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AK: Merge HashTable bucket state into one enum

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The hash table buckets had three different state booleans that are in
fact exclusive. In preparation for further states, this commit
consolidates them into one enum. This has the added benefit on not
relying on the compiler's boolean packing anymore; we definitely now
only need one byte for the bucket state.
This commit is contained in:
kleines Filmröllchen 2022-03-07 15:10:10 +01:00 • committed by Andreas Kling
parent 7d667b9f69
commit bcb8937898
Notes: sideshowbarker 2024-07-17 16:26:22 +09:00
1 changed files with 31 additions and 32 deletions
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63
AK/HashTable.h
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@ -28,6 +28,15 @@ enum class HashSetExistingEntryBehavior {
Replace
};
// FIXME: Choose specific values so that we can do bit-based checks for various classes of state.
enum class BucketState : u8 {
Free = 0,
Used,
Deleted,
Rehashed,
End,
};
template<typename HashTableType, typename T, typename BucketType>
class HashTableIterator {
friend HashTableType;
@ -46,10 +55,10 @@ private:
return;
do {
++m_bucket;
if (m_bucket->used)
if (m_bucket->state == BucketState::Used)
return;
} while (!m_bucket->end);
if (m_bucket->end)
} while (m_bucket->state != BucketState::End);
if (m_bucket->state == BucketState::End)
m_bucket = nullptr;
}
@ -87,9 +96,7 @@ class HashTable {
static constexpr size_t load_factor_in_percent = 60;
struct Bucket {
bool used;
bool deleted;
bool end;
BucketState state;
alignas(T) u8 storage[sizeof(T)];
T* slot() { return reinterpret_cast<T*>(storage); }
@ -99,8 +106,7 @@ class HashTable {
struct OrderedBucket {
OrderedBucket* previous;
OrderedBucket* next;
bool used;
bool deleted;
BucketState state;
alignas(T) u8 storage[sizeof(T)];
T* slot() { return reinterpret_cast<T*>(storage); }
const T* slot() const { return reinterpret_cast<const T*>(storage); }
@ -128,7 +134,7 @@ public:
return;
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
if (m_buckets[i].state == BucketState::Used)
m_buckets[i].slot()->~T();
}
@ -232,7 +238,7 @@ public:
return Iterator(m_collection_data.head);
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
if (m_buckets[i].state == BucketState::Used)
return Iterator(&m_buckets[i]);
}
return end();
@ -253,7 +259,7 @@ public:
return ConstIterator(m_collection_data.head);
for (size_t i = 0; i < m_capacity; ++i) {
if (m_buckets[i].used)
if (m_buckets[i].state == BucketState::Used)
return ConstIterator(&m_buckets[i]);
}
return end();
@ -281,14 +287,14 @@ public:
if constexpr (IsOrdered)
m_collection_data = { nullptr, nullptr };
else
m_buckets[m_capacity].end = true;
m_buckets[m_capacity].state = BucketState::End;
}
template<typename U = T>
ErrorOr<HashSetResult> try_set(U&& value, HashSetExistingEntryBehavior existing_entry_behavior = HashSetExistingEntryBehavior::Replace)
{
auto* bucket = TRY(try_lookup_for_writing(value));
if (bucket->used) {
if (bucket->state == BucketState::Used) {
if (existing_entry_behavior == HashSetExistingEntryBehavior::Keep)
return HashSetResult::KeptExistingEntry;
(*bucket->slot()) = forward<U>(value);
@ -296,11 +302,9 @@ public:
}
new (bucket->slot()) T(forward<U>(value));
bucket->used = true;
if (bucket->deleted) {
bucket->deleted = false;
if (bucket->state == BucketState::Deleted)
--m_deleted_count;
}
bucket->state = BucketState::Used;
if constexpr (IsOrdered) {
if (!m_collection_data.head) [[unlikely]] {
@ -393,11 +397,7 @@ public:
{
VERIFY(iterator.m_bucket);
auto& bucket = *iterator.m_bucket;
VERIFY(bucket.used);
VERIFY(!bucket.deleted);
if constexpr (!IsOrdered)
VERIFY(!bucket.end);
VERIFY(bucket.state == BucketState::Used);
delete_bucket(bucket);
--m_size;
@ -412,7 +412,7 @@ public:
size_t removed_count = 0;
for (size_t i = 0; i < m_capacity; ++i) {
auto& bucket = m_buckets[i];
if (bucket.used && predicate(*bucket.slot())) {
if (bucket.state == BucketState::Used && predicate(*bucket.slot())) {
delete_bucket(bucket);
++removed_count;
}
@ -430,7 +430,7 @@ private:
{
auto& bucket = lookup_for_writing(value);
new (bucket.slot()) T(move(value));
bucket.used = true;
bucket.state = BucketState::Used;
if constexpr (IsOrdered) {
if (!m_collection_data.head) [[unlikely]] {
@ -473,7 +473,7 @@ private:
if constexpr (IsOrdered)
m_collection_data = { nullptr, nullptr };
else
m_buckets[m_capacity].end = true;
m_buckets[m_capacity].state = BucketState::End;
if (!old_buckets)
return {};
@ -500,10 +500,10 @@ private:
for (;;) {
auto& bucket = m_buckets[hash % m_capacity];
if (bucket.used && predicate(*bucket.slot()))
if (bucket.state == BucketState::Used && predicate(*bucket.slot()))
return &bucket;
if (!bucket.used && !bucket.deleted)
if (bucket.state != BucketState::Used && bucket.state != BucketState::Deleted)
return nullptr;
hash = double_hash(hash);
@ -522,14 +522,14 @@ private:
for (;;) {
auto& bucket = m_buckets[hash % m_capacity];
if (bucket.used && TraitsForT::equals(*bucket.slot(), value))
if (bucket.state == BucketState::Used && TraitsForT::equals(*bucket.slot(), value))
return &bucket;
if (!bucket.used) {
if (bucket.state != BucketState::Used) {
if (!first_empty_bucket)
first_empty_bucket = &bucket;
if (!bucket.deleted)
if (bucket.state != BucketState::Deleted)
return const_cast<BucketType*>(first_empty_bucket);
}
@ -560,8 +560,7 @@ private:
void delete_bucket(auto& bucket)
{
bucket.slot()->~T();
bucket.used = false;
bucket.deleted = true;
bucket.state = BucketState::Deleted;
if constexpr (IsOrdered) {
if (bucket.previous)