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ApertureEngineer — _fibonacci PROC
Published: 2009-12-06 19:58:20 +0000 UTC; Views: 192; Favourites: 1; Downloads: 2
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Description
.686.model tiny
public _fibonacci
.code
;Author: ApertureEngineer
_fibonacci PROC
push ebp
mov ebp,esp ;Building stack frame
push esi
push edi ;saving ESI and EDI
mov ebx,[ebp+8] ;retrievieng n from stack
cmp ebx,0 ;comparing n with 0
jg cont_1 ; if n>0 then goto con_1
mov eax,0 ; if n<=0 return 0
jmp retv
cont_1: cmp ebx,2 ;comparing n with 2
jg cont_2 ;if n>2 then procedure will continue on cont_2
mov eax,1 ;if not then procedure will return 1
jmp retv
cont_2: dec ebx ; EBX = n-1
push ebx ; pushing n-1 as argument for fibonacci call
call _fibonacci ; calling fibonacci(n-1)
pop ebx ; retrievieng ebx (n-1),
;it may change during fibonacci call
dec ebx ; EBX = n-2
push eax ; saving value returned by fibonacci(n-1) on stack
push ebx ; pushing n-2 as argument for second fibonacci call
call _fibonacci ; calling fibonacci(n-2)
add esp,4 ; cleaning stack
pop ebx ; retrieving result of fibonacci(n-1) call form stack
;and saving it in EBX
add eax,ebx ; adding results of fibonacci(n-2) (in EAX)
;and fibonacci(n-1) (in EBX) calls
retv: pop edi ;resuming initial EDI value
pop esi ;resuming initial ESI value
mov esp,ebp ;removing stack frame
pop ebp
ret ; returning fibonacci(n-2)+fibonacci(n-1)
;as fibonacci(n) result
_fibonacci ENDP
END
