TWO52[2] = {
+  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
+ -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
+};
+
+double rint(double x)
+{
+	int32_t i0,j0,sx;
+	uint32_t i,i1;
+	double w,t;
+
+	EXTRACT_WORDS(i0, i1, x);
+	// FIXME: signed shift
+	sx = (i0>>31) & 1;
+	j0 = ((i0>>20)&0x7ff) - 0x3ff;
+	if (j0 < 20) {
+		if (j0 < 0) {
+			if (((i0&0x7fffffff)|i1) == 0)
+				return x;
+			i1 |= i0 & 0x0fffff;
+			i0 &= 0xfffe0000;
+			i0 |= ((i1|-i1)>>12) & 0x80000;
+			SET_HIGH_WORD(x, i0);
+			STRICT_ASSIGN(double, w, TWO52[sx] + x);
+			t = w - TWO52[sx];
+			GET_HIGH_WORD(i0, t);
+			SET_HIGH_WORD(t, (i0&0x7fffffff)|(sx<<31));
+			return t;
+		} else {
+			i = 0x000fffff>>j0;
+			if (((i0&i)|i1) == 0)
+				return x; /* x is integral */
+			i >>= 1;
+			if (((i0&i)|i1) != 0) {
+				/*
+				 * Some bit is set after the 0.5 bit.  To avoid the
+				 * possibility of errors from double rounding in
+				 * w = TWO52[sx]+x, adjust the 0.25 bit to a lower
+				 * guard bit.  We do this for all j0<=51.  The
+				 * adjustment is trickiest for j0==18 and j0==19
+				 * since then it spans the word boundary.
+				 */
+				if (j0 == 19)
+					i1 = 0x40000000;
+				else if (j0 == 18)
+					i1 = 0x80000000;
+				else
+					i0 = (i0 & ~i)|(0x20000>>j0);
+			}
+		}
+	} else if (j0 > 51) {
+		if (j0 == 0x400)
+			return x+x;  /* inf or NaN */
+		return x;            /* x is integral */
+	} else {
+		i = (uint32_t)0xffffffff>>(j0-20);
+		if ((i1&i) == 0)
+			return x;    /* x is integral */
+		i >>= 1;
+		if ((i1&i) != 0)
+			i1 = (i1 & ~i)|(0x40000000>>(j0-20));
+	}
+	INSERT_WORDS(x, i0, i1);
+	STRICT_ASSIGN(double, w, TWO52[sx] + x);
+	return w - TWO52[sx];
+}