Trait sp_state_machine::backend::Backend

pub trait Backend<H: Hasher>: Debug {
    type Error: Error;
    type Transaction: Consolidate + Default + Send;
    type TrieBackendStorage: TrieBackendStorage<H, Overlay = Self::Transaction>;
    type RawIter: StorageIterator<H, Backend = Self, Error = Self::Error>;

    fn storage(&self, key: &[u8]) -> Result<Option<StorageValue>, Self::Error>;
    fn storage_hash(&self, key: &[u8]) -> Result<Option<H::Out>, Self::Error>;
    fn child_storage(
        &self,
        child_info: &ChildInfo,
        key: &[u8]
    ) -> Result<Option<StorageValue>, Self::Error>;
    fn child_storage_hash(
        &self,
        child_info: &ChildInfo,
        key: &[u8]
    ) -> Result<Option<H::Out>, Self::Error>;
    fn next_storage_key(
        &self,
        key: &[u8]
    ) -> Result<Option<StorageKey>, Self::Error>;
    fn next_child_storage_key(
        &self,
        child_info: &ChildInfo,
        key: &[u8]
    ) -> Result<Option<StorageKey>, Self::Error>;
    fn storage_root<'a>(
        &self,
        delta: impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>,
        state_version: StateVersion
    ) -> (H::Out, Self::Transaction)
    where
        H::Out: Ord;
    fn child_storage_root<'a>(
        &self,
        child_info: &ChildInfo,
        delta: impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>,
        state_version: StateVersion
    ) -> (H::Out, bool, Self::Transaction)
    where
        H::Out: Ord;
    fn raw_iter(&self, args: IterArgs<'_>) -> Result<Self::RawIter, Self::Error>;
    fn register_overlay_stats(&self, _stats: &StateMachineStats);
    fn usage_info(&self) -> UsageInfo;

    fn exists_storage(&self, key: &[u8]) -> Result<bool, Self::Error> { ... }
    fn exists_child_storage(
        &self,
        child_info: &ChildInfo,
        key: &[u8]
    ) -> Result<bool, Self::Error> { ... }
    fn pairs<'a>(
        &'a self,
        args: IterArgs<'_>
    ) -> Result<PairsIter<'a, H, Self::RawIter>, Self::Error> { ... }
    fn keys<'a>(
        &'a self,
        args: IterArgs<'_>
    ) -> Result<KeysIter<'a, H, Self::RawIter>, Self::Error> { ... }
    fn full_storage_root<'a>(
        &self,
        delta: impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>,
        child_deltas: impl Iterator<Item = (&'a ChildInfo, impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>)>,
        state_version: StateVersion
    ) -> (H::Out, Self::Transaction)
    where
        H::Out: Ord + Encode,
    { ... }
    fn wipe(&self) -> Result<(), Self::Error> { ... }
    fn commit(
        &self,
        _: H::Out,
        _: Self::Transaction,
        _: StorageCollection,
        _: ChildStorageCollection
    ) -> Result<(), Self::Error> { ... }
    fn read_write_count(&self) -> (u32, u32, u32, u32) { ... }
    fn reset_read_write_count(&self) { ... }
    fn get_whitelist(&self) -> Vec<TrackedStorageKey>  { ... }
    fn set_whitelist(&self, _: Vec<TrackedStorageKey>) { ... }
    fn proof_size(&self) -> Option<u32> { ... }
    fn get_read_and_written_keys(&self) -> Vec<(Vec<u8>, u32, u32, bool)>  { ... }
}

A state backend is used to read state data and can have changes committed to it.

The clone operation (if implemented) should be cheap.

Required Associated Types

type Error: Error

An error type when fetching data is not possible.

type Transaction: Consolidate + Default + Send

Storage changes to be applied if committing

type TrieBackendStorage: TrieBackendStorage<H, Overlay = Self::Transaction>

Type of trie backend storage.

type RawIter: StorageIterator<H, Backend = Self, Error = Self::Error>

Type of the raw storage iterator.

Required Methods

fn storage(&self, key: &[u8]) -> Result<Option<StorageValue>, Self::Error>

Get keyed storage or None if there is nothing associated.

fn storage_hash(&self, key: &[u8]) -> Result<Option<H::Out>, Self::Error>

Get keyed storage value hash or None if there is nothing associated.

fn child_storage(
    &self,
    child_info: &ChildInfo,
    key: &[u8]
) -> Result<Option<StorageValue>, Self::Error>

Get keyed child storage or None if there is nothing associated.

fn child_storage_hash(
    &self,
    child_info: &ChildInfo,
    key: &[u8]
) -> Result<Option<H::Out>, Self::Error>

Get child keyed storage value hash or None if there is nothing associated.

fn next_storage_key(&self, key: &[u8]) -> Result<Option<StorageKey>, Self::Error>

Return the next key in storage in lexicographic order or None if there is no value.

fn next_child_storage_key(
    &self,
    child_info: &ChildInfo,
    key: &[u8]
) -> Result<Option<StorageKey>, Self::Error>

Return the next key in child storage in lexicographic order or None if there is no value.

fn storage_root<'a>(
    &self,
    delta: impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>,
    state_version: StateVersion
) -> (H::Out, Self::Transaction)where
    H::Out: Ord,

Calculate the storage root, with given delta over what is already stored in the backend, and produce a “transaction” that can be used to commit. Does not include child storage updates.

fn child_storage_root<'a>(
    &self,
    child_info: &ChildInfo,
    delta: impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>,
    state_version: StateVersion
) -> (H::Out, bool, Self::Transaction)where
    H::Out: Ord,

Calculate the child storage root, with given delta over what is already stored in the backend, and produce a “transaction” that can be used to commit. The second argument is true if child storage root equals default storage root.

fn raw_iter(&self, args: IterArgs<'_>) -> Result<Self::RawIter, Self::Error>

Returns a lifetimeless raw storage iterator.

fn register_overlay_stats(&self, _stats: &StateMachineStats)

Register stats from overlay of state machine.

By default nothing is registered.

fn usage_info(&self) -> UsageInfo

Query backend usage statistics (i/o, memory)

Not all implementations are expected to be able to do this. In the case when they don’t, empty statistics is returned.

Provided Methods

fn exists_storage(&self, key: &[u8]) -> Result<bool, Self::Error>

true if a key exists in storage.

fn exists_child_storage(
    &self,
    child_info: &ChildInfo,
    key: &[u8]
) -> Result<bool, Self::Error>

true if a key exists in child storage.

fn pairs<'a>(
    &'a self,
    args: IterArgs<'_>
) -> Result<PairsIter<'a, H, Self::RawIter>, Self::Error>

Get an iterator over key/value pairs.

fn keys<'a>(
    &'a self,
    args: IterArgs<'_>
) -> Result<KeysIter<'a, H, Self::RawIter>, Self::Error>

Get an iterator over keys.

fn full_storage_root<'a>(
    &self,
    delta: impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>,
    child_deltas: impl Iterator<Item = (&'a ChildInfo, impl Iterator<Item = (&'a [u8], Option<&'a [u8]>)>)>,
    state_version: StateVersion
) -> (H::Out, Self::Transaction)where
    H::Out: Ord + Encode,

Calculate the storage root, with given delta over what is already stored in the backend, and produce a “transaction” that can be used to commit. Does include child storage updates.

fn wipe(&self) -> Result<(), Self::Error>

Wipe the state database.

fn commit(
    &self,
    _: H::Out,
    _: Self::Transaction,
    _: StorageCollection,
    _: ChildStorageCollection
) -> Result<(), Self::Error>

Commit given transaction to storage.

fn read_write_count(&self) -> (u32, u32, u32, u32)

Get the read/write count of the db

fn reset_read_write_count(&self)

Get the read/write count of the db

fn get_whitelist(&self) -> Vec<TrackedStorageKey>

Get the whitelist for tracking db reads/writes

fn set_whitelist(&self, _: Vec<TrackedStorageKey>)

Update the whitelist for tracking db reads/writes

fn proof_size(&self) -> Option<u32>

Estimate proof size

fn get_read_and_written_keys(&self) -> Vec<(Vec<u8>, u32, u32, bool)>

Extend storage info for benchmarking db

Implementors

impl<S: TrieBackendStorage<H>, H: Hasher, C: AsLocalTrieCache<H> + Send + Sync> Backend<H> for TrieBackend<S, H, C>where
    H::Out: Ord + Codec,

type Error = String

type Transaction = <S as TrieBackendStorage<H>>::Overlay

type TrieBackendStorage = S

type RawIter = RawIter<S, H, C>