阿杜Blogger: 一种高效异步IO机制

一种高效异步IO机制

-- windows

# 背景描述

在此，简单总结一种高效的异步IO机制，话说也是在windows平台上最为高效的（没有之一）。很久之前就一直有这么一个总结的想法，可惜有时不够自信总觉得总结不到位或存在纰漏，甚至有些错误的理解吧，所以常常就搁下，放弃总结机会了。此时想法不然…即使错误理解了，那也尽快让错误更正了吧。

开始总结吧，即完成通知异步IO机制，简称IOCP。

还有一种同步非堵塞IO机制，重叠IO机制。

# 示例说明

结合Win32-API，以简单的伪代码形式描述该异步IO机制，如下：

struct asyn_io_operation
{
     WSAOVERLAPPED overlapped;
     ...
     handle_io_operation(); // do callback function when io-operation completed.
     ...
};

class more_asyn_io_operation : public asyn_io_operation
{
     ...
};

init()
{
     ...
     iocp_handle = CreateIoCompletionPort(...);
     ...
}

uninit()
{
     CloseHandle(iocp_handle);
}

post_io_handle()
{
     ...
     iocp_handle = PostQueuedCompletionStatus(iocp_handle,...);
     ...
}

commit_io_handle()
{
     ...
     asyn_io_operation* io_op_ptr = new more_asyn_io_operation(...);
     tcp_sock = socket(...);
     udp_sock = socket(...);
     ...
     WSASend(tcp_sock, ... , &io_op_ptr->overlapped, ...); //e.g 1
     ...
     WSARecv(tcp_sock, ... , &io_op_ptr->overlapped, ...); //e.g 2
     ...
     WSASendTo(tcp_sock, ... , &io_op_ptr->overlapped, ...); //e.g 3
     ...
     WSARecvFrom(tcp_sock, ... , &io_op_ptr->overlapped, ...); //e.g 4
     ...

     file_h = CreateFile(...);
     ...
     ReadFile(file_h, ... , &io_op_ptr->overlapped, ...); //e.g 5
     ...
     WriteFile(file_h, ... , &io_op_ptr->overlapped, ...); //e.g 6
     ...
}

main_thread_do()
{
     ...
     while (true)
     {
          ...
          LPWSAOVERLAPPED lpOverlapped;
          get_res = GetQueuedCompletionStatus(iocp_handle, ..., lpOverlapped, ...);
          asyn_io_operation* io_op_ptr = change_asyn_io_operation(lpOverlapped);
          io_op_ptr->handle_io_operation();
          ...
          delete io_op_ptr;
          ...
          if (is_exit)
               break;
     }
     ...
}

other_thread_do()
{
     ...
     commit_io_handle();
     ...
}

（... 待续 ...)

# 涉及Win32-API

http://msdn.microsoft.com/en-us/library/windows/desktop/ms741394(v=vs.85).aspx

typedef struct _WSAOVERLAPPED {

ULONG_PTR Internal;

ULONG_PTR InternalHigh;

union {

struct {

DWORD Offset;

DWORD OffsetHigh;

};

PVOID Pointer;

};

HANDLE hEvent;

} WSAOVERLAPPED,

*LPWSAOVERLAPPED;

HANDLE WINAPI CreateIoCompletionPort(

__in HANDLE FileHandle,

__in HANDLE ExistingCompletionPort,

__in ULONG_PTR CompletionKey,

__in DWORD NumberOfConcurrentThreads

);

BOOL WINAPI GetQueuedCompletionStatus(

__in HANDLE CompletionPort,

__out LPDWORD lpNumberOfBytes,

__out PULONG_PTR lpCompletionKey,

__out LPOVERLAPPED* lpOverlapped,

__in DWORD dwMilliseconds

);

BOOL WINAPI GetQueuedCompletionStatusEx(

__in HANDLE CompletionPort,

__out LPOVERLAPPED_ENTRY lpCompletionPortEntries,

__in ULONG ulCount,

__out PULONG ulNumEntriesRemoved,

__in DWORD dwMilliseconds,

__in BOOL fAlertable

);

BOOL WINAPI PostQueuedCompletionStatus(

__in HANDLE CompletionPort,

__in DWORD dwNumberOfBytesTransferred,

__in ULONG_PTR dwCompletionKey,

__in LPOVERLAPPED lpOverlapped

);

BOOL WSAAPI WSAGetOverlappedResult(

__in SOCKET s,

__in LPWSAOVERLAPPED lpOverlapped,

__out LPDWORD lpcbTransfer,

__in BOOL fWait,

__out LPDWORD lpdwFlags

);

SOCKET WSAAPI socket(

__in int af,

__in int type,

__in int protocol

);

SOCKET WSASocket(

__in int af,

__in int type,

__in int protocol,

__in LPWSAPROTOCOL_INFO lpProtocolInfo,

__in GROUP g,

__in DWORD dwFlags

);

int WSAIoctl(

__in SOCKET s,

__in DWORD dwIoControlCode,

__in LPVOID lpvInBuffer,

__in DWORD cbInBuffer,

__out LPVOID lpvOutBuffer,

__in DWORD cbOutBuffer,

__out LPDWORD lpcbBytesReturned,

__in LPWSAOVERLAPPED lpOverlapped,

__in LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine

);

int WSASend(

__in SOCKET s,

__in LPWSABUF lpBuffers,

__in DWORD dwBufferCount,

__out LPDWORD lpNumberOfBytesSent,

__in DWORD dwFlags,

__in LPWSAOVERLAPPED lpOverlapped,

__in LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine

);

int WSASend(

__in SOCKET s,

__in LPWSABUF lpBuffers,

__in DWORD dwBufferCount,

__out LPDWORD lpNumberOfBytesSent,

__in DWORD dwFlags,

__in LPWSAOVERLAPPED lpOverlapped,

__in LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine

);

int WSASendTo(

__in SOCKET s,

__in LPWSABUF lpBuffers,

__in DWORD dwBufferCount,

__out LPDWORD lpNumberOfBytesSent,

__in DWORD dwFlags,

__in const struct sockaddr* lpTo,

__in int iToLen,

__in LPWSAOVERLAPPED lpOverlapped,

__in LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine

);

int WSARecvFrom(

__in SOCKET s,

__in_out LPWSABUF lpBuffers,

__in DWORD dwBufferCount,

__out LPDWORD lpNumberOfBytesRecvd,

__in_out LPDWORD lpFlags,

__out struct sockaddr* lpFrom,

__in_out LPINT lpFromlen,

__in LPWSAOVERLAPPED lpOverlapped,

__in LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine

);

BOOL WINAPI ReadFile(

__in HANDLE hFile,

__out LPVOID lpBuffer,

__in DWORD nNumberOfBytesToRead,

__out LPDWORD lpNumberOfBytesRead,

__in LPOVERLAPPED lpOverlapped

);

BOOL WINAPI ReadFileEx(

__in HANDLE hFile,

__out LPVOID lpBuffer,

__in DWORD nNumberOfBytesToRead,

__in LPOVERLAPPED lpOverlapped,

__in LPOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine

);

HANDLE WINAPI CreateFile(

__in LPCTSTR lpFileName,

__in DWORD dwDesiredAccess,

__in DWORD dwShareMode,

__in LPSECURITY_ATTRIBUTES lpSecurityAttributes,

__in DWORD dwCreationDisposition,

__in DWORD dwFlagsAndAttributes,

__in HANDLE hTemplateFile

);

BOOL WINAPI WriteFileEx(

__in HANDLE hFile,

__in LPCVOID lpBuffer,

__in DWORD nNumberOfBytesToWrite,

__in LPOVERLAPPED lpOverlapped,

__in LPOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine

);

BOOL WINAPI WriteFile(

__in HANDLE hFile,

__in LPCVOID lpBuffer,

__in DWORD nNumberOfBytesToWrite,

__out LPDWORD lpNumberOfBytesWritten,

__in LPOVERLAPPED lpOverlapped

);

BOOL WINAPI CancelIo(

__in HANDLE hFile

);

阿杜Blogger

2012年3月30日星期五

一种高效异步IO机制

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