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SDFI, SDFO–System Data Format I/O Routines
Example
The following example generates the packet (FCT) for SDFI with the S$DFCT PROC:
1. $ASCII
2. $INCLUDE ‘MAXR$’
3. $INCLUDE ‘SDFP$’
4. $(2)
5. PKT S$DFCT,‘DGL’ ‘TPF$’,R$,1792 448,BUF1,BUF2;
6. 20,LINE ,X7
7. BUF1 $RES 448
8. BUF2 $RES 448
9. LINE $RES 20
.
.
.
10. $(1)
11. START
12. L,U X7,PKT . Get address of packet
.
.
.
13. L A6,PKTICW . Get Image Control Word
In this example, the packet (FCT) for SDFI is generated on line 5 by the S$DFCT PROC.
The D option displays the packet in the MASM assembly. The G option initializes the
packet with the information contained in the S$DFCT parameter fields 1, 2, and 3. The
L option generates dynamic $EQUF definitions using the label field on the S$DFCT
PROC and information in parameter field 4. In this case, the $EQUF labels are prefixed
with 'PKT', use X-register X7, and are externalized to the main assembly level.
Line 13 accesses word 10 of the SDFI packet using the $EQUF generated by the
S$DFCT PROC.
21.1.2. Calling Sequence
The following subsections explain how to open the SDFI routine, read an image, and
close the routine.
21.1.2.1. Open SDFI
The calling program must open SDFI before any images can be read. There are two
entry points that perform the open function.
SDFIO$ Open SDFI at sector address
SDFIOA$ Open SDFI at sector address and word offset
When the SDFIO$ entry point is called, SDFI fills the I/O buffer or buffers and tests if the
file accessed is an SDF file. Reading begins at the sector address specified in word 5 of
the packet.
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