wiasWritePageBufToFile function (wiamdef.h)

Article
10/21/2021

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

Syntax

HRESULT wiasWritePageBufToFile(
  [in] PMINIDRV_TRANSFER_CONTEXT pmdtc
);

Parameters

[in] pmdtc

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.

Requirements

Requirement	Value
Minimum supported client	Available in Microsoft Windows Me and in Windows XP and later versions of the Windows operating systems.
Target Platform	Desktop
Header	wiamdef.h (include Wiamdef.h)
Library	Wiaservc.lib
DLL	Wiaservc.dll