Function deserialize_view_state

atomic-core/src/pristine/txn/helpers.rs:87–152

Deserialize bytes to a ViewState Backward-compatible: if the v2 fields (`kind`, `parent`) are missing (i.e., the data was written by an older version), defaults to `ViewScope::Shared` and `parent: None`.

(bytes: &[u8])

/// (i.e., the data was written by an older version), defaults to
/// `ViewScope::Shared` and `parent: None`.
pub fn deserialize_view_state(bytes: &[u8]) -> PristineResult<ViewState> {
    const MIN_SIZE: usize = 8 + 4; // id + name_len

    if bytes.len() < MIN_SIZE {
        return Err(PristineError::Serialization {
            message: "view state too short".to_string(),
        });
    }

    let id = u64::from_le_bytes(bytes[0..8].try_into().unwrap());
    let name_len = u32::from_le_bytes(bytes[8..12].try_into().unwrap()) as usize;

    // v1 size: header(12) + name + merkle(32) + change_count(8)
    let v1_size = 12 + name_len + 32 + 8;
    if bytes.len() < v1_size {
        return Err(PristineError::Serialization {
            message: "view state truncated".to_string(),
        });
    }

    let name = String::from_utf8(bytes[12..12 + name_len].to_vec()).map_err(|_| {
        PristineError::Serialization {
            message: "invalid view name encoding".to_string(),
        }
    })?;

    let mut merkle_bytes = [0u8; 32];
    merkle_bytes.copy_from_slice(&bytes[12 + name_len..12 + name_len + 32]);
    let state = Merkle::from_bytes(merkle_bytes);

    let change_count = u64::from_le_bytes(
        bytes[12 + name_len + 32..12 + name_len + 40]
            .try_into()
            .unwrap(),
    );

    // v2 fields: kind(1) + parent(8) = 9 additional bytes
    let v2_size = v1_size + 1 + 8;
    let (kind, parent) = if bytes.len() >= v2_size {
        let kind_byte = bytes[v1_size];
        let kind = ViewScope::from_u8(kind_byte).ok_or_else(|| PristineError::Serialization {
            message: format!("invalid view kind: {}", kind_byte),
        })?;

        let parent_val = u64::from_le_bytes(bytes[v1_size + 1..v1_size + 9].try_into().unwrap());
        let parent = if parent_val == NO_PARENT {
            None
        } else {
            Some(parent_val)
        };

        (kind, parent)
    } else {
        // v1 data — default to Shared with no parent
        (ViewScope::Shared, None)
    };

    Ok(ViewState {