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13.4. Examples
MFDSP$–Master File Directory Service Package
The following MASM instructions illustrate how the M$FDSP can be used:
$INCLUDE ‘MAXR$/’
$ASCII
$(2)
FNCT $EQU 0
VALUE + 0
BUFFER $RES 4400
BUFFLN $EQU $-BUFFER
$(1)
START .
DL A0,($CFS(‘MFD ‘))
DS A0,BUFFER
M$FDSP,‘CB’ BUFFLN,BUFFER,0
J MFDERR
M$FDSP,‘CB’ BUFFLN,BUFFER,FNCT
J MFDERR
LXI,U X11,0
LXI,U A0,BUFFLN
LXM,U A0,BUFFER
M$FDSP ,, VALUE
J MFDERR
J DONE
MFDERR .
L$SNAP ‘MFDERR’,2,0,0
DONE .
ER EXIT$
$END START
The structure of the MFD is described in the Exec Administration Reference Manual.
Every filename has a lead item entry in the MFD. For every F-cycle of that particular
filename, a main item entry exists. The lead item contains links to all the main items,
and it can be up to two sectors, sector 0 and sector 1. If there are more main items than
sector 0 can hold links to, a sector 1 of the lead item will contain the links to the rest of
the main items. To access all possible main items in the MFD, you must use the
following algorithm:
Call MFDSP$ specifying function 0 to initialize and get
the first lead item.
GETNEXTMAIN:
Call MFDSP$ specifying function 4, (Get-Next-Main-Item),
and continue calling Get-Next-Main-Item until a
No-Find condition (A1=0) occurs.
Call Get-Sector-1-of-Lead-Item (MFDSP$ function 3).
IF a No-Find condition (A1=0) occurs, jump to GETNEXTLEAD.
Call Get-Next-Main-Item and continue to call it until a
No-Find condition occurs (A1=0).
GETNEXTLEAD:
Call Get-Next-Lead-Item (MFDSP$ function 2).
IF a No-Find condition (A1=0) occurs, exit the program,
OTHERWISE jump to GETNEXTMAIN.
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