1 files changed, 82 insertions, 0 deletions
diff --git a/src/math/floor.c b/src/math/floor.c
new file mode 100644
index 00000000..521a148e
--- /dev/null
+++ b/src/math/floor.c
@@ -0,0 +1,82 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_floor.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.
+ * ====================================================
+ */
+/*
+ * floor(x)
+ * Return x rounded toward -inf to integral value
+ * Method:
+ *      Bit twiddling.
+ * Exception:
+ *      Inexact flag raised if x not equal to floor(x).
+ */
+
+#include "libm.h"
+
+static const double huge = 1.0e300;
+
+double floor(double x)
+{
+	int32_t i0,i1,j0;
+	uint32_t i,j;
+
+	EXTRACT_WORDS(i0, i1, x);
+	// FIXME: signed shift
+	j0 = ((i0>>20)&0x7ff) - 0x3ff;
+	if (j0 < 20) {
+		if (j0 < 0) {  /* |x| < 1 */
+			/* raise inexact if x != 0 */
+			if (huge+x > 0.0) {
+				if (i0 >= 0) {  /* x >= 0 */
+					i0 = i1 = 0;
+				} else if (((i0&0x7fffffff)|i1) != 0) {
+					i0 = 0xbff00000;
+					i1 = 0;
+				}
+			}
+		} else {
+			i = 0x000fffff>>j0;
+			if (((i0&i)|i1) == 0)
+				return x; /* x is integral */
+			 /* raise inexact flag */
+			if (huge+x > 0.0) {
+				if (i0 < 0)
+					i0 += 0x00100000>>j0;
+				i0 &= ~i;
+				i1=0;
+			}
+		}
+	} else if (j0 > 51) {
+		if (j0 == 0x400)
+			return x+x; /* inf or NaN */
+		else
+			return x;   /* x is integral */
+	} else {
+		i = ((uint32_t)(0xffffffff))>>(j0-20);
+		if ((i1&i) == 0)
+			return x;   /* x is integral */
+		/* raise inexact flag */
+		if (huge+x > 0.0) {
+			if (i0 < 0) {
+				if (j0 == 20)
+					i0+=1;
+				else {
+					j = i1+(1<<(52-j0));
+					if (j < i1)
+						i0 += 1; /* got a carry */
+					i1 = j;
+				}
+			}
+			i1 &= ~i;
+		}
+	}
+	INSERT_WORDS(x, i0, i1);
+	return x;
+}