mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-06-10 14:29:27 +00:00
60 lines
2.2 KiB
NASM
60 lines
2.2 KiB
NASM
*``````````````````````````````*
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* STRCMP (NATHAN RIGGS) *
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* *
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* COMPARES A STRING TO ANOTHER *
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* STRING AND SETS THE FLAGS *
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* ACCORDINGLY: *
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* *
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* Z = 1 IF STRINGS MATCH *
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* Z = 0 IF STRINGS DON'T MATCH *
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* *
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* IF THE STRINGS MATCH UP TO *
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* THE LENGTH OF THE SHORTEST *
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* STRING, THE STRING LENGTHS *
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* ARE THEN COMPARED AND THE *
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* CARRY FLAG IS SET AS SUCH: *
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* *
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* C = 0 IF 1ST STRING < 2ND *
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* C = 1 IF 1ST STRING >= 2ND *
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* *
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* INPUT: *
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* *
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* ZPW1 = 1ST STRING ADDRESS *
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* ZPW2 = 2ND STRING ADDRESS *
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* *
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* DESTROY: NZCIDV *
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* ^^^ ^ *
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* *
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* CYCLES: 68+ *
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* SIZE: 32 BYTES *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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]STR1 EQU ZPW1 ; ZP POINTER TO 1ST STRING
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]STR2 EQU ZPW2 ; ZP POINTER TO 2ND STRING
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*
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STRCMP
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*
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LDY #0 ; {3C2B} RESET .Y COUNTER
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LDA (]STR1),Y ; {5C2B} GET LENGTH OF 1ST STRING
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CMP (]STR2),Y ; {5C2B} IF STR1 LENGTH < STR2 LENGTH
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BCC :BEGCMP ; {3C2B} THEN BEGIN COMPARISON; ELSE
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LDA (]STR2),Y ; {5C2B} USE STR2 LENGTH INSTEAD
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:BEGCMP
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TAX ; {2C1B} X IS LENGTH OF SHORTER STRING
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BEQ :TSTLEN ; {3C2B} IF LENGTH IS 0, TEST LENGTH
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LDY #1 ; {3C2B} ELSE SET .Y TO 1ST CHAR
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:CMPLP
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LDA (]STR1),Y ; {5C2B} GET INDEXED CHAR OF 1ST STRING
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CMP (]STR2),Y ; {5C2B} COMPARE TO INDEXED CHAR OF 2ND
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BNE :EXIT ; {3C2B} EXIT IF THE CHARS ARE NOT EQUAL
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; Z,C WILL BE PROPERLY SET
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INY ; {2C1B} INCREASE CHARACTER INDEX
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DEX ; {2C1B} DECREMENT COUNTER
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BNE :CMPLP ; {3C2B} CONT UNTIL ALL CHARS CHECKED
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:TSTLEN
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LDY #0 ; {3C2B} NOW COMPARE LENGTHS
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LDA (]STR1),Y ; {5C2B} GET LENGTH OF 1ST STRING
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CMP (]STR2),Y ; {5C2B} SET OR CLEAR THE FLAGS
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:EXIT
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RTS ; {6C1B}
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