MDAC 2.5 SDK - OLE DB Programmer's Reference
Appendix H: Data Type Conversion Interfaces

IDataConvert::DataConvert

Converts the data from the source type to the destination type.

HRESULT DataConvert (
   DBTYPE          wSrcType,
   DBTYPE          wDstType,
   ULONG           cbSrcLength,
   ULONG *         pcbDstLength,
   void *          pSrc,
   void *          pDst,
   ULONG           cbDstMaxLength,
   DBSTATUS        dbsSrcStatus,
   DBSTATUS *      pdbsStatus,
   BYTE            bPrecision,
   BYTE            bScale,
   DBDATACONVERT   dwFlags);

Parameters

wSrcType

[in]
The source type of the data to be converted.

wDstType

[in]
The destination type of the data to be converted.

cbSrcLength

[in]
The length of the source data in bytes.

pcbDstLength

[out]
A pointer to memory in which to return the length in bytes of the output data after conversion.

pSrc

[in]
A pointer to the source data. This is a pointer to the underlying data type, based on the value of wSrcType. For example, this would be the address of the BSTR pointer if wSrcType is DBTYPE_BSTR, not the BSTR pointer itself.

pDst

[out]
A pointer to memory in which to return the destination data. As in the case of pSrc, this is a pointer to the underlying data type, based on the value of wDstType.

cbDstMaxLength

[in]
The maximum allowable length of the destination data in bytes. This is used only for variable-length destination data types.

dbsSrcStatus

[in]
The status value for the source data.

pdbsStatus

[out]
A pointer to the status for the conversion.

bPrecision

[in]
The precision of the output data in bytes, if applicable. This argument is used when converting to DBTYPE_NUMERIC data only.

bScale

[in]
The scale of the output data in bytes, if applicable. This argument is used when converting to DBTYPE_NUMERIC data only.

dwFlags

[in]
The data conversion flag indicating the requested conversion behavior. These flags can be combined.

The following flags are available:

   typedef DWORD DBDATACONVERT;
   enum DBDATACONVERTENUM{
      DBDATACONVERT_DEFAULT           = 0,
      DBDATACONVERT_SETDATABEHAVIOR   = 1,
      DBDATACONVERT_LENGTHFROMNTS     = 2
   };

The DBDATACONVERT_SETDATABEHAVIOR flag indicates that data truncation is an error and that the memory pointed to by pDst will not be changed if any error occurs.

The DBDATACONVERT_LENGTHFROMNTS flag indicates that the data conversion library should calculate cbSrcLength for string (DBTYPE_STR, DBTYPE_WSTR) source data.

Return Code

S_OK

The conversion succeeded.

E_FAIL

pSrc was a null pointer.

E_OUTOFMEMORY

The data conversion object was unable to allocate memory.

DB_E_BADBINDINFO

The source or destination data type was invalid.

DB_E_DATAOVERFLOW

The requested conversion resulted in an overflow.

DB_E_ERRORSOCCURRED

Errors occurred while converting data. The requested conversion can fail for a number of reasons, including the following:

• The source data was unavailable.
  
  
• Data truncation occurred.
  
  
• The precision and scale arguments did not make sense for the data type.
  
  
• There was an invalid character or second decimal point in the source data.

DB_E_UNSUPPORTEDCONVERSION

The requested conversion was not supported.