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test/single_producer_sequencer_tests.cpp

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+///////////////////////////////////////////////////////////////////////////////
+// Copyright (c) Lewis Baker
+// Licenced under MIT license. See LICENSE.txt for details.
+///////////////////////////////////////////////////////////////////////////////
+
+#include <cppcoro/single_producer_sequencer.hpp>
+
+#include <cppcoro/config.hpp>
+#include <cppcoro/sequence_barrier.hpp>
+#include <cppcoro/sequence_traits.hpp>
+#include <cppcoro/on_scope_exit.hpp>
+#include <cppcoro/sync_wait.hpp>
+#include <cppcoro/when_all.hpp>
+#include <cppcoro/task.hpp>
+#include <cppcoro/static_thread_pool.hpp>
+
+#include <thread>
+
+#include <ostream>
+#include "doctest/cppcoro_doctest.h"
+
+DOCTEST_TEST_SUITE_BEGIN("single_producer_sequencer");
+
+using namespace cppcoro;
+
+DOCTEST_TEST_CASE("multi-threaded usage single consumer")
+{
+	static_thread_pool tp{ 2 };
+
+	constexpr std::size_t bufferSize = 256;
+
+	sequence_barrier<std::size_t> readBarrier;
+	single_producer_sequencer<std::size_t> sequencer(readBarrier, bufferSize);
+
+	constexpr std::size_t iterationCount = 1'000'000;
+
+	std::uint64_t buffer[bufferSize];
+
+	auto[result, dummy] = sync_wait(when_all(
+		[&]() -> task<std::uint64_t>
+	{
+		// Consumer
+		std::uint64_t sum = 0;
+
+		bool reachedEnd = false;
+		std::size_t nextToRead = 0;
+		do
+		{
+			const std::size_t available = co_await sequencer.wait_until_published(nextToRead, tp);
+			do
+			{
+				sum += buffer[nextToRead % bufferSize];
+			} while (nextToRead++ != available);
+
+			// Zero value is sentinel that indicates the end of the stream.
+			reachedEnd = buffer[available % bufferSize] == 0;
+
+			// Notify that we've finished processing up to 'available'.
+			readBarrier.publish(available);
+		} while (!reachedEnd);
+
+		co_return sum;
+	}(),
+		[&]() -> task<>
+	{
+		// Producer
+		constexpr std::size_t maxBatchSize = 10;
+
+		std::size_t i = 0;
+		while (i < iterationCount)
+		{
+			const std::size_t batchSize = std::min(maxBatchSize, iterationCount - i);
+			auto sequences = co_await sequencer.claim_up_to(batchSize, tp);
+			for (auto seq : sequences)
+			{
+				buffer[seq % bufferSize] = ++i;
+			}
+			sequencer.publish(sequences.back());
+		}
+
+		auto finalSeq = co_await sequencer.claim_one(tp);
+		buffer[finalSeq % bufferSize] = 0;
+		sequencer.publish(finalSeq);
+	}()));
+
+	// Suppress unused variable warning.
+	(void)dummy;
+
+	constexpr std::uint64_t expectedResult =
+		std::uint64_t(iterationCount) * std::uint64_t(iterationCount + 1) / 2;
+
+	CHECK(result == expectedResult);
+}
+
+DOCTEST_TEST_SUITE_END();