1 files changed, 57 insertions, 0 deletions
diff --git a/webrtc/test/random.cc b/webrtc/test/random.cc
new file mode 100644
index 0000000000..c4c405f6b8
--- /dev/null
+++ b/webrtc/test/random.cc
@@ -0,0 +1,57 @@
+/*
+ *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/test/random.h"
+
+#include <math.h>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+namespace test {
+
+Random::Random(uint32_t seed) : a_(0x531FDB97 ^ seed), b_(0x6420ECA8 + seed) {
+}
+
+float Random::Rand() {
+  const double kScale = 1.0f / (static_cast<uint64_t>(1) << 32);
+  double result = kScale * b_;
+  a_ ^= b_;
+  b_ += a_;
+  return static_cast<float>(result);
+}
+
+int Random::Rand(int low, int high) {
+  RTC_DCHECK(low <= high);
+  float uniform = Rand() * (high - low + 1) + low;
+  return static_cast<int>(uniform);
+}
+
+int Random::Gaussian(int mean, int standard_deviation) {
+  // Creating a Normal distribution variable from two independent uniform
+  // variables based on the Box-Muller transform, which is defined on the
+  // interval (0, 1], hence the mask+add below.
+  const double kPi = 3.14159265358979323846;
+  const double kScale = 1.0 / 0x80000000ul;
+  double u1 = kScale * ((a_ & 0x7ffffffful) + 1);
+  double u2 = kScale * ((b_ & 0x7ffffffful) + 1);
+  a_ ^= b_;
+  b_ += a_;
+  return static_cast<int>(
+      mean + standard_deviation * sqrt(-2 * log(u1)) * cos(2 * kPi * u2));
+}
+
+int Random::Exponential(float lambda) {
+  float uniform = Rand();
+  return static_cast<int>(-log(uniform) / lambda);
+}
+}  // namespace test
+}  // namespace webrtc