c++ - 对 ReadFile 函数的异步调用返回 6 错误代码

Question

为了异步读取文件，我写了下面的 C++ 代码:

#define BUF_SIZE 1024
HANDLE hFile;
DWORD NumberOfBytesRead = 0;
BYTE *buf = (BYTE*)malloc(BUF_SIZE*sizeof(BYTE));
OVERLAPPED overlapped;
overlapped.Offset = overlapped.OffsetHigh = 0;  

hFile = CreateFile("C:\\Users\\Desktop\\FOO.cpp",
                  GENERIC_READ,
                  FILE_SHARE_READ | FILE_SHARE_WRITE,
                  NULL,
                  OPEN_EXISTING,
                  FILE_FLAG_OVERLAPPED,
                  NULL);



 if (hFile == INVALID_HANDLE_VALUE)
        printf("invalid hfile\n");

   int i;   
   i= ReadFile(hFile,
                 &buf,
                 BUF_SIZE,
                 &NumberOfBytesRead,
                 &overlapped);

  if(!i && GetLastError() != ERROR_IO_PENDING)
         printf ("ReadFile failed with error %d.\n", GetLastError());
   else
   {  
     WaitForSingleObject(&(overlapped.hEvent), 0);
     printf("here it is %d",NumberOfBytesRead );
   }

   CloseHandle(hFile);  

但是 ReadFile 的返回值为 0，最后一个错误等于 6。有谁知道为什么？ 6 个错误代码表示什么？

谢谢!

Answer 1

也许您的问题出在 OVERLAPPED 结构上，您没有正确初始化它。请参阅:“在函数调用中使用结构之前，应始终将此结构的任何未使用成员初始化为零。否则，函数可能会失败并返回 ERROR_INVALID_PARAMETER。”在这里备注:here .您可以使用 memset 清除所有内容。