Random Read bug fix for DRI CPM3

[dxf]

; ZPM3's Random Read bug fix applied to DRI BDOS30.ASM
; Source: http://cpmarchives.classiccmp.org/cpm/mirrors/www.triton.vg/tesseract/pds/093/zpm3s.arc
; NOTE: ONLY BRIEFLY TESTED

; Extent is in same directory fcb
push b! call get$dir$ext! pop b
cmp c
jz rrfix ;*** in last extent: treat as new area!
jnc rseek2 ; jmp if dir$ext > ext
pop d! push d! inr e! jnz rseek2 ; jmp if write fx
inr e! pop d! jmp set$lret1 ; error - reading unwritten data
rrfix:
pop d! push d ;*** get&save read flag (in E)
inr e! jnz rseek2 ;*** are we reading? no: ok, open this extent
lhld info! xchg! jmp ranclose ;*** yes: close extent and open
rseek2:

Additions are marked ***.

To verify the random read bug is quashed see rrbug.zip
https://drive.google.com/drive/folders/1kh2WcPUc3hQpLcz7TQ-YQiowrozvxfGw