passport/src/compare.a

WILDCARD =     $97

;-------------------------------
; SearchTrack subroutine
; written by qkumba
; search for a string occurring anywhere
; in the data buffer for the current track
; #WILDCARD in search string matches any 1 byte
; (like "." character in regular expressions)
; in:  Y = string length
;      stack = string to find
; out: C clear if string found
;        or set if not found
;      If C is clear, then
;      A = @gDisplayBytes = sector where string was found
;      X = starting offset where string was found
;      all other registers and flags clobbered
;-------------------------------
SearchTrack
;set end point for the search

         lda   #BASEPAGE+$10
         sta   .endvalue+1
         lda   #BASEPAGE
         bne   SearchSectors

;-------------------------------
; SearchSector subroutine
; written by qkumba
; same as SearchTrack, but for a single sector
; in:  A = high byte of sector address in data buffer (e.g. $10 for sector 0)
;      Y = string length
;      stack = string to find
; out: C clear if string found
;        or set if not found
;      If C is clear, then
;      X = starting offset where string was found
;      all other registers and flags clobbered
;-------------------------------

SearchSector
;set end point for the search

         tax
         inx
         stx   .endvalue+1

; set high part of initial search position

SearchSectors
         sta   search+2
         pla
         sta   match_buffer1+1
         sta   match_all+1
         pla
         sta   match_buffer1+2
         sta   match_all+2
         tax
         sty   match_size1+1
         sty   match_size2+1

; fetch last byte to improve search speed

match_buffer1
         lda   $d1d1,y    ; modified at runtime
         sta   check_byte1+1
         sta   check_byte2+1

; set low part of initial search position

         tya
         dey
         sty   cont_search+1

; set return address

         clc
         adc   match_buffer1+1
         tay
         bcc   plus01
         inx
plus01
         txa
         pha
         tya
         pha

; set match position

         inc   match_all+1
         bne   plus02
         inc   match_all+2
plus02

         lda   #<cont_search-branch_cont-2
         sta   branch_cont+1

; search...

cont_search
         ldy   #$d1       ; modified at runtime

search
         lda   $d100,y    ; modified at runtime
         iny
         beq   check_end

check_byte1
         cmp   #$d1       ; modified at runtime
         bne   search

; point to first byte

         sty   cont_search+1

check_match
         tya

match_size1
         sbc   #$d1       ; modified at runtime
         sta   match_buffer2+1
         ldx   search+2
         bcs   plus03
         dex
plus03
         stx   match_buffer2+2
         ldy   #$00

match_all
         lda   $d1d1,y    ; modified at runtime
         cmp   #WILDCARD
         beq   found_wild

match_buffer2
         cmp   $d1d1,y    ; modified at runtime

branch_cont
         bne   cont_search

found_wild
         iny

match_size2
         cpy   #$d1       ; modified at runtime
         bne   match_all

; point to start of match

         ldx   match_buffer2+1
         lda   match_buffer2+2
         sec
         sbc   #BASEPAGE
         sta   gDisplayBytes
         clc
         rts

; cold path

check_end
         inc   search+2
         ldx   search+2
.endvalue
         cpx   #$D1
         bne   check_byte1
         ldx   #<all_done_set-branch_cont-2
         stx   branch_cont+1

check_byte2
         cmp   #$d1       ; modified at runtime
         beq   check_match

all_done_set
         sec
         rts

; utility functions for common cases
; (from the caller's perspective, these have the side effect of setting Y,
; since the compare routine will 'save' and 'restore' the value we're setting here)
compare3
         ldy   #$03
         !byte $2C
         ; /!\ execution falls through here
compare2
         ldy   #$02
         !byte $2C
         ; /!\ execution falls through here
compare1
         ldy   #$01
         ; /!\ execution falls through here
;-------------------------------
; compare subroutine
; in:  A = sector
;      X = offset
;      Y = string length
;      stack = string to compare
; #WILDCARD in search string matches any 1 byte
; (like "." character in regular expressions)
; out: C = 0 if string matches, and gDisplayBytes set to A
;      C = 1 if not matched
;      A,X,Y preserved
;      $tmp zero page clobbered
;      $cmp1 zero page clobbered
;      $cmp2 zero page clobbered
;      stack set to first instruction after string
;-------------------------------
compare
         sta   tmpa
         clc
         adc   #BASEPAGE
         !byte $2C
CompareMemory
         sta   tmpa
         sta   cmp1+1
         stx   cmp1
         sty   tmpy
         pla
         sta   cmp2
         pla
         sta   cmp2+1
         tax
         tya
         clc
         adc   cmp2
         bcc   +
         inx
+        sta   modtmp
         txa
         pha
         lda   modtmp
         pha
@cmp
         lda   (cmp2),y
         dey
         bmi   @success
         cmp   (cmp1),y
         beq   @cmp
         cmp   #WILDCARD
         beq   @cmp
         sec
         !byte $24        ; hide CLC
@success clc
         lda   tmpa
         ldx   cmp1
         ldy   tmpy
         bcs   +
         sta   gDisplayBytes
+        rts