Information Regarding Buffered I/O and MSCDEX (69974)
The information in this article applies to:
- Microsoft Windows Software Development Kit (SDK) 3.0
This article was previously published under Q69974 SUMMARY
In the Microsoft Multimedia Windows environment, the MSCDEX driver
provides buffered input and output (I/O) from the CD-ROM device. The
information below discusses using buffered I/O in an application.
MORE INFORMATION
When 32K of data is read from the disk in response to a request from
an application, 32K additional data is read from the disk into a
buffer in anticipation of another sequential read request.
Currently, all information read from the CD-ROM is in response to a
synchronous MS-DOS file I/O request. This prevents an application from
requesting that a particular portion of data be read from the disk
while the application performs some other processing. Although an
implementation of asynchronous I/O is being researched, it will not be
implemented soon. It would be necessary to rewrite all CD-ROM drivers
currently in use to implement asynchronous I/O.
To fill the buffer with an arbitrary selection from the CD-ROM, an
application can request one byte of data from the beginning of the
selection to be read. After the CD-ROM seeks to the data and reads one
byte, control is returned. The driver reads the remainder of the data
into the buffer asynchronously.
| Modification Type: | Major | Last Reviewed: | 11/6/1999 |
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| Keywords: | kb16bitonly KB69974 |
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