CIGAL Reference Manual, Chapter 6 (RealTime): r_fread
r_fread -- Read data from a file
usage: r_fread opflg eflag ltime Databuf Nbytes Lunit [Asyncflag]
R_FREAD is a REALTIME operator. It initiates a data transfer of NBYTES from the open file specified by LUNIT to the DATABUF variable. NBYTES is assumed to be a long integer value. LUNIT must have been previously set by a call to R_FOPEN. If LUNIT is missing it defaults to 1.
R_FREAD normally operates synchronously, not finishing until the data transfer is completed. To perform an asynchronous read, make ASYNCFLAG non-zero. In that case you should issue a R_FWAIT operation before assuming that the data have all been read.
Note 1: If LUNIT is not an open file this operation returns immediately. If a previous asynchronous I/O operation was still pending, this operation will wait until that has completed before starting. This is therefore equivalent to inserting a R_FWAIT operation.
Note 2: All REALTIME file I/O operations are performed asynchronously, regardless of the ASYNCFLAG; this allows multiple independent processing streams to continue while file data transfers are underway. The ASYNCFLAG option therefore only specifies whether this particular processing stream should wait until the I/O finishes.
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