FSM – על זומבים ומפלצות ספגטי מעופפות

[kirill578]

החלק הזה מאוד מבלבל, תוכל להסביר מה הוא עושה?

lea di,[si+@end-@loop-0c00h+4h]

lea sp,[si-800h+4h]

mov si,0a5f3h ; 0a5f3h = opcode of rep movsw

push sp ; protection from int 87h

push si

push sp

pop sp

mov bx,-0c00h

mov dx,-800h+2h

mov bp,-400h+4h

mov ax,0815eh ; ax is a clock

mov si,4h

mov cx,200h-2h

[FSM]

This is the initialization part. After this part the survivor will jump to the main loop, which is pointed by sp.

The main loop contains of 2 bytes: F3 A5
which is:

rep
movsw

At the end of this code the values of the registers are:
sp – pointer to the loop
di – the destination of the "movsw", which is a bit more than (sp – 400h)
si – the source of the "movsw", which is in the beginning of the survivor's private memory
cx – the length of the loop: 1feh iterations

During the loop, the code from @loop…@end is copied upon the running code, and will run right when the loop ends.
In that code, the survivor changes location, and therefore changes the registers: sp, di, si, cx. The offsets of these registers are saved in dx, bx, bp respectively.

The last register is ax, which holds a clock. When the countdown gets to zero, the slaves are being slaughtered.

I hope it was helpfull.

[מאת]

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