feat: make hasher accept iterators rather than arrays (#594)

* feat: poseidon_hash_may takes an iterator

* feat: compute_hash_on_elements takes ExactSizeIterator

* fix bug

starknet-core/src/crypto.rs

@@ -46,14 +46,19 @@ mod errors {
 }
 pub use errors::{EcdsaSignError, EcdsaVerifyError};
 
-pub fn compute_hash_on_elements(data: &[Felt]) -> Felt {
+pub fn compute_hash_on_elements<'a, ESI, II>(data: II) -> Felt
+where
+    ESI: ExactSizeIterator<Item = &'a Felt>,
+    II: IntoIterator<IntoIter = ESI>,
+{
     let mut current_hash = Felt::ZERO;
+    let data_iter = data.into_iter();
+    let data_len = Felt::from(data_iter.len());
 
-    for item in data.iter() {
-        current_hash = pedersen_hash(&current_hash, item);
+    for elem in data_iter {
+        current_hash = pedersen_hash(&current_hash, elem);
     }
 
-    let data_len = Felt::from(data.len());
     pedersen_hash(&current_hash, &data_len)
 }
 

starknet-crypto/src/poseidon_hash.rs

@@ -72,20 +72,29 @@ pub fn poseidon_hash_single(x: Felt) -> Felt {
 /// Computes the Starknet Poseidon hash of an arbitrary number of [Felt]s.
 ///
 /// Using this function is the same as using [PoseidonHasher].
-pub fn poseidon_hash_many(msgs: &[Felt]) -> Felt {
+pub fn poseidon_hash_many<'a, I: IntoIterator<Item = &'a Felt>>(msgs: I) -> Felt {
     let mut state = [Felt::ZERO, Felt::ZERO, Felt::ZERO];
-    let mut iter = msgs.chunks_exact(2);
+    let mut iter = msgs.into_iter();
+
+    loop {
+        match iter.next() {
+            Some(v) => state[0] += *v,
+            None => {
+                state[0] += Felt::ONE;
+                break;
+            }
+        }
+
+        match iter.next() {
+            Some(v) => state[1] += *v,
+            None => {
+                state[1] += Felt::ONE;
+                break;
+            }
+        }
 
-    for msg in iter.by_ref() {
-        state[0] += msg[0];
-        state[1] += msg[1];
         poseidon_permute_comp(&mut state);
     }
-    let r = iter.remainder();
-    if r.len() == 1 {
-        state[0] += r[0];
-    }
-    state[r.len()] += Felt::ONE;
     poseidon_permute_comp(&mut state);
 
     state[0]