NAME
        LockRecord -- Locks a portion of a file (V36)

   SYNOPSIS
        success = LockRecord(fh,offset,length,mode,timeout)
        D0                   D1   D2     D3    D4    D5

        bool lockrecord(bptr,ulong,ulong,ulong,ulong)

   FUNCTION
        This locks a portion of a file for exclusive access.  Timeout is how
        long to wait in ticks (1/50 sec) for the record to be available.

        Valid modes are:
                REC_EXCLUSIVE
                REC_EXCLUSIVE_IMMED
                REC_SHARED
                REC_SHARED_IMMED
        For the IMMED modes, the timeout is ignored.

        Record locks are tied to the filehandle used to create them.  The
        same filehandle can get any number of exclusive locks on the same
        record, for example.  These are cooperative locks, they only
        affect other people calling LockRecord().

   INPUTS
        fh      - File handle for which to lock the record
        offset  - Record start position
        length  - Length of record in bytes
        mode    - Type of lock requester
        timeout - Timeout interval in ticks.  0 is legal.

   RESULT
        success - Success or failure

   BUGS
        In 2.0 through 2.02 (V36), LockRecord() only worked in the ramdisk.
        Attempting to lock records on the disk filesystem causes a crash.
        This was fixed for V37.

   SEE ALSO
        lockrecords(), unlockrecord(), unlockrecords()