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SDFI, SDFO–System Data Format I/O Routines
The SDFI and SDFO routines are available as relocatable elements and also in the
SYSLIB common banks. SDFI is in the common bank absolute SYSLIB$3, and SDFO is
in the common bank absolute SYSLIB$4. Both routines are reentrant. The relocatable
and common bank entry points for SDFI and SDFO are listed in Appendix E.
The following compatibility considerations apply to FURPUR and Processor Common
Input/Output System (PCIOS):
• SDFI and SDFO are fully compatible with FURPUR level 28R3 and higher levels.
• SDFI and SDFO are compatible with PCIOS levels 4R1 and 4R1A, except for the
handling of multireel tape files:
− When SDFI reads multireel tape files created by PCIOS, I/O error 01 (unlabeled
tape) or TLBL$ error 013 (labeled tape) occurs.
− When PCIOS reads multireel tape files created by SDFO, unlabeled tapes are
read correctly, but labeled tapes encounter I/O error 01.
• SDFI returns segmented PCIOS records one segment at a time. The caller must
examine the segment flag in the PCIOS data record control word to determine how
the data record is segmented.
A description of each routine and its corresponding packet is in the following
subsections.
For details on system data format, see the Data Structures Programming Reference
Manual.
21.1. SDFI–System Data Format Input Routine
The SDFI routine returns one SDF image at a time from an SDF file or element. SDFI
has the following functions and entry points:
• Open SDFI (SDFIO$, SDFIOA$)
• Read an image (SDFI$, SDFINT$)
• Close SDFI (SDFIC$)
The calling program must open SDFI before reading images from the file or element and
close SDFI after all images are read.
The packet (or FCT) for SDFI is described in 21.1.1. The open, read, and close functions
of SDFI are described in 21.1.2.1, 21.1.2.2, and 21.1.2.3, respectively.
21.1.1. Packet
The calling program must provide an 11-word packet for SDFI. The SDFI packet format
is described in Figure 21–1. The packet may be generated with the S$DFCT procedure
described in 21.1.1.2.
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