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Index > MenuetOS > "find_free_mem" questions (kernel side)

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xemean



Joined: 21 Jan 2004
Posts: 3
xemean
I try to modify the kernel files to add some Chinese fuctions ( just for fun),and i need to load the font file to a block of free memory before the first application(launcher) started, the code is:

; load 12*12 Chinese bitmap font file
; cnsbfname db 'SCN12X12BIN'
; cmemlocation dd 0 ; file location

mov esi,boot_cns ; show message
call boot_log
pusha
cli
mov edi,200*1024 ; I don't know edi means,anyone help me?I think it is the size of memory you want ,so i set to 200* 1024(my bitmap font nearly 200k)
call find_free_mem ; call find_free_mem
cmp esi,0 ; no memory available
je .c_error
mov [cmemlocation],esi ; save address to 'cmemlocation'
mov eax,cnsbfname ; eax point to 11 filename
mov ebx,0 ; first block wanted read
mov ecx,-1 ; number of blocks to read
mov edx,[cmemlocation] ; file location
mov esi,12 ; length of filename
call fileread ; read file
; ret ebx = size or 0xffffffff file not found
; eax = 0 ok read or other = errormsg
cmp eax,0
jne .c_error
cmp ebx,-1
jne cok

popa
cli
mov esi,nofontfile
call boot_log
jmp $
.c_error:
popa
cli
mov esi,fileerror
call boot_log
jmp $ ; halted here
cok:
popa

; LOAD FIRST APPLICATION

my question is: "find_free_mem" need edi for what? and the result in esi means what?

i compiled the new kernel,Menuet boot normally. but my own function does not work, the following code may be the problem:

add eax,dword [cmemlocation]

here,eax is the offset of the bitmap. is "cmemlocation" saved the correct address which point to bitmap i want?

dsok:
checkbit:
push eax

movzx eax,word [ecx]
test ah,0x80
jz .checkok1
test al,0x80
jz .checkok1

pop eax ; save positon to ebx

push eax
push ebx
push ecx
push edx
movzx eax,word [ecx]
; mov ax,0xf7c3
movzx edx,ah
and ax,0x00ff
sub al,0xa0
sub dl,0xa0
dec eax
dec edx
imul eax,94
add eax,edx
imul eax,24
add eax,dword [cmemlocation] ;<-- cmemlocation save the addr.?
mov esi,eax
pop edx
pop ecx
pop ebx
pop eax

pusha
mov ecx,ebx
movzx ebx,ax
shr eax,16
call drawcharacter
popa

add eax,13*65536
add ecx,2
sub dx,2
jnz checkbit
popa
ret

.checkok1:
pop eax

letnew:

sorry for my English.
Post 30 Apr 2004, 07:26
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Ville



Joined: 17 Jun 2003
Posts: 226
Ville
Find_free_mem is only for application management. Menuet uses find_free_mem for searching free memory for a new process. You can load your files directly to a free memory position up to 16mb, see memmap.inc.
Post 30 Apr 2004, 08:31
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xemean



Joined: 21 Jan 2004
Posts: 3
xemean
Wink
Thank you
Do you mean i just code as following without set any "flag" to tells system that "this block of memory is useing"?
mov eax,cnsbfname ; eax point to 11 filename
mov ebx,0 ; first block wanted read
mov ecx,-1 ; number of blocks to read
mov edx,0x1000000+0xXXXXXXXX ;<- directly set edx ?
mov esi,12 ; length of filename
call fileread ; read file
Post 30 Apr 2004, 09:08
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Ville



Joined: 17 Jun 2003
Posts: 226
Ville
xemean wrote:

Do you mean i just code as following without set any "flag" to tells system that "this block of memory is useing"?


You can use the memory from 0 to 16 MB. You don't have to set any flags, since all the used areas are listed in memmap.inc.
Post 30 Apr 2004, 10:53
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xemean



Joined: 21 Jan 2004
Posts: 3
xemean
Quote:

You can use the memory from 0 to 16 MB. You don't have to set any flags, since all the used areas are listed in memmap.inc.


Thank you very much,I found a block of free memory for bitmap_font:
; 780000 -> 7fffff free
It is enough.
Greate,I'll post the Simplified Chinese Menuet version later!
Regards,
E-mean X.
Post 30 Apr 2004, 11:23
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