Rewrote the PRNG using an xorshift* algorithm and moved the files from test/ to base/.

webrtc/base/random.h

Index: webrtc/base/random.h
diff --git a/webrtc/test/random.h b/webrtc/base/random.h
similarity index 63%
rename from webrtc/test/random.h
rename to webrtc/base/random.h
index c7254a9b4946e41f6e62d333af79bfd45dad5e96..647b84c9c947b8d11f711012c9deb5e09b151d3f 100644
--- a/webrtc/test/random.h
+++ b/webrtc/base/random.h
@@ -8,23 +8,23 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef WEBRTC_TEST_RANDOM_H_
-#define WEBRTC_TEST_RANDOM_H_
+#ifndef WEBRTC_BASE_RANDOM_H_
+#define WEBRTC_BASE_RANDOM_H_
 
 #include <limits>
 
 #include "webrtc/typedefs.h"
 #include "webrtc/base/constructormagic.h"
+#include "webrtc/base/checks.h"
 
 namespace webrtc {
 
-namespace test {
-
 class Random {
  public:
-  explicit Random(uint32_t seed);
+  explicit Random(uint64_t seed);
 
   // Return pseudo-random integer of the specified type.
+  // We need to limit the size to 32 bits to keep the output close to uniform.
   template <typename T>
   T Rand() {
     static_assert(std::numeric_limits<T>::is_integer &&
@@ -32,7 +32,7 @@ class Random {
                       std::numeric_limits<T>::digits <= 32,
                   "Rand is only supported for built-in integer types that are "
                   "32 bits or smaller.");
-    return static_cast<T>(Rand(std::numeric_limits<uint32_t>::max()));
+    return static_cast<T>(NextOutput());
   }
 
   // Uniformly distributed pseudo-random number in the interval [0, t].
@@ -41,18 +41,26 @@ class Random {
   // Uniformly distributed pseudo-random number in the interval [low, high].
   uint32_t Rand(uint32_t low, uint32_t high);
 
+  // Uniformly distributed pseudo-random number in the interval [low, high].
+  int32_t Rand(int32_t low, int32_t high);
+
   // Normal Distribution.
-  int Gaussian(int mean, int standard_deviation);
+  double Gaussian(double mean, double standard_deviation);
 
   // Exponential Distribution.
-  int Exponential(float lambda);
-
-  // TODO(solenberg): Random from histogram.
-  // template<typename T> int Distribution(const std::vector<T> histogram) {
+  double Exponential(double lambda);
 
  private:
-  uint32_t a_;
-  uint32_t b_;
+  // Outputs a nonzero 64-bit random number.
+  uint64_t NextOutput() {
+    state_ ^= state_ >> 12;
+    state_ ^= state_ << 25;
+    state_ ^= state_ >> 27;
+    RTC_DCHECK(state_ != 0x0ULL);
+    return state_ * 2685821657736338717ull;
+  }
+
+  uint64_t state_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(Random);
 };
@@ -61,11 +69,14 @@ class Random {
 template <>
 float Random::Rand<float>();
 
+// Return pseudo-random number in the interval [0.0, 1.0).
+template <>
+double Random::Rand<double>();
+
 // Return pseudo-random boolean value.
 template <>
 bool Random::Rand<bool>();
 
-}  // namespace test
 }  // namespace webrtc
 
-#endif  // WEBRTC_TEST_RANDOM_H_
+#endif  // WEBRTC_BASE_RANDOM_H_