Clean up ordered bitset (implementation & usages) and write tests

src/argparse.rs

@@ -94,8 +94,6 @@ impl From<core::num::ParseFloatError> for ParseError<'_> {
 
 impl core::error::Error for ParseError<'_> {}
 
-type RequiredParamsBitSet = ordered_bitset::OrderedBitSet<BitSetType, BITSET_SLOTS>;
-
 /// Internal state tracked by the parser
 struct ParserState<ID: 'static> {
   positional_index: usize,

src/options.rs

@@ -13,10 +13,10 @@ pub struct Opts<ID: 'static> {
   description: Option<&'static str>,
 }
 
-type BitSetType = u32;
-const BITSET_SLOTS: usize = 4;
+type RequiredParamsBitSet = ordered_bitset::OrderedBitSet<u32, 4>;
+
 /// The maximum amount of allowed required non-positional options.
-pub const MAX_REQUIRED_OPTIONS: usize = BitSetType::BITS as usize * BITSET_SLOTS;
+pub const MAX_REQUIRED_OPTIONS: usize = RequiredParamsBitSet::CAPACITY;
 
 impl<ID: 'static> Opts<ID> {
   /// Build argument parser options with the default flag character of '-'
@@ -30,7 +30,7 @@ impl<ID: 'static> Opts<ID> {
       }
       opt_idx += 1;
     }
-    assert!(num_required_parameters <= MAX_REQUIRED_OPTIONS,
+    assert!(num_required_parameters <= RequiredParamsBitSet::CAPACITY,
       "More than 128 non-positional required option entries is not supported at this time");
 
     Self {

src/ordered_bitset.rs

@@ -15,12 +15,15 @@ impl<T: OrderedBitSetStorage, const S: usize> Default for OrderedBitSet<T, S> {
 
 // TODO: Obvious target for improvement when const traits land
 impl<T: OrderedBitSetStorage, const S: usize> OrderedBitSet<T, S> {
+  /// Number of slots in the bit set.
+  pub(crate) const CAPACITY: usize = T::BITS as usize * S;
+
+  /// Creates a new, empty bit set.
   pub(crate) const fn new() -> Self { Self([T::ZERO; S]) }
 
+  /// Sets the slot at `index` to a binary value.
   pub(crate) fn insert(&mut self, index: usize, value: bool) {
-    let array_idx = index >> T::SHIFT;
-    debug_assert!(array_idx < S, "Index out of range");
-    let bit_idx = index & T::MASK;
+    let (array_idx, bit_idx) = self.internal_index(index);
     let bit_mask = T::from_usize(0b1) << T::from_usize(bit_idx);
     if value {
       self.0[array_idx] |= bit_mask;
@@ -29,21 +32,30 @@ impl<T: OrderedBitSetStorage, const S: usize> OrderedBitSet<T, S> {
     }
   }
 
+  /// Gets the binary value at slot `index`.
   pub(crate) fn get(&self, index: usize) -> bool {
-    let array_idx = index >> T::SHIFT;
-    debug_assert!(array_idx < S, "Index out of range");
-    let bit_idx = index & T::MASK;
+    let (array_idx, bit_idx) = self.internal_index(index);
     let bit_mask = T::from_usize(0b1) << T::from_usize(bit_idx);
     (self.0[array_idx] & bit_mask) != T::from_usize(0)
   }
+
+  #[inline]
+  const fn internal_index(&self, index: usize) -> (usize, usize) {
+    debug_assert!(index < Self::CAPACITY, "Index out of range");
+    let array_idx = index >> T::SHIFT;
+    let bit_idx = index & T::MASK;
+    (array_idx, bit_idx)
+  }
 }
 
-trait OrderedBitSetStorage: Default + Copy + Clone + Eq + PartialEq
+trait OrderedBitSetStorage: core::fmt::Debug
+    + Default + Copy + Clone + Eq + PartialEq
     + BitAnd<Output = Self> + Shl<Output = Self> + Not<Output = Self>
     + BitAndAssign + BitOrAssign {
   const ZERO: Self;
   const SHIFT: u32;
   const MASK: usize;
+  const BITS: u32;
   fn from_usize(value: usize) -> Self;
 }
 
@@ -53,6 +65,8 @@ macro_rules! impl_bitset_storage {
       const ZERO: $t = 0;
       const SHIFT: u32 = $b.ilog2();
       const MASK: usize = $b as usize - 1;
+      const BITS: u32 = $b;
+      #[inline(always)]
       fn from_usize(value: usize) -> $t { value as $t }
     }
   };
@@ -63,3 +77,49 @@ impl_bitset_storage!(u16, u16::BITS);
 impl_bitset_storage!(u32, u32::BITS);
 impl_bitset_storage!(u64, u64::BITS);
 impl_bitset_storage!(u128, u128::BITS);
+
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn test_bitset_storage() {
+    fn harness<T: OrderedBitSetStorage + core::fmt::Debug>(bits_expect: u32, shift_expect: u32) {
+      assert_eq!(T::ZERO, T::from_usize(0));
+      assert_eq!(T::SHIFT, shift_expect);
+      assert_eq!(T::MASK, bits_expect as usize - 1);
+      assert_eq!(T::BITS, bits_expect);
+    }
+
+    harness::<u8>(8, 3);
+    harness::<u16>(16, 4);
+    harness::<u32>(32, 5);
+    harness::<u64>(64, 6);
+    harness::<u128>(128, 7);
+  }
+
+  #[test]
+  fn test_ordered_bitset() {
+    fn harness<T: OrderedBitSetStorage, const S: usize>(indices: &[usize]) {
+      let mut bitset = OrderedBitSet::<T, S>::new();
+      for &index in indices {
+        bitset.insert(index, true);
+      }
+      for slot in 0..OrderedBitSet::<u32, 4>::CAPACITY {
+        assert_eq!(bitset.get(slot), indices.contains(&slot));
+      }
+      for &index in indices {
+        bitset.insert(index, false);
+        assert!(!bitset.get(index));
+      }
+    }
+
+    let indices = [1, 32, 33, 127, 44, 47, 49];
+    harness::<u8, 16>(&indices);
+    harness::<u16, 8>(&indices);
+    harness::<u32, 4>(&indices);
+    harness::<u64, 2>(&indices);
+    harness::<u128, 1>(&indices);
+  }
+}