mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-11-23 15:32:08 +00:00
95 lines
2.5 KiB
Plaintext
95 lines
2.5 KiB
Plaintext
STRCAT
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PLA
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STA RETADR
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PLA
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STA RETADR+1
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PLA
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STA :MLEN ; MAXIMUM CONCAT LENGTH
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PLA
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STA ADDR2 ; STRING 1 ADDRESS
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PLA ; IN ZERO PAGE
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STA ADDR2+1
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PLA
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STA ADDR1 ; STRING 2 ADDRESS
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PLA ; IN ZERO PAGE
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STA ADDR1+1
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LDY #0
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LDA (ADDR1),Y ; GET CUR LGTH OF S1, STORE
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STA :S1LEN
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STA :S1IND
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INC :S1IND ; START CONCAT AT END OF S1
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LDA (ADDR2),Y ; GET LENGTH OF S2, STORE
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STA :S2LEN
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LDA #1
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STA :S2IND ; START CONCAT AT BEGIN OF S2
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LDA :S2LEN ; GET S2 LENGTH
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CLC
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ADC :S1LEN ; ADD TO LENGTH OF S1
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STA :S3LEN ; STORE CONCAT LENGTH
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BCS :TOOLONG ; BR IF LENGTH > 255
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CMP :MLEN ; CHECK AGAINST MAX LENGTH
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BEQ :LENOK ; BR IF LENGTH < MAX
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BCC :LENOK
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:TOOLONG
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LDA #$0FF
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STA :SOVF ; INDICATE OVERFLOW
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LDA :MLEN
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SEC
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SBC :S1LEN
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BCC :EXIT
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STA :SCNT ; ORIG STR WAS TOO LONG
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LDA :MLEN
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STA :S1LEN ; SET STR1 LENGTH TO MAX
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JMP :DOCAT
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:LENOK
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STA :S1LEN
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LDA #0 ; SAVE SUM OF 2 LENGTHS
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STA :SOVF ; INDICATE NO OVERFLOW
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LDA :S2LEN
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STA :SCNT ; COUNT = LENGTH OF STRING 2
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:DOCAT
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LDA :SCNT
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BEQ :EXIT ; EXIT IF NO BYTES LEFT
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:CATLP
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LDY :S2IND
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LDA (ADDR2),Y ; GET NEXT BYTE FROM S2
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LDY :S1IND
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STA (ADDR1),Y ; MOVE IT TO END OF STR 1
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INC :S1IND ;INC STRING 1 INDEX
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INC :S2IND ; INC STRING 2 INDEX
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DEC :SCNT ; DECREMENT COUNTER
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BNE :CATLP ; CONT UNTIL __SCNT = 0
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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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LDA :SOVF
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ROR A
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LDA RETADR+1
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PHA
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LDA RETADR
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PHA
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LDY #0
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LDA (ADDR1),Y ; LENGTH OF STRING
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STA RETLEN
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LDA #1
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:RLP
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LDA (ADDR1),Y
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STA RETURN,Y
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CPY RETLEN
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INY
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BNE :RLP
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LDA RETLEN
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LDY #0
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STA (ADDR1),Y
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LDX :S3LEN ; RETURN FINAL LENGTH
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RTS
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:S3LEN DS 1
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:S1LEN DS 1
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:S1IND DS 1
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:S2LEN DS 1
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:S2IND DS 1
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:MLEN DS 1
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:SCNT DS 1
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:SOVF DS 1
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