feat(starknet_patricia,starknet_committer): abstract storage prefix trait

[dorimedini-starkware]

No description provided.

[reviewable-StarkWare]

This change is 

[dorimedini-starkware]

• feat(starknet_patricia_storage): split between dynamic and static prefix #4045
• feat(starknet_patricia_storage): rename StorageKey/Value with a Db prefix #4024
• feat(starknet_patricia_storage): move storage abstractions to separate crate #4022
• feat(starknet_patricia): use external Felt type in storage trait #4021
• feat(starknet_patricia): small change in error heirarchy #4020
• feat(starknet_patricia,starknet_committer): abstract storage prefix trait #4019 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[dorimedini-starkware]

Reviewable status: 0 of 9 files reviewed, all discussions resolved

---

a discussion (no related file):
Basic idea:

1. Define a StoragePrefix trait, that can output the prefix as bytes.
2. The DBObject get_prefix method should return an impl StoragePrefix
3. The patricia (generic nodes) and committer (specific leaves) prefixes (PatriciaPrefix and CommitterLeafPrefix, respectively) should not be defined in the storage area: the patricia crate defines a generic prefix enum (generic in the leaf prefix), and the committer defines the specific leaf prefixes enum.
4. In general, the get_prefix method requires self - for example, the FilledNode<L> prefix depends on the variant of the enum (inner node or leaf). Leaves, on the other hand, do not require an instance - so we define a storage_prefix() -> impl StoragePrefix associated method on the Leaf trait, and use it when implementing DBObject for leaf types.

[dorimedini-starkware]

Reviewable status: 0 of 9 files reviewed, all discussions resolved

---

a discussion (no related file):

Previously, dorimedini-starkware wrote…

Basic idea:

1. Define a StoragePrefix trait, that can output the prefix as bytes.
2. The DBObject get_prefix method should return an impl StoragePrefix
3. The patricia (generic nodes) and committer (specific leaves) prefixes (PatriciaPrefix and CommitterLeafPrefix, respectively) should not be defined in the storage area: the patricia crate defines a generic prefix enum (generic in the leaf prefix), and the committer defines the specific leaf prefixes enum.
4. In general, the get_prefix method requires self - for example, the FilledNode<L> prefix depends on the variant of the enum (inner node or leaf). Leaves, on the other hand, do not require an instance - so we define a storage_prefix() -> impl StoragePrefix associated method on the Leaf trait, and use it when implementing DBObject for leaf types.

Correction: StoragePrefix is a struct, not a trait; implemented From<X> for StoragePrefix for the specific prefix enums in (3).

[AvivYossef-starkware]

Reviewed 9 of 9 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @TzahiTaub)

[dorimedini-starkware]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @TzahiTaub)

---

crates/starknet_patricia/src/patricia_merkle_tree/node_data/leaf.rs line 20 at r2 (raw file):

    type Output: Send + Debug + 'static;

    fn storage_prefix() -> StoragePrefix;

occasionally I have a type parameter L available (impl<L: Leaf> blocks), but not an instance of a leaf, and I need a prefix. hence, this associated function is required, in addition to the get_prefix method of DBObject.
get_prefix is still required, because sometimes a instance is required to determine the prefix

Code quote:

fn storage_prefix() -> StoragePrefix;

---

crates/starknet_patricia/src/storage/db_object.rs line 15 at r2 (raw file):

        create_db_key(self.get_prefix(), suffix)
    }
}

annoying issue and some code dup...
what I would like to do is

pub trait HasDbPrefix {
    /// Returns the storage key prefix of the DB object.
    fn get_prefix(&self) -> StoragePrefix;
}

pub trait DBObject: HasDbPrefix { .. }

and then auto-impl on leaves:

impl<L: Leaf> HasDbPrefix for L {
    fn get_prefix(&self) -> StoragePrefix {
        Self::storage_prefix()
    }
}

however, we can't do that when the HasDbPrefix trait is not in the same crate as Leaf

Code quote:

pub trait DBObject {
    /// Serializes the given value.
    fn serialize(&self) -> StorageValue;

    /// Returns the storage key prefix of the DB object.
    fn get_prefix(&self) -> StoragePrefix;

    /// Returns a `StorageKey` from a prefix and a suffix.
    fn get_db_key(&self, suffix: &[u8]) -> StorageKey {
        create_db_key(self.get_prefix(), suffix)
    }
}

[dorimedini-starkware]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @TzahiTaub)

---

crates/starknet_patricia/src/patricia_merkle_tree/node_data/leaf.rs line 20 at r2 (raw file):

Previously, dorimedini-starkware wrote…

occasionally I have a type parameter L available (impl<L: Leaf> blocks), but not an instance of a leaf, and I need a prefix. hence, this associated function is required, in addition to the get_prefix method of DBObject.
get_prefix is still required, because sometimes a instance is required to determine the prefix

this is later removed here, but for simplicity of this PR (and simplicity of rebasing a PR with file movements up the stack...) I'll keep it as is here