IDebugDocumentChecksum2::GetChecksumAndAlgorithmId

Note

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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