Trait Backend 

pub trait Backend<H: Hasher>: Debug {
    type Error: Error;
    type Transaction: Consolidate + Default + Send;
    type TrieBackendStorage: TrieBackendStorage<H>;

    // Required methods
    fn storage(&self, key: &[u8]) -> Result<Option<StorageValue>, Self::Error>;
    fn child_storage(
        &self,
        child_info: &ChildInfo,
        key: &[u8],
    ) -> Result<Option<StorageValue>, 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_child_keys_while<F: FnMut(&[u8]) -> bool>(
        &self,
        child_info: &ChildInfo,
        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]>)>,
    ) -> (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]>)>,
    ) -> (H::Out, bool, Self::Transaction)
       where H::Out: Ord;
    fn pairs(&self) -> Vec<(StorageKey, StorageValue)>;
    fn register_overlay_stats(&mut self, _stats: &StateMachineStats);
    fn usage_info(&self) -> UsageInfo;

    // Provided methods
    fn storage_hash(&self, key: &[u8]) -> Result<Option<H::Out>, Self::Error> { ... }
    fn child_storage_hash(
        &self,
        child_info: &ChildInfo,
        key: &[u8],
    ) -> Result<Option<H::Out>, Self::Error> { ... }
    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 as_trie_backend(
        &mut self,
    ) -> Option<&TrieBackend<Self::TrieBackendStorage, H>> { ... }
    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]>)>)>,
    ) -> (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>) { ... }
}

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>

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 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 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_child_keys_while<F: FnMut(&[u8]) -> bool>( &self, child_info: &ChildInfo, f: F, )

Retrieve all entries keys of child 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]>)>, ) -> (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]>)>, ) -> (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(&mut 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 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_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 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 as_trie_backend( &mut self, ) -> Option<&TrieBackend<Self::TrieBackendStorage, H>>

Try convert into trie backend.

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]>)>)>, ) -> (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

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl<'a, T: Backend<H>, H: Hasher> Backend<H> for &'a T

type Error = <T as Backend<H>>::Error

type Transaction = <T as Backend<H>>::Transaction

type TrieBackendStorage = <T as Backend<H>>::TrieBackendStorage

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

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

fn apply_to_child_keys_while<F: FnMut(&[u8]) -> bool>( &self, child_info: &ChildInfo, f: F, )

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 for_keys_with_prefix<F: FnMut(&[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<'b>( &self, delta: impl Iterator<Item = (&'b [u8], Option<&'b [u8]>)>, ) -> (H::Out, Self::Transaction)

where H::Out: Ord,

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

where H::Out: Ord,

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

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

fn register_overlay_stats(&mut self, _stats: &StateMachineStats)

fn usage_info(&self) -> UsageInfo

Implementors

impl<'a, S, H> Backend<H> for ProvingBackend<'a, S, H>

where S: 'a + TrieBackendStorage<H>, H: 'a + Hasher, H::Out: Ord + Codec,

type Error = String

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

type TrieBackendStorage = S

impl<S: TrieBackendStorage<H>, H: Hasher> Backend<H> for TrieBackend<S, H>

where H::Out: Ord + Codec,

type Error = String

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

type TrieBackendStorage = S