Add custom hasher & comparator for hash_set keys

asl/hash_set.hpp

@@ -11,8 +11,43 @@
 namespace asl
 {
 
-template<is_object T, allocator Allocator = DefaultAllocator>
-requires hashable<T> && move_constructible<T> && move_assignable<T> && equality_comparable<T>
+template<typename H, typename T>
+concept key_hasher = requires (const T& value)
+{
+    { H::hash(value) } -> same_as<uint64_t>;
+};
+
+template<hashable T>
+struct default_key_hasher
+{
+    constexpr static uint64_t hash(const T& value)
+    {
+        return hash_value(value);
+    }
+};
+
+template<typename C, typename U, typename V = U>
+concept key_comparator = requires(const U& a, const V& b)
+{
+    { C::eq(a, b) } -> same_as<bool>;
+};
+
+template<equality_comparable T>
+struct default_key_comparator
+{
+    constexpr static bool eq(const T& a, const T& b)
+    {
+        return a == b;
+    }
+};
+
+template<
+    is_object T,
+    allocator Allocator = DefaultAllocator,
+    key_hasher<T> KeyHasher = default_key_hasher<T>,
+    key_comparator<T> KeyComparator = default_key_comparator<T>
+>
+requires move_constructible<T> && move_assignable<T>
 class hash_set
 {
     static constexpr uint8_t kHasValue  = 0x80;
@@ -49,7 +84,7 @@ class hash_set
         ASL_ASSERT(is_pow2(capacity));
 
         const isize_t capacity_mask = capacity - 1;
-        const uint64_t hash = hash_value(value);
+        const uint64_t hash = KeyHasher::hash(value);
         const uint8_t tag = static_cast<uint8_t>(hash & kHashMask) | kHasValue;
         const auto starting_index = static_cast<isize_t>(hash >> 7) & capacity_mask;
 
@@ -70,7 +105,7 @@ class hash_set
                 first_available_index = i;
             }
 
-            if (t == tag && values[i].as_init_unsafe() == value)
+            if (t == tag && KeyComparator::eq(values[i].as_init_unsafe(), value))
             {
                 ASL_ASSERT(already_present_index < 0);
                 already_present_index = i;
@@ -112,14 +147,16 @@ class hash_set
         // NOLINTEND(*-pointer-arithmetic)
     }
 
-    isize_t find_slot(const T& value) const
+    template<typename U>
+    requires key_hasher<KeyHasher, U> && key_comparator<KeyComparator, T, U>
+    isize_t find_slot(const U& value) const
     {
         if (m_size <= 0) { return -1; };
 
         ASL_ASSERT(is_pow2(m_capacity));
 
         const isize_t capacity_mask = m_capacity - 1;
-        const uint64_t hash = hash_value(value);
+        const uint64_t hash = KeyHasher::hash(value);
         const uint8_t tag = static_cast<uint8_t>(hash & kHashMask) | kHasValue;
         const auto starting_index = static_cast<isize_t>(hash >> 7) & capacity_mask;
 
@@ -130,7 +167,7 @@ class hash_set
         {
             const uint8_t t = m_tags[i];
             
-            if (t == tag && m_values[i].as_init_unsafe() == value) { return i; }
+            if (t == tag && KeyComparator::eq(m_values[i].as_init_unsafe(), value)) { return i; }
             if (t == kEmpty) { break; }
             
             i = (i + 1) & capacity_mask;
@@ -246,14 +283,16 @@ public:
         insert_inner(ASL_MOVE(T{ASL_FWD(args)...}), m_tags, m_values, m_capacity, &m_size);
     }
 
-    bool contains(const T& value) const
+    template<typename U>
+    requires key_hasher<KeyHasher, U> && key_comparator<KeyComparator, T, U>
+    bool contains(const U& value) const
     {
         return find_slot(value) >= 0;
     }
 
-    // @Todo Remove with something comparable, but not equal? How to hash?
-    // @Todo Same with contains
-    bool remove(const T& value)
+    template<typename U>
+    requires key_hasher<KeyHasher, U> && key_comparator<KeyComparator, T, U>
+    bool remove(const U& value)
     {
         isize_t slot = find_slot(value);
         if (slot < 0) { return false; }

asl/tests/hash_set_tests.cpp

@@ -32,7 +32,6 @@ ASL_TEST(a_bunch_of_strings)
     ASL_TEST_EXPECT(set.contains("Hello, world!"_sv));
     ASL_TEST_EXPECT(set.contains("Hello, puppy!"_sv));
     ASL_TEST_EXPECT(!set.contains("Hello, Steven!"_sv));
-    
 }
 
 ASL_TEST(a_bunch_of_ints)
@@ -67,11 +66,31 @@ struct HashWithDestructor: public DestructorObserver
     {
         return x == other.x;
     }
+};
 
-    template<typename H>
-    friend H AslHashValue(H h, const HashWithDestructor& value)
+struct CustomComparator
+{
+    static bool eq(const HashWithDestructor& a, const HashWithDestructor& b)
     {
-        return H::combine(ASL_MOVE(h), value.x);
+        return a.x == b.x;
+    }
+    
+    static bool eq(const HashWithDestructor& a, int b)
+    {
+        return a.x == b;
+    }
+};
+
+struct CustomHasher
+{
+    static uint64_t hash(const HashWithDestructor& b)
+    {
+        return asl::hash_value(b.x);
+    }
+    
+    static uint64_t hash(int x)
+    {
+        return asl::hash_value(x);
     }
 };
 
@@ -81,7 +100,7 @@ ASL_TEST(destructor_and_remove)
     bool destroyed[kCount]{};
 
     {
-        asl::hash_set<HashWithDestructor> set;
+        asl::hash_set<HashWithDestructor, asl::DefaultAllocator, CustomHasher, CustomComparator> set;
 
         for (int i = 0; i < kCount; ++i)
         {
@@ -97,14 +116,13 @@ ASL_TEST(destructor_and_remove)
 
         for (int i = 0; i < kCount; i += 2)
         {
-            // @Todo Remove with something comparable
-            ASL_TEST_EXPECT(set.remove(HashWithDestructor{i, nullptr}));
+            ASL_TEST_EXPECT(set.remove(i));
         }
 
         for (int i = 0; i < kCount; i += 2)
         {
-            ASL_TEST_EXPECT(!set.contains(HashWithDestructor{i, nullptr}));
-            ASL_TEST_EXPECT(set.contains(HashWithDestructor{i+1, nullptr}));
+            ASL_TEST_EXPECT(!set.contains(i));
+            ASL_TEST_EXPECT(set.contains(i+1));
             ASL_TEST_EXPECT(destroyed[i]); // NOLINT
             ASL_TEST_EXPECT(!destroyed[i + 1]); // NOLINT
         }