ceph/src/jaegertracing/opentelemetry-cpp/sdk/src/common/random.cc

   1
   2 // Copyright The OpenTelemetry Authors
   3 // SPDX-License-Identifier: Apache-2.0
   4
   5 #include "src/common/random.h"
   6 #include "src/common/platform/fork.h"
   7
   8 #include <cstring>
   9 #include <random>
  10
  11 OPENTELEMETRY_BEGIN_NAMESPACE
  12 namespace sdk
  13 {
  14 namespace common
  15 {
  16 // Wraps a thread_local random number generator, but adds a fork handler so that
  17 // the generator will be correctly seeded after forking.
  18 //
  19 // See https://stackoverflow.com/q/51882689/4447365 and
  20 //     https://github.com/opentracing-contrib/nginx-opentracing/issues/52
  21 namespace
  22 {
  23 class TlsRandomNumberGenerator
  24 {
  25 public:
  26   TlsRandomNumberGenerator() noexcept
  27   {
  28     Seed();
  29     platform::AtFork(nullptr, nullptr, OnFork);
  30   }
  31
  32   static FastRandomNumberGenerator &engine() noexcept { return engine_; }
  33
  34 private:
  35   static thread_local FastRandomNumberGenerator engine_;
  36
  37   static void OnFork() noexcept { Seed(); }
  38
  39   static void Seed() noexcept
  40   {
  41     std::random_device random_device;
  42     std::seed_seq seed_seq{random_device(), random_device(), random_device(), random_device()};
  43     engine_.seed(seed_seq);
  44   }
  45 };
  46
  47 thread_local FastRandomNumberGenerator TlsRandomNumberGenerator::engine_{};
  48 }  // namespace
  49
  50 FastRandomNumberGenerator &Random::GetRandomNumberGenerator() noexcept
  51 {
  52   static thread_local TlsRandomNumberGenerator random_number_generator{};
  53   return TlsRandomNumberGenerator::engine();
  54 }
  55
  56 uint64_t Random::GenerateRandom64() noexcept
  57 {
  58   return GetRandomNumberGenerator()();
  59 }
  60
  61 void Random::GenerateRandomBuffer(opentelemetry::nostd::span<uint8_t> buffer) noexcept
  62 {
  63   auto buf_size = buffer.size();
  64
  65   for (size_t i = 0; i < buf_size; i += sizeof(uint64_t))
  66   {
  67     uint64_t value = GenerateRandom64();
  68     if (i + sizeof(uint64_t) <= buf_size)
  69     {
  70       memcpy(&buffer[i], &value, sizeof(uint64_t));
  71     }
  72     else
  73     {
  74       memcpy(&buffer[i], &value, buf_size - i);
  75     }
  76   }
  77 }
  78 }  // namespace common
  79 }  // namespace sdk
  80 OPENTELEMETRY_END_NAMESPACE