Brainfuck compiler

brain86.rs

//    Brain86
// This program compiles well-formed brainfuck code to x86 assembler.
// Requires rust nightly, nasm, and ld
//
// An interesting sample program:
// https://raw.githubusercontent.com/JustAPerson/brainrust/master/tests/mandelbrot.bf
//
// $ rustc brain86.rs
// $ cat mandelbrot.bf | ./brain86 > mandelbrot.s
// $ nasm -f elf64 mandelbrot.s
// $ ld mandelbrot.o -o mandelbrot
// $ ./mandelbrot
#![feature(io)]
use std::io::Read;
fn main() {
    let mut labels = Vec::new();
    let mut label_counter = 0;
    println!("section .bss");
    println!("    stack: resb 30000");
    println!("section .text");
    println!("    global _start");
    println!("_start:");
    println!("    xor esi, esi"); // esi will be the stack pointer
    for char in std::io::stdin().chars() {
        match char.unwrap() {
            '+' => {
                println!("    add byte [stack+esi], 1");
            },
            '-' => {
                println!("    sub byte [stack+esi], 1");
            },
            '>' => { println!("    add esi, 1"); },
            '<' => { println!("    sub esi, 1"); },
            '[' => {
                let label = format!("loop{}", label_counter);
                label_counter += 1;
                labels.push(label.clone());
                println!(".{}_start:", &label);
                println!("    cmp byte [stack+esi], 0");
                println!("    jz .{}_end", &label);
            },
            ']' => {
                let label = labels.pop().unwrap();
                println!("    jmp .{}_start", &label);
                println!(".{}_end:", &label);
            },
            '.' => {
                println!("    mov edx, 1");
                println!("    lea ecx, [stack+esi]");
                println!("    mov ebx, 1"); // stdout
                println!("    mov eax, 4"); // sys_write
                println!("    int 0x80");
            },
            ',' => {
                println!("    mov edx, 1");
                println!("    lea ecx, [stack+esi]");
                println!("    mov ebx, 0"); // stdin
                println!("    mov eax, 3"); // sys_read
                println!("    int 0x80");
            },
            _ => { },
        }
    }
    println!("    mov ebx, 0"); // exit code = 0
    println!("    mov eax, 1"); // sys_exit
    println!("    int 0x80");
}