;             call #  val  val2
; int $0x80   eax     eax  edx  -
;
; arg1  arg2  arg3  arg4  arg5  arg6  arg7  
; ebx   ecx   edx   esi   edi   ebp   -

exit:
mov eax, 1 ; exit
int 0x80

; filename in EBX
; return handle in EBX 
; read only
open_file:
push eax
push ecx
mov eax, 5 ; open
xor ecx, ecx ; read only
int 0x80
mov ebx, eax
pop ecx
pop eax
ret

; file handle in EBX
; buffer in ECX
; count of bytes to read in EDX
; return bytes actually read in EAX
; exits on error
read_file:
mov eax, 3 ; read
int 0x80
test eax, eax
js .err
ret
.err:
mov eax, 4 ; write
mov ebx, 1 ; stdout
mov ecx, .err_str
mov edx, 21
int 0x80
jmp exit
.err_str: db `Could not read file.\n`

; string input in ESI
; value in EAX
; CF set if none, clear if some
; ESI set past checked area
dec_parse:
push ebx
push edx
push edi
xor eax, eax
xor edi, edi
mov ebx, 10  ; base
lodsb
sub al, '0'
js .no_input
cmp al, 9
jle .got_char
.no_input:
stc ; set CF
jmp .done
.loop:
lodsb
sub al, '0'
js .dec_done
cmp al, 9
jg .dec_done
.got_char:
xchg edi,eax
mul ebx
add edi,eax
jmp .loop
.dec_done:
clc ; clear CF
.done:
mov eax,edi
pop edi
pop edx
pop ebx
ret

; input in EAX, all regs unmodified
print_dec:
pushad ; save regs
; max 4294967296 is 10 chars
; round to nearest 32-bit boundary
sub esp, 12
; string in ECX, length in EDX
lea ecx, [esp+11] ; last possible byte
; check for 0
test eax, eax
jz .zero
mov ebx, 10 ; base 10
xor esi, esi ; counter
.div_shit:
xor edx, edx
; divide
div ebx
dec ecx ; next char
inc esi
; store
add dl, '0'
mov byte [ecx], dl
; check if done
test eax, eax
jnz .div_shit ; continue
mov edx, esi ; counter in edx
jmp .write
.zero:
mov byte [ecx], '0'
mov edx, 1 ; length
.write:
mov eax, 4 ; write
mov ebx, 1 ; stdout
int 0x80
add esp, 12 ; restore stack
popad ; restore regs
ret