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mmioSetBuffer function

  • Article

The mmioSetBuffer function enables or disables buffered I/O, or changes the buffer or buffer size for a file opened by using the mmioOpen function.

Syntax

MMRESULT mmioSetBuffer(
   HMMIO hmmio,
   LPSTR pchBuffer,
   LONG  cchBuffer,
   UINT  wFlags
);

Parameters

  • hmmio
    File handle of the file.

  • pchBuffer
    Pointer to an application-defined buffer to use for buffered I/O. If this parameter is NULL, mmioSetBuffer allocates an internal buffer for buffered I/O.

  • cchBuffer
    Size, in characters, of the application-defined buffer, or the size of the buffer for mmioSetBuffer to allocate.

  • wFlags
    Reserved; must be zero.

Return value

Returns zero if successful or an error otherwise. If an error occurs, the file handle remains valid. The following values are defined.

Return code Description
MMIOERR_CANNOTWRITE

The contents of the old buffer could not be written to disk, so the operation was aborted.
MMIOERR_OUTOFMEMORY

The new buffer could not be allocated, probably due to a lack of available memory.

 

Remarks

To enable buffering using an internal buffer, set pchBuffer to NULL and cchBuffer to the desired buffer size.

To supply your own buffer, set pchBuffer to point to the buffer, and set cchBuffer to the size of the buffer.

To disable buffered I/O, set pchBuffer to NULL and cchBuffer to zero.

If buffered I/O is already enabled using an internal buffer, you can reallocate the buffer to a different size by setting pchBuffer to NULL and cchBuffer to the new buffer size. The contents of the buffer can be changed after resizing.

Requirements

Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

Header

 Mmsystem.h (include Windows.h)

Library

 Winmm.lib

DLL

 Winmm.dll