Add function to fill a buffer with random bytes (open-telemetry#87)

sdk/src/common/random.cc

@@ -1,6 +1,9 @@
 #include "src/common/random.h"
 #include "src/common/platform/fork.h"
 
+#include <cstring>
+#include <random>
+
 OPENTELEMETRY_BEGIN_NAMESPACE
 namespace sdk
 {
@@ -40,11 +43,34 @@ class TlsRandomNumberGenerator
 thread_local FastRandomNumberGenerator TlsRandomNumberGenerator::engine_{};
 }  // namespace
 
-FastRandomNumberGenerator &GetRandomNumberGenerator() noexcept
+FastRandomNumberGenerator &Random::GetRandomNumberGenerator() noexcept
 {
   static thread_local TlsRandomNumberGenerator random_number_generator{};
   return TlsRandomNumberGenerator::engine();
 }
+
+uint64_t Random::GenerateRandom64() noexcept
+{
+  return GetRandomNumberGenerator()();
+}
+
+void Random::GenerateRandomBuffer(opentelemetry::nostd::span<uint8_t> buffer) noexcept
+{
+  auto buf_size = buffer.size();
+
+  for (size_t i = 0; i < buf_size; i += sizeof(uint64_t))
+  {
+    uint64_t value = GenerateRandom64();
+    if (i + sizeof(uint64_t) <= buf_size)
+    {
+      memcpy(&buffer[i], &value, sizeof(uint64_t));
+    }
+    else
+    {
+      memcpy(&buffer[i], &value, buf_size - i);
+    }
+  }
+}
 }  // namespace common
 }  // namespace sdk
 OPENTELEMETRY_END_NAMESPACE

sdk/src/common/random.h

@@ -1,7 +1,6 @@
 #pragma once
 
-#include <random>
-
+#include "opentelemetry/nostd/span.h"
 #include "opentelemetry/version.h"
 #include "src/common/fast_random_number_generator.h"
 
@@ -11,9 +10,29 @@ namespace sdk
 namespace common
 {
 /**
- * @return a seeded thread-local random number generator.
+ * Utility methods for creating random data, based on a seeded thread-local
+ * number generator.
  */
-FastRandomNumberGenerator &GetRandomNumberGenerator() noexcept;
+class Random
+{
+public:
+  /**
+   * @return an unsigned 64 bit random number
+   */
+  static uint64_t GenerateRandom64() noexcept;
+  /**
+   * Fill the passed span with random bytes.
+   *
+   * @param buffer A span of bytes.
+   */
+  static void GenerateRandomBuffer(opentelemetry::nostd::span<uint8_t> buffer) noexcept;
+
+private:
+  /**
+   * @return a seeded thread-local random number generator.
+   */
+  static FastRandomNumberGenerator &GetRandomNumberGenerator() noexcept;
+};
 }  // namespace common
 }  // namespace sdk
 OPENTELEMETRY_END_NAMESPACE

sdk/test/common/fast_random_number_generator_test.cc

@@ -1,6 +1,9 @@
 #include "src/common/random.h"
 
+#include <random>
+
 #include <gtest/gtest.h>
+
 using opentelemetry::sdk::common::FastRandomNumberGenerator;
 
 TEST(FastRandomNumberGeneratorTest, GenerateUniqueNumbers)

sdk/test/common/random_benchmark.cc

@@ -1,18 +1,19 @@
 #include "src/common/random.h"
 
-#include <benchmark/benchmark.h>
 #include <cstdint>
+#include <random>
+
+#include <benchmark/benchmark.h>
 
 namespace
 {
-using opentelemetry::sdk::common::GetRandomNumberGenerator;
+using opentelemetry::sdk::common::Random;
 
 void BM_RandomIdGeneration(benchmark::State &state)
 {
-  auto &generator = GetRandomNumberGenerator();
   while (state.KeepRunning())
   {
-    benchmark::DoNotOptimize(generator());
+    benchmark::DoNotOptimize(Random::GenerateRandom64());
   }
 }
 BENCHMARK(BM_RandomIdGeneration);

sdk/test/common/random_fork_test.cc

@@ -11,14 +11,12 @@
 #  include <cstdio>
 #  include <cstdlib>
 #  include <iostream>
-using opentelemetry::sdk::common::GetRandomNumberGenerator;
+using opentelemetry::sdk::common::Random;
 
 static uint64_t *child_id;
 
 int main()
 {
-  auto &random_number_generator = GetRandomNumberGenerator();
-
   // Set up shared memory to communicate between parent and child processes.
   //
   // See https://stackoverflow.com/a/13274800/4447365
@@ -27,13 +25,13 @@ int main()
   *child_id = 0;
   if (fork() == 0)
   {
-    *child_id = random_number_generator();
+    *child_id = Random::GenerateRandom64();
     exit(EXIT_SUCCESS);
   }
   else
   {
     wait(nullptr);
-    auto parent_id     = random_number_generator();
+    auto parent_id     = Random::GenerateRandom64();
     auto child_id_copy = *child_id;
     munmap(static_cast<void *>(child_id), sizeof(*child_id));
     if (parent_id == child_id_copy)

sdk/test/common/random_test.cc

@@ -1,10 +1,32 @@
 #include "src/common/random.h"
 
+#include <algorithm>
+#include <iterator>
+
 #include <gtest/gtest.h>
-using opentelemetry::sdk::common::GetRandomNumberGenerator;
+using opentelemetry::sdk::common::Random;
+
+TEST(RandomTest, GenerateRandom64)
+{
+  EXPECT_NE(Random::GenerateRandom64(), Random::GenerateRandom64());
+}
 
-TEST(RandomTest, GenerateRandomNumbers)
+TEST(RandomTest, GenerateRandomBuffer)
 {
-  auto &random_number_generator = GetRandomNumberGenerator();
-  EXPECT_NE(random_number_generator(), random_number_generator());
+  uint8_t buf1[8] = {0};
+  uint8_t buf2[8] = {0};
+  Random::GenerateRandomBuffer(buf1);
+  Random::GenerateRandomBuffer(buf2);
+  EXPECT_FALSE(std::equal(std::begin(buf1), std::end(buf1), std::begin(buf2)));
+
+  // Edge cases.
+  for (auto size : {1, 7, 8, 9, 16, 17})
+  {
+    std::vector<uint8_t> buf1(size);
+    std::vector<uint8_t> buf2(size);
+
+    Random::GenerateRandomBuffer(buf1);
+    Random::GenerateRandomBuffer(buf2);
+    EXPECT_FALSE(std::equal(std::begin(buf1), std::end(buf1), std::begin(buf2)));
+  }
 }