Simple Brainfuck Interpreter

bf.rs

use text_io::read;
use std::collections::VecDeque;

fn main() {
    loop {
        print!("BF) ");
        let code: String = read!();
        if code.trim() == "!".to_string() {
            println!("Exit");
            break;
        }
        let chars = &code.trim().chars().collect::<Vec<char>>();
        let mut m = [0u8; 256];
        let mut i = 0usize;
        let mut mp = 0usize;
        let mut lstart = VecDeque::<usize>::new();
        let mut buffer = Vec::<u8>::new();
        while i < chars.len() {
            match chars[i] {
                '+' => {
                    m[mp] = ((m[mp] as u16 + 1) % 256) as u8;
                    i += 1;
                },
                '-' => {
                    m[mp] = ((256 + m[mp] as u16 - 1) % 256) as u8;
                    i += 1;
                },
                '>' => {
                    mp = (mp + 1) % 256;
                    i += 1;
                },
                '<' => {
                    mp = (256 + mp - 1) % 256;
                    i += 1;
                },
                '[' => {
                    lstart.push_back(i + 1);
                    i += 1;
                },
                ']' => {
                    if m[mp] == 0 {
                        lstart.pop_back();
                        i += 1;
                    } else {
                        i = (&lstart)[lstart.len() - 1];
                    }
                },
                ',' => {
                    print!("char: ");
                    let s: String = read!();
                    let c = s.chars().next().unwrap_or('\0');
                    m[mp] = c as u8;
                    i += 1;
                },
                '.' => {
                    buffer.push(m[mp]);
                    i += 1;
                },
                _ => {
                    i += 1;
                },
            }
        }
        println!("{}", String::from_utf8(buffer).unwrap());
    }
}