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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef __BLI_MAP_H__
#define __BLI_MAP_H__
/** \file
* \ingroup bli
*
* This file provides a map implementation that uses open addressing with probing.
*
* The key and value objects are stored directly in the hash table to avoid indirect memory
* lookups. Keys and values are stored in groups of four to avoid wasting memory due to padding.
*/
#include "BLI_hash_cxx.h"
#include "BLI_array_ref.h"
#include "BLI_open_addressing.h"
namespace BLI {
// clang-format off
#define ITER_SLOTS_BEGIN(KEY, ARRAY, OPTIONAL_CONST, R_ITEM, R_OFFSET) \
uint32_t hash = DefaultHash<KeyT>{}(KEY); \
uint32_t perturb = hash; \
while (true) { \
uint32_t item_index = (hash & ARRAY.slot_mask()) >> OFFSET_SHIFT; \
uint8_t R_OFFSET = hash & OFFSET_MASK; \
uint8_t initial_offset = R_OFFSET; \
OPTIONAL_CONST Item &R_ITEM = ARRAY.item(item_index); \
do {
#define ITER_SLOTS_END(R_OFFSET) \
R_OFFSET = (R_OFFSET + 1u) & OFFSET_MASK; \
} while (R_OFFSET != initial_offset); \
perturb >>= 5; \
hash = hash * 5 + 1 + perturb; \
} ((void)0)
// clang-format on
template<typename KeyT, typename ValueT, typename Allocator = GuardedAllocator> class Map {
private:
static constexpr uint OFFSET_MASK = 3;
static constexpr uint OFFSET_SHIFT = 2;
class Item {
private:
static constexpr uint8_t IS_EMPTY = 0;
static constexpr uint8_t IS_SET = 1;
static constexpr uint8_t IS_DUMMY = 2;
uint8_t m_status[4];
char m_keys[4 * sizeof(KeyT)];
char m_values[4 * sizeof(ValueT)];
public:
static constexpr uint slots_per_item = 4;
Item()
{
for (uint offset = 0; offset < 4; offset++) {
m_status[offset] = IS_EMPTY;
}
}
~Item()
{
for (uint offset = 0; offset < 4; offset++) {
if (m_status[offset] == IS_SET) {
this->key(offset)->~KeyT();
this->value(offset)->~ValueT();
}
}
}
Item(const Item &other)
{
for (uint offset = 0; offset < 4; offset++) {
uint8_t status = other.m_status[offset];
m_status[offset] = status;
if (status == IS_SET) {
new (this->key(offset)) KeyT(*other.key(offset));
new (this->value(offset)) ValueT(*other.value(offset));
}
}
}
Item(Item &&other) noexcept
{
for (uint offset = 0; offset < 4; offset++) {
uint8_t status = other.m_status[offset];
m_status[offset] = status;
if (status == IS_SET) {
new (this->key(offset)) KeyT(std::move(*other.key(offset)));
new (this->value(offset)) ValueT(std::move(*other.value(offset)));
}
}
}
bool has_key(uint offset, const KeyT &key) const
{
return m_status[offset] == IS_SET && key == *this->key(offset);
}
bool is_set(uint offset) const
{
return m_status[offset] == IS_SET;
}
bool is_empty(uint offset) const
{
return m_status[offset] == IS_EMPTY;
}
bool is_dummy(uint offset) const
{
return m_status[offset] == IS_DUMMY;
}
KeyT *key(uint offset) const
{
return (KeyT *)(m_keys + offset * sizeof(KeyT));
}
ValueT *value(uint offset) const
{
return (ValueT *)(m_values + offset * sizeof(ValueT));
}
void copy_in(uint offset, const KeyT &key, const ValueT &value)
{
BLI_assert(m_status[offset] != IS_SET);
m_status[offset] = IS_SET;
new (this->key(offset)) KeyT(key);
new (this->value(offset)) ValueT(value);
}
void move_in(uint offset, KeyT &key, ValueT &value)
{
BLI_assert(m_status[offset] != IS_SET);
m_status[offset] = IS_SET;
new (this->key(offset)) KeyT(std::move(key));
new (this->value(offset)) ValueT(std::move(value));
}
void set_dummy(uint offset)
{
BLI_assert(m_status[offset] == IS_SET);
m_status[offset] = IS_DUMMY;
destruct(this->key(offset));
destruct(this->value(offset));
}
};
using ArrayType = OpenAddressingArray<Item, 1, Allocator>;
ArrayType m_array;
public:
Map() = default;
/**
* Allocate memory such that at least min_usable_slots can be added before the map has to grow
* again.
*/
void reserve(uint min_usable_slots)
{
if (m_array.slots_usable() < min_usable_slots) {
this->grow(min_usable_slots);
}
}
/**
* Remove all elements from the map.
*/
void clear()
{
this->~Map();
new (this) Map();
}
/**
* Insert a new key-value-pair in the map.
* Asserts when the key existed before.
*/
void add_new(const KeyT &key, const ValueT &value)
{
BLI_assert(!this->contains(key));
this->ensure_can_add();
ITER_SLOTS_BEGIN (key, m_array, , item, offset) {
if (item.is_empty(offset)) {
item.copy_in(offset, key, value);
m_array.update__empty_to_set();
return;
}
}
ITER_SLOTS_END(offset);
}
/**
* Insert a new key-value-pair in the map if the key does not exist yet.
* Returns true when the pair was newly inserted, otherwise false.
*/
bool add(const KeyT &key, const ValueT &value)
{
this->ensure_can_add();
ITER_SLOTS_BEGIN (key, m_array, , item, offset) {
if (item.is_empty(offset)) {
item.copy_in(offset, key, value);
m_array.update__empty_to_set();
return true;
}
else if (item.has_key(offset, key)) {
return false;
}
}
ITER_SLOTS_END(offset);
}
/**
* Remove the key from the map.
* Asserts when the key does not exist in the map.
*/
void remove(const KeyT &key)
{
BLI_assert(this->contains(key));
ITER_SLOTS_BEGIN (key, m_array, , item, offset) {
if (item.has_key(offset, key)) {
item.set_dummy(offset);
m_array.update__set_to_dummy();
return;
}
}
ITER_SLOTS_END(offset);
}
/**
* Get the value for the given key and remove it from the map.
* Asserts when the key does not exist in the map.
*/
ValueT pop(const KeyT &key)
{
BLI_assert(this->contains(key));
ITER_SLOTS_BEGIN (key, m_array, , item, offset) {
if (item.has_key(offset, key)) {
ValueT value = std::move(*item.value(offset));
item.set_dummy(offset);
m_array.update__set_to_dummy();
return value;
}
}
ITER_SLOTS_END(offset);
}
/**
* Returns true when the key exists in the map, otherwise false.
*/
bool contains(const KeyT &key) const
{
ITER_SLOTS_BEGIN (key, m_array, const, item, offset) {
if (item.is_empty(offset)) {
return false;
}
else if (item.has_key(offset, key)) {
return true;
}
}
ITER_SLOTS_END(offset);
}
/**
* Check if the key exists in the map.
* If it does exist, call the modify function with a reference to the corresponding value.
* If it does not exist, call the create function and insert a new key-value-pair.
* Returns true when a new pair was inserted, otherwise false.
*/
template<typename CreateValueF, typename ModifyValueF>
bool add_or_modify(const KeyT &key,
const CreateValueF &create_value,
const ModifyValueF &modify_value)
{
this->ensure_can_add();
ITER_SLOTS_BEGIN (key, m_array, , item, offset) {
if (item.is_empty(offset)) {
item.copy_in(offset, key, create_value());
m_array.update__empty_to_set();
return true;
}
else if (item.has_key(offset, key)) {
modify_value(*item.value(offset));
return false;
}
}
ITER_SLOTS_END(offset);
}
/**
* Similar to add, but overrides the value for the key when it exists already.
*/
bool add_override(const KeyT &key, const ValueT &value)
{
return this->add_or_modify(
key, [&value]() { return value; }, [&value](ValueT &old_value) { old_value = value; });
}
/**
* Check if the key exists in the map.
* Return a pointer to the value, when it exists.
* Otherwise return nullptr.
*/
const ValueT *lookup_ptr(const KeyT &key) const
{
ITER_SLOTS_BEGIN (key, m_array, const, item, offset) {
if (item.is_empty(offset)) {
return nullptr;
}
else if (item.has_key(offset, key)) {
return item.value(offset);
}
}
ITER_SLOTS_END(offset);
}
/**
* Lookup the value that corresponds to the key.
* Asserts when the key does not exist.
*/
const ValueT &lookup(const KeyT &key) const
{
const ValueT *ptr = this->lookup_ptr(key);
BLI_assert(ptr != nullptr);
return *ptr;
}
ValueT *lookup_ptr(const KeyT &key)
{
const Map *const_this = this;
return const_cast<ValueT *>(const_this->lookup_ptr(key));
}
ValueT &lookup(const KeyT &key)
{
const Map *const_this = this;
return const_cast<ValueT &>(const_this->lookup(key));
}
/**
* Check if the key exists in the map.
* If it does, return a copy of the value.
* Otherwise, return the default value.
*/
ValueT lookup_default(const KeyT &key, ValueT default_value) const
{
const ValueT *ptr = this->lookup_ptr(key);
if (ptr != nullptr) {
return *ptr;
}
else {
return default_value;
}
}
/**
* Return the value that corresponds to the given key.
* If it does not exist yet, create and insert it first.
*/
template<typename CreateValueF>
ValueT &lookup_or_add(const KeyT &key, const CreateValueF &create_value)
{
this->ensure_can_add();
ITER_SLOTS_BEGIN (key, m_array, , item, offset) {
if (item.is_empty(offset)) {
item.copy_in(offset, key, create_value());
m_array.update__empty_to_set();
return *item.value(offset);
}
else if (item.has_key(offset, key)) {
return *item.value(offset);
}
}
ITER_SLOTS_END(offset);
}
/**
* Get the number of elements in the map.
*/
uint32_t size() const
{
return m_array.slots_set();
}
void print_table() const
{
std::cout << "Hash Table:\n";
std::cout << " Size: " << m_array.slots_set() << '\n';
std::cout << " Capacity: " << m_array.slots_total() << '\n';
uint32_t item_index = 0;
for (const Item &item : m_array) {
std::cout << " Item: " << item_index++ << '\n';
for (uint offset = 0; offset < 4; offset++) {
std::cout << " " << offset << " \t";
if (item.is_empty(offset)) {
std::cout << " <empty>\n";
}
else if (item.is_set(offset)) {
const KeyT &key = *item.key(offset);
const ValueT &value = *item.value(offset);
uint32_t collisions = this->count_collisions(key);
std::cout << " " << key << " -> " << value << " \t Collisions: " << collisions
<< '\n';
}
else if (item.is_dummy(offset)) {
std::cout << " <dummy>\n";
}
}
}
}
template<typename SubIterator> class BaseIterator {
protected:
const Map *m_map;
uint32_t m_slot;
public:
BaseIterator(const Map *map, uint32_t slot) : m_map(map), m_slot(slot)
{
}
BaseIterator &operator++()
{
m_slot = m_map->next_slot(m_slot + 1);
return *this;
}
friend bool operator==(const BaseIterator &a, const BaseIterator &b)
{
BLI_assert(a.m_map == b.m_map);
return a.m_slot == b.m_slot;
}
friend bool operator!=(const BaseIterator &a, const BaseIterator &b)
{
return !(a == b);
}
SubIterator begin() const
{
return SubIterator(m_map, m_map->next_slot(0));
}
SubIterator end() const
{
return SubIterator(m_map, m_map->m_array.slots_total());
}
};
class KeyIterator final : public BaseIterator<KeyIterator> {
public:
KeyIterator(const Map *map, uint32_t slot) : BaseIterator<KeyIterator>(map, slot)
{
}
const KeyT &operator*() const
{
uint32_t item_index = this->m_slot >> OFFSET_SHIFT;
uint offset = this->m_slot & OFFSET_MASK;
const Item &item = this->m_map->m_array.item(item_index);
BLI_assert(item.is_set(offset));
return *item.key(offset);
}
};
class ValueIterator final : public BaseIterator<ValueIterator> {
public:
ValueIterator(const Map *map, uint32_t slot) : BaseIterator<ValueIterator>(map, slot)
{
}
ValueT &operator*() const
{
uint32_t item_index = this->m_slot >> OFFSET_SHIFT;
uint offset = this->m_slot & OFFSET_MASK;
const Item &item = this->m_map->m_array.item(item_index);
BLI_assert(item.is_set(offset));
return *item.value(offset);
}
};
class ItemIterator final : public BaseIterator<ItemIterator> {
public:
ItemIterator(const Map *map, uint32_t slot) : BaseIterator<ItemIterator>(map, slot)
{
}
struct UserItem {
const KeyT &key;
ValueT &value;
friend std::ostream &operator<<(std::ostream &stream, const Item &item)
{
stream << item.key << " -> " << item.value;
return stream;
}
};
UserItem operator*() const
{
uint32_t item_index = this->m_slot >> OFFSET_SHIFT;
uint offset = this->m_slot & OFFSET_MASK;
const Item &item = this->m_map->m_array.item(item_index);
BLI_assert(item.is_set(offset));
return {*item.key(offset), *item.value(offset)};
}
};
template<typename SubIterator> friend class BaseIterator;
/**
* Iterate over all keys in the map.
*/
KeyIterator keys() const
{
return KeyIterator(this, 0);
}
/**
* Iterate over all values in the map.
*/
ValueIterator values() const
{
return ValueIterator(this, 0);
}
/**
* Iterate over all key-value-pairs in the map.
* They can be accessed with item.key and item.value.
*/
ItemIterator items() const
{
return ItemIterator(this, 0);
}
private:
uint32_t next_slot(uint32_t slot) const
{
for (; slot < m_array.slots_total(); slot++) {
uint32_t item_index = slot >> OFFSET_SHIFT;
uint offset = slot & OFFSET_MASK;
const Item &item = m_array.item(item_index);
if (item.is_set(offset)) {
return slot;
}
}
return slot;
}
uint32_t count_collisions(const KeyT &key) const
{
uint32_t collisions = 0;
ITER_SLOTS_BEGIN (key, m_array, const, item, offset) {
if (item.is_empty(offset) || item.has_key(offset, key)) {
return collisions;
}
collisions++;
}
ITER_SLOTS_END(offset);
}
void ensure_can_add()
{
if (UNLIKELY(m_array.should_grow())) {
this->grow(this->size() + 1);
}
}
BLI_NOINLINE void grow(uint32_t min_usable_slots)
{
ArrayType new_array = m_array.init_reserved(min_usable_slots);
for (Item &old_item : m_array) {
for (uint offset = 0; offset < 4; offset++) {
if (old_item.is_set(offset)) {
this->add_after_grow(*old_item.key(offset), *old_item.value(offset), new_array);
}
}
}
m_array = std::move(new_array);
}
void add_after_grow(KeyT &key, ValueT &value, ArrayType &new_array)
{
ITER_SLOTS_BEGIN (key, new_array, , item, offset) {
if (item.is_empty(offset)) {
item.move_in(offset, key, value);
return;
}
}
ITER_SLOTS_END(offset);
}
};
#undef ITER_SLOTS_BEGIN
#undef ITER_SLOTS_END
} // namespace BLI
#endif /* __BLI_MAP_H__ */
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