mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-11-24 07:31:09 +00:00
240 lines
6.1 KiB
Plaintext
240 lines
6.1 KiB
Plaintext
*``````````````````````````````*
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* SUBINS :: INSERT SUBSTRING *
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*- -*
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* INSERT A SUBSTRING INTO *
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* ANOTHER STRING. *
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*- -*
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* CLOBBERS: *
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* *
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* FLAGS: ????---- REG: AXYM *
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*- -*
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* CYCLES: ??? *
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* SIZE: *
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*- -*
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* USAGE: *
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* *
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* LDA #STR ; STRING TO INS TO *
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* PHA *
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* LDA #<STR *
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* PHA *
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* LDA IND ; INDEX TO START INS *
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* PHA *
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* LDA MLEN ; MAX LENGTH OF STR *
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* PHA *
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* LDA #>SUB ; SUBSTRING TO INS *
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* PHA *
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* LDA #<SUB *
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* PHA *
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* JST SUBINS *
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*- -*
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* ENTRY *
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* *
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* TOP OF STACK *
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* *
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* LOW BYTE OF RETURN ADDRESS *
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* HI BYTE OF RETURN ADDRESS *
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* LO BYTE OF SUBSTRING ADDRESS *
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* HI BYTE OF SUBSTRING ADDRESS *
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* MAX LENGTH OF FINAL STRING *
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* STARTING INDEX FOR INSERTION *
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* LO BYTE OF SRC STRING ADDR *
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* HI BYTE OF SOURCE STR ADDR *
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*- -*
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* EXIT *
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* *
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* TOP OF STACK *
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* *
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* LOW BYTE OF RETURN ADDRESS *
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* HI BYTE OF RETURN ADDRESS *
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* *
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* .Y = TRASH *
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* .X = TRASH *
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* .A = TRASH *
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* *
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* CARRY = 0 IF NO ERRORS; ELSE *
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* CARRY = 1 *
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*- -*
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* ADAPTED FROM LEVANTHAL AND *
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* WINTHROP'S /6502 ASSEMBLY *
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* LANGUAGE ROUTINES/. *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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SUBINS
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*
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** GET RETURN ADDRESS
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*
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PLA
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TAY
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PLA
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TAX
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*
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** GET PARAMETERS
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*
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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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*
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** RESTORE RETURN ADDRESS
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*
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TXA
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PHA
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TYA
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PHA
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*
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*
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** ASSUME NO ERRORS
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*
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LDA #0
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STA :SCERR ; ASSUME NO ERR WILL BE FOUND
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*
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** GET SUBSTRING AND STRING LENGTHS
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** IF SUB LENGTH = 0 THEN EXIT NO ERROR
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*
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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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*
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** IF STARTING INDEX IS 0 THEN ERROR EXIT
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*
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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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*
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** CHECK THAT THE RESULTING STRING AFTER THE
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** INSERTION FITS IN THE SOURCE STRING. IF NOT
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** THEN TRUNCATE THE SUBSTRING AND SET
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** THE TRUNCATION FLAG.
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*
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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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*
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** SUBSTRING DOES NOT FIT, SO TRUNCATE IT
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*
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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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; (ORIGINAL STRING WAS TOO LONG)
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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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*
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** CHECK THAT INDEX IS WITHIN STRING. IF NOT, CONCAT
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** SUBSTR ONTO THE END OF THE STRING.
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*
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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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*
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** OPEN UP A SPACE IN THE SOURCE STRING FOR THE
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** SUBSTRING BY MOVING THE CHARACTERS FROM THE END
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** OF THE SOURCE STRING DOWN TO INDEX, UP BY
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** THE SIZE OF THE STRING.
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*
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:LENOK
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*
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** CALC NUMBER OF CHARS TO MOVE
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** COUNT = STR LEN - START INDEX + 1
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*
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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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*
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** SET THE SOURCE INDEX AND CALC DEST INDEX
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*
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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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*
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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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*
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** MOVE THE SUBSTR INTO THE OPEN AREA
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*
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:MVESUB
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LDA #1
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STA :SIDX
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; START AT ONE IN THE SUBSTR
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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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*
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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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*
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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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*
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** DATA
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*
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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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*
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