1 files changed, 58 insertions, 0 deletions
diff --git a/random_float.c b/random_float.c
new file mode 100644
index 0000000..b4b6557
--- /dev/null
+++ b/random_float.c
@@ -0,0 +1,58 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+#include <math.h>
+
+
+long double
+libsimple_random_float(uintmax_t (*rng)(size_t bits, void *user), void *user, long double min, long double postmax) /* TODO add test */
+{
+	long double range, offset, mantissa, value;
+	uintmax_t r;
+	int exp;
+	size_t bits;
+
+	if (min < postmax) {
+		range = postmax - min;
+		offset = min;
+	} else if (min > postmax) {
+		range = min - postmax;
+		offset = postmax;
+	} else {
+		return min;
+	}
+
+	mantissa = frexpl(range, &exp);
+	do {
+		bits = sizeof(uintmax_t) * CHAR_BIT;
+		r = (*rng)(bits, user);
+		while (bits && (r & 1)) {
+			exp -= 1;
+			bits -= 1;
+			r >>= 1;
+		}
+	} while (!bits);
+
+	bits = sizeof(uintmax_t) * CHAR_BIT;
+	r = (*rng)(bits, user);
+	value = (long double)r;
+	value = fmal(value, 0.5, 0.5);
+	value = ldexpl(value, -(int)bits);
+
+	value = ldexpl(value, exp);
+	value *= mantissa;
+	return value + offset;
+}
+
+
+#else
+#include "test.h"
+
+int
+main(void)
+{
+	return 0;
+}
+
+#endif