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Created November 20, 2024 19:57
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Reverse Polish Notation (RPN) in Assembly x86_64
Raw
README.md

RPN in ASM x86_64

nasm -f elf64 -g rpn.asm -o rpn.o
ld rpn.o -o rpn
./rpn

Output

Insira a expressão RPN: 
1 2 +
Resultado: 3

Insira a expressão RPN: 
1 2 3 * +
Resultado: 7
Raw
rpn.asm
global _start
%define SYS_read 0
%define SYS_write 1
%define SYS_exit 60
%define EXIT_SUCCESS 0
%define STDIN 0
%define STDOUT 1
section .bss
input: resb 256 ; Buffer de entrada (input)
output: resb 256 ; Buffer de saída (output)
section .data
prompt: db "Insira a expressão RPN: ", 0xA
promptLen: equ $ - prompt
msgResult: db "Resultado: ", 0
msgResultLen: equ $ - msgResult
newLine: db 0xA, 0
section .text
_start:
; Prompt de entrada
mov rdi, STDOUT
mov rsi, prompt
mov rdx, promptLen
mov rax, SYS_write
syscall
mov rdi, STDIN
mov rsi, input
mov rdx, 256
mov rax, SYS_read
syscall
; Mensagem de saída (resultado)
mov rdi, STDOUT
mov rsi, msgResult
mov rdx, msgResultLen
mov rax, SYS_write
syscall
; Rotina de cálculo RPN
lea rsi, [input]
call parseRpn
; Imprime resultado
lea rsi, [output]
add rax, '0'
mov byte [rsi], al
mov rdi, STDOUT
mov rdx, 8
mov rax, SYS_write
syscall
; Imprime newline \n no final
mov rdi, STDOUT
mov rsi, newLine
mov rdx, 1
mov rax, SYS_write
syscall
.exit:
mov rdi, EXIT_SUCCESS
mov rax, SYS_exit
syscall
parseRpn:
mov rdx, 0
.nextToken:
; move para o próximo token
mov al, byte [rsi + rdx]
; ignora espaços
cmp al, 0x20
je .skipSpace
; chegou ao fim?
cmp al, 0xA
je .doneParse
cmp al, '0'
jl .parseOperator
cmp al, '9'
jg .parseOperator
; converte dígito ASCII para inteiro e empilha
sub al, '0'
push rax
; segue para o próximo token
inc rdx
jmp .nextToken
.parseOperator:
cmp al, '+'
je .add
cmp al, '-'
je .sub
cmp al, '*'
je .mul
cmp al, '/'
je .div
; segue para o próximo token
inc rdx
jmp .nextToken
.add:
pop rbx
pop rax
add rax, rbx
; empilha resultado
push rax
inc rdx
jmp .nextToken
.sub:
pop rbx
pop rax
sub rax, rbx
; empilha resultado
push rax
inc rdx
jmp .nextToken
.mul:
pop rbx
pop rax
imul rax, rbx
; empilha resultado
push rax
inc rdx
jmp .nextToken
.div:
pop rbx
pop rax
xor rdx, rdx
div rbx
; empilha resultado
push rax
inc rdx
jmp .nextToken
.skipSpace:
inc rdx
jmp .nextToken
.doneParse:
pop rax
ret
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