Share via

IDebugDocumentChecksum2::GetChecksumAndAlgorithmId

  • Article

Note

This article applies to Visual Studio 2015. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

Retrieves the document checksum and algorithm identifier given the maximum number of bytes to use.

Syntax

HRESULT GetChecksumAndAlgorithmId(   
   GUID  *pRetVal,  
   ULONG cMaxBytes,  
   BYTE  *pChecksum,  
   ULONG *pcNumBytes  
);  

public int GetChecksumAndAlgorithmId(   
   out Guid pRetVal,  
   uint     cMaxBytes,  
   out byte pChecksum,  
   out uint pcNumBytes  
);

Parameters

pRetVal
[out] Unique identifier for the checksum algorithm.

cMaxBytes
[in] Maximum number of bytes to be used for the checksum.

pChecksum
[out] Value of the checksum.

pcNumBytes
[out] Actual number of bytes used for the checksum.

Return Value

If successful, returns S_OK; otherwise, returns an error code.

Example

The following example uses this method to get the checksum and algorithm for a document.

HRESULT CDebugCodeContext::GetDocumentChecksumAndAlgorithmId(GUID *pguidAlgorithm, BYTE **ppChecksum, ULONG *pcNumBytes)  
{  
    HRESULT hRes = E_FAIL;  
  
    *ppChecksum = NULL;  
    *pcNumBytes = 0;  
  
    CComPtr<IDebugDocumentContext2> pDocContext;  
  
    hRes = this->GetDocumentContext(&pDocContext);  
  
    if ( HREVAL(S_OK, hRes) )  
    {  
        CComQIPtr<IDebugDocumentChecksum2> pDocChecksum(pDocContext);  
  
        if ( pDocChecksum != NULL )  
        {  
            // Figure out the size of the checksum buffer required  
            ULONG cNumBytes = 0;  
  
            hRes = pDocChecksum->GetChecksumAndAlgorithmId(pguidAlgorithm, 0, NULL, &cNumBytes);  
  
            if ( S_OK == hRes )  
            {  
                // check to see if we got back valid values  
                if ( cNumBytes && GUID_NULL != (*pguidAlgorithm) )  
                {  
                    // Alloc space for the checksum data  
                    BYTE *pChecksum = (BYTE*) CoTaskMemAlloc(cNumBytes);  
  
                    if ( pChecksum )  
                    {  
                        // Get the buffer containing the checksum info  
                        hRes = pDocChecksum->GetChecksumAndAlgorithmId(pguidAlgorithm, cNumBytes, pChecksum, &cNumBytes);  
  
                        if ( HREVAL(S_OK, hRes) )  
                        {  
                            *ppChecksum = pChecksum;  
                            *pcNumBytes = cNumBytes;  
                        }  
                        else  
                        {  
                            CoTaskMemFree(pChecksum);  
                        }  
                    }  
                    else  
                        hRes = E_OUTOFMEMORY;  
                }  
                else  
                    hRes = S_FALSE; // lang doesn't support checksums  
            }  
            else  
                hRes = S_FALSE; // failed to work out checksum info  
        }  
        else  
            hRes = S_FALSE; // SH doesn't support checksums  
    }  
  
    return ( hRes );  
}

See Also

IDebugDocumentChecksum2