feat: wasm felt to little endian string (#729)

---------

Co-authored-by: Alexander Camuto <45801863+alexander-camuto@users.noreply.github.com>

.github/workflows/rust.yml

@@ -575,7 +575,7 @@ jobs:
       - name: Install Anvil
         run: cargo install --git https://github.com/foundry-rs/foundry --rev b320f350156a0fb15c2eb13dc380deb2367c4474 --profile local --locked anvil --force
       - name: Build python ezkl
-        run: source .env/bin/activate; maturin develop --features python-bindings --release
+        run: source .env/bin/activate; unset CONDA_PREFIX; maturin develop --features python-bindings --release
       - name: Run pytest
         run: source .env/bin/activate; pytest -vv
 
@@ -599,7 +599,7 @@ jobs:
       - name: Setup Virtual Env and Install python dependencies
         run: python -m venv .env; source .env/bin/activate; pip install -r requirements.txt;
       - name: Build python ezkl
-        run: source .env/bin/activate; maturin develop --features python-bindings --release
+        run: source .env/bin/activate; unset CONDA_PREFIX; maturin develop --features python-bindings --release
       - name: Div rebase
         run: source .env/bin/activate; cargo nextest run --release --verbose tests::accuracy_measurement_div_rebase_
       - name: Public inputs
@@ -634,7 +634,7 @@ jobs:
       - name: Setup Virtual Env and Install python dependencies
         run: python -m venv .env; source .env/bin/activate; pip install -r requirements.txt;
       - name: Build python ezkl
-        run: source .env/bin/activate; maturin develop --features python-bindings --release
+        run: source .env/bin/activate; unset CONDA_PREFIX; maturin develop --features python-bindings --release
       # - name: authenticate-kaggle-cli
       #   shell: bash
       #   env:

src/wasm.rs

@@ -78,6 +78,17 @@ pub fn feltToBigEndian(array: wasm_bindgen::Clamped<Vec<u8>>) -> Result<String,
     Ok(format!("{:?}", felt))
 }
 
+/// Converts a felt to a little endian string
+#[wasm_bindgen]
+#[allow(non_snake_case)]
+pub fn feltToLittleEndian(array: wasm_bindgen::Clamped<Vec<u8>>) -> Result<String, JsError> {
+    let felt: Fr = serde_json::from_slice(&array[..])
+        .map_err(|e| JsError::new(&format!("Failed to deserialize field element: {}", e)))?;
+    let repr = serde_json::to_string(&felt).unwrap();
+    let b: String = serde_json::from_str(&repr).unwrap();
+    Ok(b)
+}
+
 /// Converts a hex string to a byte array
 #[wasm_bindgen]
 #[allow(non_snake_case)]

tests/wasm.rs

@@ -9,8 +9,8 @@ mod wasm32 {
     use ezkl::pfsys;
     use ezkl::wasm::{
         bufferToVecOfFelt, compiledCircuitValidation, encodeVerifierCalldata, feltToBigEndian,
-        feltToFloat, feltToInt, genPk, genVk, genWitness, inputValidation, pkValidation,
-        poseidonHash, proofValidation, prove, settingsValidation, srsValidation,
+        feltToFloat, feltToInt, feltToLittleEndian, genPk, genVk, genWitness, inputValidation,
+        pkValidation, poseidonHash, proofValidation, prove, settingsValidation, srsValidation,
         u8_array_to_u128_le, verify, vkValidation, witnessValidation,
     };
     use halo2_solidity_verifier::encode_calldata;
@@ -89,9 +89,16 @@ mod wasm32 {
                     .unwrap();
             assert_eq!(integer, i as i128);
 
-            let hex_string = format!("{:?}", field_element);
-            let returned_string: String = feltToBigEndian(clamped).map_err(|_| "failed").unwrap();
+            let hex_string = format!("{:?}", field_element.clone());
+            let returned_string: String = feltToBigEndian(clamped.clone())
+                .map_err(|_| "failed")
+                .unwrap();
             assert_eq!(hex_string, returned_string);
+            let repr = serde_json::to_string(&field_element).unwrap();
+            let little_endian_string: String = serde_json::from_str(&repr).unwrap();
+            let returned_string: String =
+                feltToLittleEndian(clamped).map_err(|_| "failed").unwrap();
+            assert_eq!(little_endian_string, returned_string);
         }
     }