HRESULT 数据类型和显示错误信息

HRESULT

What we should know about HRESULT ?
- HRSULT is a kind of Data Type ( Long 32bit) which is used for Windows.
- It is The return codes used by COM interfaces.
- To test an HRESULT value, use the FAILED and SUCCESSED macros.
- This type is declared in WinNT.h as follows:
   typedef LONG HRESULT;

Structure of COM Error Codes.
- HRESULT value has 32bits and is divided into 3 fields:  a severity code, a facility code, and an error code.

Bit    31 30 29 28 27, 26 25 24 ... 16, 15 14 ... 0
Field  S   R  C   N   r , Facility           , Error

Convert HRSULT retrun codes to error messages.
法(1) We can use  AMGetErrorText Function.
- Syntax :

DWORD AMGetErrorText (

	HRESULT hr,           // HRESULT value.

	TCHAR *pBuffer,     // Pointer to a character buffer that receives the error message.

 	DWORD MaxLen     // Number of characters in pBuffer.

);

- Requirement:
   Header: Errors.h (dshow.h)
   Lib : Quarz.lib
- Example:

void ShowError(HRESULT hr)

{

    if (FAILED(hr))

    {

        TCHAR szErr[MAX_ERROR_TEXT_LEN];

        DWORD res = AMGetErrorText(hr, szErr, MAX_ERROR_TEXT_LEN);

        if (res == 0)

        {

            StringCchPrintf(szErr, MAX_ERROR_TEXT_LEN, "Unknown Error: 0x%2x", hr);

        }

        MessageBox(0, szErr, TEXT("Error!"), MB_OK | MB_ICONERROR);

    }

}

 

 

//But , 我尝试上述，似乎总是找不到AMGetErrorText函数，找不到合适的H文件，可能需要安装额外的SDK.

法 (2) 

CString HrToMessage( HRESULT hr )

{

     LPVOID lpMsgBuf;

     CString strTmp;

     ::FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER |

         FORMAT_MESSAGE_FROM_SYSTEM,

         NULL,

         hr,

         MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),

         (LPTSTR) &lpMsgBuf,

         0,

         NULL );

     strTmp.Format( _T("%s"), (char *) lpMsgBuf );

     ::LocalFree( lpMsgBuf );

     return strTmp;

}