Trait transact::state::Write

pub trait Write: Sync + Send + Clone {
type StateId;
type Key;
type Value;
    fn commit(
        &self, 
        state_id: &Self::StateId, 
        state_changes: &[StateChange]
    ) -> Result<Self::StateId, StateWriteError>;
    fn compute_state_id(
        &self, 
        state_id: &Self::StateId, 
        state_changes: &[StateChange]
    ) -> Result<Self::StateId, StateWriteError>;
}

state::Write provides a way to write to a particular state storage system.

It provides the ability for the caller to either compute the next StateId - useful for validating expected results - or committing the results to an underlying store.

A StateId, in the context of Write, is used to indicate the starting state on which the changes will be applied. It can be thought of as the identifier of a checkpoint or snapshot.

All operations are made using StateChange instances. These are the ordered set of changes to be applied onto the given StateId.

Implementations are expected to be thread-safe.

Associated Types

type StateId

A reference to a checkpoint in state. It could be a merkle hash for a merkle database.

type Key

The Key that is being stored in state.

type Value

The Value that is being stored in state.

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Required methods

fn commit(
    &self,
    state_id: &Self::StateId,
    state_changes: &[StateChange]
) -> Result<Self::StateId, StateWriteError>

Given a StateId and a slice of StateChange values, persist the state changes and return the resulting next StateId value.

This function will persist the state values to the underlying storage mechanism.

Errors

Any issues with committing the processing results will return a StateWriteError.

fn compute_state_id(
    &self,
    state_id: &Self::StateId,
    state_changes: &[StateChange]
) -> Result<Self::StateId, StateWriteError>

Given a StateId and a slice of StateChange values, compute the next StateId value.

This function will compute the value of the next StateId without actually persisting the state changes. Effectively, it is a dry-run.

Returns the next StateId value;

Errors

StateWriteError is returned if any issues occur while trying to generate this next id.

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Implementors

impl Write for HashMapState

type StateId = String

type Key = String

type Value = Vec<u8>

fn commit(
    &self,
    state_id: &Self::StateId,
    state_changes: &[StateChange]
) -> Result<Self::StateId, StateWriteError>

fn compute_state_id(
    &self,
    state_id: &Self::StateId,
    state_changes: &[StateChange]
) -> Result<Self::StateId, StateWriteError>

impl Write for MerkleState

type StateId = String

type Key = String

type Value = Vec<u8>

fn commit(
    &self,
    state_id: &Self::StateId,
    state_changes: &[StateChange]
) -> Result<Self::StateId, StateWriteError>

fn compute_state_id(
    &self,
    state_id: &Self::StateId,
    state_changes: &[StateChange]
) -> Result<Self::StateId, StateWriteError>

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