AppleIIAsm-Collection/source/disk19_demo_builds_1/T.MIN.SUB.SUBDEL
nathanriggs c8cac53c5e Rev 0.4 updates
Massive updates that changes the way most subroutines are handled. Major bugfixes, various utilities added, started higher-level libraries.
2019-04-26 18:49:10 -04:00

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SUBDEL
PLA
TAY
PLA
TAX
PLA
STA :SCNT
PLA
STA :SINDEX
PLA
STA ADDR1
PLA
STA ADDR1+1
TXA
PHA
TYA
PHA
LDY #0
STY :SCERR
LDA (ADDR1),Y
STA :S1LEN
LDA :SCNT
BEQ :OKEXIT
LDA :SINDEX
BEQ :ERREXIT
LDA :S1LEN
CMP :SINDEX
BCC :ERREXIT
LDA :SINDEX
CLC
ADC :SCNT
BCS :TRUNC ;TRUNCATE IF INDEX
STA :SIDX
TAX
DEX
CPX :S1LEN
BCC :CNTOK
BEQ :TRUNC
LDA #$0FF
STA :SCERR
:TRUNC
LDX :SINDEX
DEX
STX :S1LEN
LDA :SCERR
BEQ :OKEXIT
BNE :ERREXIT
:CNTOK
LDA :S1LEN
SEC
SBC :SIDX
TAX
INX
BEQ :OKEXIT
; CHAR
:MVLP
LDY :SIDX
LDA (ADDR1),Y
LDY :SINDEX
STA (ADDR1),Y ;MOVE IT DOWN
INC :SINDEX
INC :SIDX
DEX
BNE :MVLP
LDX :SINDEX
DEX
STX :S1LEN
:OKEXIT
CLC
BCC :EXIT
:ERREXIT
SEC
:EXIT
LDA :S1LEN
LDY #0
STA (ADDR1),Y
RTS
:S1LEN DS 1
:SCNT DS 1
:SINDEX DS 1
:SIDX DS 1
:SCERR DS 1