Enum depends::core::NodeHash

pub enum NodeHash {
    NotHashed,
    Hashed(u64),
}

A Hash of the current node state used to signal whether a dependent node needs to update its internal state.

Every edge in a depends graph tracks the previously observed NodeHash of the child node and signals to the dependee whether this has changed since the last run using the IsDirty trait. This is used to cache internal computations.

NotHashed

If NotHashed is used, dependent nodes will never consider previously observed states equal and will therefore update their internal state every time they’re resolved. For this reason, it’s recommended that NotHashed be used sparingly (in cases where computing a hash of a node’s state is impossible or costlier than recomputing the dependee’s state).

Whichever implementation is chosen, it’s important to structure graphs so that the number of nodes and edges to nodes implementing NotHashed is kept to a minimum, especially where performance is a concern.

// not equal
assert_ne!(NodeHash::NotHashed, NodeHash::NotHashed);
assert_ne!(NodeHash::NotHashed, NodeHash::Hashed(0));
assert_ne!(NodeHash::Hashed(0), NodeHash::Hashed(1));
// equal
assert_eq!(NodeHash::Hashed(1), NodeHash::Hashed(1));

Variants

NotHashed

Never equal to another value.

Hashed(u64)

Equal to another value if the internal number is equal.

Trait Implementations

impl Clone for NodeHash

fn clone(&self) -> NodeHash

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for NodeHash

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for NodeHash

fn default() -> NodeHash

Returns the “default value” for a type.

impl PartialEq<NodeHash> for NodeHash

fn eq(&self, other: &NodeHash) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for NodeHash

impl Eq for NodeHash

impl StructuralEq for NodeHash