1 files changed, 37 insertions, 0 deletions
diff --git a/lib/libm/modf.c b/lib/libm/modf.c
new file mode 100644
index 00000000..94fe5439
--- /dev/null
+++ b/lib/libm/modf.c
@@ -0,0 +1,37 @@
+#include "libm.h"
+
+double modf(double x, double *iptr)
+{
+	union {
+		double f;
+		uint64_t i;
+	} u = { x };
+	uint64_t mask;
+	int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff;
+
+	/* no fractional part */
+	if (e >= 52) {
+		*iptr = x;
+		if (e == 0x400 && u.i << 12 != 0) /* nan */
+			return x;
+		u.i &= 1ULL << 63;
+		return u.f;
+	}
+
+	/* no integral part*/
+	if (e < 0) {
+		u.i &= 1ULL << 63;
+		*iptr = u.f;
+		return x;
+	}
+
+	mask = -1ULL >> 12 >> e;
+	if ((u.i & mask) == 0) {
+		*iptr = x;
+		u.i &= 1ULL << 63;
+		return u.f;
+	}
+	u.i &= ~mask;
+	*iptr = u.f;
+	return x - u.f;
+}