mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
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9b12b6fd9b
- getting ready for major changes for 0.6.0. - be sure to download the 0.5.0 release to ensure proper functionality, as these rountines will not work together in the SRC or BIN folder during the transition - Beginning to significantly alter documentation
48 lines
1.6 KiB
NASM
48 lines
1.6 KiB
NASM
*``````````````````````````````*
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* SUBCOPY (NATHAN RIGGS) *
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* *
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* COPY A SUBSTRING FROM A *
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* STRING AND STORE IN RETURN. *
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* *
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* INPUT: *
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* *
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* BPAR1 = SUBSTRING LENGTH *
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* BPAR2 = SUBSTRING INDEX *
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* WPAR1 = SOURCE STRING ADDR *
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* *
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* OUTPUT: *
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* *
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* .A = SUBSTRING LENGTH *
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* RETURN = SUBSTRING *
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* RETLEN = SUBSTRING LENGTH *
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* *
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* DESTROY: AXYNVBDIZCMS *
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* ^^^^^ ^^^ *
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* *
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* CYCLES: 46+ *
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* SIZE: 27 BYTES *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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]SUBLEN EQU BPAR1 ; SUBSTRING LENGTH
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]SUBIND EQU BPAR2 ; SUBSTRING INDEX
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]STR EQU WPAR1 ; SOURCE STRING
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*
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SUBCOPY
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*
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LDY ]SUBIND ; STARTING COPY INDEX
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LDA ]SUBLEN ; SUBSTRING LENGTH
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STA RETLEN ; STORE SUBSTRING LENGTH IN RETLEN
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LDX #0
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:COPY
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LDA (]STR),Y ; GET SUBSTRING CHARACTER
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STA RETURN,X ; STORE CHAR IN RETURN
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CPX ]SUBLEN ; IF .X COUNTER = SUBSTRING LENGTH
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BEQ :EXIT ; THEN FINISHED WITH LOOP
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INY ; OTHERWISE, INCREMENT .Y
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INX ; AND INCREMENT .X
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CLC ; CLEAR CARRY FOR FORCED BRANCH
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BCC :COPY ; LOOP
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:EXIT
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LDA ]SUBLEN ; RETURN SUBSTRING LENGTH IN .A
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RTS
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