1 files changed, 39 insertions, 0 deletions
diff --git a/ieee754.c b/ieee754.c
new file mode 100644
index 0000000..3b21351
--- /dev/null
+++ b/ieee754.c
@@ -0,0 +1,39 @@
+#include <assert.h>
+#include <math.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "ieee754.h"
+
+// ieee754f: convert f32 to float
+float ieee754f(unsigned long b)
+{
+	bool isneg;
+	int exp;
+	float n;
+
+	isneg = (b >> 31) & 0x1;
+	exp = (b >> 23) & 0xff;
+	n = b & 0x7fffff;
+
+	if (exp == 0xff) {
+		if (n) {
+			/* TODO: work out what a negative NaN means */
+			assert(!isneg);
+			return NAN;
+		} else {
+			return isneg ? -INFINITY : INFINITY;
+		}
+	} else if (exp == 0) {
+		if (n == 0)
+			return isneg ? -0 : 0;
+		exp = -126;
+	} else {
+		n += 0x1p23f;
+		exp -= 127;
+	}
+
+	n = ldexpf(n, exp - 23);
+
+	return isneg ? -n : n;
+}