1 files changed, 60 insertions, 1 deletions
diff --git a/lib/libc/gen/rand48.h b/lib/libc/gen/rand48.h
index 9861e99683cb..d3326e851491 100644
--- a/lib/libc/gen/rand48.h
+++ b/lib/libc/gen/rand48.h
@@ -14,10 +14,11 @@
 #ifndef _RAND48_H_
 #define _RAND48_H_
 
+#include <sys/types.h>
 #include <math.h>
 #include <stdlib.h>
 
-void		_dorand48(unsigned short[3]);
+#include "fpmath.h"
 
 #define	RAND48_SEED_0	(0x330e)
 #define	RAND48_SEED_1	(0xabcd)
@@ -27,4 +28,62 @@ void		_dorand48(unsigned short[3]);
 #define	RAND48_MULT_2	(0x0005)
 #define	RAND48_ADD	(0x000b)
 
+typedef uint64_t uint48;
+
+extern uint48 _rand48_seed;
+extern uint48 _rand48_mult;
+extern uint48 _rand48_add;
+
+#define	TOUINT48(x, y, z)						\
+	((uint48)(x) + (((uint48)(y)) << 16) + (((uint48)(z)) << 32))
+
+#define	RAND48_SEED	TOUINT48(RAND48_SEED_0, RAND48_SEED_1, RAND48_SEED_2)
+#define	RAND48_MULT	TOUINT48(RAND48_MULT_0, RAND48_MULT_1, RAND48_MULT_2)
+
+#define	LOADRAND48(l, x) do {						\
+	(l) = TOUINT48((x)[0], (x)[1], (x)[2]);				\
+} while (0)
+
+#define	STORERAND48(l, x) do {						\
+	(x)[0] = (unsigned short)(l);					\
+	(x)[1] = (unsigned short)((l) >> 16);				\
+	(x)[2] = (unsigned short)((l) >> 32);				\
+} while (0)
+
+#define	_DORAND48(l) do {						\
+	(l) = (l) * _rand48_mult + _rand48_add;				\
+} while (0)
+
+#define	DORAND48(l, x) do {						\
+	LOADRAND48(l, x);						\
+	_DORAND48(l);							\
+	STORERAND48(l, x);						\
+} while (0)
+
+#define	ERAND48_BEGIN							\
+	union {								\
+		union IEEEd2bits ieee;					\
+		uint64_t u64;						\
+	} u;								\
+	int s
+
+/*
+ * Optimization for speed: assume doubles are IEEE 754 and use bit fiddling
+ * rather than converting to double.  Specifically, clamp the result to 48 bits
+ * and convert to a double in [0.0, 1.0) via division by 2^48.  Normalize by
+ * shifting the most significant bit into the implicit one position and
+ * adjusting the exponent accordingly.  The store to the exponent field
+ * overwrites the implicit one.
+ */
+#define	ERAND48_END(x) do {						\
+	u.u64 = ((x) & 0xffffffffffffULL);				\
+	if (u.u64 == 0)							\
+		return (0.0);						\
+	u.u64 <<= 5;							\
+	for (s = 0; !(u.u64 & (1LL << 52)); s++, u.u64 <<= 1)		\
+		;							\
+	u.ieee.bits.exp = 1022 - s;					\
+	return (u.ieee.d);						\
+} while (0)
+
 #endif /* _RAND48_H_ */