drawpicture.s

symbian 的一个 二维飞行游戏 源码 及相关技术文章

@@  Copyright 2002 Kenneth Guy,
@@  
        	.global	DrawPictureAsm__12RScreenUtilsPQ212RScreenUtils8TPicture
DrawPictureAsm__12RScreenUtilsPQ212RScreenUtils8TPicture:

        @@ r0, TScreenUtils* this
               @  0 - iScreenBase 
        @@ r1, TDrawPicture*
        @@   offset - 0    const TUint16* iData;
        @@   offset - 4    TUint32 iXSize;
        @@   offset - 8    TUint32 iYSize;
        @@   offset - 12   TUint32 iXPos;
        @@   offset - 16   TUint32 iYPos;

        @@ X is in 2 pixel blocks, (ie one 32bit word), so 0-319
        @@ Y is 0-199

        
        @@ save registers and return address on full declining stack 
        stmfd   sp!, {r0-r12,lr}
        ldr     r0,[r0]         @ r0 = iScreenBase
        ldmia   r1,{r2,r3,r4,r5,r6} @ iData,iXSize,iYSize,iXPos,iYPos;

        add     r0,r0,r6,lsl#10       @ add iYPos*1280 to iScreenBase
        add     r0,r0,r6,lsl#8
        add     r0,r0,r5,lsl#2 @ iXPos*4

        mov     r7,r0           @ remember start of pixel line;
        mov     r9,#0
drawPictureAreaLineLoop:      
        mov     r1,r3      
drawPictureAreaPixelLoop:
        ldr     r8,[r2],#4
        str     r8,[r0],#4
        subs    r1,r1,#1
        bne     drawPictureAreaPixelLoop

        add     r7,r7,#1280
        mov     r0,r7
        subs    r4,r4,#1
        bne     drawPictureAreaLineLoop

        ldmfd   sp!, {r0-r12,lr}
        bx      lr