AppleIIAsm-Collection/disks/disk3_arrays/T.ARRAYS82.DIM

*
*``````````````````````````````*
* DIM82 :: INIT 2D ARRAY       *
*-                            -*
* THIS SIMPLY CREATES A 1D     *
* ARRAY WITH THE DIM OF        *
* ARRAYX BY ARRAYY.            *
*-                            -*
* FIRST BYTE OF MEMORY USED    *
* HOLDS LENGTH OF X (ROWS);    *
* SECOND BYTE HOLDS LENGTH OF  *
* Y (COLUMNS); THIRD BYTE      *
* HOLDS LENGTH OF EACH ELEMENT *
*-                            -*
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: AXYM  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*   LDA #>$300 ; ARRAY ADDR    *
*   PHA                        *
*   LDA #<$300                 *
*   PHA                        *
*   LDA #4 ; X DIMENSION BOUND *
*   PHA                        *
*   LDA #4 ; Y DIMENSION BOUND *
*   PHA                        *
*   LDA #1 ; ELEMENT BYTESIZE  *
*   PHA                        *
*   JSR DIM82                  *
*-                            -*
* ENTRY                        *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
* ELEMENT SIZE IN BYTES        *
* Y DIMENSION BOUNDARY         *
* X DIMENSION BOUNDARY         *
* ARRAY ADDRESS, LOW BYTE      *
* ARRAY ADDRESS, HIGH BYTE     *
*-                            -*
* EXIT                         *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
*                              *
*   Y = ARRAY ADDRESS LO BYTE  *
*   X = ARRAY ADDRESS HI BYTE  *
*   A = CLOBBERED              *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
DIM82
*
** SAVE RETURN ADDRESS
*
         PLA
         STA   RETADR
         PLA
         STA   RETADR+1
*
** GET PARAMETERS
*
         PLA
         STA   :MCAND     ; ELEMENT LENGTH
         PLA
         STA   :AYSIZE
         STA   :AYBAK
         PLA
         STA   :AXSIZE
         STA   :AXBAK
         PLA
         STA   ADDR1
         PLA
         STA   ADDR1+1
*
** LOOP THROUGH Y, CLEARING MEMORY
** FOR X BYTES TIMES ELEMENT SIZE,
** MOVING TO END OF LAST CLEAR
** UNTIL FINISHED
*
** MULTIPLY X AND Y
*
         LDA   #0
         TAY
         STY   SCRATCH
         BEQ   :ENTLP
*
:DOADD
         CLC
         ADC   :AXSIZE
         TAX
*
         TYA
         ADC   SCRATCH
         TAY
         TXA
*
:LP
         ASL   :AXSIZE
         ROL   SCRATCH
:ENTLP
         LSR   :AYSIZE
         BCS   :DOADD
         BNE   :LP
*
         STX   :MLIER
         STY   :MLIER+1
*
** NOW MULTIPLY BY LENGTH OF ELEMENTS
*
         LDA   #0
         STA   :PROD+2
         STA   :PROD+3
         LDX   #$10
:SHIFTR  LSR   :MLIER+1
         ROR   :MLIER
         BCC   :ROTR
         LDA   :PROD+2
         CLC
         ADC   :MCAND
         STA   :PROD+2
         LDA   :PROD+3
         ADC   :MCAND+1
:ROTR
         ROR
         STA   :PROD+3
         ROR   :PROD+2
         ROR   :PROD+1
         ROR   :PROD
         DEX
         BNE   :SHIFTR
*
         INC   :PROD      ; INCREASE BY 3
         INC   :PROD
         INC   :PROD
         LDX   :PROD
         LDY   :PROD+1
*
** NOW CLEAR MEMORY BLOCKS, WHOLE PAGES FIRST
*
         LDA   #$00       ; FILL VALUE
         LDX   :PROD+1    ; NOTE THAT THIS WON'T
                          ; GO BEYOND A 16BIT VALUE;
                          ; ANYTHING HIGHER THAN
                          ; 16BITS IS MORE THAN
                          ; THERE IS MEMORY IN A
                          ; STANDARD APPLE ][
         BEQ   :PART
         LDY   #0
:FULL
         STA   (ADDR1),Y
         INY
         BNE   :FULL
         INC   ADDR1+1
         DEX
         BNE   :FULL      ; LOOP UNTIL PAGES DONE
*
** NOW DO REMAINING BYTES
*
:PART
         LDX   :PROD
         BEQ   :MFEXIT
         LDY   #0
:PARTLP
         STA   (ADDR1),Y
         INY
         DEX
         BNE   :PARTLP    ; LOOP UNTIL DONE
:MFEXIT
*
** NOW SET SIZES
*
         LDY   #0
         LDA   :AXBAK
         STA   (ADDR1),Y
         INY
         LDA   :AYBAK
         STA   (ADDR1),Y
         INY
         LDA   :MCAND
         STA   (ADDR1),Y
*
** RESTORE RETURN ADDRESS
*
         LDA   RETADR+1
         PHA
         LDA   RETADR
         PHA
*
** RETURN POINTER TO STARTING ADDRESS OF ARRAY
*
         LDY   ADDR1
         LDX   ADDR1+1
*
         RTS
*
** DATA
*
:PROD    DS    4
:AXSIZE  DS    1
:AYSIZE  DS    1
:AXBAK   DS    1
:AYBAK   DS    1
:MLIER   DS    2
:MCAND   DS    2
*