advent-of-code/2021/rust/common.rs

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2021-12-16 17:00:15 -06:00
use std::env::var as envvar;
use std::path::Path;
use std::fs;
const ASCII_UPPER_A: u8 = 65;
const ASCII_LOWER_A: u8 = 97;
const ASCII_0: u8 = 48;
pub fn day_input(day: u8) -> String {
let home = &envvar("HOME").unwrap();
let home_path = Path::new(home);
let path_buf = home_path.join(format!("./.cache/aoc2021/{0}.input", day));
let file_path = path_buf.to_str().unwrap();
fs::read_to_string(file_path).unwrap()
}
pub const fn hex_val(c: char) -> Result<u8, &'static str> {
match c {
'A'..='F' => Ok(c as u8 - ASCII_UPPER_A + 10),
'a'..='f' => Ok(c as u8 - ASCII_LOWER_A + 10),
'0'..='9' => Ok(c as u8 - ASCII_0 as u8),
_ => Err("invalid hex char"),
}
}