util: introduce kernel utils for pseudorandom number generation

Currently there are two generators. The fast one is the same one the scheduler is using. The standard one is the same algorithm libroot's rand() uses. Should there be a need for more cryptographically PRNG MD4 or MD5 might be a good candidates.
2013-04-11 04:34:59 +02:00
parent feae2b5a00
commit 6003243ef3
3 changed files with 124 additions and 0 deletions
@@ -0,0 +1,69 @@
+/*
+ * Copyright 2013 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Paweł Dziepak, [email protected]
+ */
+#ifndef KERNEL_UTIL_RANDOM_H
+#define KERNEL_UTIL_RANDOM_H
+
+
+#include <smp.h>
+#include <SupportDefs.h>
+
+
+#define MAX_FAST_RANDOM_VALUE		0x7fff
+#define MAX_RANDOM_VALUE			0x7fffffffu
+
+const int	kFastRandomShift		= 15;
+const int	kRandomShift			= 31;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+unsigned int	fast_random_value(void);
+unsigned int	random_value(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#ifdef __cplusplus
+
+template<typename T>
+T
+fast_get_random()
+{
+	size_t shift = 0;
+	T random = 0;
+	while (shift < sizeof(T) * 8) {
+		random |= (T)fast_random_value() << shift;
+		shift += kFastRandomShift;
+	}
+
+	return random;
+}
+
+
+template<typename T>
+T
+get_random()
+{
+	size_t shift = 0;
+	T random = 0;
+	while (shift < sizeof(T) * 8) {
+		random |= (T)random_value() << shift;
+		shift += kRandomShift;
+	}
+
+	return random;
+}
+
+
+#endif	// __cplusplus
+
+#endif	// KERNEL_UTIL_RANDOM_H
+