Function rerank_codec_from_bytes

nodedb-vector/src/rerank/codec.rs:79–123

Reconstruct a `RerankCodec` from its byte form. The `name` tag tells us which wrapper to dispatch into; the bytes are the codec's own format.

(
    name: CodecName,
    bytes: &[u8],
)

/// Reconstruct a `RerankCodec` from its byte form. The `name` tag tells us
/// which wrapper to dispatch into; the bytes are the codec's own format.
pub fn rerank_codec_from_bytes(
    name: CodecName,
    bytes: &[u8],
) -> Result<Arc<dyn RerankCodec>, RerankError> {
    use crate::quantize::pq::PqCodec;
    use crate::quantize::sq8::Sq8Codec;
    use crate::rerank::codecs::{BbqRerank, BinaryRerank, PqRerank, RaBitQRerank, Sq8Rerank};
    use nodedb_codec::vector_quant::bbq::BbqCodec;
    use nodedb_codec::vector_quant::rabitq::RaBitQCodec;

    match name {
        CodecName::Sq8 => {
            let inner = Sq8Codec::from_bytes(bytes)
                .map_err(|e| RerankError::BadInput(format!("sq8 from_bytes: {e}")))?;
            Ok(Arc::new(Sq8Rerank::from_codec(inner)))
        }
        CodecName::Binary => {
            // Format: [NDBIN\0 (6 bytes)][version u8 = 1][dim u32 LE (4 bytes)] — 11 bytes total.
            if bytes.len() < 11 {
                return Err(RerankError::BadInput("binary from_bytes: too short".into()));
            }
            if &bytes[..6] != b"NDBIN\0" {
                return Err(RerankError::BadInput("binary from_bytes: bad magic".into()));
            }
            // bytes[6] is version, bytes[7..11] is dim as u32 LE.
            let dim = u32::from_le_bytes([bytes[7], bytes[8], bytes[9], bytes[10]]) as usize;
            Ok(Arc::new(BinaryRerank::new(dim)))
        }
        CodecName::Pq => {
            let inner = PqCodec::from_bytes(bytes)
                .map_err(|e| RerankError::BadInput(format!("pq from_bytes: {e}")))?;
            Ok(Arc::new(PqRerank::from_codec(inner)))
        }
        CodecName::RaBitQ => {
            let inner = RaBitQCodec::from_bytes(bytes)
                .map_err(|e| RerankError::BadInput(format!("rabitq from_bytes: {e}")))?;
            Ok(Arc::new(RaBitQRerank::from_codec(inner)))
        }
        CodecName::Bbq => {
            let inner = BbqCodec::from_bytes(bytes)
                .map_err(|e| RerankError::BadInput(format!("bbq from_bytes: {e}")))?;
            Ok(Arc::new(BbqRerank::from_codec(inner)))
        }
    }
}