Installing Custom I/O Procedures

To install an I/O procedure associated with the .ARC filename extension, use the mmioInstallIOProc function as follows:

mmioInstallIOProc (mmioFOURCC('A', 'R', 'C', ' '),


When you install an I/O procedure using mmioInstallIOProc, the procedure remains installed until you remove it. The I/O procedure is used for any file you open as long as the file has the appropriate filename extension.

You can also temporarily install an I/O procedure by using the mmioOpen function. In this case, the I/O procedure is used only with a file opened by using mmioOpen and is removed when the file is closed by using the mmioClose function. To specify an I/O procedure when you open a file by using mmioOpen, use the lpmmioinfo parameter to reference an MMIOINFO structure as follows:

  1. Set the fccIOProc member to NULL.

  2. Set the pIOProc member to the procedure-instance address of the I/O procedure.

  3. Set all other members to zero (unless you are opening a memory file, or directly reading or writing to the file I/O buffer).

Be sure to remove any I/O procedures you have installed before you exit your application.

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