Trait frame_support::storage::StorageDecodeLength

pub trait StorageDecodeLength: Sealed + DecodeLength {
    fn decode_len(key: &[u8]) -> Option<usize> { ... }
}

Marker trait that will be implemented for types that support to decode their length in an efficient way. It is expected that the length is at the beginning of the encoded object and that the length is a Compact<u32>.

This trait is sealed.

Provided Methods

fn decode_len(key: &[u8]) -> Option<usize>

Decode the length of the storage value at key.

This function assumes that the length is at the beginning of the encoded object and is a Compact<u32>.

Returns None if the storage value does not exist or the decoding failed.

Examples found in repository

src/storage/mod.rs (line 153)

	fn decode_len() -> Option<usize>
	where
		T: StorageDecodeLength,
	{
		T::decode_len(&Self::hashed_key())
	}
}

/// A strongly-typed map in storage.
///
/// Details on implementation can be found at [`generator::StorageMap`].
pub trait StorageMap<K: FullEncode, V: FullCodec> {
	/// The type that get/take return.
	type Query;

	/// Get the storage key used to fetch a value corresponding to a specific key.
	fn hashed_key_for<KeyArg: EncodeLike<K>>(key: KeyArg) -> Vec<u8>;

	/// Does the value (explicitly) exist in storage?
	fn contains_key<KeyArg: EncodeLike<K>>(key: KeyArg) -> bool;

	/// Load the value associated with the given key from the map.
	fn get<KeyArg: EncodeLike<K>>(key: KeyArg) -> Self::Query;

	/// Store or remove the value to be associated with `key` so that `get` returns the `query`.
	fn set<KeyArg: EncodeLike<K>>(key: KeyArg, query: Self::Query);

	/// Try to get the value for the given key from the map.
	///
	/// Returns `Ok` if it exists, `Err` if not.
	fn try_get<KeyArg: EncodeLike<K>>(key: KeyArg) -> Result<V, ()>;

	/// Swap the values of two keys.
	fn swap<KeyArg1: EncodeLike<K>, KeyArg2: EncodeLike<K>>(key1: KeyArg1, key2: KeyArg2);

	/// Store a value to be associated with the given key from the map.
	fn insert<KeyArg: EncodeLike<K>, ValArg: EncodeLike<V>>(key: KeyArg, val: ValArg);

	/// Remove the value under a key.
	fn remove<KeyArg: EncodeLike<K>>(key: KeyArg);

	/// Mutate the value under a key.
	fn mutate<KeyArg: EncodeLike<K>, R, F: FnOnce(&mut Self::Query) -> R>(key: KeyArg, f: F) -> R;

	/// Mutate the item, only if an `Ok` value is returned.
	fn try_mutate<KeyArg: EncodeLike<K>, R, E, F: FnOnce(&mut Self::Query) -> Result<R, E>>(
		key: KeyArg,
		f: F,
	) -> Result<R, E>;

	/// Mutate the value under a key.
	///
	/// Deletes the item if mutated to a `None`.
	fn mutate_exists<KeyArg: EncodeLike<K>, R, F: FnOnce(&mut Option<V>) -> R>(
		key: KeyArg,
		f: F,
	) -> R;

	/// Mutate the item, only if an `Ok` value is returned. Deletes the item if mutated to a `None`.
	/// `f` will always be called with an option representing if the storage item exists (`Some<V>`)
	/// or if the storage item does not exist (`None`), independent of the `QueryType`.
	fn try_mutate_exists<KeyArg: EncodeLike<K>, R, E, F: FnOnce(&mut Option<V>) -> Result<R, E>>(
		key: KeyArg,
		f: F,
	) -> Result<R, E>;

	/// Take the value under a key.
	fn take<KeyArg: EncodeLike<K>>(key: KeyArg) -> Self::Query;

	/// Append the given items to the value in the storage.
	///
	/// `V` is required to implement `codec::EncodeAppend`.
	///
	/// # Warning
	///
	/// If the storage item is not encoded properly, the storage will be overwritten
	/// and set to `[item]`. Any default value set for the storage item will be ignored
	/// on overwrite.
	fn append<Item, EncodeLikeItem, EncodeLikeKey>(key: EncodeLikeKey, item: EncodeLikeItem)
	where
		EncodeLikeKey: EncodeLike<K>,
		Item: Encode,
		EncodeLikeItem: EncodeLike<Item>,
		V: StorageAppend<Item>;

	/// Read the length of the storage value without decoding the entire value under the
	/// given `key`.
	///
	/// `V` is required to implement [`StorageDecodeLength`].
	///
	/// If the value does not exists or it fails to decode the length, `None` is returned.
	/// Otherwise `Some(len)` is returned.
	///
	/// # Warning
	///
	/// `None` does not mean that `get()` does not return a value. The default value is completly
	/// ignored by this function.
	fn decode_len<KeyArg: EncodeLike<K>>(key: KeyArg) -> Option<usize>
	where
		V: StorageDecodeLength,
	{
		V::decode_len(&Self::hashed_key_for(key))
	}

	/// Migrate an item with the given `key` from a defunct `OldHasher` to the current hasher.
	///
	/// If the key doesn't exist, then it's a no-op. If it does, then it returns its value.
	fn migrate_key<OldHasher: StorageHasher, KeyArg: EncodeLike<K>>(key: KeyArg) -> Option<V>;

	/// Migrate an item with the given `key` from a `blake2_256` hasher to the current hasher.
	///
	/// If the key doesn't exist, then it's a no-op. If it does, then it returns its value.
	fn migrate_key_from_blake<KeyArg: EncodeLike<K>>(key: KeyArg) -> Option<V> {
		Self::migrate_key::<crate::hash::Blake2_256, KeyArg>(key)
	}
}

/// A strongly-typed map in storage whose keys and values can be iterated over.
pub trait IterableStorageMap<K: FullEncode, V: FullCodec>: StorageMap<K, V> {
	/// The type that iterates over all `(key, value)`.
	type Iterator: Iterator<Item = (K, V)>;
	/// The type that itereates over all `key`s.
	type KeyIterator: Iterator<Item = K>;

	/// Enumerate all elements in the map in lexicographical order of the encoded key. If you
	/// alter the map while doing this, you'll get undefined results.
	fn iter() -> Self::Iterator;

	/// Enumerate all elements in the map after a specified `starting_raw_key` in lexicographical
	/// order of the encoded key. If you alter the map while doing this, you'll get undefined
	/// results.
	fn iter_from(starting_raw_key: Vec<u8>) -> Self::Iterator;

	/// Enumerate all keys in the map in lexicographical order of the encoded key, skipping over
	/// the elements. If you alter the map while doing this, you'll get undefined results.
	fn iter_keys() -> Self::KeyIterator;

	/// Enumerate all keys in the map after a specified `starting_raw_key` in lexicographical order
	/// of the encoded key. If you alter the map while doing this, you'll get undefined results.
	fn iter_keys_from(starting_raw_key: Vec<u8>) -> Self::KeyIterator;

	/// Remove all elements from the map and iterate through them in lexicographical order of the
	/// encoded key. If you add elements to the map while doing this, you'll get undefined results.
	fn drain() -> Self::Iterator;

	/// Translate the values of all elements by a function `f`, in the map in lexicographical order
	/// of the encoded key.
	/// By returning `None` from `f` for an element, you'll remove it from the map.
	///
	/// NOTE: If a value fail to decode because storage is corrupted then it is skipped.
	fn translate<O: Decode, F: FnMut(K, O) -> Option<V>>(f: F);
}

/// A strongly-typed double map in storage whose secondary keys and values can be iterated over.
pub trait IterableStorageDoubleMap<K1: FullCodec, K2: FullCodec, V: FullCodec>:
	StorageDoubleMap<K1, K2, V>
{
	/// The type that iterates over all `key2`.
	type PartialKeyIterator: Iterator<Item = K2>;

	/// The type that iterates over all `(key2, value)`.
	type PrefixIterator: Iterator<Item = (K2, V)>;

	/// The type that iterates over all `(key1, key2)`.
	type FullKeyIterator: Iterator<Item = (K1, K2)>;

	/// The type that iterates over all `(key1, key2, value)`.
	type Iterator: Iterator<Item = (K1, K2, V)>;

	/// Enumerate all elements in the map with first key `k1` in lexicographical order of the
	/// encoded key. If you add or remove values whose first key is `k1` to the map while doing
	/// this, you'll get undefined results.
	fn iter_prefix(k1: impl EncodeLike<K1>) -> Self::PrefixIterator;

	/// Enumerate all elements in the map with first key `k1` after a specified `starting_raw_key`
	/// in lexicographical order of the encoded key. If you add or remove values whose first key is
	/// `k1` to the map while doing this, you'll get undefined results.
	fn iter_prefix_from(k1: impl EncodeLike<K1>, starting_raw_key: Vec<u8>)
		-> Self::PrefixIterator;

	/// Enumerate all second keys `k2` in the map with the same first key `k1` in lexicographical
	/// order of the encoded key. If you add or remove values whose first key is `k1` to the map
	/// while doing this, you'll get undefined results.
	fn iter_key_prefix(k1: impl EncodeLike<K1>) -> Self::PartialKeyIterator;

	/// Enumerate all second keys `k2` in the map with the same first key `k1` after a specified
	/// `starting_raw_key` in lexicographical order of the encoded key. If you add or remove values
	/// whose first key is `k1` to the map while doing this, you'll get undefined results.
	fn iter_key_prefix_from(
		k1: impl EncodeLike<K1>,
		starting_raw_key: Vec<u8>,
	) -> Self::PartialKeyIterator;

	/// Remove all elements from the map with first key `k1` and iterate through them in
	/// lexicographical order of the encoded key. If you add elements with first key `k1` to the
	/// map while doing this, you'll get undefined results.
	fn drain_prefix(k1: impl EncodeLike<K1>) -> Self::PrefixIterator;

	/// Enumerate all elements in the map in lexicographical order of the encoded key. If you add
	/// or remove values to the map while doing this, you'll get undefined results.
	fn iter() -> Self::Iterator;

	/// Enumerate all elements in the map after a specified `starting_raw_key` in lexicographical
	/// order of the encoded key. If you add or remove values to the map while doing this, you'll
	/// get undefined results.
	fn iter_from(starting_raw_key: Vec<u8>) -> Self::Iterator;

	/// Enumerate all keys `k1` and `k2` in the map in lexicographical order of the encoded key. If
	/// you add or remove values to the map while doing this, you'll get undefined results.
	fn iter_keys() -> Self::FullKeyIterator;

	/// Enumerate all keys `k1` and `k2` in the map after a specified `starting_raw_key` in
	/// lexicographical order of the encoded key. If you add or remove values to the map while
	/// doing this, you'll get undefined results.
	fn iter_keys_from(starting_raw_key: Vec<u8>) -> Self::FullKeyIterator;

	/// Remove all elements from the map and iterate through them in lexicographical order of the
	/// encoded key. If you add elements to the map while doing this, you'll get undefined results.
	fn drain() -> Self::Iterator;

	/// Translate the values of all elements by a function `f`, in the map in lexicographical order
	/// of the encoded key.
	/// By returning `None` from `f` for an element, you'll remove it from the map.
	///
	/// NOTE: If a value fail to decode because storage is corrupted then it is skipped.
	fn translate<O: Decode, F: FnMut(K1, K2, O) -> Option<V>>(f: F);
}

/// A strongly-typed map with arbitrary number of keys in storage whose keys and values can be
/// iterated over.
pub trait IterableStorageNMap<K: ReversibleKeyGenerator, V: FullCodec>: StorageNMap<K, V> {
	/// The type that iterates over all `(key1, key2, key3, ... keyN)` tuples.
	type KeyIterator: Iterator<Item = K::Key>;

	/// The type that iterates over all `(key1, key2, key3, ... keyN), value)` tuples.
	type Iterator: Iterator<Item = (K::Key, V)>;

	/// Enumerate all elements in the map with prefix key `kp` in lexicographical order of the
	/// encoded key. If you add or remove values whose prefix is `kp` to the map while doing this,
	/// you'll get undefined results.
	fn iter_prefix<KP>(kp: KP) -> PrefixIterator<(<K as HasKeyPrefix<KP>>::Suffix, V)>
	where
		K: HasReversibleKeyPrefix<KP>;

	/// Enumerate all elements in the map with prefix key `kp` after a specified `starting_raw_key`
	/// in lexicographical order of the encoded key. If you add or remove values whose prefix is
	/// `kp` to the map while doing this, you'll get undefined results.
	fn iter_prefix_from<KP>(
		kp: KP,
		starting_raw_key: Vec<u8>,
	) -> PrefixIterator<(<K as HasKeyPrefix<KP>>::Suffix, V)>
	where
		K: HasReversibleKeyPrefix<KP>;

	/// Enumerate all suffix keys in the map with prefix key `kp` in lexicographical order of the
	/// encoded key. If you add or remove values whose prefix is `kp` to the map while doing this,
	/// you'll get undefined results.
	fn iter_key_prefix<KP>(kp: KP) -> KeyPrefixIterator<<K as HasKeyPrefix<KP>>::Suffix>
	where
		K: HasReversibleKeyPrefix<KP>;

	/// Enumerate all suffix keys in the map with prefix key `kp` after a specified
	/// `starting_raw_key` in lexicographical order of the encoded key. If you add or remove values
	/// whose prefix is `kp` to the map while doing this, you'll get undefined results.
	fn iter_key_prefix_from<KP>(
		kp: KP,
		starting_raw_key: Vec<u8>,
	) -> KeyPrefixIterator<<K as HasKeyPrefix<KP>>::Suffix>
	where
		K: HasReversibleKeyPrefix<KP>;

	/// Remove all elements from the map with prefix key `kp` and iterate through them in
	/// lexicographical order of the encoded key. If you add elements with prefix key `kp` to the
	/// map while doing this, you'll get undefined results.
	fn drain_prefix<KP>(kp: KP) -> PrefixIterator<(<K as HasKeyPrefix<KP>>::Suffix, V)>
	where
		K: HasReversibleKeyPrefix<KP>;

	/// Enumerate all elements in the map in lexicographical order of the encoded key. If you add
	/// or remove values to the map while doing this, you'll get undefined results.
	fn iter() -> Self::Iterator;

	/// Enumerate all elements in the map after a specified `starting_raw_key` in lexicographical
	/// order of the encoded key. If you add or remove values to the map while doing this, you'll
	/// get undefined results.
	fn iter_from(starting_raw_key: Vec<u8>) -> Self::Iterator;

	/// Enumerate all keys in the map in lexicographical order of the encoded key. If you add or
	/// remove values to the map while doing this, you'll get undefined results.
	fn iter_keys() -> Self::KeyIterator;

	/// Enumerate all keys in the map after `starting_raw_key` in lexicographical order of the
	/// encoded key. If you add or remove values to the map while doing this, you'll get undefined
	/// results.
	fn iter_keys_from(starting_raw_key: Vec<u8>) -> Self::KeyIterator;

	/// Remove all elements from the map and iterate through them in lexicographical order of the
	/// encoded key. If you add elements to the map while doing this, you'll get undefined results.
	fn drain() -> Self::Iterator;

	/// Translate the values of all elements by a function `f`, in the map in lexicographical order
	/// of the encoded key.
	/// By returning `None` from `f` for an element, you'll remove it from the map.
	///
	/// NOTE: If a value fail to decode because storage is corrupted then it is skipped.
	fn translate<O: Decode, F: FnMut(K::Key, O) -> Option<V>>(f: F);
}

/// An implementation of a map with a two keys.
///
/// Details on implementation can be found at [`generator::StorageDoubleMap`].
pub trait StorageDoubleMap<K1: FullEncode, K2: FullEncode, V: FullCodec> {
	/// The type that get/take returns.
	type Query;

	/// Get the storage key used to fetch a value corresponding to a specific key.
	fn hashed_key_for<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Vec<u8>
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>;

	/// Does the value (explicitly) exist in storage?
	fn contains_key<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> bool
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>;

	/// Load the value associated with the given key from the double map.
	fn get<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Self::Query
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>;

	/// Try to get the value for the given key from the double map.
	///
	/// Returns `Ok` if it exists, `Err` if not.
	fn try_get<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Result<V, ()>
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>;

	/// Store or remove the value to be associated with `key` so that `get` returns the `query`.
	fn set<KArg1: EncodeLike<K1>, KArg2: EncodeLike<K2>>(k1: KArg1, k2: KArg2, query: Self::Query);

	/// Take a value from storage, removing it afterwards.
	fn take<KArg1, KArg2>(k1: KArg1, k2: KArg2) -> Self::Query
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>;

	/// Swap the values of two key-pairs.
	fn swap<XKArg1, XKArg2, YKArg1, YKArg2>(x_k1: XKArg1, x_k2: XKArg2, y_k1: YKArg1, y_k2: YKArg2)
	where
		XKArg1: EncodeLike<K1>,
		XKArg2: EncodeLike<K2>,
		YKArg1: EncodeLike<K1>,
		YKArg2: EncodeLike<K2>;

	/// Store a value to be associated with the given keys from the double map.
	fn insert<KArg1, KArg2, VArg>(k1: KArg1, k2: KArg2, val: VArg)
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>,
		VArg: EncodeLike<V>;

	/// Remove the value under the given keys.
	fn remove<KArg1, KArg2>(k1: KArg1, k2: KArg2)
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>;

	/// Remove all values under the first key `k1` in the overlay and up to `limit` in the
	/// backend.
	///
	/// All values in the client overlay will be deleted, if there is some `limit` then up to
	/// `limit` values are deleted from the client backend, if `limit` is none then all values in
	/// the client backend are deleted.
	///
	/// # Note
	///
	/// Calling this multiple times per block with a `limit` set leads always to the same keys being
	/// removed and the same result being returned. This happens because the keys to delete in the
	/// overlay are not taken into account when deleting keys in the backend.
	#[deprecated = "Use `clear_prefix` instead"]
	fn remove_prefix<KArg1>(k1: KArg1, limit: Option<u32>) -> sp_io::KillStorageResult
	where
		KArg1: ?Sized + EncodeLike<K1>;

	/// Remove all values under the first key `k1` in the overlay and up to `maybe_limit` in the
	/// backend.
	///
	/// All values in the client overlay will be deleted, if `maybe_limit` is `Some` then up to
	/// that number of values are deleted from the client backend, otherwise all values in the
	/// client backend are deleted.
	///
	/// ## Cursors
	///
	/// The `maybe_cursor` parameter should be `None` for the first call to initial removal.
	/// If the resultant `maybe_cursor` is `Some`, then another call is required to complete the
	/// removal operation. This value must be passed in as the subsequent call's `maybe_cursor`
	/// parameter. If the resultant `maybe_cursor` is `None`, then the operation is complete and no
	/// items remain in storage provided that no items were added between the first calls and the
	/// final call.
	fn clear_prefix<KArg1>(
		k1: KArg1,
		limit: u32,
		maybe_cursor: Option<&[u8]>,
	) -> sp_io::MultiRemovalResults
	where
		KArg1: ?Sized + EncodeLike<K1>;

	/// Iterate over values that share the first key.
	fn iter_prefix_values<KArg1>(k1: KArg1) -> PrefixIterator<V>
	where
		KArg1: ?Sized + EncodeLike<K1>;

	/// Mutate the value under the given keys.
	fn mutate<KArg1, KArg2, R, F>(k1: KArg1, k2: KArg2, f: F) -> R
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>,
		F: FnOnce(&mut Self::Query) -> R;

	/// Mutate the value under the given keys when the closure returns `Ok`.
	fn try_mutate<KArg1, KArg2, R, E, F>(k1: KArg1, k2: KArg2, f: F) -> Result<R, E>
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>,
		F: FnOnce(&mut Self::Query) -> Result<R, E>;

	/// Mutate the value under the given keys. Deletes the item if mutated to a `None`.
	fn mutate_exists<KArg1, KArg2, R, F>(k1: KArg1, k2: KArg2, f: F) -> R
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>,
		F: FnOnce(&mut Option<V>) -> R;

	/// Mutate the item, only if an `Ok` value is returned. Deletes the item if mutated to a `None`.
	/// `f` will always be called with an option representing if the storage item exists (`Some<V>`)
	/// or if the storage item does not exist (`None`), independent of the `QueryType`.
	fn try_mutate_exists<KArg1, KArg2, R, E, F>(k1: KArg1, k2: KArg2, f: F) -> Result<R, E>
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>,
		F: FnOnce(&mut Option<V>) -> Result<R, E>;

	/// Append the given item to the value in the storage.
	///
	/// `V` is required to implement [`StorageAppend`].
	///
	/// # Warning
	///
	/// If the storage item is not encoded properly, the storage will be overwritten
	/// and set to `[item]`. Any default value set for the storage item will be ignored
	/// on overwrite.
	fn append<Item, EncodeLikeItem, KArg1, KArg2>(k1: KArg1, k2: KArg2, item: EncodeLikeItem)
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>,
		Item: Encode,
		EncodeLikeItem: EncodeLike<Item>,
		V: StorageAppend<Item>;

	/// Read the length of the storage value without decoding the entire value under the
	/// given `key1` and `key2`.
	///
	/// `V` is required to implement [`StorageDecodeLength`].
	///
	/// If the value does not exists or it fails to decode the length, `None` is returned.
	/// Otherwise `Some(len)` is returned.
	///
	/// # Warning
	///
	/// `None` does not mean that `get()` does not return a value. The default value is completly
	/// ignored by this function.
	fn decode_len<KArg1, KArg2>(key1: KArg1, key2: KArg2) -> Option<usize>
	where
		KArg1: EncodeLike<K1>,
		KArg2: EncodeLike<K2>,
		V: StorageDecodeLength,
	{
		V::decode_len(&Self::hashed_key_for(key1, key2))
	}

	/// Migrate an item with the given `key1` and `key2` from defunct `OldHasher1` and
	/// `OldHasher2` to the current hashers.
	///
	/// If the key doesn't exist, then it's a no-op. If it does, then it returns its value.
	fn migrate_keys<
		OldHasher1: StorageHasher,
		OldHasher2: StorageHasher,
		KeyArg1: EncodeLike<K1>,
		KeyArg2: EncodeLike<K2>,
	>(
		key1: KeyArg1,
		key2: KeyArg2,
	) -> Option<V>;
}

/// An implementation of a map with an arbitrary number of keys.
///
/// Details of implementation can be found at [`generator::StorageNMap`].
pub trait StorageNMap<K: KeyGenerator, V: FullCodec> {
	/// The type that get/take returns.
	type Query;

	/// Get the storage key used to fetch a value corresponding to a specific key.
	fn hashed_key_for<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg) -> Vec<u8>;

	/// Does the value (explicitly) exist in storage?
	fn contains_key<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg) -> bool;

	/// Load the value associated with the given key from the map.
	fn get<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg) -> Self::Query;

	/// Try to get the value for the given key from the map.
	///
	/// Returns `Ok` if it exists, `Err` if not.
	fn try_get<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg) -> Result<V, ()>;

	/// Store or remove the value to be associated with `key` so that `get` returns the `query`.
	fn set<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg, query: Self::Query);

	/// Swap the values of two keys.
	fn swap<KOther, KArg1, KArg2>(key1: KArg1, key2: KArg2)
	where
		KOther: KeyGenerator,
		KArg1: EncodeLikeTuple<K::KArg> + TupleToEncodedIter,
		KArg2: EncodeLikeTuple<KOther::KArg> + TupleToEncodedIter;

	/// Store a value to be associated with the given key from the map.
	fn insert<KArg, VArg>(key: KArg, val: VArg)
	where
		KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter,
		VArg: EncodeLike<V>;

	/// Remove the value under a key.
	fn remove<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg);

	/// Remove all values starting with `partial_key` in the overlay and up to `limit` in the
	/// backend.
	///
	/// All values in the client overlay will be deleted, if there is some `limit` then up to
	/// `limit` values are deleted from the client backend, if `limit` is none then all values in
	/// the client backend are deleted.
	///
	/// # Note
	///
	/// Calling this multiple times per block with a `limit` set leads always to the same keys being
	/// removed and the same result being returned. This happens because the keys to delete in the
	/// overlay are not taken into account when deleting keys in the backend.
	#[deprecated = "Use `clear_prefix` instead"]
	fn remove_prefix<KP>(partial_key: KP, limit: Option<u32>) -> sp_io::KillStorageResult
	where
		K: HasKeyPrefix<KP>;

	/// Attempt to remove items from the map matching a `partial_key` prefix.
	///
	/// Returns [`MultiRemovalResults`](sp_io::MultiRemovalResults) to inform about the result. Once
	/// the resultant `maybe_cursor` field is `None`, then no further items remain to be deleted.
	///
	/// NOTE: After the initial call for any given map, it is important that no further items
	/// are inserted into the map which match the `partial key`. If so, then the map may not be
	/// empty when the resultant `maybe_cursor` is `None`.
	///
	/// # Limit
	///
	/// A `limit` must be provided in order to cap the maximum
	/// amount of deletions done in a single call. This is one fewer than the
	/// maximum number of backend iterations which may be done by this operation and as such
	/// represents the maximum number of backend deletions which may happen. A `limit` of zero
	/// implies that no keys will be deleted, though there may be a single iteration done.
	///
	/// # Cursor
	///
	/// A *cursor* may be passed in to this operation with `maybe_cursor`. `None` should only be
	/// passed once (in the initial call) for any given storage map and `partial_key`. Subsequent
	/// calls operating on the same map/`partial_key` should always pass `Some`, and this should be
	/// equal to the previous call result's `maybe_cursor` field.
	fn clear_prefix<KP>(
		partial_key: KP,
		limit: u32,
		maybe_cursor: Option<&[u8]>,
	) -> sp_io::MultiRemovalResults
	where
		K: HasKeyPrefix<KP>;

	/// Iterate over values that share the partial prefix key.
	fn iter_prefix_values<KP>(partial_key: KP) -> PrefixIterator<V>
	where
		K: HasKeyPrefix<KP>;

	/// Mutate the value under a key.
	fn mutate<KArg, R, F>(key: KArg, f: F) -> R
	where
		KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter,
		F: FnOnce(&mut Self::Query) -> R;

	/// Mutate the item, only if an `Ok` value is returned.
	fn try_mutate<KArg, R, E, F>(key: KArg, f: F) -> Result<R, E>
	where
		KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter,
		F: FnOnce(&mut Self::Query) -> Result<R, E>;

	/// Mutate the value under a key.
	///
	/// Deletes the item if mutated to a `None`.
	fn mutate_exists<KArg, R, F>(key: KArg, f: F) -> R
	where
		KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter,
		F: FnOnce(&mut Option<V>) -> R;

	/// Mutate the item, only if an `Ok` value is returned. Deletes the item if mutated to a `None`.
	/// `f` will always be called with an option representing if the storage item exists (`Some<V>`)
	/// or if the storage item does not exist (`None`), independent of the `QueryType`.
	fn try_mutate_exists<KArg, R, E, F>(key: KArg, f: F) -> Result<R, E>
	where
		KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter,
		F: FnOnce(&mut Option<V>) -> Result<R, E>;

	/// Take the value under a key.
	fn take<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg) -> Self::Query;

	/// Append the given items to the value in the storage.
	///
	/// `V` is required to implement `codec::EncodeAppend`.
	///
	/// # Warning
	///
	/// If the storage item is not encoded properly, the storage will be overwritten
	/// and set to `[item]`. Any default value set for the storage item will be ignored
	/// on overwrite.
	fn append<Item, EncodeLikeItem, KArg>(key: KArg, item: EncodeLikeItem)
	where
		KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter,
		Item: Encode,
		EncodeLikeItem: EncodeLike<Item>,
		V: StorageAppend<Item>;

	/// Read the length of the storage value without decoding the entire value under the
	/// given `key`.
	///
	/// `V` is required to implement [`StorageDecodeLength`].
	///
	/// If the value does not exists or it fails to decode the length, `None` is returned.
	/// Otherwise `Some(len)` is returned.
	///
	/// # Warning
	///
	/// `None` does not mean that `get()` does not return a value. The default value is completly
	/// ignored by this function.
	fn decode_len<KArg: EncodeLikeTuple<K::KArg> + TupleToEncodedIter>(key: KArg) -> Option<usize>
	where
		V: StorageDecodeLength,
	{
		V::decode_len(&Self::hashed_key_for(key))
	}

Implementations on Foreign Types

impl<T: Encode> StorageDecodeLength for BTreeSet<T>

Implementors

impl<K, V, S> StorageDecodeLength for BoundedBTreeMap<K, V, S>

impl<T, S> StorageDecodeLength for BoundedBTreeSet<T, S>

impl<T, S> StorageDecodeLength for BoundedVec<T, S>

impl<T, S> StorageDecodeLength for WeakBoundedVec<T, S>

impl<T: Encode> StorageDecodeLength for Vec<T>