[base] Added UniformRandom helper class.

Signed-off-by: Viktor Govako <viktor.govako@gmail.com>

base/CMakeLists.txt

@@ -56,7 +56,6 @@ set(SRC
   observer_list.hpp
   pprof.cpp
   pprof.hpp
-  random.cpp
   random.hpp
   range_iterator.hpp
   ref_counted.hpp

base/random.cpp

@@ -1,21 +0,0 @@
-#include "base/random.hpp"
-
-#include <numeric>
-
-namespace base
-{
-std::vector<size_t> RandomSample(size_t n, size_t k, std::minstd_rand & rng)
-{
-  std::vector<size_t> result(std::min(k, n));
-  std::iota(result.begin(), result.end(), 0);
-
-  for (size_t i = k; i < n; ++i)
-  {
-    size_t const j = rng() % (i + 1);
-    if (j < k)
-      result[j] = i;
-  }
-
-  return result;
-}
-}  // base

base/random.hpp

@@ -1,10 +1,22 @@
 #pragma once
 
+#include <limits>
 #include <random>
-#include <vector>
 
 namespace base
 {
-// Selects a fair random subset of size min(|n|, |k|) from [0, 1, 2, ..., n - 1].
+template <class T> class UniformRandom
-std::vector<size_t> RandomSample(size_t n, size_t k, std::minstd_rand & rng);
+{
-}  // base
+  static_assert(std::is_integral<T>::value);
+
+  std::random_device m_rd;
+  std::mt19937 m_gen;
+  std::uniform_int_distribution<T> m_distr;
+
+public:
+  UniformRandom(T min, T max) : m_gen(m_rd()), m_distr(min, max) {}
+  UniformRandom() : UniformRandom(std::numeric_limits<T>::min(), std::numeric_limits<T>::max()) {}
+
+  T operator()() { return m_distr(m_gen); }
+};
+} // namespace base

platform/platform.cpp

@@ -4,10 +4,10 @@
 
 #include "base/file_name_utils.hpp"
 #include "base/logging.hpp"
+#include "base/random.hpp"
 #include "base/string_utils.hpp"
 
 #include <algorithm>
-#include <random>
 #include <thread>
 
 #include "private.h"
@@ -18,17 +18,15 @@ namespace
 {
 std::string RandomString(size_t length)
 {
+  /// @todo Used for temp file name, so lower-upper case is strange here, no?
   static std::string_view constexpr kCharset =
       "0123456789"
       "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
       "abcdefghijklmnopqrstuvwxyz";
-  std::random_device rd;
+
-  std::mt19937 gen(rd());
+  base::UniformRandom<size_t> rand(0, kCharset.size() - 1);
-  std::uniform_int_distribution<size_t> dis(0, kCharset.size() - 1);
   std::string str(length, 0);
-  std::generate_n(str.begin(), length, [&]() {
+  std::generate_n(str.begin(), length, [&rand]() { return kCharset[rand()]; });
-    return kCharset[dis(gen)];
-  });
   return str;
 }
 

xcode/base/base.xcodeproj/project.pbxproj

@@ -78,9 +78,7 @@
 		3D78157B1F3D89EC0068B6AC /* waiter.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 3D78157A1F3D89EC0068B6AC /* waiter.hpp */; };
 		56290B8A206D0887003892E0 /* lru_cache.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 56290B89206D0887003892E0 /* lru_cache.hpp */; };
 		564BB445206E89ED00BDD211 /* fifo_cache.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 564BB444206E89ED00BDD211 /* fifo_cache.hpp */; };
-		564C197B254AF896007471CE /* optional_lock_guard.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 564C197A254AF895007471CE /* optional_lock_guard.hpp */; };
 		564C197F254AF8AF007471CE /* optional_lock_guard_tests.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 564C197E254AF8AF007471CE /* optional_lock_guard_tests.cpp */; };
-		56B1A0741E69DE4D00395022 /* random.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 56B1A0711E69DE4D00395022 /* random.cpp */; };
 		56B1A0751E69DE4D00395022 /* random.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 56B1A0721E69DE4D00395022 /* random.hpp */; };
 		56B1A0761E69DE4D00395022 /* small_set.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 56B1A0731E69DE4D00395022 /* small_set.hpp */; };
 		670E39441C46C76900E9C0A6 /* sunrise_sunset.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 670E39421C46C76900E9C0A6 /* sunrise_sunset.cpp */; };
@@ -228,9 +226,7 @@
 		56290B8B206D0937003892E0 /* lru_cache_tests.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = lru_cache_tests.cpp; sourceTree = "<group>"; };
 		564BB444206E89ED00BDD211 /* fifo_cache.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = fifo_cache.hpp; sourceTree = "<group>"; };
 		564BB446206E8A4D00BDD211 /* fifo_cache_test.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = fifo_cache_test.cpp; sourceTree = "<group>"; };
-		564C197A254AF895007471CE /* optional_lock_guard.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = optional_lock_guard.hpp; sourceTree = "<group>"; };
 		564C197E254AF8AF007471CE /* optional_lock_guard_tests.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = optional_lock_guard_tests.cpp; sourceTree = "<group>"; };
-		56B1A0711E69DE4D00395022 /* random.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = random.cpp; sourceTree = "<group>"; };
 		56B1A0721E69DE4D00395022 /* random.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = random.hpp; sourceTree = "<group>"; };
 		56B1A0731E69DE4D00395022 /* small_set.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = small_set.hpp; sourceTree = "<group>"; };
 		670E39421C46C76900E9C0A6 /* sunrise_sunset.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = sunrise_sunset.cpp; sourceTree = "<group>"; };
@@ -451,10 +447,8 @@
 				397DC50C22BB8EBF007126DB /* non_intersecting_intervals.hpp */,
 				675341A21A3F57E400A0A8C3 /* normalize_unicode.cpp */,
 				672DD4B71E04255F0078E13C /* observer_list.hpp */,
-				564C197A254AF895007471CE /* optional_lock_guard.hpp */,
 				3917FA5A211E00BA00937DF4 /* pprof.cpp */,
 				3917FA5B211E00BB00937DF4 /* pprof.hpp */,
-				56B1A0711E69DE4D00395022 /* random.cpp */,
 				56B1A0721E69DE4D00395022 /* random.hpp */,
 				672DD4B81E0425600078E13C /* range_iterator.hpp */,
 				672DD4B91E0425600078E13C /* ref_counted.hpp */,
@@ -556,7 +550,6 @@
 				397DC50D22BB8EBF007126DB /* bidirectional_map.hpp in Headers */,
 				3446C6711DDCA96300146687 /* dfa_helpers.hpp in Headers */,
 				6753420C1A3F57E400A0A8C3 /* threaded_list.hpp in Headers */,
-				564C197B254AF896007471CE /* optional_lock_guard.hpp in Headers */,
 				675341DB1A3F57E400A0A8C3 /* exception.hpp in Headers */,
 				6753453E1A3F6F6A00A0A8C3 /* message.hpp in Headers */,
 				39BC0FD01FD057FA00B6C276 /* control_flow.hpp in Headers */,
@@ -747,7 +740,6 @@
 				670E39441C46C76900E9C0A6 /* sunrise_sunset.cpp in Sources */,
 				6753420E1A3F57E400A0A8C3 /* timer.cpp in Sources */,
 				675341F61A3F57E400A0A8C3 /* shared_buffer_manager.cpp in Sources */,
-				56B1A0741E69DE4D00395022 /* random.cpp in Sources */,
 				675341DA1A3F57E400A0A8C3 /* exception.cpp in Sources */,
 				3D74EF111F8B902C0081202C /* suffix_array.cpp in Sources */,
 				3917FA57211E009700937DF4 /* geo_object_id.cpp in Sources */,