Add polyfill implementation of std::latch

test/cfoa/latch_tests.cpp

@@ -0,0 +1,154 @@
+// Copyright (C) 2023 Christian Mazakas
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#define BOOST_ENABLE_ASSERT_HANDLER
+
+#include "latch.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::latch::max(), INT_MAX); }
+
+  void test_constructor()
+  {
+    {
+      auto const f = [] {
+        boost::latch l(-1);
+        (void)l;
+      };
+      BOOST_TEST_THROWS(f(), exception);
+    }
+
+    {
+      std::ptrdiff_t n = 0;
+
+      boost::latch l(n);
+      BOOST_TEST(l.try_wait());
+    }
+
+    {
+      std::ptrdiff_t n = 16;
+
+      boost::latch l(n);
+      BOOST_TEST_NOT(l.try_wait());
+
+      l.count_down(16);
+      BOOST_TEST(l.try_wait());
+    }
+
+#if PTRDIFF_MAX > INT_MAX
+    {
+      auto const f = [] {
+        std::ptrdiff_t n = INT_MAX;
+        n += 10;
+        boost::latch l(n);
+        (void)l;
+      };
+      BOOST_TEST_THROWS(f(), exception);
+    }
+#endif
+  }
+
+  void test_count_down_and_wait()
+  {
+    constexpr std::ptrdiff_t n = 1024;
+
+    boost::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()
+  {
+    constexpr std::ptrdiff_t n = 16;
+
+    boost::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] {
+        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();
+}