6502basiccompiler/arch/6502/__sandbox__/library-asm/_2_converting/load.asm

#include once <alloc.asm>
#include once <free.asm>
#include once <print.asm>

LOAD_CODE:
; This function will implement the LOAD CODE Routine
; Parameters in the stack are HL => String with LOAD name
; (only first 12 chars will be taken into account)
; DE = START address of CODE to save
; BC = Length of data in bytes
; A = 1 => LOAD 0 => Verify
                    ;- PROC
                    ;- LOCAL LOAD_CONT, LOAD_CONT2, LOAD_CONT3
                    ;- LOCAL LD_BYTES
                    ;- LOCAL LOAD_HEADER
                    ;- LOCAL LD_LOOK_H
                    ;- LOCAL HEAD1
                    ;- LOCAL TMP_HEADER
                    ;- LOCAL LD_NAME
                    ;- LOCAL LD_CH_PR
                    ;- LOCAL LOAD_END
                    ;- LOCAL VR_CONTROL, VR_CONT_1, VR_CONT_2

HEAD1 EQU MEM0 + 8
; Uses CALC Mem for temporary storage
; Must skip first 8 bytes used by
; PRINT routine
TMP_HEADER EQU HEAD1 + 17 ; Temporary HEADER2 pointer storage

LD_BYTES EQU 0556h ; ROM Routine LD-BYTES
TMP_FLAG EQU 23655 ; Uses BREG as a Temporary FLAG

                    ;- pop hl         ; Return address
                    ;- pop af         ; A = 1 => LOAD; A = 0 => VERIFY
                    ;- pop bc         ; data length in bytes
                    ;- pop de         ; address start
                    ;- ex (sp), hl    ; CALLE => now hl = String

__LOAD_CODE: ; INLINE version
                    ;- push ix ; saves IX
                    ;- ld (TMP_FLAG), a ; Stores verify/load flag

; Prepares temporary 1st header descriptor
                    ;- ld ix, HEAD1
                    ;- ld (ix + 0), 3     ; ZXBASIC ALWAYS uses CODE
                    ;- ld (ix + 1), 0FFh  ; Wildcard for empty string

                    ;- ld (ix + 11), c
                    ;- ld (ix + 12), b ; Store length in bytes
                    ;- ld (ix + 13), e
                    ;- ld (ix + 14), d ; Store address in bytes

                    ;- ld a, h
                    ;- or l
                    ;- ld b, h
                    ;- ld c, l
                    ;- jr z, LOAD_HEADER ; NULL STRING => LOAD ""

                    ;- ld c, (hl)
                    ;- inc hl
                    ;- ld b, (hl)
                    ;- inc hl

                    ;- ld a, b
                    ;- or c
                    ;- jr z, LOAD_CONT2 ; NULL STRING => LOAD ""

; Fill with blanks
                    ;- push hl
                    ;- push bc
                    ;- ld hl, HEAD1 + 2
                    ;- ld de, HEAD1 + 3
                    ;- ld bc, 8
                    ;- ld (hl), ' '
                    ;- ldir
                    ;- pop bc
                    ;- pop hl

LOAD_HEADER:
                    ;- ex de, hl  ; Saves HL in DE
                    ;- ld hl, 10
                    ;- or a
                    ;- sbc hl, bc ; Test BC > 10?
                    ;- ex de, hl  ; Retrieve HL
                    ;- jr nc, LOAD_CONT ; Ok BC <= 10
                    ;- ld bc, 10 ; BC at most 10 chars

LOAD_CONT:
                    ;- ld de, HEAD1 + 1
                    ;- ldir     ; Copy String block NAME in header

LOAD_CONT2:
                    ;- ld bc, 17; 2nd Header
                    ;- call __MEM_ALLOC

                    ;- ld a, h
                    ;- or l
                    ;- jr nz, LOAD_CONT3; there's memory

                    ;- ld a, ERROR_OutOfMemory
                    ;- jp __ERROR

LOAD_CONT3:
                    ;- ld (TMP_HEADER), hl
                    ;- push hl
                    ;- pop ix

;; LD-LOOK-H --- RIPPED FROM ROM at 0x767
LD_LOOK_H:
                    ;- push ix                 ; save IX
                    ;- ld de, 17               ; seventeen bytes
                    ;- xor a                   ; reset zero flag
                    ;- scf                     ; set carry flag

                    ;- call LD_BYTES           ; routine LD-BYTES loads a header from tape
                    ;-                         ; to second descriptor.
                    ;- pop ix                  ; restore IX
                    ;- jr nc, LD_LOOK_H        ; loop back to LD-LOOK-H until header found.

                    ;- ld c, 80h               ; C has bit 7 set to indicate header type mismatch as
                    ;-                         ; a default startpoint.

                    ;- ld a, (ix + 0)          ; compare loaded type
                    ;- cp 3		            ; with expected bytes header
                    ;- jr nz, LD_TYPE          ; forward to LD-TYPE with mis-match.

                    ;- ld c, -10               ; set C to minus ten - will count characters
                    ;-                         ; up to zero.
LD_TYPE:
                    ;- cp 4                    ; check if type in acceptable range 0 - 3.
                    ;- jr nc, LD_LOOK_H        ; back to LD-LOOK-H with 4 and over.
                    ;-                         ; else A indicates type 0-3.
                    ;- call PRINT_TAPE_MESSAGES; Print tape msg
                    ;- ld hl, HEAD1 + 1        ; point HL to 1st descriptor.
                    ;- ld de, (TMP_HEADER)     ; point DE to 2nd descriptor.
                    ;- ld b, 10                ; the count will be ten characters for the
                    ;-                         ; filename.

                    ;- ld a, (hl)              ; fetch first character and test for
                    ;- inc a                   ; value 255.
                    ;- jr nz, LD_NAME          ; forward to LD-NAME if not the wildcard.

;   but if it is the wildcard, then add ten to C which is minus ten for a type
;   match or -128 for a type mismatch. Although characters have to be counted
;   bit 7 of C will not alter from state set here.

                    ;- ld a, c                 ; transfer $F6 or $80 to A
                    ;- add a, b                ; add 10
                    ;- ld c, a                 ; place result, zero or -118, in C.

;   At this point we have either a type mismatch, a wildcard match or ten
;   characters to be counted. The characters must be shown on the screen.

;; LD-NAME
LD_NAME:
                    ;- inc de                  ; address next input character
                    ;- ld a, (de)              ; fetch character
                    ;- cp (hl)                 ; compare to expected
                    ;- inc hl                  ; address next expected character
                    ;- jr nz, LD_CH_PR         ; forward to LD-CH-PR with mismatch

                    ;- inc c                   ; increment matched character count

;; LD-CH-PR
LD_CH_PR:
                    ;- call __PRINTCHAR        ; PRINT-A prints character
                    ;- djnz LD_NAME            ; loop back to LD-NAME for ten characters.

                    ;- bit 7, c                ; test if all matched
                    ;- jr nz, LD_LOOK_H        ; back to LD-LOOK-H if not

;   else print a terminal carriage return.

                    ;- ld a, 0Dh               ; prepare carriage return.
                    ;- call __PRINTCHAR        ; PRINT-A outputs it.

                    ;- ld a, (HEAD1)
                    ;- cp 03                   ; Only "bytes:" header is used un ZX BASIC
                    ;- jr nz, LD_LOOK_H

; Ok, ready to check for bytes start and end

VR_CONTROL:
                    ;- ld e, (ix + 11)         ; fetch length of new data
                    ;- ld d, (ix + 12)         ; to DE.
                    ;- ld hl, HEAD1 + 11
                    ;- ld a, (hl)              ; fetch length of old data (orig. header)
                    ;- inc hl
                    ;- ld h, (hl)              ; to HL
                    ;- ld l, a
                    ;- or h                    ; check length of old for zero. (Carry reset)
                    ;- jr z, VR_CONT_1         ; forward to VR-CONT-1 if length unspecified e.g. LOAD "x" CODE
                    ;- sbc hl, de
                    ;- jr nz, LOAD_ERROR       ; Lenghts don't match

VR_CONT_1:
                    ;- ld hl, HEAD1 + 13       ; fetch start of old data (orig. header)
                    ;- ld a, (hl)
                    ;- inc hl
                    ;- ld h, (hl)
                    ;- ld l, a
                    ;- or h                    ; check start for zero (unespecified)
                    ;- jr nz, VR_CONT_2        ; Jump if there was a start
                    ;- ld l, (ix + 13)         ; otherwise use destination in header
                    ;- ld h, (ix + 14)         ; and load code at addr. saved from

VR_CONT_2:
lda z80_l            ;- push hl
pha
lda z80_h
pha
                    ;- pop ix                  ; Transfer load addr to IX
                    ;- ld a, (TMP_FLAG)        ; load verify/load flag
                    ;- sra a                   ; shift bit 0 to Carry (1 => Load, 0 = Verify), A = 0
                    ;- dec a                   ; a = 0xFF (Data)
                    ;- call LD_BYTES
                    ;- jr c, LOAD_END         ; if carry, load/verification was ok

LOAD_ERROR:
; Sets ERR_NR with Tape Loading, and returns
                    ;- ld a, ERROR_TapeLoadingErr
                    ;- ld (ERR_NR), a

LOAD_END:
pla                 ;- pop ix                  ; Recovers stack frame pointer
sta z80_ix+1
pla
sta z80_ix
                    ;- ld hl, (TMP_HEADER)     ; Recovers tmp_header pointer
                    ;- jp MEM_FREE             ; Returns via FREE_MEM, freeing tmp header
                    ;- ENDP

PRINT_TAPE_MESSAGES:
                    ;- PROC
                    ;- LOCAL LOOK_NEXT_TAPE_MSG
                    ;- LOCAL PRINT_TAPE_MSG
; Print tape messages according to A value
; Each message starts with a carriage return and
; ends with last char having its bit 7 set
; A = 0 => '\nProgram: '
; A = 1 => '\nNumber array: '
; A = 2 => '\nCharacter array: '
; A = 3 => '\nBytes: '
lda z80_c           ;- push bc
pha
lda z80_b
pha
                    ;- ld hl,09C0h       ; address base of last 4 tape messages
lda z80_a           ;- ld b,a
sta z80_b
inc z80_b           ;- inc b              ; avoid 256-loop if b == 0
                    ;- ld a,0Dh          ; Msg start mark
; skip memory bytes looking for next tape msg entry
; each msg ends when 0Dh is fond
LOOK_NEXT_TAPE_MSG:
inc z80_l           ;- inc hl             ; Point to next char
bne *+4
inc z80_h
                    ;- cp (hl)            ; Is it 0Dh?
                    ;- jr nz, LOOK_NEXT_TAPE_MSG
; Ok next message found
                    ;- djnz LOOK_NEXT_TAPE_MSG ; Repeat if more msg to skip

PRINT_TAPE_MSG:
; Ok. This will print bytes after (HL)
; until one of them has bit 7 set
ldy #$00            ;- ld a,(hl)
lda (z80_hl),y
sta z80_a
and #$7F            ;- and $7F  ; Clear bit 7 of A
jsr __PRINTCHAR     ;- call __PRINTCHAR
ldy #$00            ;- ld a,(hl)
lda (z80_hl),y
sta z80_a
inc z80_l           ;- inc hl
bne *+4
inc z80_h
clc                 ;- add a,a                ; Carry if A >= 128
adc z80_a
jcs PRINT_TAPE_MSG  ;- jr nc, PRINT_TAPE_MSG
pla                 ;- pop bc
sta z80_b
pla
sta z80_c
rts                 ;- ret
                    ;- ENDP