usr: libc: Add math.h + musl math impl portexpt

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/lib/libc/src/musl-math/modff.c b/lib/libc/src/musl-math/modff.c
new file mode 100644
index 0000000..639514e
--- /dev/null
+++ b/lib/libc/src/musl-math/modff.c
@@ -0,0 +1,34 @@
+#include "libm.h"
+
+float modff(float x, float *iptr)
+{
+	union {float f; uint32_t i;} u = {x};
+	uint32_t mask;
+	int e = (int)(u.i>>23 & 0xff) - 0x7f;
+
+	/* no fractional part */
+	if (e >= 23) {
+		*iptr = x;
+		if (e == 0x80 && u.i<<9 != 0) { /* nan */
+			return x;
+		}
+		u.i &= 0x80000000;
+		return u.f;
+	}
+	/* no integral part */
+	if (e < 0) {
+		u.i &= 0x80000000;
+		*iptr = u.f;
+		return x;
+	}
+
+	mask = 0x007fffff>>e;
+	if ((u.i & mask) == 0) {
+		*iptr = x;
+		u.i &= 0x80000000;
+		return u.f;
+	}
+	u.i &= ~mask;
+	*iptr = u.f;
+	return x - u.f;
+}