From 8d721ccaaa8d19044f97c419da5f7c68dc35805b Mon Sep 17 00:00:00 2001
From: Erki <erki.meinberg@gmail.com>
Date: Fri, 30 Apr 2021 18:31:24 +0300
Subject: [PATCH] Add Utility/Rand module

---
 Tests/CMakeLists.txt         |  3 +-
 Tests/rand.cpp               | 62 ++++++++++++++++++++++++++++++++++++
 Utility/CMakeLists.txt       |  1 +
 Utility/Inc/utility_rand.hpp | 40 +++++++++++++++++++++++
 Utility/Src/utility_rand.cpp | 27 ++++++++++++++++
 5 files changed, 132 insertions(+), 1 deletion(-)
 create mode 100644 Tests/rand.cpp
 create mode 100644 Utility/Inc/utility_rand.hpp
 create mode 100644 Utility/Src/utility_rand.cpp

diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index 1a472f1..7a2c9f2 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -14,7 +14,8 @@ add_executable(tests
     ringbuffer.cpp
     packet.cpp
     parser.cpp
-    button.cpp)
+    button.cpp
+    rand.cpp)
 
 target_link_libraries(tests
     PUBLIC
diff --git a/Tests/rand.cpp b/Tests/rand.cpp
new file mode 100644
index 0000000..b73bd1d
--- /dev/null
+++ b/Tests/rand.cpp
@@ -0,0 +1,62 @@
+//
+// Created by erki on 29.04.21.
+//
+
+#include <catch2/catch.hpp>
+
+#include "utility_rand.hpp"
+
+TEST_CASE("rand32 is deterministic.", "[utility],[rand]")
+{
+  const std::uint32_t original_state = 34;
+  std::uint32_t state = original_state;
+  std::vector<std::uint32_t> generated;
+
+  for (int i = 0; i < 10; i++)
+  {
+    generated.push_back(Peripherals::rand32(state));
+  }
+
+  std::uint32_t new_state = original_state;
+  for (int i = 0; i < 10; i++)
+  {
+    REQUIRE(generated[i] == Peripherals::rand32(new_state));
+  }
+}
+
+TEST_CASE("rand64 is deterministic.", "[utility],[rand]")
+{
+  const std::uint64_t original_state = 10e4;
+  std::uint64_t state = original_state;
+  std::vector<std::uint64_t> generated;
+
+  for (int i = 0; i < 10; i++)
+  {
+    generated.push_back(Peripherals::rand64(state));
+  }
+
+  std::uint64_t new_state = original_state;
+  for (int i = 0; i < 10; i++)
+  {
+    REQUIRE(generated[i] == Peripherals::rand64(new_state));
+  }
+}
+
+TEST_CASE("rand and srand are deterministic", "[utility],[rand]")
+{
+  const std::uint32_t original_state = 34;
+
+  Peripherals::srand(original_state);
+  std::vector<std::uint32_t> generated;
+
+  for (int i = 0; i < 10; i++)
+  {
+    generated.push_back(Peripherals::rand());
+  }
+
+  Peripherals::srand(original_state);
+  for (int i = 0; i < 10; i++)
+  {
+    REQUIRE(generated[i] == Peripherals::rand());
+  }
+}
diff --git a/Utility/CMakeLists.txt b/Utility/CMakeLists.txt
index 0ff13a7..34b11ff 100644
--- a/Utility/CMakeLists.txt
+++ b/Utility/CMakeLists.txt
@@ -7,6 +7,7 @@ cmake_minimum_required(VERSION 3.8 FATAL_ERROR)
 
 add_library(utility STATIC
         Src/utility_logging.cpp
+        Src/utility_rand.cpp
         ${additional_sources}
 )
 
diff --git a/Utility/Inc/utility_rand.hpp b/Utility/Inc/utility_rand.hpp
new file mode 100644
index 0000000..4ed0c9a
--- /dev/null
+++ b/Utility/Inc/utility_rand.hpp
@@ -0,0 +1,40 @@
+//
+// Created by erki on 29.04.21.
+//
+
+#ifndef SKULLC_UTILITY_RAND_HPP
+#define SKULLC_UTILITY_RAND_HPP
+
+#include <cstdint>
+
+namespace Peripherals
+{
+
+inline std::uint32_t rand32(std::uint32_t& state)
+{
+  std::uint32_t x = state;
+  x ^= x << 13;
+  x ^= x >> 17;
+  x ^= x << 5;
+  state = x;
+
+  return state;
+}
+
+inline std::uint64_t rand64(std::uint64_t& state)
+{
+  std::uint64_t x = state;
+  x ^= x << 13;
+  x ^= x >> 7;
+  x ^= x << 17;
+  state = x;
+
+  return state;
+}
+
+void srand(const std::uint32_t& seed);
+std::uint32_t rand();
+
+}
+
+#endif //SKULLC_UTILITY_RAND_HPP
diff --git a/Utility/Src/utility_rand.cpp b/Utility/Src/utility_rand.cpp
new file mode 100644
index 0000000..2de4713
--- /dev/null
+++ b/Utility/Src/utility_rand.cpp
@@ -0,0 +1,27 @@
+//
+// Created by erki on 29.04.21.
+//
+
+#include "utility_rand.hpp"
+
+namespace
+{
+
+std::uint32_t rand_state = 0;
+
+}
+
+namespace Peripherals
+{
+
+void srand(const std::uint32_t& seed)
+{
+  rand_state = seed;
+}
+
+std::uint32_t rand()
+{
+  return rand32(rand_state);
+}
+
+}