1 files changed, 79 insertions, 0 deletions
diff --git a/LibOVRKernel/Src/Kernel/OVR_Rand.cpp b/LibOVRKernel/Src/Kernel/OVR_Rand.cpp
new file mode 100644
index 0000000..3d6f50e
--- /dev/null
+++ b/LibOVRKernel/Src/Kernel/OVR_Rand.cpp
@@ -0,0 +1,79 @@
+/**************************************************************************
+
+Filename    :   OVR_Rand.cpp
+Content     :   Random number generator
+Created     :   Aug 28, 2014
+Author      :   Chris Taylor
+
+Copyright   :   Copyright 2014 Oculus VR, Inc. All Rights reserved.
+
+Licensed under the Oculus VR Rift SDK License Version 3.2 (the "License"); 
+you may not use the Oculus VR Rift SDK except in compliance with the License, 
+which is provided at the time of installation or download, or which 
+otherwise accompanies this software in either electronic or hard copy form.
+
+You may obtain a copy of the License at
+
+http://www.oculusvr.com/licenses/LICENSE-3.2 
+
+Unless required by applicable law or agreed to in writing, the Oculus VR SDK 
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+************************************************************************************/
+
+#include "OVR_Rand.h"
+#include "OVR_Timer.h"
+
+namespace OVR {
+
+
+void RandomNumberGenerator::SeedRandom()
+{
+    uint64_t seed = Timer::GetTicksNanos();
+
+    uint32_t x = (uint32_t)seed, y = (uint32_t)(seed >> 32);
+
+    Seed(x, y);
+}
+
+void RandomNumberGenerator::Seed(uint32_t x, uint32_t y)
+{
+    // Based on the mixing functions of MurmurHash3
+    static const uint64_t C1 = 0xff51afd7ed558ccdULL;
+    static const uint64_t C2 = 0xc4ceb9fe1a85ec53ULL;
+
+    x += y;
+    y += x;
+
+    uint64_t seed_x = 0x9368e53c2f6af274ULL ^ x;
+    uint64_t seed_y = 0x586dcd208f7cd3fdULL ^ y;
+
+    seed_x *= C1;
+    seed_x ^= seed_x >> 33;
+    seed_x *= C2;
+    seed_x ^= seed_x >> 33;
+
+    seed_y *= C1;
+    seed_y ^= seed_y >> 33;
+    seed_y *= C2;
+    seed_y ^= seed_y >> 33;
+
+    Rx = seed_x;
+    Ry = seed_y;
+
+    // Inlined Next(): Discard first output
+
+    Rx = (uint64_t)0xfffd21a7 * (uint32_t)Rx + (uint32_t)(Rx >> 32);
+    Ry = (uint64_t)0xfffd1361 * (uint32_t)Ry + (uint32_t)(Ry >> 32);
+
+    // Throw away any saved RandN() state
+    HaveRandN = false;
+
+    Seeded = true;
+}
+
+
+} // namespace OVR