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// Copyright 2020 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once
#include <atomic>
#include <functional>
#include <memory>
#include <thread>
#include <utility>
#include <variant>
#include <vector>
#include "Common/Assert.h"
#include "Common/Event.h"
#include "Common/Result.h"
namespace DiscIO
{
enum class ConversionResultCode
{
Success,
Canceled,
ReadFailed,
WriteFailed,
InternalError,
};
template <typename T>
using ConversionResult = Common::Result<ConversionResultCode, T>;
// This class starts a number of compression threads and one output thread.
// The set_up_compress_thread_state function is called at the start of each compression thread.
// When CompressAndWrite is called, the compress function will be called on one of the
// compression threads, and then the output function will be called on the output thread.
// The output thread handles data in the order that data was submitted using CompressAndWrite,
// but the compression threads are not guaranteed to handle data in a predictable order.
// Remember to check GetStatus regularly and cancel if it doesn't return Success,
// and call Shutdown when you want to ensure that everything finishes.
template <typename CompressThreadState, typename CompressParameters, typename OutputParameters>
class MultithreadedCompressor
{
public:
MultithreadedCompressor(
std::function<ConversionResultCode(CompressThreadState*)> set_up_compress_thread_state,
std::function<ConversionResult<OutputParameters>(CompressThreadState*, CompressParameters)>
compress,
std::function<ConversionResultCode(OutputParameters)> output)
: m_set_up_compress_thread_state(std::move(set_up_compress_thread_state)),
m_compress(std::move(compress)), m_output(std::move(output)),
m_threads(std::max<unsigned int>(1, std::thread::hardware_concurrency()))
{
m_compress_threads = std::make_unique<CompressThread[]>(m_threads);
for (size_t i = 0; i < m_threads; ++i)
{
m_compress_threads[i].thread =
std::thread(std::mem_fn(&MultithreadedCompressor::CompressThreadFunction), this,
&m_compress_threads[i]);
}
m_output_thread =
std::thread(std::mem_fn(&MultithreadedCompressor::OutputThreadFunction), this);
}
~MultithreadedCompressor()
{
if (!m_shutting_down.load())
Shutdown();
}
void CompressAndWrite(CompressParameters parameters)
{
if (GetStatus() != ConversionResultCode::Success)
return;
CompressThread& compress_thread = m_compress_threads[m_current_index];
compress_thread.compress_ready_event.Wait();
compress_thread.compress_parameters = std::move(parameters);
compress_thread.compress_event.Set();
++m_current_index;
if (m_current_index >= m_threads)
m_current_index -= m_threads;
}
void SetError(ConversionResultCode result)
{
ASSERT(result != ConversionResultCode::Success);
// If we already have an error, don't overwrite it
ConversionResultCode expected = ConversionResultCode::Success;
m_result.compare_exchange_strong(expected, result);
}
ConversionResultCode GetStatus() const { return m_result.load(); }
void Shutdown()
{
for (size_t i = 0; i < m_threads; ++i)
m_compress_threads[i].compress_ready_event.Wait();
for (size_t i = 0; i < m_threads; ++i)
m_compress_threads[i].compress_done_event.Wait();
for (size_t i = 0; i < m_threads; ++i)
m_compress_threads[i].output_ready_event.Wait();
m_shutting_down.store(true);
for (size_t i = 0; i < m_threads; ++i)
m_compress_threads[i].compress_event.Set();
for (size_t i = 0; i < m_threads; ++i)
m_compress_threads[i].output_event.Set();
for (size_t i = 0; i < m_threads; ++i)
m_compress_threads[i].thread.join();
m_output_thread.join();
}
private:
struct CompressThread
{
std::thread thread;
Common::Event compress_ready_event;
Common::Event compress_event;
Common::Event compress_done_event;
Common::Event output_ready_event;
Common::Event output_event;
CompressParameters compress_parameters;
OutputParameters output_parameters;
};
void CompressThreadFunction(CompressThread* state)
{
CompressThreadState compress_thread_state;
ConversionResultCode setup_result = m_set_up_compress_thread_state(&compress_thread_state);
if (setup_result != ConversionResultCode::Success)
SetError(setup_result);
state->compress_ready_event.Set();
state->compress_done_event.Set();
while (true)
{
state->compress_event.Wait();
if (m_shutting_down.load())
return;
CompressParameters parameters = std::move(state->compress_parameters);
state->compress_done_event.Reset();
state->compress_ready_event.Set();
ConversionResult<OutputParameters> result =
m_compress(&compress_thread_state, std::move(parameters));
if (result)
{
state->output_ready_event.Wait();
state->output_parameters = std::move(*result);
state->output_event.Set();
}
else
{
SetError(result.Error());
}
state->compress_done_event.Set();
}
}
void OutputThreadFunction()
{
for (size_t i = 0; i < m_threads; ++i)
m_compress_threads[i].output_ready_event.Set();
size_t index = 0;
while (true)
{
CompressThread& compress_thread = m_compress_threads[index];
compress_thread.output_event.Wait();
if (m_shutting_down.load())
return;
OutputParameters parameters = std::move(compress_thread.output_parameters);
compress_thread.output_ready_event.Set();
const ConversionResultCode result = m_output(std::move(parameters));
if (result != ConversionResultCode::Success)
SetError(result);
++index;
if (index >= m_threads)
index -= m_threads;
}
}
std::function<ConversionResultCode(CompressThreadState*)> m_set_up_compress_thread_state;
std::function<ConversionResult<OutputParameters>(CompressThreadState*, CompressParameters)>
m_compress;
std::function<ConversionResultCode(OutputParameters)> m_output;
// We can't use std::vector for this, because Common::Event is not movable
std::unique_ptr<CompressThread[]> m_compress_threads;
std::thread m_output_thread;
const size_t m_threads;
size_t m_current_index = 0;
std::atomic<ConversionResultCode> m_result = ConversionResultCode::Success;
std::atomic<bool> m_shutting_down = false;
};
} // namespace DiscIO
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