refactor: move transaction hash calculation to sn api

[MohammadNassar1]

This change is 

[yair-starkware]

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @giladchase and @MohammadNassar1)

---

src/transaction_hash.rs line 44 at r1 (raw file):

    static ref ONE: StarkFelt = StarkFelt::from(1_u8);
    static ref TWO: StarkFelt = StarkFelt::from(2_u8);
    static ref THREE: StarkFelt = StarkFelt::from(3_u8);

You can use StarkFelt::ZERO etc.

Code quote:

    pub(crate) static ref ZERO: StarkFelt = StarkFelt::from(0_u8);
    static ref ONE: StarkFelt = StarkFelt::from(1_u8);
    static ref TWO: StarkFelt = StarkFelt::from(2_u8);
    static ref THREE: StarkFelt = StarkFelt::from(3_u8);

---

src/transaction_hash.rs line 48 at r1 (raw file):

/// Calculates hash of a Starknet transaction.
pub fn get_transaction_hash(

Consider implementing as methods (can be in a separate PR)

---

src/transaction_hash.rs line 216 at r1 (raw file):

        poseidon_hash_many(&self.elements).into()
    }
}

Consider moving to the crypto module

Code quote:

// Collect elements for applying hash chain.
pub(crate) struct HashChain {
    elements: Vec<FieldElement>,
}

impl HashChain {
    pub fn new() -> HashChain {
        HashChain { elements: Vec::new() }
    }

    // Chains a felt to the hash chain.
    pub fn chain(mut self, felt: &StarkFelt) -> Self {
        self.elements.push(FieldElement::from(*felt));
        self
    }

    // Chains the result of a function to the hash chain.
    pub fn chain_if_fn<F: Fn() -> Option<StarkFelt>>(self, f: F) -> Self {
        match f() {
            Some(felt) => self.chain(&felt),
            None => self,
        }
    }

    // Chains many felts to the hash chain.
    pub fn chain_iter<'a>(self, felts: impl Iterator<Item = &'a StarkFelt>) -> Self {
        felts.fold(self, |current, felt| current.chain(felt))
    }

    // Returns the pedersen hash of the chained felts, hashed with the length of the chain.
    pub fn get_pedersen_hash(&self) -> StarkHash {
        let current_hash = self
            .elements
            .iter()
            .fold(FieldElement::ZERO, |current_hash, felt| pedersen_hash(&current_hash, felt));
        let n_elements = FieldElement::from(self.elements.len());
        pedersen_hash(&current_hash, &n_elements).into()
    }

    // Returns the poseidon hash of the chained felts.
    pub fn get_poseidon_hash(&self) -> StarkHash {
        poseidon_hash_many(&self.elements).into()
    }
}

[giladchase]

@MohammadNassar1,

To clarify, this PR is only extracting code from papyrus into SNAPI, without any logic changes, with a refactor to follow, correct?

Should we wait to review until after the refactor, or would you like initial, non-blocking feedback now, with the understanding that fixes are for subsequent PRs?

Reviewed all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @MohammadNassar1)

[MohammadNassar1]

Yes, this PR is without any changes.
The next PR is for refactoring. I haven't opened it yet.
Please review it, so we can merge it and use transaction hash calculation in mempool.

Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @MohammadNassar1)

[MohammadNassar1]

Reviewable status: 1 of 4 files reviewed, 2 unresolved discussions (waiting on @giladchase and @yair-starkware)

---

src/transaction_hash.rs line 44 at r1 (raw file):

Previously, yair-starkware (Yair) wrote…

You can use StarkFelt::ZERO etc.

Will be done in the next PR.

---

src/transaction_hash.rs line 48 at r1 (raw file):

Previously, yair-starkware (Yair) wrote…

Consider implementing as methods (can be in a separate PR)

Will be done in the next PR.

[yair-starkware]

Reviewed 3 of 3 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MohammadNassar1)

[giladchase]

Reviewed 2 of 3 files at r1, 1 of 1 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MohammadNassar1)

[giladchase]

Reviewed 2 of 3 files at r3, 1 of 1 files at r4, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MohammadNassar1)