mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2025-02-17 09:30:26 +00:00
121 lines
3.2 KiB
Plaintext
121 lines
3.2 KiB
Plaintext
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SUBINS
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PLA
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TAY
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PLA
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TAX
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PLA
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STA ADDR2
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PLA
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STA ADDR2+1
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PLA
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STA :MLEN
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PLA
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STA :SINDEX
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PLA
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STA ADDR1
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PLA
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STA ADDR1+1
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TXA
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PHA
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TYA
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PHA
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LDA #0
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STA :SCERR ; ASSUME NO ERR WILL BE FOUND
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LDY #0
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LDA (ADDR1),Y
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STA :S1LEN ; GET LENGTH OF STRING
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LDA (ADDR2),Y
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STA :S2LEN ; GET LENGTH OF SUB
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BNE :IDX0
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JMP :OKEXIT ; EXIT OF NO INSERT/ERR
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:IDX0
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LDA :SINDEX
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BNE :CHKLEN ; BR OF INDEX NOT 0
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JMP :EREXIT ; ELSE ERROR EXIT
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:CHKLEN
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LDA :S2LEN ; GET SUBSTR LENGTH
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CLC
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ADC :S1LEN
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BCS :TRUNC ;TRUN IF S1+S2 LENGTH > 255
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CMP :MLEN ;
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BCC :IDXLEN ; BR IF S1+S2 LEN < MAX LENGTH
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BEQ :IDXLEN ; BR IF EQUAL
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:TRUNC
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LDA :MLEN ; SUBSTR LEN = MLEN - STR LEN
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SEC
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SBC :S1LEN
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BCC :EREXIT
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BEQ :EREXIT ; ERR IF MLEN < STR LEN OR 0
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STA :S2LEN
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LDA #$0FF
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STA :SCERR ; INDICATE SUBSTR WAS TRUNCATED
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:IDXLEN
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LDA :S1LEN
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CMP :SINDEX ;
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BCS :LENOK ; BR IF INDEX WITHIN STR
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LDX :S1LEN ; ELSE CONCAT SUB AT END OF STR
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INX
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STX :SINDEX ; START RIGHT AFTER END OF STR
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LDA #$0FF
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STA :SCERR ; INDICATE ERR IN INSERT
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LDA :S1LEN
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CLC
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ADC :S2LEN
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STA :S1LEN ; ADD LENGTHS TOGETHER
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JMP :MVESUB ; PERFORM MOVE, NOTHING ELSE TODO
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:LENOK
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LDA :S1LEN
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SEC
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SBC :SINDEX
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TAX
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INX ; X= NUM OF CHARS TO MOV
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LDA :S1LEN
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STA :SIDX ; SRC ENDS AT ORIG STR END
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CLC
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ADC :S2LEN
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STA :SBIDX ; DEST ENDS FURTHER BY SUB LEN
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STA :S1LEN ; SET NEW LENGTH TO THIS ALSO
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:OPNLP
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LDY :SIDX
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LDA (ADDR1),Y
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LDY :SBIDX
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STA (ADDR1),Y ; MOVE IT UP IN MEM
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DEC :SIDX
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DEC :SBIDX ; DE DEST IDX, COUNTER
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DEX
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BNE :OPNLP ; CONT UNTIL COUNTER = 0
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:MVESUB
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LDA #1
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STA :SIDX
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; START AT INDEX IN THE STRING
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LDX :S2LEN ; X = NUM OF CHARS TO MOVE
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:MVELP
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LDY :SIDX
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LDA (ADDR2),Y ; GET NEXT CHAR
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LDY :SINDEX
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STA (ADDR1),Y
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INC :SIDX ; INC SUBSTR INDEX
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INC :SINDEX ; INC STR INDEX
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DEX ; DEC COUNTER
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BNE :MVELP ; CONT UNTIL COUNTER = 0
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LDA :SCERR ; GET ERROR FLAG
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BNE :EREXIT ; BR IF SUBSTR WAS TRUNCED
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:OKEXIT
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CLC
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BCC :EXIT
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:EREXIT
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SEC ; ERROR EXIT
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:EXIT
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LDA :S1LEN
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LDY #0
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STA (ADDR1),Y
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RTS
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:S1LEN DS 1
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:S2LEN DS 1
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:SUBLEN DS 1
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:MLEN DS 1
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:SINDEX DS 1
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:SIDX DS 1
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:SBIDX DS 1
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:SCERR DS 1
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