arcly-stream 0.8.3

//! Standard (RFC 4648) base64 encode/decode for the RTSP module: Basic-auth
//! credentials (`auth`) and SDP `sprop-*` parameter sets (`sdp`). Kept dependency
//! free — the crate carries no `base64` crate.

/// Encode `data` as standard base64 (with `=` padding).
pub(super) fn encode(data: &[u8]) -> String {
    const A: &[u8; 64] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    let mut out = String::with_capacity(data.len().div_ceil(3) * 4);
    for chunk in data.chunks(3) {
        let b = [
            chunk[0],
            *chunk.get(1).unwrap_or(&0),
            *chunk.get(2).unwrap_or(&0),
        ];
        let n = (b[0] as u32) << 16 | (b[1] as u32) << 8 | b[2] as u32;
        out.push(A[(n >> 18 & 63) as usize] as char);
        out.push(A[(n >> 12 & 63) as usize] as char);
        out.push(if chunk.len() > 1 {
            A[(n >> 6 & 63) as usize] as char
        } else {
            '='
        });
        out.push(if chunk.len() > 2 {
            A[(n & 63) as usize] as char
        } else {
            '='
        });
    }
    out
}

/// Decode standard (RFC 4648) base64, tolerating missing padding and embedded
/// whitespace. Returns `None` on an invalid character.
pub(super) fn decode(s: &str) -> Option<Vec<u8>> {
    fn val(c: u8) -> Option<u8> {
        match c {
            b'A'..=b'Z' => Some(c - b'A'),
            b'a'..=b'z' => Some(c - b'a' + 26),
            b'0'..=b'9' => Some(c - b'0' + 52),
            b'+' => Some(62),
            b'/' => Some(63),
            _ => None,
        }
    }
    let mut bits: u32 = 0;
    let mut nbits = 0;
    let mut out = Vec::with_capacity(s.len() * 3 / 4);
    for &c in s.as_bytes() {
        if c == b'=' || c.is_ascii_whitespace() {
            continue;
        }
        bits = (bits << 6) | val(c)? as u32;
        nbits += 6;
        if nbits >= 8 {
            nbits -= 8;
            out.push((bits >> nbits) as u8);
        }
    }
    Some(out)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn encode_known_vectors() {
        assert_eq!(encode(b"user:pass"), "dXNlcjpwYXNz");
        assert_eq!(
            encode(b"Aladdin:open sesame"),
            "QWxhZGRpbjpvcGVuIHNlc2FtZQ=="
        );
    }

    #[test]
    fn decode_round_trips_and_tolerates_padding() {
        assert_eq!(decode("dXNlcjpwYXNz").as_deref(), Some(&b"user:pass"[..]));
        // missing padding + whitespace are tolerated.
        assert_eq!(decode("Zm9v").as_deref(), Some(&b"foo"[..]));
        assert_eq!(decode("Zm 9v\n").as_deref(), Some(&b"foo"[..]));
        // invalid character rejected.
        assert!(decode("****").is_none());
    }
}