181 lines
5.5 KiB
ArmAsm
181 lines
5.5 KiB
ArmAsm
; %help
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; setyear - Patch the ProDOS year table in-memory
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;
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; usage: setyear <00-99> [-v] [-n]
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;
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; Patches the ProDOS year table to include the given year plus at least
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; 4 more years beyond.
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;
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; Options: -v Show generated year table
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; -n Don't actually patch ProDOS.
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; %hend
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.p02
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.include "davex-mg.inc"
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tmp = xczpage
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year = tmp+1
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count = year+1
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;prbyte = $fdda
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;cout = $fded
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DX_start dx_mg_auto_origin ; load address
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DX_info $01,$12,dx_cc_any,$00
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DX_ptab
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DX_parm $00,t_int1 ; year (two-digit)
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DX_parm 'v',t_nil ; verbose
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DX_parm 'n',t_nil ; no-patch
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DX_end_ptab
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DX_desc "Set ProDOS year table."
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DX_main
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lda #$00 ; parm
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jsr xgetparm_n ; davex ensures this is here
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cpy #100
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bcs badparms
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jsr mkyt
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lda #'v'|$80 ; "verbose"
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jsr xgetparm_ch
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bcs :+ ; not given, don't display
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jsr dispyt
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: lda #'n'|$80 ; "no patch"
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jsr xgetparm_ch
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bcs :+ ; not given, do it
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rts
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; see if we can patch the driver
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: lda $c08b
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lda $c08b
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ldx #$03
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: lda $d7b4,x ; tdays table, at september
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cmp tdaysv,x ; that what ProDOS has?
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bne setyterr ; not the thunderclock driver
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dex
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bpl :-
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; go ahead and patch
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ldx #6
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: lda yeartab,x
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sta $d7b8,x ; address of year table in P8
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dex
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bpl :-
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bit $c082 ; ROM back before exit
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rts
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setyterr: bit $c082 ; ROM back before death
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lda #$01
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jsr xredirect
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jsr xmess
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asc_hi "Can't patch clock driver!"
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.byte $00
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jmp exiterr
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badparms: lda #$01
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jsr xredirect
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jsr xmess
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asc_hi "Bad year!"
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.byte $00
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exiterr: lda #$ff
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jsr xredirect
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jmp xerr
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;
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.proc mkyt
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tya
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and #%00000011 ; divisible by 4?
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bne :+ ; nope
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dey ; avoid starting table on leap year
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bpl :+ ; did't wrap around
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ldy #99 ; 1999
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: sty year
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lda #$06 ; do for 6 years
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sta count
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yloop: lda year
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cmp #40 ; 40 or greater?
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bcs :+ ; Do not adjust for 1940-1999
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adc #100 ; add 100 years for 2000-2039
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: tay ; year
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lda #1 ; day
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tax ; month
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jsr weekday
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tax
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ldy dayidx,x ; get index into ProDOS year table
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lda year
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cmp #100 ; need to account for incrementing past 100
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bcc :+
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sbc #100
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: sta yeartab,y ; put year in the appropriate slot
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inc year
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dec count
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bne yloop
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; now fix leap year gap
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ldy yeartab ; first year
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ldx #$06 ; index of last year
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lloop: lda yeartab,x
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cmp #$ff ; not filled in?
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bne :+
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tya ; yes, use previous value
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: sta yeartab,x ; write back
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tay ; and save as new 'previous' value
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dex
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bpl lloop
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rts
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.endproc
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.proc dispyt
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lda #$00
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sta year
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lda #$07
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sta count
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prloop: ldx year
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ldy yeartab,x
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sty tmp
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lda #$20
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cpy #40
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bcc :+
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lda #$19
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: jsr prbyte
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lda tmp
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cmp #$10
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bcs :+
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lda #'0'|$80
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jsr cout
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: ldy tmp
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lda #$00
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jsr xprdec_2
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lda #$8d
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jsr cout
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inc year
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dec count
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bne prloop
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rts
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.endproc
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; table to index into year-starts in P8 tclock driver
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dayidx: .byte 1,0,6,5,4,3,2 ; MonSunSatFriThuWedTue
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; Table we will copy into ProDOS
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yeartab: .res 7,$ff
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; table to validate the P8 tclock driver, 4 bytes at $d7b4
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tdaysv: .byte 242,20,51,81
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; adapted from http://6502.org/source/misc/dow.htm
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; inputs: y = year (0-255 = 1900-2155)
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; x = month
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; a = day
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; output: a = weekday (0 = Sunday)
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.proc weekday
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cpx #3 ; year starts in march to bypass
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bcs march ; leap year problem
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dey ; if jan or feb, decrement year
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march: eor #$7f ; invert a so carry works right
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cpy #200 ; carry will be 1 if 22nd century
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adc mtab-1,x ; a is now day+month offset
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sta tmp
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tya ; get the year
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jsr mod7 ; do a modulo to prevent overflow
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sbc tmp ; combine with day+month
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sta tmp
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tya ; get the year again
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lsr ; divide it by 4
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lsr
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clc ; add it to y+m+d and fall through
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adc tmp
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mod7: adc #7 ; returns (a+3) modulo 7
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bcc mod7 ; for a in 0..255
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rts
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mtab: .byte 1,5,6,3,1,5,3,0,4,2,6,4 ; month offsets
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.endproc
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DX_end
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