wiasWritePageBufToFile function

Description

The wiasWritePageBufToFile function writes the contents of a temporary page buffer to an image file.

Parameters

pmdtc [in]

Pointer to a MINIDRV_TRANSFER_CONTEXT structure.

Return value

On success, the function returns S_OK. If the function fails, it returns a standard COM error or one of the WIA_ERROR_XXX errors (described in the Microsoft Windows SDK documentation).

Remarks

The function writes data from a minidriver-allocated temporary page buffer to the image file opened by the WIA service. Minidrivers typically call this function after acquiring a page of data for which the minidriver allocated a temporary buffer.

This function is similar to wiasWriteBufToFile, which can be used to write a buffer of image data to any type of image file. If a WIA minidriver intends to write a page of image data to a multipage TIFF file, including all appropriate tags, image file directory (IFD) entries, and other nonimage data, it should call this function, rather than wiasWriteBufToFile.

The expression pmdtc->hFile contains the handle to the file in TYMED_FILE (and TYMED_MULTIPAGE_FILE) transfers. This can be used to directly access the file that is being written to.

An example of how to use it is:

SetFilePointer((HANDLE)(LONG_PTR)pmdtc->hFile,0,NULL,FILE_BEGIN);
if (!WriteFile((HANDLE)(LONG_PTR)pmdtc->hFile,
    pMyBuffer,
    dwNumBytesToWrite,
   &dwNumBytesWritten,
    NULL)) {
     //
     // Some error happened
     //
     .
     .
     .
    }

However, if you are considering using just the file handle in your TYMED_FILE and TYMED_MULTIPAGE_FILE transfers (to write data directly to the file using the file handle, instead of calling wiasWritePageBufToFile), use wiasWriteBufToFile. This function performs the equivalent of:

bRet = WriteFile((HANDLE)ULongToPtr(pmdtc->hFile),
    pmdtc->pTransferBuffer,
    pmdtc->lItemSize,
    &ulWritten,
    NULL);

This is essentially what you would do if you used the file handle directly. The advantage of the first example is that if the implementation was changed in a future release of WIA (for example, if the WIA service began using pipes instead of files, internally), the driver would not need to be updated.

See also

MINIDRV_TRANSFER_CONTEXT

wiasWriteBufToFile

wiasWritePageBufToStream