[Feature] Add xoroshiro+ fast rng for non-crypto purposes

2 files changed, 70 insertions, 5 deletions

diff --git a/src/libutil/util.c b/src/libutil/util.c
index 6a60f854a..762c8d557 100644
--- a/src/libutil/util.c
+++ b/src/libutil/util.c
@@ -2055,6 +2055,7 @@ rspamd_init_libs (void)
 	SSL_CTX_set_options (ctx->ssl_ctx, ssl_options);
 #endif
 	g_random_set_seed (ottery_rand_uint32 ());
+	rspamd_random_seed_fast ();
 
 	/* Set stack size for pcre */
 	getrlimit (RLIMIT_STACK, &rlim);
@@ -2152,21 +2153,72 @@ rspamd_hash_seed (void)
 	return seed;
 }
 
-gdouble
-rspamd_random_double (void)
+static inline gdouble
+rspamd_double_from_int64 (guint64 rnd_int)
 {
-	guint64 rnd_int;
 	double res;
 	const double transform_bias = 2.2204460492503130808472633361816e-16;
 
-	rnd_int = ottery_rand_uint64 () >> 12;
-	res = rnd_int;
+	res = rnd_int >> 12;
 	res *= transform_bias;
 
 	return res;
 }
 
 gdouble
+rspamd_random_double (void)
+{
+	guint64 rnd_int;
+
+	rnd_int = ottery_rand_uint64 ();
+
+	return rspamd_double_from_int64 (rnd_int);
+}
+
+
+static guint64 xorshifto_seed[2];
+
+static inline guint64
+xoroshiro_rotl (const guint64 x, int k) {
+	return (x << k) | (x >> (64 - k));
+}
+
+
+gdouble
+rspamd_random_double_fast (void)
+{
+	const guint64 s0 = xorshifto_seed[0];
+	guint64 s1 = xorshifto_seed[1];
+	const guint64 result = s0 + s1;
+
+	s1 ^= s0;
+	xorshifto_seed[0] = xoroshiro_rotl(s0, 55) ^ s1 ^ (s1 << 14);
+	xorshifto_seed[1] = xoroshiro_rotl (s1, 36);
+
+	return rspamd_double_from_int64 (result);
+}
+
+guint64
+rspamd_random_uint64_fast (void)
+{
+	const guint64 s0 = xorshifto_seed[0];
+	guint64 s1 = xorshifto_seed[1];
+	const guint64 result = s0 + s1;
+
+	s1 ^= s0;
+	xorshifto_seed[0] = xoroshiro_rotl(s0, 55) ^ s1 ^ (s1 << 14);
+	xorshifto_seed[1] = xoroshiro_rotl (s1, 36);
+
+	return result;
+}
+
+void
+rspamd_random_seed_fast (void)
+{
+	ottery_rand_bytes (xorshifto_seed, sizeof (xorshifto_seed));
+}
+
+gdouble
 rspamd_time_jitter (gdouble in, gdouble jitter)
 {
 	if (jitter == 0) {
diff --git a/src/libutil/util.h b/src/libutil/util.h
index 2497d538f..76a02d198 100644
--- a/src/libutil/util.h
+++ b/src/libutil/util.h
@@ -430,6 +430,19 @@ gdouble rspamd_time_jitter (gdouble in, gdouble jitter);
 gdouble rspamd_random_double (void);
 
 /**
+ * Return random double in range [0..1) using xoroshiro128+ algorithm (not crypto secure)
+ * @return
+ */
+gdouble rspamd_random_double_fast (void);
+
+guint64 rspamd_random_uint64_fast (void);
+
+/**
+ * Seed fast rng
+ */
+void rspamd_random_seed_fast (void);
+
+/**
  * Constant time version of memcmp
  */
 gboolean rspamd_constant_memcmp (const guchar *a, const guchar *b, gsize len);