AppleIIAsm-Collection/source/disk2_common/T.SUB.MEMMOVE

*
*``````````````````````````````*
* MEMMOVE ::    MOVE MEM BLOCK *
*-                            -*
* MOVES A SPECIFIED BLOCK OF   *
* MEMORY FROM A SOURCE ADDRESS *
* TO A DESTINATION ADDRESS     *
* RANGE.                       *
*-                            -*
* CLOBBERS:                    *
*                              *
* FLAGS:  ????----  REG: AXYM  *
*-                            -*
* CYCLES: ???                  *
* SIZE:                        *
*-                            -*
* USAGE:                       *
*                              *
*  LDA #>$6A00                 *
*  PHA                         *
*  LDA #<$6A00                 *
*  PHA                         *
*  LDA #>$7000 ; DEST          *
*  PHA                         *
*  LDA #<$7000                 *
*  PHA                         *
*  LDA #>1024                  *
*  PHA                         *
*  LDA #<1024                  *
*  PHA                         *
*  JSR MEMMOVE                 *
*-                            -*
* ENTRY                        *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
* NUMBER OF BYTES TO MOVE      *
* LOW BYTE OF DESTINATION      *
* HIGH BYTE OF DESTINATION     *
* LOW BYTE OF SOURCE ADDRESS   *
* HIGH BYTE OF SOURCE ADDRESS  *
*-                            -*
* EXIT                         *
*                              *
* TOP OF STACK                 *
*                              *
* LOW BYTE OF RETURN ADDRESS   *
* HI BYTE OF RETURN ADDRESS    *
*                              *
* Y = COUNTER; TRASH           *
* X = COUNTER; TRASH           *
* A = LOW BYTE OF RET ADDR     *
*-                            -*
* ADAPTED FROM LEVANTHAL AND   *
* WINTHROP'S /6502 ASSEMBLY    *
* LANGUAGE ROUTINES/.          *
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
*
MEMMOVE
*
** SAVE RETURN ADDRESS
*
         PLA
         STA   RETADR
         PLA
         STA   RETADR+1
*
** GET PARAMETERS
*
         PLA
         STA   :MVELEN
         PLA
         STA   :MVELEN+1
         PLA
         STA   ADDR2      ; ZERO PAGE POINTER
         PLA
         STA   ADDR2+1
         PLA
         STA   ADDR1
         PLA
         STA   ADDR1+1
*
** DETERMINE IF DEST AREA IS
** ABOVE SRC AREA BUT OVERLAPS
** IT. REMEMBER, OVERLAP CAN BE
** MOD 64K. OVERLAP OCCURS IF
** STARTING DEST ADDRESS MINUS
** STARTING SRC ADDRESS (MOD
** 64K) IS LESS THAN NUMBER
** OF BYTES TO MOVE.
*
         LDA   ADDR2      ;CALC DEST-SRC
         SEC
         SBC   ADDR1
         TAX
         LDA   ADDR2+1
         SBC   ADDR1+1    ; MOD 64K AUTOMATIC
                          ; -- DISCARD CARRY
         TAY
         TXA              ; CMP WITH # OF BYTES TO MOVE
         CMP   :MVELEN
         TYA
         SBC   :MVELEN+1
         BCS   :DOLEFT    ; BRANCH IF NO OVERLAP
*
** DEST AREA IS ABOVE SRC AREA
** BUT OVERLAPS IT.
** MOVE FROM HIGHEST ADDR TO
** AVOID DESTROYING DATA
*
         JSR   :MVERHT
         JMP   :EXIT
*
** NO PROB DOING ORDINARY MOVE
** STARTING AT LOWEST ADDR
*
:DOLEFT
         JSR   :MVELEFT
:EXIT
         JMP   :MREXIT
*
********************************
* SUBROUTINE: MVELEFT          *
********************************
*
:MVELEFT
         LDY   #0         ; ZERO INDEX
         LDX   :MVELEN+1  ; X=# OF FULL PP TO MOVE
         BEQ   :MLPART    ; IF X=0, DO PARTIAL PAGE
:MLPAGE
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ;MOVE ONE BYTE
         INY              ; NEXT BYTE
         BNE   :MLPAGE    ; CONT UNTIL 256B MOVED
         INC   ADDR1+1    ; ADV TO NEXT SRC PAGE
         INC   ADDR2+1    ; ADV NEXT DEST PAGE
         DEX              ; DEC PAGE COUNT
         BNE   :MLPAGE    ; CONT UNTIL ALL FULL
                          ; PAGES ARE MOVED
:MLPART
         LDX   :MVELEN    ; GET LENGTH OF LAST PAGE
         BEQ   :MLEXIT    ; BR IF LENGTH OF LAST
                          ; PAGE = 0
                          ; REG Y IS 0
:MLLAST
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ; MOVE BYTE
         INY              ; NEXT BYTE
         DEX              ; DEC COUNTER
         BNE   :MLLAST    ; CONT UNTIL LAST P DONE
:MLEXIT
         JMP   :MREXIT
*
********************************
* SUBROUTINE: MVERHT           *
********************************
*
:MVERHT
*
** MOVE THE PARTIAL PAGE FIRST
*
         LDA   :MVELEN+1
         CLC
         ADC   ADDR1+1
         STA   ADDR1+1    ;POINT TO LAST P OF SRC
         LDA   :MVELEN+1
         CLC
         ADC   ADDR2+1
         STA   ADDR2+1    ; POINT TO LAST P OF DEST
*
** MOVE THE LAST PARTIAL PAGE FIRST
*
         LDY   :MVELEN    ;GET LENGTH OF LAST PAGE
         BEQ   :MRPAGE    ; IF Y=0 DO THE FULL PAGES
:MR0
         DEY              ; BACK UP Y TO NEXT BYTE
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ; MOVE BYTE
         CPY   #0
         BNE   :MR0       ; BR IF NOT DONE W LAST P
:MRPAGE
         LDX   :MVELEN+1  ; GET BYTE OF COUNT AS P CT
         BEQ   :MREXIT    ; BR IF HYBYTE = 0 (NO FULL P)
:MR1
         DEC   ADDR1+1    ; BACK UP TO PREV SRC PAGE
         DEC   ADDR2+1    ; AND DEST
:MR2
         DEY              ; BACK UP Y TO NEXT BYTE
         LDA   (ADDR1),Y
         STA   (ADDR2),Y  ; MOVE BYTE
         CPY   #0
         BNE   :MR2       ; BR IF NOT DONE W THIS PAGE
         DEX
         BNE   :MR1       ; BR IF NOT ALL PAGES MOVED
:MREXIT
*
** RESTORE RETURN ADDRESS
*
         LDA   RETADR+1
         PHA
         LDA   RETADR
         PHA
         RTS
*
** DATA
*
:MVELEN  DS    2
*