Panic if Sieve::new() is called with max_bit_length == 0

Author: fjarri

CHANGELOG.md

@@ -4,6 +4,16 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
+## [0.3.1] - Unreleased
+
+### Fixed
+
+- `Sieve::new()` now panics when `max_bit_length == 0` (which would lead to incorrect results anyway, so it is not considered a breaking change). ([#26])
+
+
+[#26]: https://github.com/nucypher/rust-umbral/pull/26
+
+
 ## [0.3.0] - 2023-05-05
 
 ### Changed

src/hazmat/sieve.rs

@@ -75,10 +75,14 @@ impl<const L: usize> Sieve<L> {
     /// Note that `start` is adjusted to `2`, or the next `1 mod 2` number (`safe_primes = false`);
     /// and `5`, or `3 mod 4` number (`safe_primes = true`).
     ///
-    /// Panics if `max_bit_length` is greater than the size of the target `Uint`.
+    /// Panics if `max_bit_length` is zero or greater than the size of the target `Uint`.
     ///
     /// If `safe_primes` is `true`, both the returned `n` and `n/2` are sieved.
     pub fn new(start: &Uint<L>, max_bit_length: usize, safe_primes: bool) -> Self {
+        if max_bit_length == 0 {
+            panic!("The requested bit length cannot be zero");
+        }
+
         if max_bit_length > Uint::<L>::BITS {
             panic!(
                 "The requested bit length ({}) is larger than the chosen Uint size",
@@ -333,6 +337,12 @@ mod tests {
         check_sieve(13, 4, true, &[]);
     }
 
+    #[test]
+    #[should_panic(expected = "The requested bit length cannot be zero")]
+    fn sieve_zero_bits() {
+        let _sieve = Sieve::new(&U64::ONE, 0, false);
+    }
+
     #[test]
     #[should_panic(expected = "The requested bit length (65) is larger than the chosen Uint size")]
     fn sieve_too_many_bits() {