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81 lines
3.2 KiB
Plaintext
81 lines
3.2 KiB
Plaintext
;C02 stack module assembly language subroutines
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;Requires external zero page variables
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;STKLO, STKHI, DSTLO, DSTHI, SRCLO, SRCHI
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;external variables
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;STKSLO, STKSHI, STKELO, STKEHI, TEMP0, TEMP1, TEMP2, TEMP3
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;external routines
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;MEMCPL, STKADD, STKDRN, STKPSA, STKRSP, STKSRC, STKSSP, STRLEN
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;stkstr(n, &m) - Push String onto Stack
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;Args: Y,X = Address of Source Array
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STKSTR: JSR STRLEN ;Get Length of String
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BEQ STKSTY ;If Length > 0
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BMI STKSTY ; and < 128
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INY ; Increment Length to
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TYA ; include null terminator
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STKSTY: LDY #0 ;Clear Y Index
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JMP STKPSA ;Push Bytes onto Stack
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;stktop(&m) - Copy Top Entry off Stack
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;Args: Y,X = Address of Source Array
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;Uses: STKSLO, STKSHI = Stack Start Address
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;Affects: C,N,Z
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;Returns: A,Y = Number of Bytes in Entry
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; 0 = Error: Stack Underflow
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STKTOP: JSR STKPOP ;Pop Top Entry Off Stack
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BEQ STKSWR ;If Underflow, Return 0
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JMP STKRSP ;Else Restore Stack Pointer and Return
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;stkdup(&m) - Duplicate Top Entry on Stack
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;Uses: STKSLO, STKSHI = Stack Start Address
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; STKELO, STKEHI = Stack End Address
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;Updates: STKLO, STKHI = Stack Pointer
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;Affects: C,N,Z
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;Returns: A,Y = Number of Bytes in Entry
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; 0 = Error: Stack Overflow or Underflow
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STKDUP: JSR STKDRP ;Deallocate Top Entry
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STKDUS: JSR STKSRC ;Set Source Pointer to Stack Pointer
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JSR STKRSP ;Restore Stack Pointer
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JMP STKSTY ;Push Top Entry onto Stack
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;stkovr(&m) - Duplicate Second Entry on Stack
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;Uses: STKSLO, STKSHI = Stack Start Address
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; STKELO, STKEHI = Stack End Address
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;Updates: STKLO, STKHI = Stack Pointer
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;Affects: C,N,Z
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;Returns: A,Y = Number of Bytes in Entry
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; 0 = Error: Stack Overflow or Underflow
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STKOVR: JSR STKDRP ;Deallocate Top Entry
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JSR STKDRN ;Deallocate Second Entry
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JMP STKDUS ;Restore Pointer and Duplicate
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;stkswp() - Swap Top Entry with Entry Below it
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;Uses: STKSLO, STKSHI = Stack Start Address
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; STKELO, STKEHI = Stack End Address
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;Destroys: DSTLO,TEMP0,TEMP0,TEMP1,TEMP2,TEMP3
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;Affects: C,N,Z
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;Returns: A,Y = Number of Bytes in Entry
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; 0 = Error: Stack Overflow or Underflow
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STKSWP: JSR STKOVR ;Duplicate Second Entry
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BEQ STKSWR ;Exit if Error
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JSR STKDRN ;Deallocate Duplicate
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STA TEMP3 ;Save Size of Duplicate
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JSR STKSSP ;Save Pointer to Duplicate
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JSR STKDRN ;Deallocate Top Entry
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JSR STKSRC ;Set Source to Top Entry
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STA DSTLO ;Save Top Entry Size
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JSR STKDRN ;Deallocate Second Entry
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LDA DSTLO ;Retrieve Top Entry Size
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JSR STKSWC ;Copy Top Entry Down
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JSR RESSRC ;Set Duplicate as Source
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LDA TEMP3 ;Get Duplicate Length
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STKSWC: STA TEMP0 ;Save Number of Bytes
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JSR STKDST ;Set Destination to Stack Pointer
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LDY #0 ;Clear Index Register
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JSR MEMCPL ;Copy Bytes and Return
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STA (DSTLO),Y ;Store Number of Bytes after Entry
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SEC ;Add Number of Bytes plus 1
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JSR STKADC ;to Stack Pointer
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TYA ;Return Number of Bytes
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STKSWR: RTS
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