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Fix sherwood_v8_block memory alignment #54

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Fix sherwood_v8_block memory alignment #54

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58 changes: 25 additions & 33 deletions bytell_hash_map.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -107,13 +107,14 @@ struct sherwood_v8_block

static sherwood_v8_block * empty_block()
{
static std::array<int8_t, BlockSize> empty_bytes = []
{
std::array<int8_t, BlockSize> result;
result.fill(sherwood_v8_constants<>::magic_for_empty);
return result;
alignas(sherwood_v8_block) static std::array<std::byte, sizeof(sherwood_v8_block)> storage{};
static const bool initialized = [] {
auto *block = reinterpret_cast<sherwood_v8_block *>(storage.data());
block->fill_control_bytes(sherwood_v8_constants<>::magic_for_empty);
return true;
}();
return reinterpret_cast<sherwood_v8_block *>(&empty_bytes);
(void)initialized;
return reinterpret_cast<sherwood_v8_block *>(storage.data());
}

int first_empty_index() const
Expand Down Expand Up @@ -523,7 +524,7 @@ class sherwood_v8_table : private ByteAlloc, private Hasher, private Equal

void rehash(size_t num_items)
{
num_items = std::max(num_items, static_cast<size_t>(std::ceil(num_elements / static_cast<double>(_max_load_factor))));
num_items = std::max(num_items, static_cast<size_t>(std::ceil(static_cast<double>(num_elements) / static_cast<double>(_max_load_factor))));
if (num_items == 0)
{
reset_to_empty_state();
Expand All @@ -535,14 +536,12 @@ class sherwood_v8_table : private ByteAlloc, private Hasher, private Equal
size_t num_blocks = num_items / BlockSize;
if (num_items % BlockSize)
++num_blocks;
size_t memory_requirement = calculate_memory_requirement(num_blocks);
unsigned char * new_memory = &*AllocatorTraits::allocate(*this, memory_requirement);

BlockPointer new_buckets = reinterpret_cast<BlockPointer>(new_memory);
const size_t total_blocks = num_blocks + 1; // include sentinel block
BlockPointer new_buckets = AllocatorTraits::allocate(*this, total_blocks);

BlockPointer special_end_item = new_buckets + num_blocks;
for (BlockPointer it = new_buckets; it <= special_end_item; ++it)
for (BlockPointer it = new_buckets, end = new_buckets + total_blocks; it != end; ++it) {
it->fill_control_bytes(Constants::magic_for_empty);
}
using std::swap;
swap(entries, new_buckets);
swap(num_slots_minus_one, num_items);
Expand Down Expand Up @@ -749,7 +748,7 @@ class sherwood_v8_table : private ByteAlloc, private Hasher, private Equal

size_t num_buckets_for_reserve(size_t num_elements) const
{
return static_cast<size_t>(std::ceil(num_elements / static_cast<double>(_max_load_factor)));
return static_cast<size_t>(std::ceil(static_cast<double>(num_elements) / static_cast<double>(_max_load_factor)));
}
void rehash_for_other_container(const sherwood_v8_table & other)
{
Expand All @@ -760,7 +759,7 @@ class sherwood_v8_table : private ByteAlloc, private Hasher, private Equal
if (!num_slots_minus_one)
return true;
else
return num_elements + 1 > (num_slots_minus_one + 1) * static_cast<double>(_max_load_factor);
return static_cast<double>(num_elements + 1U) > static_cast<double>(num_slots_minus_one + 1U) * static_cast<double>(_max_load_factor);
}

void swap_pointers(sherwood_v8_table & other)
Expand Down Expand Up @@ -808,7 +807,7 @@ class sherwood_v8_table : private ByteAlloc, private Hasher, private Equal
}
int8_t jump_index() const
{
return Constants::distance_from_metadata(metadata());
return static_cast<int8_t>(Constants::distance_from_metadata(metadata()));
}
int8_t metadata() const
{
Expand Down Expand Up @@ -969,25 +968,18 @@ class sherwood_v8_table : private ByteAlloc, private Hasher, private Equal
rehash(std::max(size_t(10), 2 * bucket_count()));
}

size_t calculate_memory_requirement(size_t num_blocks)
{
size_t memory_required = sizeof(BlockType) * num_blocks;
memory_required += BlockSize; // for metadata of past-the-end pointer
return memory_required;
}

void deallocate_data(BlockPointer begin, size_t num_slots_minus_one)
{
if (begin == BlockType::empty_block())
return;

++num_slots_minus_one;
size_t num_blocks = num_slots_minus_one / BlockSize;
if (num_slots_minus_one % BlockSize)
const size_t num_slots = num_slots_minus_one + 1;
size_t num_blocks = num_slots / BlockSize;
if (num_slots % BlockSize)
++num_blocks;
size_t memory = calculate_memory_requirement(num_blocks);
unsigned char * as_byte_pointer = reinterpret_cast<unsigned char *>(begin);
AllocatorTraits::deallocate(*this, typename AllocatorTraits::pointer(as_byte_pointer), memory);
// Account for sentinel block used for the metadata past-the-end pointer.
++num_blocks;
AllocatorTraits::deallocate(*this, begin, num_blocks);
}

void reset_to_empty_state()
Expand Down Expand Up @@ -1072,7 +1064,7 @@ class bytell_hash_map
E,
detailv8::KeyOrValueEquality<K, std::pair<K, V>, E>,
A,
typename std::allocator_traits<A>::template rebind_alloc<unsigned char>,
typename std::allocator_traits<A>::template rebind_alloc<detailv8::sherwood_v8_block<std::pair<K, V>, detailv8::CalculateBytellBlockSize<K, V>::value>>,
detailv8::CalculateBytellBlockSize<K, V>::value
>
{
Expand All @@ -1085,7 +1077,7 @@ class bytell_hash_map
E,
detailv8::KeyOrValueEquality<K, std::pair<K, V>, E>,
A,
typename std::allocator_traits<A>::template rebind_alloc<unsigned char>,
typename std::allocator_traits<A>::template rebind_alloc<detailv8::sherwood_v8_block<std::pair<K, V>, detailv8::CalculateBytellBlockSize<K, V>::value>>,
detailv8::CalculateBytellBlockSize<K, V>::value
>;
public:
Expand Down Expand Up @@ -1193,7 +1185,7 @@ class bytell_hash_set
E,
detailv8::functor_storage<bool, E>,
A,
typename std::allocator_traits<A>::template rebind_alloc<unsigned char>,
typename std::allocator_traits<A>::template rebind_alloc<detailv8::sherwood_v8_block<T, detailv8::CalculateBytellBlockSize<T>::value>>,
detailv8::CalculateBytellBlockSize<T>::value
>
{
Expand All @@ -1206,7 +1198,7 @@ class bytell_hash_set
E,
detailv8::functor_storage<bool, E>,
A,
typename std::allocator_traits<A>::template rebind_alloc<unsigned char>,
typename std::allocator_traits<A>::template rebind_alloc<detailv8::sherwood_v8_block<T, detailv8::CalculateBytellBlockSize<T>::value>>,
detailv8::CalculateBytellBlockSize<T>::value
>;
public:
Expand Down