Change to use local Random object instead of global rand() in the RtcEventLog unit test.

webrtc/test/random.h

Index: webrtc/test/random.h
diff --git a/webrtc/test/random.h b/webrtc/test/random.h
index 5cc54f212970c8269cf2093c199ef6be55fb4a45..cd3b799ba4995c5c1f643917eca269bd22732670 100644
--- a/webrtc/test/random.h
+++ b/webrtc/test/random.h
@@ -11,6 +11,8 @@
 #ifndef WEBRTC_TEST_RANDOM_H_
 #define WEBRTC_TEST_RANDOM_H_
 
+#include <limits>
+
 #include "webrtc/typedefs.h"
 #include "webrtc/base/constructormagic.h"
 
@@ -25,8 +27,26 @@ class Random {
   // Return pseudo-random number in the interval [0.0, 1.0).
   float Rand();
 
-  // Return pseudo-random number mapped to the interval [low, high].
-  int Rand(int low, int high);
+  template <typename T>
+  T Rand() {

[the sun, 2015/10/22 12:30:38]

This is very pretty!

Why are some functions called Rand() and some Uniform()?

Should the float version also be a template specialization or is that just
adding cumbersome syntax?

[terelius, 2015/10/26 18:18:41]

I considered both ideas, but couldn't make up my mind. :)

My (weak) argument for doing it this way was that the functions which takes a
distribution parameter should be named after that distribution, e.g Uniform. I
kept Rand in analogy with the C rand() function when you want a random element
but haven't explicitly specified a distribution.

I don't have any strong opinions. What would you prefer?

[the sun, 2015/10/27 09:03:12]

Ok, I understand your argument. I think we should stick to Rand() though (leave
Gaussian and Exponential as they are), but rename the Uniform() functions. I
don't have super solid reasons either:

1. The distribution is a property of the implementation and doesn't differ
between the Rand() and Uniform() functions.
2. The different naming will likely cause more confusion than it is helping. I
imagine users commonly will look for a function to return a PRN within a range,
of a certain type and so, rather than a certain distribution.

Also, leave the float impl as it is now.

[terelius, 2015/10/29 12:54:04]

But isn't it a bit weird (and error prone) to overload Rand such that it
computes something completely differently when called with a parameter compared
to no parameter?

For example:
int i = prng.Rand(99) // Works. Sets i to a random number in [0,99].
int i = prng.Rand()   // Compiles and runs without errors, but i=0.

+    static_assert(std::numeric_limits<T>::is_integer &&
+                      std::numeric_limits<T>::radix == 2 &&
+                      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>(Uniform(std::numeric_limits<uint32_t>::max()));
+  }
+
+  template <bool>
+  bool Rand() {
+    return Uniform(0, 1) == 1;
+  }
+
+  // Uniformly distributed pseudo-random number in the interval [0, t].
+  uint32_t Uniform(uint32_t t);
+
+  // Uniformly distributed pseudo-random number in the interval [low, high].
+  uint32_t Uniform(uint32_t low, uint32_t high);
 
   // Normal Distribution.
   int Gaussian(int mean, int standard_deviation);