brainfuck/bfi-rust/src/interpreter/simple.rs

//!
//! The very basic interpreter without any optimizations
#![allow(dead_code)]

use crate::interpreter::{MEM_SIZE, minify};
use std::io::{stdin, Read};

pub fn run(program: &str) -> String{
    let program = minify(program);
    let out = interpret(program.chars().collect());
    out
}

fn interpret(pgm: Vec<char>) -> String {
    let mut out = String::new();
    let mut pointer: usize = 0;
    let mut mem: [u8; MEM_SIZE] = [0; MEM_SIZE];
    let mut in_buffer = [0; 1];
    let mut pc = 0;
    let len = pgm.len();

    while pc < len {
        match pgm[pc] {
            '>' => if pointer == MEM_SIZE - 1 { pointer = 0 } else { pointer += 1 },
            '<' => if pointer == 0 { pointer = MEM_SIZE - 1 } else { pointer -= 1 },
            '+' => mem[pointer] = mem[pointer].wrapping_add(1),
            '-' => mem[pointer] = mem[pointer].wrapping_sub(1),
            '.' => out.push(mem[pointer] as u8 as char),
            ',' => {
                stdin().read_exact(&mut in_buffer).unwrap();
                mem[pointer] = in_buffer[0] as u8;
            }
            '[' => {
                //jump to corresponding ]
                if mem[pointer] == 0 {
                    let mut level = 0;
                    while pgm[pc] != ']' || level > -1 {
                        pc += 1;
                        match pgm[pc] {
                            '[' => {
                                level += 1
                            }
                            ']' => {
                                level -= 1
                            }
                            _ => (),
                        }
                    }
                }
            }
            ']' => {
                if mem[pointer] != 0 {
                    //jump to corresponding [
                    let mut level = 0;
                    while pgm[pc] != '[' || level > -1 {
                        pc -= 1;
                        match pgm[pc] {
                            '[' => level -= 1,
                            ']' => level += 1,
                            _ => (),
                        }
                    }
                }
            }
            _ => (),
        }
        pc += 1;
    }

    out
}