Function decode_sparse_tile

nodedb-array/src/codec/tile_decode.rs:53–82

Decode a tile payload previously written by `encode_sparse_tile`. The `payload` slice must start at the tag byte (i.e. after BlockFraming has been unwrapped by the segment reader).

(payload: &[u8])

/// The `payload` slice must start at the tag byte (i.e. after BlockFraming
/// has been unwrapped by the segment reader).
pub fn decode_sparse_tile(payload: &[u8]) -> ArrayResult<SparseTile> {
    if payload.len() < 2 {
        return Err(ArrayError::SegmentCorruption {
            detail: "sparse tile payload too short".into(),
        });
    }

    let tag_result = peek_tag(payload).ok_or_else(|| {
        // peek_tag returns None for both legacy msgpack and unknown bytes.
        // The reader should never call us with a legacy payload.
        ArrayError::SegmentCorruption {
            detail: format!(
                "decode_sparse_tile called with legacy or unknown tag byte: {:#04x}",
                payload[0]
            ),
        }
    })?;

    let version = payload[1];
    if version != SUPPORTED_PAYLOAD_VERSION {
        return Err(ArrayError::SegmentCorruption {
            detail: format!("unsupported tile payload version: {version}"),
        });
    }

    match tag_result {
        CodecTag::Raw => decode_raw(&payload[2..]),
        CodecTag::Structural => decode_structural(&payload[2..]),
    }
}

fn decode_raw(body: &[u8]) -> ArrayResult<SparseTile> {
    zerompk::from_msgpack(body).map_err(|e| ArrayError::SegmentCorruption {