fix tests

src/reader.rs

@@ -296,10 +296,13 @@ fn read_header<R: Read>(
         .read_exact(&mut prime_size)
         .map_err(|err| ReadBytesError { source: err.into() })?;
     let prime = U256::from_le_slice(&prime_size);
-    let prime = &prime.to_string().to_ascii_lowercase();
 
-    if prime != &expected_prime[2..] {
-        // get rid of '0x' in the front
+    let expected_prime =
+        U256::from_str_radix(&expected_prime[2..], 16).map_err(|_err| NonMatchingPrime {
+            expected: expected_prime.to_string(),
+            value: prime.to_string(),
+        })?;
+    if prime != expected_prime {
         return Err(NonMatchingPrime {
             expected: expected_prime.to_string(),
             value: prime.to_string(),

src/util.rs

@@ -23,16 +23,27 @@ pub fn ff_as_limbs<F: PrimeField>(f: &F) -> &[u32; 8] {
     unsafe { transmute(repr) }
 }
 
+// /// Assumes little endian
+// pub fn limbs_as_ff<F: PrimeField>(limbs: [u32; 8]) -> F {
+//     let mut repr = F::ZERO.to_repr();
+//     let limbs: [u8; 32] = unsafe { transmute(limbs) };
+//     for (i, digit) in repr.as_mut().iter_mut().enumerate() {
+//         // this doesn't work if the platform we're on is not little endian :scream:
+//         *digit = limbs[i];
+//     }
+
+//     F::from_repr(repr).unwrap()
+// }
+
+// TODO(winston): This is slower than the above, but does not fail
 /// Assumes little endian
 pub fn limbs_as_ff<F: PrimeField>(limbs: [u32; 8]) -> F {
-    let mut repr = F::ZERO.to_repr();
-    let limbs: [u8; 32] = unsafe { transmute(limbs) };
-    for (i, digit) in repr.as_mut().iter_mut().enumerate() {
-        // this doesn't work if the platform we're on is not little endian :scream:
-        *digit = limbs[i];
+    let mut res = F::ZERO;
+    let radix = F::from(0x0001_0000_0000_u64);
+    for val in limbs {
+        res = res * radix + F::from(u64::from(val));
     }
-
-    F::from_repr(repr).unwrap()
+    res
 }
 
 /// Assumes little endian