feat: add from_bytes_(l|n)e methods

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 #### Upcoming Changes
 
+* feat: add `from_bytes_le` and `from_bytes_ne` methods [#1326](https://github.com/lambdaclass/cairo-vm/pull/1326)
+
 #### [0.8.2] - 2023-7-10
 
 * chore: update dependencies, particularly lamdaworks 0.1.2 -> 0.1.3 [#1323](https://github.com/lambdaclass/cairo-vm/pull/1323)

felt/src/bigint_felt.rs

@@ -170,11 +170,11 @@ impl FeltOps for FeltBigInt<FIELD_HIGH, FIELD_LOW> {
     }
 
     fn from_bytes_be(bytes: &[u8]) -> FeltBigInt<FIELD_HIGH, FIELD_LOW> {
-        let mut value = BigUint::from_bytes_be(bytes);
-        if value >= *CAIRO_PRIME_BIGUINT {
-            value = value.mod_floor(&CAIRO_PRIME_BIGUINT);
-        }
-        Self::from(value)
+        Self::from(BigUint::from_bytes_be(bytes))
+    }
+
+    fn from_bytes_le(bytes: &[u8]) -> FeltBigInt<FIELD_HIGH, FIELD_LOW> {
+        Self::from(BigUint::from_bytes_le(bytes))
     }
 
     #[cfg(any(feature = "std", feature = "alloc"))]

felt/src/lib_bigint_felt.rs

@@ -40,6 +40,8 @@ pub(crate) trait FeltOps {
 
     fn from_bytes_be(bytes: &[u8]) -> Self;
 
+    fn from_bytes_le(bytes: &[u8]) -> Self;
+
     #[cfg(any(feature = "std", feature = "alloc"))]
     fn to_str_radix(&self, radix: u32) -> String;
 
@@ -177,6 +179,19 @@ impl Felt252 {
             value: FeltBigInt::from_bytes_be(bytes),
         }
     }
+    pub fn from_bytes_le(bytes: &[u8]) -> Self {
+        Self {
+            value: FeltBigInt::from_bytes_le(bytes),
+        }
+    }
+    pub fn from_bytes_ne(bytes: &[u8]) -> Self {
+        // Call either version depending on target endianness
+        #[cfg(target_endian = "little")]
+        let res = Self::from_bytes_le(bytes);
+        #[cfg(target_endian = "big")]
+        let res = Self::from_bytes_be(bytes);
+        res
+    }
     #[cfg(any(feature = "std", feature = "alloc"))]
     pub fn to_str_radix(&self, radix: u32) -> String {
         self.value.to_str_radix(radix)

felt/src/lib_lambdaworks.rs

@@ -248,9 +248,24 @@ impl Felt252 {
     }
 
     pub fn from_bytes_be(bytes: &[u8]) -> Self {
+        // TODO: use upstream's version when it's more lenient
         Self::from(BigUint::from_bytes_be(bytes))
     }
 
+    pub fn from_bytes_le(bytes: &[u8]) -> Self {
+        // TODO: use upstream's version when it's more lenient
+        Self::from(BigUint::from_bytes_le(bytes))
+    }
+
+    pub fn from_bytes_ne(bytes: &[u8]) -> Self {
+        // Call either version depending on target endianness
+        #[cfg(target_endian = "little")]
+        let res = Self::from_bytes_le(bytes);
+        #[cfg(target_endian = "big")]
+        let res = Self::from_bytes_be(bytes);
+        res
+    }
+
     #[cfg(any(feature = "std", feature = "alloc"))]
     pub fn to_str_radix(&self, radix: u32) -> String {
         if radix == 16 {