compiling module for deterministic hashset

src/utils/hashmap.rs

@@ -50,6 +50,7 @@ pub fn deserialize_hashmap_capacity<
 /*
  * FxHasher taken from rustc_hash, except that it does not depend on the pointer size.
  */
+/// Deterministic hashmap using [`indexmap::IndexMap`]
 #[cfg(feature = "enhanced-determinism")]
 pub type FxHashMap32<K, V> = indexmap::IndexMap<K, V, std::hash::BuildHasherDefault<FxHasher32>>;
 #[cfg(feature = "enhanced-determinism")]

src/utils/hashset.rs

@@ -0,0 +1,138 @@
+//! A hash-map that behaves deterministically when the
+//! `enhanced-determinism` feature is enabled.
+
+#[cfg(all(feature = "enhanced-determinism", feature = "serde-serialize"))]
+use indexmap::IndexSet as StdHashSet;
+#[cfg(all(not(feature = "enhanced-determinism"), feature = "serde-serialize"))]
+use std::collections::HashSet as StdHashSet;
+use std::mem::size_of;
+
+/// Serializes only the capacity of a hash-map instead of its actual content.
+#[cfg(feature = "serde-serialize")]
+pub fn serialize_hashmap_capacity<S: serde::Serializer, K, H: std::hash::BuildHasher>(
+    map: &StdHashSet<K, H>,
+    s: S,
+) -> Result<S::Ok, S::Error> {
+    s.serialize_u64(map.capacity() as u64)
+}
+
+/// Creates a new hash-map with its capacity deserialized from `d`.
+#[cfg(feature = "serde-serialize")]
+pub fn deserialize_hashmap_capacity<
+    'de,
+    D: serde::Deserializer<'de>,
+    K,
+    V,
+    H: std::hash::BuildHasher + Default,
+>(
+    d: D,
+) -> Result<StdHashSet<K, H>, D::Error> {
+    struct CapacityVisitor;
+    impl<'de> serde::de::Visitor<'de> for CapacityVisitor {
+        type Value = u64;
+
+        fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+            write!(formatter, "an integer between 0 and 2^64")
+        }
+
+        fn visit_u64<E: serde::de::Error>(self, val: u64) -> Result<Self::Value, E> {
+            Ok(val)
+        }
+    }
+
+    let capacity = d.deserialize_u64(CapacityVisitor)? as usize;
+    Ok(StdHashSet::with_capacity_and_hasher(
+        capacity,
+        Default::default(),
+    ))
+}
+
+/*
+ * FxHasher taken from rustc_hash, except that it does not depend on the pointer size.
+ */
+/// Deterministic hashset using [`indexmap::IndexSet`]
+#[cfg(feature = "enhanced-determinism")]
+pub type FxHashSet32<K> = indexmap::IndexSet<K, std::hash::BuildHasherDefault<FxHasher32>>;
+#[cfg(feature = "enhanced-determinism")]
+pub use self::FxHashSet32 as HashSet;
+#[cfg(not(feature = "enhanced-determinism"))]
+pub use rustc_hash::FxHashSet as HashSet;
+
+const K: u32 = 0x9e3779b9;
+
+/// This is the same as FxHasher, but with the guarantee that the internal hash is
+/// an u32 instead of something that depends on the platform.
+pub struct FxHasher32 {
+    hash: u32,
+}
+
+impl Default for FxHasher32 {
+    #[inline]
+    fn default() -> FxHasher32 {
+        FxHasher32 { hash: 0 }
+    }
+}
+
+impl FxHasher32 {
+    #[inline]
+    fn add_to_hash(&mut self, i: u32) {
+        use std::ops::BitXor;
+        self.hash = self.hash.rotate_left(5).bitxor(i).wrapping_mul(K);
+    }
+}
+
+impl std::hash::Hasher for FxHasher32 {
+    #[inline]
+    fn write(&mut self, mut bytes: &[u8]) {
+        let read_u32 = |bytes: &[u8]| u32::from_ne_bytes(bytes[..4].try_into().unwrap());
+        let mut hash = FxHasher32 { hash: self.hash };
+        assert!(size_of::<u32>() <= 8);
+        while bytes.len() >= size_of::<u32>() {
+            hash.add_to_hash(read_u32(bytes));
+            bytes = &bytes[size_of::<u32>()..];
+        }
+        if (size_of::<u32>() > 4) && (bytes.len() >= 4) {
+            hash.add_to_hash(u32::from_ne_bytes(bytes[..4].try_into().unwrap()));
+            bytes = &bytes[4..];
+        }
+        if (size_of::<u32>() > 2) && bytes.len() >= 2 {
+            hash.add_to_hash(u16::from_ne_bytes(bytes[..2].try_into().unwrap()) as u32);
+            bytes = &bytes[2..];
+        }
+        if (size_of::<u32>() > 1) && !bytes.is_empty() {
+            hash.add_to_hash(bytes[0] as u32);
+        }
+        self.hash = hash.hash;
+    }
+
+    #[inline]
+    fn write_u8(&mut self, i: u8) {
+        self.add_to_hash(i as u32);
+    }
+
+    #[inline]
+    fn write_u16(&mut self, i: u16) {
+        self.add_to_hash(i as u32);
+    }
+
+    #[inline]
+    fn write_u32(&mut self, i: u32) {
+        self.add_to_hash(i);
+    }
+
+    #[inline]
+    fn write_u64(&mut self, i: u64) {
+        self.add_to_hash(i as u32);
+        self.add_to_hash((i >> 32) as u32);
+    }
+
+    #[inline]
+    fn write_usize(&mut self, i: usize) {
+        self.add_to_hash(i as u32);
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.hash as u64
+    }
+}

src/utils/mod.rs

@@ -48,6 +48,8 @@ mod hashable_partial_eq;
 #[cfg(feature = "std")]
 pub mod hashmap;
 #[cfg(feature = "std")]
+pub mod hashset;
+#[cfg(feature = "std")]
 mod interval;
 mod inv;
 mod isometry_ops;