From 21a2e7fd51acfa397a711f1ff5522677c8af7e4b Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Sat, 2 May 2026 13:12:22 +0300
Subject: [PATCH] BAN: Fix HashSet

---
 BAN/include/BAN/HashSet.h | 111 ++++++++++++++++++++++----------------
 1 file changed, 65 insertions(+), 46 deletions(-)

diff --git a/BAN/include/BAN/HashSet.h b/BAN/include/BAN/HashSet.h
index af5392da..c6058511 100644
--- a/BAN/include/BAN/HashSet.h
+++ b/BAN/include/BAN/HashSet.h
@@ -60,7 +60,7 @@ namespace BAN
 
 		void skip_to_valid_bucket()
 		{
-			while (!m_bucket->used && !m_bucket->end)
+			while (m_bucket->state != Bucket::USED && !m_bucket->end)
 				m_bucket++;
 			if (m_bucket->end)
 				m_bucket = nullptr;
@@ -83,10 +83,13 @@ namespace BAN
 	private:
 		struct Bucket
 		{
+			static constexpr uint8_t UNUSED  = 0;
+			static constexpr uint8_t USED    = 1;
+			static constexpr uint8_t REMOVED = 2;
+
 			alignas(T) uint8_t storage[sizeof(T)];
 			hash_t hash;
-			uint8_t used        : 1;
-			uint8_t removed     : 1;
+			uint8_t state       : 2;
 			uint8_t chain_start : 1;
 			uint8_t end         : 1;
 
@@ -148,38 +151,7 @@ namespace BAN
 		{
 			if (should_rehash_with_size(m_size + 1))
 				TRY(rehash(m_size * 2));
-
-			bool first = true;
-			const hash_t orig_hash = HASH()(value);
-			for (auto hash = orig_hash;; hash = get_next_hash_in_chain(hash, orig_hash), first = false)
-			{
-				auto& bucket = m_buckets[hash & (m_capacity - 1)];
-
-				if (!first)
-					bucket.chain_start = false;
-
-				if (bucket.used)
-				{
-					if (!COMP()(*bucket.element(), value))
-						continue;
-					bucket.element()->~T();
-					new (bucket.element()) T(BAN::move(value));
-				}
-				else
-				{
-					m_removed -= bucket.removed;
-					bucket.used    = true;
-					bucket.removed = false;
-					new (bucket.element()) T(BAN::move(value));
-					m_size++;
-				}
-
-				if (first)
-					bucket.chain_start = true;
-				bucket.hash = orig_hash;
-
-				return iterator(&bucket);
-			}
+			return insert_impl(BAN::move(value), HASH()(value));
 		}
 
 		template<detail::HashSetFindable<T, HASH, COMP> U>
@@ -193,8 +165,7 @@ namespace BAN
 		{
 			auto& bucket = *it.m_bucket;
 			bucket.element()->~T();
-			bucket.used    = false;
-			bucket.removed = true;
+			bucket.state = Bucket::REMOVED;
 			m_size--;
 			m_removed++;
 			return iterator(&bucket);
@@ -218,11 +189,8 @@ namespace BAN
 				return;
 
 			for (size_type i = 0; i < m_capacity; i++)
-			{
-				auto& bucket = m_buckets[i];
-				if (bucket.used)
-					bucket.element()->~T();
-			}
+				if (m_buckets[i].state == Bucket::USED)
+					m_buckets[i].element()->~T();
 
 			BAN::deallocator(m_buckets);
 			m_buckets  = nullptr;
@@ -281,9 +249,9 @@ namespace BAN
 			for (size_type i = 0; i < old_capacity; i++)
 			{
 				auto& old_bucket = old_buckets[i];
-				if (!old_bucket.used)
+				if (old_bucket.state != Bucket::USED)
 					continue;
-				MUST(insert(BAN::move(*old_bucket.element())));
+				insert_impl(BAN::move(*old_bucket.element()), old_bucket.hash);
 				old_bucket.element()->~T();
 			}
 
@@ -305,15 +273,66 @@ namespace BAN
 			for (auto hash = orig_hash;; hash = get_next_hash_in_chain(hash, orig_hash), first = false)
 			{
 				auto& bucket = m_buckets[hash & (m_capacity - 1)];
-				if (bucket.used && bucket.hash == orig_hash && COMP()(*bucket.element(), value))
+				if (bucket.state == Bucket::USED && bucket.hash == orig_hash && COMP()(*bucket.element(), value))
 					return const_iterator(&bucket);
-				if (!bucket.used && !bucket.removed)
+				if (bucket.state == Bucket::UNUSED)
 					return end();
 				if (!first && bucket.chain_start)
 					return end();
 			}
 		}
 
+		iterator insert_impl(T&& value, hash_t orig_hash)
+		{
+			ASSERT(!should_rehash_with_size(m_size + 1));
+
+			Bucket* target = nullptr;
+
+			bool first = true;
+			for (auto hash = orig_hash;; hash = get_next_hash_in_chain(hash, orig_hash), first = false)
+			{
+				auto& bucket = m_buckets[hash & (m_capacity - 1)];
+
+				if (!first)
+					bucket.chain_start = false;
+
+				if (bucket.state == Bucket::USED)
+				{
+					if (bucket.hash != orig_hash || !COMP()(*bucket.element(), value))
+						continue;
+					target = &bucket;
+					break;
+				}
+
+				if (target == nullptr)
+					target = &bucket;
+
+				if (bucket.state == Bucket::UNUSED)
+					break;
+			}
+
+			switch (target->state)
+			{
+				case Bucket::USED:
+					target->element()->~T();
+					break;
+				case Bucket::REMOVED:
+					m_removed--;
+					[[fallthrough]];
+				case Bucket::UNUSED:
+					m_size++;
+					break;
+			}
+
+			target->chain_start = first && target->state == Bucket::UNUSED;
+			target->hash = orig_hash;
+			target->state = Bucket::USED;
+
+			new (target->element()) T(BAN::move(value));
+
+			return iterator(target);
+		}
+
 		bool should_rehash_with_size(size_type size) const
 		{
 			if (m_capacity < 16)