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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
#include <zencore/zencore.h>
#include <zencore/thread.h>
#if ZEN_PLATFORM_WINDOWS
# include <zencore/windows.h>
# include <memory>
# include <system_error>
namespace zen {
/**
* @brief Abstract base class for I/O thread pools used by the http.sys server.
*
* Two implementations are available:
* - WinTpIoThreadPool: Uses the Windows Thread Pool API (default, current behavior)
* - ExplicitIoThreadPool: Uses raw IOCP + std::thread with load-based scaling
*/
class WinIoThreadPool
{
public:
virtual ~WinIoThreadPool() = default;
/**
* @brief Bind an I/O handle to this pool with the given callback
*/
virtual void CreateIocp(HANDLE IoHandle, PTP_WIN32_IO_CALLBACK Callback, void* Context, std::error_code& ErrorCode) = 0;
/**
* @brief Called before issuing an async I/O operation.
* The Windows TP implementation calls StartThreadpoolIo; the explicit implementation is a no-op.
*/
virtual void StartIo() = 0;
/**
* @brief Called when an async I/O operation fails synchronously (to undo StartIo).
* The Windows TP implementation calls CancelThreadpoolIo; the explicit implementation is a no-op.
*/
virtual void CancelIo() = 0;
/**
* @brief Factory method to create an I/O thread pool
* @param UseExplicitThreads If true, creates an ExplicitIoThreadPool; otherwise creates a WinTpIoThreadPool
* @param MinThreads Minimum number of threads
* @param MaxThreads Maximum number of threads
*/
static std::unique_ptr<WinIoThreadPool> Create(bool UseExplicitThreads, int MinThreads, int MaxThreads);
};
/**
* @brief Windows Thread Pool implementation (wraps CreateThreadpool/CreateThreadpoolIo)
*/
class WinTpIoThreadPool : public WinIoThreadPool
{
public:
WinTpIoThreadPool(int InThreadCount, int InMaxThreadCount);
~WinTpIoThreadPool();
virtual void CreateIocp(HANDLE IoHandle, PTP_WIN32_IO_CALLBACK Callback, void* Context, std::error_code& ErrorCode) override;
virtual void StartIo() override;
virtual void CancelIo() override;
private:
PTP_POOL m_ThreadPool = nullptr;
PTP_CLEANUP_GROUP m_CleanupGroup = nullptr;
PTP_IO m_ThreadPoolIo = nullptr;
TP_CALLBACK_ENVIRON m_CallbackEnvironment;
};
/**
* @brief Explicit IOCP + std::thread implementation with load-based thread scaling
*
* Creates a raw I/O completion port and manages worker threads directly. Threads
* scale up when all are busy servicing completions, and scale down when idle for
* an extended period.
*/
class ExplicitIoThreadPool : public WinIoThreadPool
{
public:
ExplicitIoThreadPool(int InMinThreadCount, int InMaxThreadCount);
~ExplicitIoThreadPool();
virtual void CreateIocp(HANDLE IoHandle, PTP_WIN32_IO_CALLBACK Callback, void* Context, std::error_code& ErrorCode) override;
virtual void StartIo() override;
virtual void CancelIo() override;
private:
void WorkerThreadMain();
void SpawnWorkerThread();
HANDLE m_Iocp = nullptr;
PTP_WIN32_IO_CALLBACK m_Callback = nullptr;
void* m_Context = nullptr;
int m_MinThreads;
int m_MaxThreads;
std::atomic<int> m_TotalThreads{0};
std::atomic<int> m_ActiveCount{0};
std::atomic<bool> m_ShuttingDown{false};
RwLock m_ThreadListLock;
std::vector<std::thread> m_Threads;
};
} // namespace zen
#endif
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