AkurAI-Framework / crates/crypto/src/hexcodec.rs

Latest change 3aae9f4e85241bcb775c31f5c03094becd3da56a - Pure-Rust UI layer: akurai-ui, akurai-crypto, Tailwind-grade akurai-css by Ólafur Búi Ólafsson

//! Lowercase hex encoding and decoding.

const DIGITS: &[u8; 16] = b"0123456789abcdef";

/// Encode `bytes` as lowercase hex.
pub fn hex(bytes: &[u8]) -> String {
    let mut s = String::with_capacity(bytes.len() * 2);
    for b in bytes {
        s.push(DIGITS[usize::from(b >> 4)] as char);
        s.push(DIGITS[usize::from(b & 0x0f)] as char);
    }
    s
}

/// Decode hex (either case). `None` on odd length or a non-hex character.
pub fn from_hex(s: &str) -> Option<Vec<u8>> {
    let bytes = s.as_bytes();
    if !bytes.len().is_multiple_of(2) {
        return None;
    }
    bytes
        .as_chunks::<2>()
        .0
        .iter()
        .map(|pair| Some(nibble(pair[0])? << 4 | nibble(pair[1])?))
        .collect()
}

fn nibble(c: u8) -> Option<u8> {
    char::from(c).to_digit(16).map(|d| d as u8)
}