Interface ChangeStore

atomic-core/src/change/store.rs:89–241

A trait for storing and retrieving changes. The primary operations are: - Loading complete changes by hash - Reading content bytes for specific vertices - Checking for change/content existence # Type Parameters Implementations define their own `Error` type, which must be convertible from `ChangeError` for change loading operations. # Thread Safety Implementations should be safe for concurrent

/// Implementations should be safe for concurrent read access. The trait
/// methods take `&self`, enabling shared references across threads.
pub trait ChangeStore: Send + Sync {
    /// Error type for change store operations.
    type Error: std::error::Error + Send + Sync + 'static;

    /// Load a complete change by its hash.
    ///
    /// # Arguments
    ///
    /// * `hash` - The content hash of the change
    ///
    /// # Returns
    ///
    /// The complete [`Change`] if found.
    ///
    /// # Errors
    ///
    /// Returns an error if the change is not found or cannot be loaded.
    fn get_change(&self, hash: &Hash) -> Result<Change, Self::Error>;

    /// Check if a change exists.
    ///
    /// # Arguments
    ///
    /// * `hash` - The content hash of the change
    ///
    /// # Returns
    ///
    /// `true` if the change exists in the store.
    fn has_change(&self, hash: &Hash) -> bool {
        self.get_change(hash).is_ok()
    }

    /// Check if a change has content bytes.
    ///
    /// Some changes may have empty content sections (e.g., metadata-only changes).
    ///
    /// # Arguments
    ///
    /// * `hash` - The content hash of the change
    ///
    /// # Returns
    ///
    /// `true` if the change exists and has non-empty content.
    fn has_contents(&self, hash: &Hash) -> bool {
        self.get_change(hash)
            .map(|c| !c.contents.is_empty())
            .unwrap_or(false)
    }

    /// Read content bytes for a span.
    ///
    /// This is the core method for retrieving file content during output.
    /// It reads the byte range `[span.start, span.end)` from the change
    /// that introduced this span.
    ///
    /// # Arguments
    ///
    /// * `hash_fn` - Function to map `NodeId` to `Hash`