https://wikiti.brandonw.net/index.php?action=history&feed=atom&title=83Plus%3ABCALLs%3A803083Plus:BCALLs:8030 - Revision history2026-04-09T11:33:48ZRevision history for this page on the wikiMediaWiki 1.23.5https://wikiti.brandonw.net/index.php?title=83Plus:BCALLs:8030&diff=3862&oldid=prevFloppusMaximus: This one is ugly!2006-02-08T00:03:06Z<p>This one is ugly!</p>
<p><b>New page</b></p><div>[[Category:83Plus:BCALLs:By_Name:Other|FindGroupedField]] [[Category:83Plus:BCALLs:By_Name|FindGroupedField]] [[Category:83Plus:BCALLs:By_Address|8030 - FindGroupedField]]<br />
== Synopsis ==<br />
'''Unofficial Name:''' FindGroupedField<br />
<br />
'''BCALL Address:''' 8030<br />
<br />
Search for a given field within a "group."<br />
<br />
=== Inputs ===<br />
* AHL = address (first type byte) to start searching<br />
* DE = field to search for (e.g. 0A10 to search for the calculator ID)<br />
<br />
=== Outputs ===<br />
* HL = address of the first data byte (''not'' the first type byte) of the first matching field<br />
* BC = length of the field<br />
* NZ set if not found.<br />
<br />
=== Destroys ===<br />
* AF<br />
* [[83Plus:RAM:8478|OP1]], [[83Plus:RAM:8100|ramCode]]<br />
<br />
== Comments ==<br />
This routine will stop when it reaches any field of a different major field type. Unless you are explicitly searching for a minor-type-1 field, it will also stop when it reaches one.<br />
<br />
The behavior of this routine is perhaps best illustrated by an example. Public keys are stored on the certificate page as a series of two fields: an 071 field which contains the key ID (e.g. 0104) and an 073 field which contains the key itself.<br />
<br />
So to find a particular public key, you want to first scan through the 071 fields to find the key ID you're looking for. You then want to find the first 073 field following this one, ''but you want to stop before you get to another 071 field, or any other unrelated field.'' "Unrelated" in this case means non-major-type-7, since only major-type-7 fields are allowed within the public key block.<br />
<br />
Unlike most of the field search routines, this routine calls [[83Plus:BCALLs:805A|GetFieldSize]] after finding the field, so HL points to the first data byte and BC is the length of the field.<br />
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== Example ==<br />
Find public key number 0104 (requires [[83Plus:Ports:14|Flash write-enabled]]):<br />
<br />
; Find the certificate patch block<br />
ld de,0300h<br />
B_CALL [[83Plus:BCALLs:8027|FindFirstCertificateField]]<br />
ret nz<br />
<br />
; Find the public key block (a subfield of the certificate patch block)<br />
ld a,7eh ; or 1e, or 3e, depending on model<br />
ld de,0700h<br />
B_CALL [[83Plus:BCALLs:805D|FindSubField]]<br />
ret nz<br />
<br />
; Enter the public key block<br />
inc hl<br />
ld a,7eh<br />
B_CALL [[83Plus:BCALLs:805A|GetFieldSize]]<br />
<br />
; Find our public key<br />
Loop:<br />
ld a,7eh<br />
ld de,0710h<br />
B_CALL FindGroupedField<br />
ret nz<br />
; HL -> key number, BC = length thereof<br />
; check if it is 0104<br />
ld a,7eh<br />
B_CALL [[83Plus:BCALLs:8051|LoadAIndPaged]]<br />
cp 1<br />
jr nz,Skip<br />
inc hl<br />
dec bc<br />
ld a,7eh<br />
B_CALL [[83Plus:BCALLs:8051|LoadAIndPaged]]<br />
cp 4<br />
jr nz,Skip<br />
inc hl<br />
dec bc<br />
ld a,b<br />
or c<br />
jr z,Found0104<br />
Skip:<br />
add hl,bc<br />
jr Loop<br />
Found0104:<br />
ld a,7eh<br />
ld de,0730h<br />
B_CALL FindGroupedField<br />
; HL -> modulus; BC = length</div>FloppusMaximus