Function encode

nodedb-codec/src/double_delta.rs:117–152

Encode a slice of i64 values using DoubleDelta compression.

(values: &[i64])

/// Encode a slice of i64 values using DoubleDelta compression.
pub fn encode(values: &[i64]) -> Vec<u8> {
    let count = values.len() as u32;
    let mut out = Vec::with_capacity(20 + values.len() / 4);

    out.extend_from_slice(&count.to_le_bytes());

    if values.is_empty() {
        return out;
    }

    out.extend_from_slice(&values[0].to_le_bytes());

    if values.len() == 1 {
        return out;
    }

    let first_delta = values[1].wrapping_sub(values[0]);
    out.extend_from_slice(&first_delta.to_le_bytes());

    if values.len() == 2 {
        return out;
    }

    let mut bs = BitWriter::new();
    let mut prev_delta = first_delta;

    for i in 2..values.len() {
        let delta = values[i].wrapping_sub(values[i - 1]);
        let dod = delta.wrapping_sub(prev_delta);
        encode_dod(&mut bs, dod);
        prev_delta = delta;
    }

    out.extend_from_slice(bs.as_bytes());
    out
}

/// Decode DoubleDelta-compressed bytes back to i64 values.
pub fn decode(data: &[u8]) -> Result<Vec<i64>, CodecError> {