///////////////////////////////////////////////////////////////////////////////

// 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();