Code: Select all
;; scrollfwd - moves text n lines up.
;; arguments -
;; ah = number of rows to scroll
scrollfwd:
pushad ; save the registers to be used
cld ; make sure direction flag is set to increment
mov cx, CurrPageSize ; get the size of the text pages in bytes
mov di, SwapPageTop ; set the destination to the new text screen
push cx ; CX, and DI need to have same values
push di ; used and modified in two different places
mov al, 0 ; clear the swap page of any garbage
rep stosb ; copy zero into every byte of the swap text page
pop di
pop cx
mov al, ah ; put parameter into al, where it can be used
mov bl, ScrWidth
shl bl, 1 ; multiply by two to get size of line in bytes
mul bl ; multiply total columns by rows to scroll
mov si, ax
add si, CurrPageTop ; get the new top of the screen
sub cx, ax ; and subtract by the removed section to get
; the size of the block to be moved
rep movsb ; copy scrolled block to new text screen
mov cx, CurrPageSize ; reset the size of the buffer for swapping back
mov si, SwapPageTop
mov di, CurrPageTop
rep movsb ; move the data back to the current page, shifted up n lines
popad ; restore used registers
retCode: Select all
/* assumes page size and other related constants defined elsewhere */
void scrollfwd(int lines)
{
char* scroll_region;
long scroll_size;
memset((void *) SwapPageTop, 0, (size_t) CurrPageSize);
scroll_size = (lines * ScrWidth) << 1;
scroll_region = CurrPageTop - scroll_size;
memcpy((void *) SwapPageTop, (const void *) scroll_region, (size_t) scroll_size);
memcpy((void *) CurrPageTop, (const void*) SwapPageTop, (size_t) CurrPageSize);
}Code: Select all
_memcpy:
push ebp
mov ebp, esp
mov esi, [ebp + 8] ; first arg - src pointer
mov edi, [ebp +12] ; 2nd arg - dest pointer
mov ecx, [ebp + 16] ; 3rd arg - string size in bytes
mov eax, edi ; return value - save now, before EDI gets trashed
cdl ; make sure direction flag set correctly
rep movsb ; block-copy from src to dest
pop ebp ; restore caller's stack frame
ret
_memset:
push ebp
mov ebp, esp
mov edi, [ebp + 8] ; first arg - buffer pointer
mov edi, [ebp +12] ; 2nd arg - value to write
mov eax, [ebp + 16] ; 3rd arg - string size in bytes
push edi ; return value - save now, before EDI gets trashed
cdl ; make sure direction flag set correctly
rep stosb
pop eax ; recover return value
pop ebp ; restore caller's stack frame
ret
I'm not sure it is, to be honest. If I had been able to use page-flipping, then I'm sure that it would be, as the rep functions are very highly optimized, running much faster than the equivalent loops. The fact that I do it twice probably negates the value, though. You are correct that it should go faster if I moved the data by doubleword increments, and there are certainly other ways I could optimize it, too. I was mostly interested in getting it working, and in seeing if anyone could help with the text-page switching issue.PlayOS wrote: After browsing your code, I am not sure but are copying the visible screen to the second text page, scrolling in the process by not copying the lines that are to be scrolled. Then at the end you copy the second page back to the visible page, now the data is scrolled up. But my question is how is this faster or smoother?
Code: Select all
if (even) {
memcpy(screen1+1*LINE,screen2,24*LINE);
show(screen2);
} else {
memcpy(screen2+1*LINE,screen1,24*LINE);
show(screen1);
}
even++;