Add compile time warning for constants generation

Added a compile time warning that checks if `assets/arc.bin` has enough
bytes to store the constants needed for the hades permutation.

src/hades/round_constants.rs

@@ -17,14 +17,21 @@ use crate::hades::{FULL_ROUNDS, PARTIAL_ROUNDS, WIDTH};
 
 const ROUNDS: usize = FULL_ROUNDS + PARTIAL_ROUNDS;
 
-/// `ROUND_CONSTANTS` constists on a static reference that points to the
+/// `ROUND_CONSTANTS` consists on a static reference that points to the
 /// pre-loaded 335 constant scalar of the bls12_381 curve.
 ///
 /// These 335 `BlsScalar` constants are loaded from `assets/arc.bin`.
 ///
 /// Check `assets/HOWTO.md` to see how we generated the constants.
 pub const ROUND_CONSTANTS: [[BlsScalar; WIDTH]; ROUNDS] = {
     let bytes = include_bytes!("../../assets/arc.bin");
+
+    // make sure that there are enough bytes for (WIDTH * ROUNDS) BlsScalar
+    // stored under 'assets/arc.bin'
+    if bytes.len() < WIDTH * ROUNDS * 32 {
+        panic!("There are not enough round constants stored in 'assets/arc.bin', have a look at the HOWTO to generate enough constants.");
+    }
+
     let mut cnst = [[BlsScalar::zero(); WIDTH]; ROUNDS];
 
     let mut i = 0;