Platform SDK: Interprocess Communications

DdeCreateDataHandle

The DdeCreateDataHandle function creates a dynamic data exchange (DDE) object and fills the object with data from the specified buffer. A DDE application uses this function during transactions that involve passing data to the partner application.

HDDEDATA DdeCreateDataHandle(
  DWORD idInst, // instance identifier
  LPBYTE pSrc,  // pointer to source buffer
  DWORD cb,     // length of DDE object
  DWORD cbOff,  // offset from beginning of source buffer
  HSZ hszItem,  // handle to item name string
  UINT wFmt,    // clipboard data format
  UINT afCmd    // creation flags
);

Parameters

idInst: [in] Specifies the application instance identifier obtained by a previous call to the DdeInitialize function.
pSrc: [in] Pointer to a buffer that contains data to be copied to the DDE object. If this parameter is NULL, no data is copied to the object.
cb: [in] Specifies the amount of memory, in bytes, to copy from the buffer pointed to by pSrc. (include the terminating NULL, if the data is a string). If this parameter is zero, the pSrc parameter is ignored.
cbOff: [in] Specifies an offset, in bytes, from the beginning of the buffer pointed to by the pSrc parameter. The data beginning at this offset is copied from the buffer to the DDE object.
hszItem: [in] Handle to the string that specifies the data item corresponding to the DDE object. This handle must have been created by a previous call to the DdeCreateStringHandle function. If the data handle is to be used in an XTYP_EXECUTE transaction, this parameter must be 0L.
wFmt: [in] Specifies the standard clipboard format of the data.
afCmd: [in] Specifies the creation flags. This parameter can be HDATA_APPOWNED, which specifies that the server application calling the DdeCreateDataHandle function owns the data handle this function creates. This flag enables the application to share the data handle with other Dynamic Data Exchange Management Library (DDEML) applications rather than creating a separate handle to pass to each application. If this flag is specified, the application must eventually free the shared memory object associated with the handle by using the DdeFreeDataHandle function. If this flag is not specified, the handle becomes invalid in the application that created the handle after the data handle is returned by the application's DDE callback function or is used as a parameter in another DDEML function.

Return Values

If the function succeeds, the return value is a data handle.

If the function fails, the return value is 0L.

Errors

The DdeGetLastError function can be used to get the error code, which can be one of the following values:

DMLERR_DLL_NOT_INITIALIZED
DMLERR_INVALIDPARAMETER
DMLERR_MEMORY_ERROR
DMLERR_NO_ERROR

Remarks

Any unfilled locations in the DDE object are undefined.

After a data handle has been used as a parameter in another DDEML function or has been returned by a DDE callback function, the handle can be used only for read access to the DDE object identified by the handle.

Requirements