compat/test/latch_test.cpp

// Copyright 2023 Peter Dimov.
// Copyright 2023 Christian Mazakas.
// Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt

#define BOOST_ENABLE_ASSERT_HANDLER

#include <boost/compat/latch.hpp>
#include <boost/core/ignore_unused.hpp>
#include <boost/core/lightweight_test.hpp>

#include <thread>
#include <vector>

struct exception {};

namespace boost {
void assertion_failed(char const *expr, char const *function, char const *file,
                      long line) {
  (void)expr;
  (void)function;
  (void)file;
  (void)line;
  throw exception{};
}
} // namespace boost

namespace {
void test_max() { BOOST_TEST_EQ(boost::compat::latch::max(), PTRDIFF_MAX); }

void test_constructor() {
  {
    auto const f = [] {
      boost::compat::latch l(-1);
      (void)l;
    };
    BOOST_TEST_THROWS(f(), exception);
  }

  {
    std::ptrdiff_t n = 0;

    boost::compat::latch l(n);
    BOOST_TEST(l.try_wait());
  }

  {
    std::ptrdiff_t n = 16;

    boost::compat::latch l(n);
    BOOST_TEST_NOT(l.try_wait());

    l.count_down(16);
    BOOST_TEST(l.try_wait());
  }

  {
    auto const f = [] {
      std::ptrdiff_t n = boost::compat::latch::max();
      boost::compat::latch l(n);
      (void)l;
    };
    BOOST_TEST_NO_THROW(f());
  }
}

void test_count_down_and_wait() {
  constexpr std::ptrdiff_t n = 1024;

  boost::compat::latch l(2 * n);

  bool bs[] = {false, false};

  std::thread t1([&] {
    l.wait();
    BOOST_TEST(bs[0]);
    BOOST_TEST(bs[1]);
  });

  std::thread t2([&] {
    for (int i = 0; i < n; ++i) {
      if (i == (n - 1)) {
        bs[0] = true;
      } else {
        BOOST_TEST_NOT(l.try_wait());
      }

      l.count_down(1);
    }
  });

  for (int i = 0; i < n; ++i) {
    if (i == (n - 1)) {
      bs[1] = true;
    } else {
      BOOST_TEST_NOT(l.try_wait());
    }

    l.count_down(1);
  }

  t1.join();
  t2.join();

  BOOST_TEST(l.try_wait());
}

void test_arrive_and_wait() {
  std::ptrdiff_t const n = 16;

  boost::compat::latch l(2 * n);

  int xs[n] = {0};

  std::vector<std::thread> threads;
  for (int i = 0; i < n; ++i) {
    threads.emplace_back([&l, &xs, i, n] {
      // keep this here because msvc requires a capture but clang calls it
      // redundant
      boost::ignore_unused(n);

      for (int j = 0; j < n; ++j) {
        BOOST_TEST_EQ(xs[j], 0);
      }

      l.arrive_and_wait(2);

      xs[i] = 1;
    });
  }

  for (auto &t : threads) {
    t.join();
  }

  for (int i = 0; i < n; ++i) {
    BOOST_TEST_EQ(xs[i], 1);
  }
}
} // namespace

int main() {
  test_max();
  test_constructor();
  test_count_down_and_wait();
  test_arrive_and_wait();

  return boost::report_errors();
}