; fasm example of using the C library in Unix systems

; compile the source with commands like:
;   fasm sum.asm sum.o
;   gcc sum.o -o sum
;   strip sum



format ELF64
public main

extrn printf
extrn scanf
extrn exit

;==============================================================================
section '.code' writable
main:
; 1) vector input
        call VectorInput
; 2) get vector sum
        call VectorSum
; 3) out of sum
        mov rdi, strSumValue
        mov rsi, [sum]
        xor rax, rax
        call printf
; 4) test vector out
        call VectorOut
finish:
        xor rax, rax
        ret


;------------------------------------------------------------------------------
; 1) vector input
VectorInput:
        mov rdi, strVecSize
        xor rax, rax
        call printf

        ;push rbp
        sub  rsp, 16
        lea rdi, [strScanInt] ;loading format
        ;lea rsi, [vec_size]
        mov rsi, vec_size
        xor rax, rax
;    jmp endInputVector
        call scanf
        add rsp, 16
        ;pop rbp  ;restores stack
        
;    jmp endInputVector
        mov rax, [vec_size]
        cmp rax, 0
        jg  getVector
        
        ; fail size
        mov rdi, strIncorSize
        mov rsi, vec_size
        xor rax, rax
        call printf
        
        mov  rdi,0
        xor rax, rax
        call exit
; continue...
getVector:
        xor rcx, rcx            ; rcx = 0
        mov rbx, vec            ; rbx = &vec
getVecLoop:
        mov [tmp], rbx
        cmp rcx, [vec_size]
        jge endInputVector       ; to end of loop

        ; input element
        mov [i], rcx
        mov rdi, strVecElemI
        mov rsi, rcx
        xor rax, rax
        call printf

        push rbp
        push rbp
        lea rdi, [strScanInt] ;loading format
        mov rsi, rbx
        xor rax, rax
        call scanf
        pop rbp  ;restores stack
        pop rbp  ;restores stack

        mov rcx, [i]
        inc rcx
        mov rbx, [tmp]
        add rbx, 8
        jmp getVecLoop
endInputVector:
        ret
;------------------------------------------------------------------------------
; 2) get vector sum
VectorSum:
        xor rcx, rcx            ; rcx = 0
        mov rbx, vec            ; rbx = &vec
sumVecLoop:
        ;mov [tmp], rbx
        cmp rcx, [vec_size]
        je endSumVector      ; to end of loop
        mov rax, [sum]
        add rax, [rbx]
        mov [sum], rax
        ;mov [i], rcx

        ;mov rcx, [i]
        inc rcx
        ;mov rbx, [tmp]
        add rbx, 8
        jmp sumVecLoop
endSumVector:
        ret

;------------------------------------------------------------------------------
; 4) test vector out
VectorOut:
        ;mov [tmpStack], rsp
        xor rcx, rcx            ; rcx = 0
        mov rbx, vec            ; rbx = &vec
putVecLoop:
        mov [tmp], rbx
        cmp rcx, [vec_size]
        je endOutputVector      ; to end of loop
        mov [i], rcx

        ; output element
        mov rdi, strVecElemOut
        mov rsi, rcx
        mov rdx, [rbx] 
        xor rax, rax
        call printf

        mov rcx, [i]
        inc rcx
        mov rbx, [tmp]
        add rbx, 8
        jmp putVecLoop
endOutputVector:
        ;mov rsp, [tmpStack]
        ret
        
;==============================================================================
section '.data' writable

        strVecSize   db 'size of vector? ', 0
        strIncorSize db 'Incorrect size of vector = %d', 10, 0
        strVecElemI  db '[%d]? ', 0
        strScanInt   db '%d', 0
        strSumValue  db 'Summa = %d', 10, 0
        strVecElemOut  db '[%d] = %d', 10, 0

        vec_size     dq 3
        sum          dq 0
        i            dq ?
        tmp          dq ?
        tmpStack     dq ?
        vec          dq 5,6,7,8
;        vec          rq 100