316 lines
5.1 KiB
NASM
316 lines
5.1 KiB
NASM
default rel
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extern printf
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global exitcode
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section .data
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buf: dq 0
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dbuf: dw 0
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path: db "./input.txt", 0
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nb_lines: dw 1000
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fmt: db "Value %s: %d", 10, 0
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fd_str: db "file descriptor", 0
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close_str: db "close", 0
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content_str: db "Content: '%s'", 10, 0
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nbr_str: db "number", 0
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exitcode: dw 0
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section .text
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global _start
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printvalue:
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push rbp
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mov rbp, rsp
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sub rsp, 8H
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;; args
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mov dword [rbp-8H], edi
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mov dword [rbp-4H], esi
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;; printf
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xor rax, rax
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lea rdi, [fmt] ; format
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mov esi, dword [rbp-8H] ; arg1
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mov edx, dword [rbp-4H] ; arg2
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call printf
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;; leave
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mov rsp, rbp
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pop rbp
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ret
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;; End of printvalue
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readval:
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;; rdi: FILE DESCRIPTOR
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;; rsi: offset
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push rbp
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mov rbp, rsp
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sub rsp, 16H
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mov qword [rbp-8H], rsi
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mov qword [rbp-16H], rdi
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;; sys_read
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mov rax, 0 ; sys_read
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;; rdi has already file descriptor
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mov rdi, qword [rbp-16H]
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mov rsi, buf
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mov rdx, 5H
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syscall
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;; Go to the next number
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mov rax, 8 ; sys_lseek
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mov rdi, qword [rbp-16H] ; fd
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mov rsi, qword [rbp-8H] ; advance by n chars
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mov rdx, 1 ; origin
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syscall
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;; convert buf to an int
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xor ebx, ebx
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mov esi, buf
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mov ecx, 5
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.next_digit:
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movzx eax, byte [esi]
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inc rsi
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sub al, '0' ; convert ascii to number (remove offset of the 0 digit)
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imul ebx, 10
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add ebx, eax ; rbx = rbx*10 + rax
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loop .next_digit ; loop until ecx = 0
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xor rax, rax
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mov eax, ebx
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mov rsp, rbp
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pop rbp
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ret
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;; end of readval1
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popmin:
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push rbp
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mov rbp, rsp
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sub rsp, 22H
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;; 8H, 0 -> min value address
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;; 12H, 8H -> min value
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;; 14H, 12H -> loop counter
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;; 22H, 14H : current address
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;; rdi: list effective address
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mov qword [rbp-8H], rdi
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mov qword [rbp-22H], rdi ; current address
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mov esi, [rdi]
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mov dword [rbp-12H], esi
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mov ecx, 1000
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minloop:
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mov word [rbp-14H], cx
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mov r9, qword [rbp-22H]
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mov edi, [r9] ; current value
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mov esi, dword [rbp-12H] ; min value
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cmp esi, 0
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je updatemin
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cmp edi, 0
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je next ; skip zeroes
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cmp edi, esi
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jle updatemin
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jmp next
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updatemin:
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mov r9, qword [rbp-22H]
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mov dword [rbp-12H], edi
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mov qword [rbp-8H], r9
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next:
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mov r9, qword [rbp-22H]
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add r9, 4H
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mov qword [rbp-22H], r9
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dec cx
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jnz minloop
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mov rax, qword [rbp-8H]
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mov dword [rax], 0H
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mov eax, dword [rbp-12H]
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mov rsp, rbp
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pop rbp
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ret
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_start:
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push rbp
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mov rbp, rsp
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sub rsp, 2000H
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;; 8H -> 0 : file_descriptor
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;; 12H -> 8H : buffer for readvalue
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;; 14H -> 12H : current line
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;; 19H -> 17H: read loop counter
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;; 2000H -> 1060H : list 1 (1000 digits of 4 bytes)
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;; 1000H -> 60H : list 2
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mov rax, 2 ; sys_open
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lea rdi, [path]
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xor rsi, rsi
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xor rdx, rdx
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syscall
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;; store file descriptor
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mov qword [rbp-8H], rax
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;; print file descriptor
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lea rdi, [fd_str]
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mov rsi, rax
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call printvalue
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;; exit if open failed
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cmp dword [rbp-8H], 0
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jl exit
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mov word [rbp-14H], 0H ; line number
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mov cx, [nb_lines] ; number of lines
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loop0:
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mov [rbp-19H], cx ; store loop counter
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;; read the 1st value
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mov rdi, qword [rbp-8H]
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mov rsi, 3H ; mov to the second number
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call readval
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; store the read value
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mov [dbuf], eax
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;; calculate list position
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xor rax, rax
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mov ax, word [rbp-14H]
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mov bx, 4H
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mul bx
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;; 14H -> 12H : line counter
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mov rbx, 2000H
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sub rbx, rax
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mov r9, rbp
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sub r9, rbx
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; move the value to its position
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mov eax, [dbuf]
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mov dword [r9], eax
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;; read the 2nd value
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mov rdi, qword [rbp-8H]
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mov rsi, 1H ; mov to the next line
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call readval
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; store the read value
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mov [dbuf], eax
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;; calculate list position
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xor rax, rax
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mov ax, word [rbp-14H]
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mov bx, 4H
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mul bx
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mov rbx, 1000H
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sub rbx, rax
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mov r9, rbp
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sub r9, rbx
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; move the value to its position
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mov eax, [dbuf]
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mov dword [r9], eax
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xor rax, rax
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mov ax, word [rbp-14H]
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inc ax
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mov word [rbp-14H], ax
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mov cx, [rbp-19H] ; restore loop counter
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dec cx
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jnz loop0
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mov qword [rbp-42H], 0 ; sum = 0
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mov ecx, 1000
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sumloop:
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mov word [rbp-19H], cx
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;; 50H - 46H : min1
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;; 46H - 42H : min2
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;; 42H - 34H : sum
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lea rdi, [rbp-2000H]
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call popmin
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mov dword [rbp-50H], eax
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lea rdi, [rbp-1000H]
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call popmin
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mov dword [rbp-46H], eax
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xor rax, rax
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mov eax, dword [rbp-50H]
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mov ebx, dword [rbp-46H]
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cmp eax, ebx
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jge a
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jmp b
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a:
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sub eax, ebx
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jmp sum
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b:
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sub ebx, eax
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mov eax, ebx
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jmp sum
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sum:
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mov rbx, qword [rbp-42H]
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add rbx, rax
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mov qword [rbp-42H], rbx
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mov cx, word [rbp-19H]
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dec cx
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cmp cx, 0
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jnz sumloop
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;; print sys_close result
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lea rdi, [nbr_str]
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mov rsi, qword [rbp-42H]
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call printvalue
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close_file:
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;; sys_close
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mov rax, 3 ; sys_close
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mov edi, dword [rbp-8H]
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syscall
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;; print sys_close result
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lea rdi, [close_str]
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mov rsi, rax
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call printvalue
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exit:
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;; EXIT
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mov rax, 60 ; sys_exit
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mov rdi, [exitcode]
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syscall
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