neco-secp 0.1.1

minimum dependency secp256k1 and Nostr signing core
Documentation 
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use crate::SecpError;

pub fn hex_encode(bytes: &[u8]) -> String {
    const HEX: &[u8; 16] = b"0123456789abcdef";
    let mut s = String::with_capacity(bytes.len() * 2);
    for &b in bytes {
        s.push(HEX[(b >> 4) as usize] as char);
        s.push(HEX[(b & 0x0f) as usize] as char);
    }
    s
}

pub fn hex_decode(hex: &str) -> Result<Vec<u8>, SecpError> {
    let hex = hex.as_bytes();
    if hex.len() % 2 != 0 {
        return Err(SecpError::InvalidHex("odd length"));
    }
    let mut out = Vec::with_capacity(hex.len() / 2);
    for chunk in hex.chunks(2) {
        let high = hex_nibble(chunk[0])?;
        let low = hex_nibble(chunk[1])?;
        out.push((high << 4) | low);
    }
    Ok(out)
}

fn hex_nibble(b: u8) -> Result<u8, SecpError> {
    match b {
        b'0'..=b'9' => Ok(b - b'0'),
        b'a'..=b'f' => Ok(b - b'a' + 10),
        b'A'..=b'F' => Ok(b - b'A' + 10),
        _ => Err(SecpError::InvalidHex("invalid character")),
    }
}