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>;

    // Required methods
    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 apply_to_key_values_while<F: FnMut(Vec<u8>, Vec<u8>) -> bool>(
        &self,
        child_info: Option<&ChildInfo>,
        prefix: Option<&[u8]>,
        start_at: Option<&[u8]>,
        f: F,
        allow_missing: bool
    ) -> Result<bool, Self::Error>;
    fn apply_to_keys_while<F: FnMut(&[u8]) -> bool>(
        &self,
        child_info: Option<&ChildInfo>,
        prefix: Option<&[u8]>,
        start_at: Option<&[u8]>,
        f: F
    );
    fn for_key_values_with_prefix<F: FnMut(&[u8], &[u8])>(
        &self,
        prefix: &[u8],
        f: F
    );
    fn for_child_keys_with_prefix<F: FnMut(&[u8])>(
        &self,
        child_info: &ChildInfo,
        prefix: &[u8],
        f: F
    );
    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 pairs(&self) -> Vec<(StorageKey, StorageValue)>;
    fn register_overlay_stats(&self, _stats: &StateMachineStats);
    fn usage_info(&self) -> UsageInfo;

    // Provided methods
    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 for_keys_with_prefix<F: FnMut(&[u8])>(&self, prefix: &[u8], f: F) { ... }
    fn keys(&self, prefix: &[u8]) -> Vec<StorageKey> { ... }
    fn child_keys(
        &self,
        child_info: &ChildInfo,
        prefix: &[u8]
    ) -> Vec<StorageKey> { ... }
    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.

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 apply_to_key_values_while<F: FnMut(Vec<u8>, Vec<u8>) -> bool>( &self, child_info: Option<&ChildInfo>, prefix: Option<&[u8]>, start_at: Option<&[u8]>, f: F, allow_missing: bool ) -> Result<bool, Self::Error>

Iterate over storage starting at key, for a given prefix and child trie. Aborts as soon as f returns false. Warning, this fails at first error when usual iteration skips errors. If allow_missing is true, iteration stops when it reaches a missing trie node. Otherwise an error is produced.

Returns true if trie end is reached.

fn apply_to_keys_while<F: FnMut(&[u8]) -> bool>( &self, child_info: Option<&ChildInfo>, prefix: Option<&[u8]>, start_at: Option<&[u8]>, f: F )

Retrieve all entries keys of storage and call f for each of those keys. Aborts as soon as f returns false.

fn for_key_values_with_prefix<F: FnMut(&[u8], &[u8])>( &self, prefix: &[u8], f: F )

Retrieve all entries keys and values of which start with the given prefix and call f for each of those keys.

fn for_child_keys_with_prefix<F: FnMut(&[u8])>( &self, child_info: &ChildInfo, prefix: &[u8], f: F )

Retrieve all child entries keys which start with the given prefix and call f for each of those keys.

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 pairs(&self) -> Vec<(StorageKey, StorageValue)>

Get all key/value pairs into a Vec.

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 for_keys_with_prefix<F: FnMut(&[u8])>(&self, prefix: &[u8], f: F)

Retrieve all entries keys which start with the given prefix and call f for each of those keys.

fn keys(&self, prefix: &[u8]) -> Vec<StorageKey>

Get all keys with given prefix

fn child_keys(&self, child_info: &ChildInfo, prefix: &[u8]) -> Vec<StorageKey>

Get all keys of child storage with given prefix

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