Function encode

nodedb-codec/src/spherical.rs:28–62

Encode f32 embeddings using spherical coordinate transformation + lz4. Input: flat array of f32 values, `vectors * dims` total elements. Each consecutive `dims` values form one embedding vector.

(data: &[f32], dims: usize, vectors: usize)

/// Input: flat array of f32 values, `vectors * dims` total elements.
/// Each consecutive `dims` values form one embedding vector.
pub fn encode(data: &[f32], dims: usize, vectors: usize) -> Result<Vec<u8>, CodecError> {
    if data.is_empty() || dims == 0 {
        return Ok(build_header(dims as u32, 0, 0, &[]));
    }

    if data.len() != vectors * dims {
        return Err(CodecError::Corrupt {
            detail: format!(
                "expected {} elements ({vectors} vectors × {dims} dims), got {}",
                vectors * dims,
                data.len()
            ),
        });
    }

    // Transform each vector from Cartesian to spherical coordinates.
    let mut transformed = Vec::with_capacity(data.len());
    for v in 0..vectors {
        let start = v * dims;
        let vec_data = &data[start..start + dims];
        let spherical = cartesian_to_spherical(vec_data);
        transformed.extend_from_slice(&spherical);
    }

    // Convert f32 to bytes and compress with lz4.
    let raw_bytes: Vec<u8> = transformed.iter().flat_map(|f| f.to_le_bytes()).collect();
    let compressed = crate::lz4::encode(&raw_bytes);

    Ok(build_header(
        dims as u32,
        vectors as u32,
        1, // spherical transform
        &compressed,
    ))
}

/// Encode f32 embeddings without transformation (raw + lz4).
///