c4.asm

著名SFC模拟器Snes9x的源代码。

%include "i386/macros.mac"
;*******************************************************
; Register & Memory Access Banks (0 - 3F) / (80 - BF)
;*******************************************************
; enter : BL = bank number, CX = address location
; leave : AL = value read

%ifdef __DJGPP__
%define C4WFXVal _C4WFXVal
%define C4WFYVal _C4WFYVal
%define C4WFX2Val _C4WFX2Val
%define C4WFY2Val _C4WFY2Val
%define C4CalcWireFrame _C4CalcWireFrame

%define C4WFDist _C4WFDist
%define C4WFScale _C4WFScale
%define C4TransfWireFrame _C4TransfWireFrame
%define C4TransfWireFrame2 _C4TransfWireFrame2
%define C4WFZVal _C4WFZVal
%define C41FXVal _C41FXVal
%define C41FYVal _C41FYVal
%define C41FAngleRes _C41FAngleRes
%define C41FDist _C41FDist
%define C4Op1F _C4Op1F
%define C4Op15 _C4Op15
%define C41FDistVal _C41FDistVal
%define C4Op0D _C4Op0D
%endif

EXTSYM romdata,pressed,vidbuffer,oamram
EXTSYM C4Ram,C4RamR,C4RamW

C4ProcessVectors:
    mov esi,[C4Ram]
    mov edi,esi
    add edi,1F8Ch
    xor edx,edx
    mov dx,[esi+1F8Ah]
    cmp dx,128
    ja .ret
    cmp dx,0
    jne .nozero
.ret
    ret
.nozero
    cmp dx,10h
    jb .less
    mov dx,10h
.less
    mov esi,[C4Ram]
    add esi,800h
.loop
    mov ecx,100h
    xor ebx,ebx
    xor eax,eax
    movsx bx,byte[edi]
.spotloop
    add ah,80h
    mov byte[esi],ah
    sub ah,80h
    add ax,bx
    inc esi
    loop .spotloop
    add edi,3
    dec dx
    jnz .loop
    ret

SECTION .data
C4ObjDisp dd 0
C4ColRot db 1
NEWSYM C4ObjSelec, db 0
NEWSYM C4SObjSelec, db 0
NEWSYM C4Pause, db 0
C4DataCopy times 64 db 0
;NEWSYM C4Data times 64*4096 db 0        ; 15 sprites, 4 bytes each
                                        ; x,y,oamptr,stat (b0=oamb8,b1=16x16)
                                        ; 4 byte header (#sobj,?,?,?)
CObjNum dw 0
C4Temp dd 0

SECTION .text

C4Edit:
    ; C4 editing routines
    ; Register keyboard presses
    ;  [ = prev object, ] = next object
    ;  p = pause/unpause
    cmp byte[pressed+1Ah],0
    je .notpressed
    mov byte[pressed+1Ah],0
    inc byte[C4ObjSelec]
    inc byte[C4Temp]
.notpressed
    cmp byte[pressed+1Bh],0
    je .notpressed2
    mov byte[pressed+1Bh],0
    dec byte[C4ObjSelec]
    dec byte[C4Temp]
.notpressed2
    cmp byte[pressed+19h],0
    je .notpressed3
    mov byte[pressed+19h],0
    xor byte[C4Pause],1
.notpressed3

    ; Setup variables
    mov esi,[C4Ram]
    add byte[C4ColRot],16
    mov al,[esi+620h]
    cmp byte[C4ObjSelec],0FFh
    jne .notneg
    dec al
    mov byte[C4ObjSelec],al
    jmp .notof
.notneg
    cmp byte[C4ObjSelec],al
    jb .notof
    xor al,al
    mov [C4ObjSelec],al
.notof

    ; Draw the dots on-screen
    xor eax,eax
    mov al,[C4ObjSelec]
    shl eax,4
    add eax,[C4Ram]
    add eax,220h
    mov byte[.flipped],0
    test byte[eax+6],40h
    jz .notflip
    mov byte[.flipped],1
.notflip

;              00/01 - x position relative to BG scroll value
;              02/03 - y position relative to BG scroll value
;              04    - palette/priority settings
;              05    - OAM pointer value
;              06    - flip settings : b6 = flipx, b7 = flipy
;              07    - looks like some sprite displacement values
;              08/09 - ???
;              0A-0F - unused
    xor ebx,ebx
    mov bx,[eax+8]
    mov [CObjNum],bx
    cmp bx,4096
    jae near .skipall
    shl ebx,6
    add ebx,[C4Data]

    ; t,f,g,h = move current object
    ; q = copy current object structure, w = paste current object structure
    cmp byte[pressed+14h],0
    je .notmove
    mov byte[pressed+14h],0
    pushad
    mov ecx,15
.next
    add ebx,4
    dec byte[ebx+1]
    loop .next
    popad
.notmove
    cmp byte[pressed+21h],0
    je .notmove2
    mov byte[pressed+21h],0
    pushad
    mov ecx,15
.next2
    add ebx,4
    cmp byte[.flipped],0
    je .noflipx
    add byte[ebx],2
.noflipx
    dec byte[ebx]
    loop .next2
    popad
.notmove2
    cmp byte[pressed+22h],0
    je .notmove3
    mov byte[pressed+22h],0
    pushad
    mov ecx,15
.next3
    add ebx,4
    inc byte[ebx+1]
    loop .next3
    popad
.notmove3
    cmp byte[pressed+23h],0
    je .notmove4
    mov byte[pressed+23h],0
    pushad
    mov ecx,15
.next4
    add ebx,4
    cmp byte[.flipped],0
    je .noflipx2
    sub byte[ebx],2
.noflipx2
    inc byte[ebx]
    loop .next4
    popad
.notmove4
    cmp byte[pressed+10h],0
    je .notcopy
    mov byte[pressed+10h],0
    pushad
    mov edx,C4DataCopy
    mov ecx,64
.copylp
    mov al,[ebx]
    mov [edx],al
    inc ebx
    inc edx
    loop .copylp
    popad
.notcopy
    cmp byte[pressed+11h],0
    je .notpaste
    mov byte[pressed+11h],0
    pushad
    mov edx,C4DataCopy
    mov ecx,64
.pastelp
    mov al,[edx]
    mov [ebx],al
    inc ebx
    inc edx
    loop .pastelp
    popad
.notpaste

    ;  - = remove sub-object, + = add sub-object
    ;  ; = previous sub-object, ' = next sub-object
    cmp byte[pressed+0Ch],0
    je .notpressed4
    mov byte[pressed+0Ch],0
    cmp byte[ebx],0
    je .notpressed4
    dec byte[ebx]
.notpressed4
    cmp byte[pressed+0Dh],0
    je .notpressed5
    mov byte[pressed+0Dh],0
    cmp byte[ebx],15
    je .notpressed5
    inc byte[ebx]
.notpressed5
    cmp byte[pressed+27h],0
    je .notpressed6
    mov byte[pressed+27h],0
    dec byte[C4SObjSelec]
.notpressed6
    cmp byte[pressed+28h],0
    je .notpressed7
    mov byte[pressed+28h],0
    inc byte[C4SObjSelec]
.notpressed7

    ; get current sub-object displacement (0 if no sub-objects)
    xor ecx,ecx
    cmp byte[ebx],0
    je near .nosubobjs

    mov cl,[ebx]
    cmp byte[C4ObjSelec],0FFh
    jne .sobjokay2
    dec cl
    mov byte[C4SObjSelec],cl
    jmp .sobjokay
.sobjokay2
    cmp byte[C4SObjSelec],cl
    jb .sobjokay
    mov byte[C4SObjSelec],0
.sobjokay

    xor ecx,ecx
    mov cl,byte[C4SObjSelec]
    shl ecx,2
    add ebx,ecx
    add ebx,4

    ; i,j,k,l = move current sub-object (17,24,25,26)
    ; u = toggle between 8x8 and 16x16 tiles
    ; o = toggle between high/low oam value
    ; . = decrease oam value, / = increase oam value of sub-object
    cmp byte[pressed+17h],0
    je .notpressed8
    mov byte[pressed+17h],0
    dec byte[ebx+1]
.notpressed8
    cmp byte[pressed+24h],0
    je .notpressed9
    mov byte[pressed+24h],0
    dec byte[ebx]
    cmp byte[.flipped],0
    je .notpressed9
    add byte[ebx],2
.notpressed9
    cmp byte[pressed+26h],0
    je .notpressed11
    mov byte[pressed+26h],0
    inc byte[ebx]
    cmp byte[.flipped],0
    je .notpressed11
    sub byte[ebx],2
.notpressed11
    cmp byte[pressed+25h],0
    je .notpressed10
    mov byte[pressed+25h],0
    inc byte[ebx+1]
.notpressed10
    cmp byte[pressed+16h],0
    je .notpressed12
    mov byte[pressed+16h],0
    xor byte[ebx+3],2
.notpressed12
    cmp byte[pressed+18h],0
    je .notpressed13
    mov byte[pressed+18h],0
    xor byte[ebx+3],1
.notpressed13
    cmp byte[pressed+34h],0
    je .notpressed14
    mov byte[pressed+34h],0
    dec byte[ebx+2]
.notpressed14
    cmp byte[pressed+35h],0
    je .notpressed15
    mov byte[pressed+35h],0
    inc byte[ebx+2]
.notpressed15

    mov cl,[ebx]
    mov ch,[ebx+1]
.nosubobjs
    mov edx,ecx
    xor ebx,ebx
    xor ecx,ecx
    mov bl,[eax]
    sub bl,[esi+621h]
    add bl,dl
    mov cl,[eax+2]
    sub cl,[esi+623h]
    add cl,dh
    mov esi,[vidbuffer]
    add esi,16*2+256*2+32*2
    add esi,ebx
    add esi,ebx
    mov ebx,ecx
    shl ebx,9
    shl ecx,6
    add esi,ebx
    add esi,ecx
    mov al,[C4ColRot]
    mov ah,al
    xor ah,0FFh
    mov [esi],ax
    mov [esi+16],ax
    mov [esi+288*8*2],ax
    mov [esi+16+288*8*2],ax
.skipall
    ret

SECTION .data
.flipped db 0
SECTION .TEXT

C4AddSprite:
    cmp dword[C4count],0
    je near .nosprite
    mov [edi],ax
    mov [edi+2],bx
    mov ebx,[C4usprptr]
    and [ebx],dl
    mov al,dl
    xor al,0FFh
    and dh,al
    or [ebx],dh
    add edi,4
    rol dl,2
    rol dh,2
    dec dword[C4count]
    cmp dl,0FCh
    jne .nosprite
    inc dword[C4usprptr]
.nosprite
    ret

C4ConvOAM:
    inc byte[C4Timer]
    and byte[C4Timer],15
    inc byte[C4Timer2]
    and byte[C4Timer2],7
    mov esi,[C4Ram]
    xor ecx,ecx
    mov edi,esi
    mov cl,[esi+620h]
    mov bx,[esi+621h]
    mov [.addx],bx
    mov bx,[esi+623h]
    mov [.addy],bx
    mov [C4usprptr],esi
    add dword[C4usprptr],200h
    mov eax,[C4ObjDisp]
    add edi,eax
    shr eax,4
    add dword[C4usprptr],eax
    add esi,220h
    ; Convert from esi to edi
    mov dl,0FCh
    push ecx
    mov cl,byte[C4sprites]
    and cl,3
    add cl,cl
    rol dl,cl
    pop ecx
    cmp cl,0
    je near .none
    mov dword[C4count],128
    mov eax,[C4sprites]
    sub dword[C4count],eax

.loop
    push ecx
    push esi
;              00/01 - x position relative to BG scroll value
;              02/03 - y position relative to BG scroll value
;              04    - palette/priority settings
;              05    - OAM pointer value
;              06    - flip settings : b6 = flipx, b7 = flipy
;              07    - ???
;              08/09 - Pointer to Sprite Structure
;              0A-0F - unused
;bit 1-3 = palette number bit 4,5 = playfield priority
;bit 6   = horizontal flip bit 7   = horizonal flip
    mov ax,[esi]
    sub ax,[.addx]
    mov [C4SprX],ax
    mov ax,[esi+2]
    sub ax,[.addy]
    mov [C4SprY],ax
    mov al,[esi+5]
    mov [C4SprOAM],al
    mov al,[esi+4]
    mov ah,al
    and ah,0Eh
    cmp ah,0
    jmp .notstage2
    jne .notstage1
    cmp byte[C4Timer],0
    je .flash
    jmp .noflash
.notstage1
    jmp .notstage2
    cmp ah,4
    jne .notstage2
    cmp byte[C4Timer2],0
    je .flash
.noflash
    and al,0F1h
    or al,2
    jmp .notstage2
.flash
    and al,0F1h
.notstage2
    mov [C4SprAttr],al
    mov al,[esi+6]
    or [C4SprAttr],al
;    mov [C4SprFlip],al

    xor ecx,ecx
    mov cl,[esi+9]
    shl ecx,16
    mov cx,[esi+7]
    add cx,cx
    shr ecx,1
    add ecx,[romdata]

    mov al,[ecx]
    or al,al
    jz near .singlespr
    mov [C4SprCnt],al
    inc ecx
.nextspr
    xor ebx,ebx
    movsx bx,byte[ecx+1]
    test byte[C4SprAttr],40h
    jz .notflipx
    neg bx
    sub bx,8
.notflipx
    add bx,[C4SprX]
    xor dh,dh
    test byte[ecx],20h
    jz .no16x16
    or dh,10101010b
    test byte[C4SprAttr],40h
    jz .no16x16
    sub bx,8
.no16x16
    cmp bx,-16
    jl near .nosprite
    cmp bx,272
    jg near .nosprite
    mov al,bl
    test bx,100h
    jz .not512b
    or dh,01010101b
.not512b
    xor ebx,ebx
    movsx bx,byte[ecx+2]
    test byte[C4SprAttr],80h
    jz .notflipy
    neg bx
    sub bx,8
.notflipy
    add bx,[C4SprY]
    test byte[ecx],20h
    jz .no16x16b
    test byte[C4SprAttr],80h
    jz .no16x16b
    sub bx,8
.no16x16b
    cmp bx,-16
    jl near .nosprite
    cmp bx,224
    jg near .nosprite
    mov ah,bl
    mov bh,[C4SprAttr]
    mov bl,[ecx]
    and bl,0C0h
    xor bh,bl
    mov bl,[C4SprOAM]
    add bl,[ecx+3]
    call C4AddSprite
.nosprite
    add ecx,4
    dec byte[C4SprCnt]
    jnz near .nextspr
    jmp .donemultispr
.singlespr
    mov dh,10101010b
    test byte[C4SprX+1],1
    jz .not512
    or dh,01010101b
.not512
    mov al,[C4SprX]
    mov ah,[C4SprY]
    mov bl,[C4SprOAM]
    mov bh,[C4SprAttr]
    call C4AddSprite
.donemultispr
    pop esi
    pop ecx

;NEWSYM C4Data times 64*4096 db 0       ; 15 sprites, 4 bytes each
                                        ; x,y,oamptr,stat (b0=oamb8,b1=16x16)
                                        ; 4 byte header (#sobj,?,?,?)

    add esi,16
    dec cl
    jnz near .loop
.none
    mov esi,oamram
    mov edi,[C4Ram]
    mov ecx,544
.next
    mov al,[edi]
    mov [esi],al
    inc edi
    inc esi
    loop .next
    ret

SECTION .data
.addx dw 0
.addy dw 0

C4count   dd 0
C4usprptr dd 0
C4SprX    dw 0
C4SprY    dw 0
C4SprCnt  db 0
C4SprAttr db 0
C4SprOAM  db 0
C4SprFlip db 0
C4Timer   db 0