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use std::io::{self, Read};
use std::env;
use std::process;
fn interpret_brainfuck(code: &str) {
let mut memory = vec![0u8; 30000]; // 30,000 cells of memory initialized to 0
let mut pointer: usize = 0; // data pointer starts at the first cell
let mut pc: usize = 0; // program counter for the Brainfuck code
let code_chars: Vec<char> = code.chars().collect(); // convert the Brainfuck code to a vector of characters
// Stack to keep track of [ and ] for loops
let mut loop_stack: Vec<usize> = Vec::new();
while pc < code_chars.len() {
match code_chars[pc] {
'>' => {
pointer += 1;
if pointer >= memory.len() {
panic!("Pointer out of bounds (positive)");
}
}
'<' => {
if pointer == 0 {
panic!("Pointer out of bounds (negative)");
}
pointer -= 1;
}
'+' => {
memory[pointer] = memory[pointer].wrapping_add(1); // increment with wrap around
}
'-' => {
memory[pointer] = memory[pointer].wrapping_sub(1); // decrement with wrap around
}
'.' => {
print!("{}", memory[pointer] as char);
}
',' => {
let mut input = [0u8];
io::stdin().read_exact(&mut input).expect("Failed to read input. Unable to read a single byte from stdin");
memory[pointer] = input[0];
}
'[' => {
if memory[pointer] == 0 {
// Jump to the matching ']' if the current cell is 0
let mut open_brackets = 1;
while open_brackets > 0 {
pc += 1;
if pc >= code_chars.len() {
panic!("Unmatched [");
}
if code_chars[pc] == '[' {
open_brackets += 1;
} else if code_chars[pc] == ']' {
open_brackets -= 1;
}
}
} else {
// Push the current position to the stack if not jumping
loop_stack.push(pc);
}
}
']' => {
if memory[pointer] != 0 {
// Jump back to the matching '[' if the current cell is nonzero
if let Some(loop_start) = loop_stack.last() {
pc = *loop_start;
} else {
panic!("Unmatched ]");
}
} else {
// Pop the stack if done with the loop
loop_stack.pop();
}
}
_ => {} // Ignore any non-Brainfuck commands
}
pc += 1; // Move to the next instruction
}
}
fn main() {
let args: Vec<String> = env::args().collect();
if args.len() != 2 || !args[1].ends_with(".bf") {
eprintln!("Usage: {} <filename.bf>", args[0]);
process::exit(1);
}
let filename = &args[1];
let code = std::fs::read_to_string(filename).expect("Failed to read the file");
interpret_brainfuck(&code);
}
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