Function hex_encode_bytes

datafusion/spark/src/function/math/hex.rs:160–195

Generic hex encoding for byte array types

(
    iter: I,
    lowercase: bool,
    len: usize,
)

/// Generic hex encoding for byte array types
fn hex_encode_bytes<'a, I, T>(
    iter: I,
    lowercase: bool,
    len: usize,
) -> Result<ArrayRef, DataFusionError>
where
    I: Iterator<Item = Option<T>>,
    T: AsRef<[u8]> + 'a,
{
    let mut builder = StringBuilder::with_capacity(len, len * 64);
    let mut buffer = Vec::with_capacity(64);
    let lookup = if lowercase {
        &HEX_LOOKUP_LOWER
    } else {
        &HEX_LOOKUP_UPPER
    };

    for v in iter {
        if let Some(b) = v {
            let bytes = b.as_ref();
            buffer.clear();
            buffer.reserve(bytes.len() * 2);
            for &byte in bytes {
                buffer.extend_from_slice(&lookup[byte as usize]);
            }
            // SAFETY: buffer contains only ASCII hex digits, which are valid UTF-8.
            unsafe {
                builder.append_value(from_utf8_unchecked(&buffer));
            }
        } else {
            builder.append_null();
        }
    }

    Ok(Arc::new(builder.finish()))
}

/// Generic hex encoding for int64 type
fn hex_encode_int64(