Win32多线程异步IO之文件读取

/*
 * File: main.cpp
 * Author: Administrator
 *
 * Created on 2013年10月6日, 下午3:14
 */

#include <cstdlib>
#include <windows.h>
#include <iostream>

using namespace std;

///< 暂时不管 -> ReadFileEx
VOID CALLBACK FileIOCompletionRoutine(
        DWORD dwErrorCode,
        DWORD dwNumberOfBytesTransfered,
        LPOVERLAPPED lpOverlapped
)
{

}

DWORD ReadSomething(LPCTSTR lpFileName, LPVOID lpBuffer, DWORD nNumberOfBytesToRead)
{
    BOOL rc;
    HANDLE file; ///< typedef void * HANDLE;
    DWORD numread;
    OVERLAPPED overlap;

    ///< openg file 具体参数见 http://msdn.microsoft.com
    file = CreateFile(lpFileName,
            GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,
            NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
    if (INVALID_HANDLE_VALUE == file)
    {
        return -1;
    }

    ///< initial overlapped
    memset(&overlap, 0, sizeof(overlap));
    overlap.Offset = 0;

    ///< read data
    rc = ReadFile(file, (char *)lpBuffer, nNumberOfBytesToRead, &numread, &overlap);
    if (true == rc) ///< success
    {
        return numread;
    }
    else
    {
        ///< 是否在排队
        if (GetLastError() == ERROR_IO_PENDING)
        {
            ///< awhile...
            //WaitForSingleObject(file, INFINITE);
            if ((rc = GetOverlappedResult(file, &overlap, &numread, FALSE)))
            {
                 return  numread;
            }
            else
            {
                if (GetLastError() == ERROR_IO_INCOMPLETE)
                {
                    ///< not ok.
                    return -1;
                }
            }
        }
        else
        {
            ///< something wrong.
            return -2;
        }
    }
    CloseHandle(file);

    return 0;
}

/*
 *
 */
int main(int argc, char** argv)
{
    //cout << "just yeah!" << endl;
    //Beep(1000,500);
    //Sleep(1000);
    char buf[512] = {0};
    DWORD numread = ReadSomething("E:\\NetBeansProjects\\CppApplication_1\\dist\\Debug\\MinGW-Windows\\ddd.txt",
            buf, 10);
    cout << "counts: " << numread << "  content: " << buf << endl;
    //MessageBox(NULL,"示例用法","ddd", MB_OK);
    return 0;
}