Struct StateSchemaUpgrade 

pub struct StateSchemaUpgrade { /* private fields */ }

One directed application-schema upgrade a codec declares.

An upgrade rewrites a JSON-object payload recorded at from into the shape to expects. The framework, not the codec, selects and applies the edges, so a codec never inspects a recorded version to decide what an older payload meant.

Edges strictly increase the version and at most one edge may leave any version, which is what makes a resolved chain deterministic and bounded.

Implementations

impl StateSchemaUpgrade

pub fn new( from: StateSchemaVersion, to: StateSchemaVersion, apply: fn(&[u8]) -> Result<Vec<u8>, StateCodecError>, ) -> Result<StateSchemaUpgrade, StateError>

Declares a directed upgrade between two application schema versions.

apply must be deterministic: the same payload bytes must always produce the same result, because a restart replays the same chain over the same durable bytes.

Errors

Returns StateError::NonIncreasingUpgrade when to does not exceed from, which would let a chain loop or move backwards.

pub const fn from(&self) -> StateSchemaVersion

Returns the version this upgrade reads.

pub const fn to(&self) -> StateSchemaVersion

Returns the version this upgrade produces.

Trait Implementations

impl Clone for StateSchemaUpgrade

fn clone(&self) -> StateSchemaUpgrade

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for StateSchemaUpgrade

impl Debug for StateSchemaUpgrade

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

Formats the value using the given formatter.