New pseudo random number generator

cmdline/mingw.c

@@ -163,13 +163,10 @@ void os_init(int opt)
 	/* check for Wine presence */
 	is_wine = GetProcAddress(ntdll, "wine_get_version") != 0;
 
-	/* setup the standard random generator used as fallback */
-	srand(GetTickCount());
-
 	/* get pointer to RtlGenRandom, note that it was reported missing in some cases */
 	ptr_RtlGenRandom = (void*)GetProcAddress(dll_advapi32, "SystemFunction036");
 
-	/* get pointer to RtlGenRandom, note that it was reported missing in some cases */
+	/* get pointer to ptr_GetTickCount64 */
 	ptr_GetTickCount64 = (void*)GetProcAddress(kernel32, "GetTickCount64");
 
 	/* set the thread execution level to avoid sleep */
@@ -2239,21 +2236,9 @@ int randomize(void* void_ptr, size_t size)
 	if (ptr_RtlGenRandom != 0 && ptr_RtlGenRandom(ptr, size) != 0)
 		return 0;
 
-	/* try rand_s */
-	for (i = 0; i < size; ++i) {
-		unsigned v = 0;
-
-		if (rand_s(&v) != 0)
-			break;
-
-		ptr[i] = v;
-	}
-	if (i == size)
-		return 0;
-
 	/* fallback to standard rand */
 	for (i = 0; i < size; ++i)
-		ptr[i] = rand();
+		ptr[i] = random_u8();
 
 	return 0;
 }

cmdline/portable.h

@@ -46,11 +46,6 @@
  */
 #define _WIN32_WINNT 0x600
 
-/**
- * Enable the rand_s() function.l
- */
-#define _CRT_RAND_S
-
 #include <windows.h>
 #endif
 

cmdline/snapraid.c

@@ -1360,6 +1360,7 @@ int snapraid_main(int argc, char* argv[])
 	os_init(opt.force_scan_winfind);
 	raid_init();
 	crc32c_init();
+	random_reseed();
 
 	if (speedtest != 0) {
 		speed(period);

cmdline/support.c

@@ -28,6 +28,7 @@
 #if HAVE_THREAD
 static thread_mutex_t msg_lock;
 static thread_mutex_t memory_lock;
+static thread_mutex_t random_lock;
 #endif
 
 void lock_msg(void)
@@ -58,12 +59,28 @@ void unlock_memory(void)
 #endif
 }
 
+void lock_random(void)
+{
+#if HAVE_THREAD
+	thread_mutex_lock(&random_lock);
+#endif
+}
+
+void unlock_random(void)
+{
+#if HAVE_THREAD
+	thread_mutex_unlock(&random_lock);
+#endif
+}
+
+
 void lock_init(void)
 {
 #if HAVE_THREAD
 	/* initialize the locks as first operation as log_fatal depends on them */
 	thread_mutex_init(&msg_lock);
 	thread_mutex_init(&memory_lock);
+	thread_mutex_init(&random_lock);
 #endif
 }
 
@@ -72,9 +89,50 @@ void lock_done(void)
 #if HAVE_THREAD
 	thread_mutex_destroy(&msg_lock);
 	thread_mutex_destroy(&memory_lock);
+	thread_mutex_destroy(&random_lock);
 #endif
 }
 
+/****************************************************************************/
+/* random */
+
+static uint64_t random_state = 1;
+
+void random_reseed(void)
+{
+	random_state = tick();
+}
+
+unsigned char random_u8(void)
+{
+	return random_u64() & 0xFF;
+}
+
+/*
+ * SplitMix64
+ *
+ * - Zero-safe: Any 64-bit seed is valid (even 0).
+ * - Full period: Guaranteed to visit every 2^64 value.
+ * - Logic: Uses a Weyl sequence + MurmurHash3-style finalizer.
+ *
+ * See: https://rosettacode.org/wiki/Pseudo-random_numbers/Splitmix64
+ */
+uint64_t random_u64(void)
+{
+	uint64_t z;
+
+	lock_random();
+
+	z = random_state += 0x9E3779B97F4A7C15ULL;
+
+	unlock_random();
+
+	z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9ULL;
+	z = (z ^ (z >> 27)) * 0x94D049BB133111EBULL;
+    
+	return z ^ (z >> 31);
+}
+
 /****************************************************************************/
 /* print */
 

cmdline/support.h

@@ -52,6 +52,24 @@ void unlock_msg(void);
 void lock_memory(void);
 void unlock_memory(void);
 
+/****************************************************************************/
+/* random */
+
+/**
+ * Reseed the random pseudo random number generator
+ */ 
+void random_reseed(void);
+
+/**
+ * Return a pseudo random number of 8 bits
+ */
+unsigned char random_u8(void);
+
+/**
+ * Return a pseudo random number of 64 bits
+ */
+uint64_t random_u64(void);
+
 /****************************************************************************/
 /* log */
 

cmdline/unix.c

@@ -1622,16 +1622,6 @@ static int devup(dev_t device, const char* name)
 	void* buf;
 	uint64_t size;
 	uint64_t offset;
-	uint64_t pseudo_random;
-
-	/* get a pseudo random number */
-	ret = randomize(&pseudo_random, sizeof(pseudo_random));
-	if (ret < 0) {
-		/* LCOV_EXCL_START */
-		log_fatal("Failed to retrieve random values.\n");
-		exit(EXIT_FAILURE);
-		/* LCOV_EXCL_STOP */
-	}
 
 	if (devresolve(device, file, sizeof(file)) != 0) {
 		/* LCOV_EXCL_START */
@@ -1669,7 +1659,7 @@ static int devup(dev_t device, const char* name)
 	}
 
 	/* select a random offset */
-	offset = (pseudo_random % (size / 4096)) * 4096;
+	offset = (random_u64() % (size / 4096)) * 4096;
 
 #if HAVE_POSIX_FADVISE
 	/* clear cache */