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XPflock()
Lock binary files
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Function: XPflock()
XPflock() makes it possbile to issue locks to a
specified region of a binary file. The file must be opened
or created in shared mode (see fopen()).
Take great care when using this function. As QUITting the
applic with locks set has undefined results. Also, you
yourself have to Unlock the exact same region of the file,
so you need to keep track of the locks set. There is no
restriction on the number of locks you can set.
Also note that the Clipper locking system on .DBF files
is not at all how it is implemented in DOS, as locking
a region using XPflock() is more or less
equivalent to locking exclusive in Clipper, one
can't even read from it anymore. Clipper locks
bytes after the Eof() position for rlock() and
flock(), which CAN be implemented with this function,
but it's not recommended..
Resuming: Know what you do when you use these functions in a
real-time environment!
Syntax: XPflock(h,nOffset,nLength) --> NIL
Arguments: <h> is the file's handle. <nOffset> is the offset
where the lock starts, <nLength> is the length of the region
to lock. Note that the lock is exclusive, others users
cannot read nor write to that region!
Returns: NIL, see XPferror() for results. eg. 33 indicates region
is already locked, 6 indicates invalid handle.
Usage:
See Also:
XPferror()
XPfunlock()
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