Function decode

nodedb-codec/src/delta.rs:112–159

Decode Delta-compressed bytes back to i64 values.

(data: &[u8])

/// Decode Delta-compressed bytes back to i64 values.
pub fn decode(data: &[u8]) -> Result<Vec<i64>, CodecError> {
    if data.len() < 4 {
        return Err(CodecError::Truncated {
            expected: 4,
            actual: data.len(),
        });
    }

    let count = u32::from_le_bytes(data[0..4].try_into().map_err(|_| CodecError::Corrupt {
        detail: "invalid header".into(),
    })?) as usize;

    if count == 0 {
        return Ok(Vec::new());
    }

    if data.len() < 12 {
        return Err(CodecError::Truncated {
            expected: 12,
            actual: data.len(),
        });
    }

    let first_value =
        i64::from_le_bytes(data[4..12].try_into().map_err(|_| CodecError::Corrupt {
            detail: "invalid first value".into(),
        })?);

    let mut values = Vec::with_capacity(count);
    values.push(first_value);

    let mut offset = 12;
    for _ in 1..count {
        if offset >= data.len() {
            return Err(CodecError::Truncated {
                expected: offset + 1,
                actual: data.len(),
            });
        }
        let (encoded_delta, consumed) = read_varint(&data[offset..])?;
        let delta = zigzag_decode(encoded_delta);
        let value = values[values.len() - 1].wrapping_add(delta);
        values.push(value);
        offset += consumed;
    }

    Ok(values)
}

// ---------------------------------------------------------------------------
// Streaming encoder / decoder types