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https://github.com/ClickHouse/ClickHouse.git
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387 lines
8.8 KiB
C++
387 lines
8.8 KiB
C++
#pragma once
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#include <DB/Interpreters/HashMap.h>
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namespace DB
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{
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/** См. HashMap.h
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*/
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template
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<
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typename Key,
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typename Hash = default_hash<Key>,
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typename ZeroTraits = default_zero_traits<Key>,
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typename GrowthTraits = default_growth_traits
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>
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class HashSet : private boost::noncopyable
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{
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private:
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friend class const_iterator;
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friend class iterator;
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typedef size_t HashValue;
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typedef HashSet<Key, Hash, ZeroTraits, GrowthTraits> Self;
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size_t m_size; /// Количество элементов
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UInt8 size_degree; /// Размер таблицы в виде степени двух
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bool has_zero; /// Хэш-таблица содержит элемент со значением ключа = 0.
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Key * buf; /// Кусок памяти для всех элементов кроме элемента с ключём 0.
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Hash hash;
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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mutable size_t collisions;
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#endif
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inline size_t buf_size() const { return 1 << size_degree; }
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inline size_t buf_size_bytes() const { return buf_size() * sizeof(Key); }
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inline size_t max_fill() const { return 1 << (size_degree - 1); }
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inline size_t mask() const { return buf_size() - 1; }
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inline size_t place(HashValue x) const { return x & mask(); }
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/// Увеличить размер буфера в 2 ^ N раз
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void resize()
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{
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#ifdef DBMS_HASH_MAP_DEBUG_RESIZES
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Stopwatch watch;
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#endif
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size_t old_size = buf_size();
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size_t old_size_bytes = buf_size_bytes();
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size_degree += size_degree >= GrowthTraits::GROWTH_CHANGE_THRESHOLD
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? 1
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: GrowthTraits::FAST_GROWTH_DEGREE;
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/// Расширим пространство.
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buf = reinterpret_cast<Key *>(realloc(reinterpret_cast<void *>(buf), buf_size_bytes()));
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if (NULL == buf)
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throwFromErrno("HashSet: Cannot realloc.", ErrorCodes::CANNOT_ALLOCATE_MEMORY);
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/// Очистим новый кусок памяти.
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memset(buf + old_size, 0, buf_size_bytes() - old_size_bytes);
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/** Теперь некоторые элементы может потребоваться переместить на новое место.
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* Элемент может остаться на месте, или переместиться в новое место "справа",
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* или переместиться левее по цепочке разрешения коллизий, из-за того, что элементы левее него были перемещены в новое место "справа".
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*/
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for (size_t i = 0; i < old_size; ++i)
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if (!ZeroTraits::check(buf[i]))
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reinsert(buf[i]);
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#ifdef DBMS_HASH_MAP_DEBUG_RESIZES
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watch.stop();
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std::cerr << std::fixed << std::setprecision(3)
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<< "Resize from " << old_size << " to " << buf_size() << " took " << watch.elapsedSeconds() << " sec."
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<< std::endl;
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#endif
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}
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/** Вставить в новый буфер значение, которое было в старом буфере.
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* Используется при увеличении размера буфера.
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*/
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void reinsert(Key & x)
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{
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size_t place_value = place(hash(x));
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/// Если элемент на своём месте.
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if (&x == &buf[place_value])
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return;
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/// Вычисление нового места, с учётом цепочки разрешения коллизий.
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while (!ZeroTraits::check(buf[place_value]))
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{
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++place_value;
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place_value &= mask();
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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++collisions;
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#endif
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}
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/// Копирование на новое место и зануление старого.
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memcpy(&buf[place_value], &x, sizeof(x));
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ZeroTraits::set(x);
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/// Потом на старое место могут переместиться элементы, которые раньше были в коллизии с этим.
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}
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public:
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typedef Key key_type;
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typedef Key value_type;
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HashSet() :
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m_size(0),
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size_degree(GrowthTraits::INITIAL_SIZE_DEGREE),
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has_zero(false)
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{
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buf = reinterpret_cast<Key *>(calloc(buf_size_bytes(), 1));
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if (NULL == buf)
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throwFromErrno("HashSet: Cannot calloc.", ErrorCodes::CANNOT_ALLOCATE_MEMORY);
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}
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~HashSet()
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{
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for (iterator it = begin(); it != end(); ++it)
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it->~Key();
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free(reinterpret_cast<void *>(buf));
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}
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class iterator
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{
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Self * container;
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Key * ptr;
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friend class HashSet;
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iterator(Self * container_, Key * ptr_) : container(container_), ptr(ptr_) {}
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public:
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iterator() {}
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bool operator== (const iterator & rhs) const { return ptr == rhs.ptr; }
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bool operator!= (const iterator & rhs) const { return ptr != rhs.ptr; }
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iterator & operator++()
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{
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if (unlikely(!ptr))
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ptr = container->buf;
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else
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++ptr;
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while (ptr < container->buf + container->buf_size() && ZeroTraits::check(*ptr))
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++ptr;
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return *this;
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}
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Key & operator* () const { return *ptr; }
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Key * operator->() const { return ptr; }
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};
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class const_iterator
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{
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const Self * container;
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const Key * ptr;
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friend class HashSet;
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const_iterator(const Self * container_, const Key * ptr_) : container(container_), ptr(ptr_) {}
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public:
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const_iterator() {}
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const_iterator(const iterator & rhs) : container(rhs.container), ptr(rhs.ptr) {}
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bool operator== (const const_iterator & rhs) const { return ptr == rhs.ptr; }
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bool operator!= (const const_iterator & rhs) const { return ptr != rhs.ptr; }
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const_iterator & operator++()
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{
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if (unlikely(!ptr))
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ptr = container->buf;
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else
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++ptr;
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while (ptr < container->buf + container->buf_size() && ZeroTraits::check(*ptr))
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++ptr;
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return *this;
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}
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const Key & operator* () const { return *ptr; }
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const Key * operator->() const { return ptr; }
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};
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const_iterator begin() const
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{
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if (has_zero)
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return const_iterator(this, NULL);
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const Key * ptr = buf;
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while (ptr < buf + buf_size() && ZeroTraits::check(*ptr))
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++ptr;
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return const_iterator(this, ptr);
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}
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iterator begin()
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{
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if (has_zero)
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return iterator(this, NULL);
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Key * ptr = buf;
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while (ptr < buf + buf_size() && ZeroTraits::check(*ptr))
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++ptr;
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return iterator(this, ptr);
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}
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const_iterator end() const { return const_iterator(this, buf + buf_size()); }
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iterator end() { return iterator(this, buf + buf_size()); }
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/// Вставить ключ.
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std::pair<iterator, bool> insert(const Key & x)
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{
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if (ZeroTraits::check(x))
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{
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if (!has_zero)
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{
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++m_size;
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has_zero = true;
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return std::make_pair(begin(), true);
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}
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return std::make_pair(begin(), false);
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}
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size_t place_value = place(hash(x));
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while (!ZeroTraits::check(buf[place_value]) && buf[place_value] != x)
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{
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++place_value;
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place_value &= mask();
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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++collisions;
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#endif
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}
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iterator res(this, &buf[place_value]);
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if (!ZeroTraits::check(buf[place_value]) && buf[place_value] == x)
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return std::make_pair(res, false);
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buf[place_value] = x;
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++m_size;
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if (unlikely(m_size > max_fill()))
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{
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resize();
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return std::make_pair(find(x), true);
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}
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return std::make_pair(res, true);
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}
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void emplace(Key x, iterator & it, bool & inserted)
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{
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if (ZeroTraits::check(x))
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{
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if (!has_zero)
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{
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++m_size;
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has_zero = true;
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inserted = true;
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}
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else
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inserted = false;
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it = begin();
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return;
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}
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size_t place_value = place(hash(x));
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while (!ZeroTraits::check(buf[place_value]) && buf[place_value] != x)
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{
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++place_value;
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place_value &= mask();
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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++collisions;
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#endif
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}
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it = iterator(this, &buf[place_value]);
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if (!ZeroTraits::check(buf[place_value]) && buf[place_value] == x)
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{
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inserted = false;
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return;
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}
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new(&buf[place_value]) Key(x);
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inserted = true;
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++m_size;
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if (unlikely(m_size > max_fill()))
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{
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resize();
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it = find(x);
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}
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}
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iterator find(Key x)
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{
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if (ZeroTraits::check(x))
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return has_zero ? begin() : end();
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size_t place_value = place(hash(x));
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while (!ZeroTraits::check(buf[place_value]) && buf[place_value] != x)
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{
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++place_value;
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place_value &= mask();
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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++collisions;
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#endif
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}
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return !ZeroTraits::check(buf[place_value]) ? iterator(this, &buf[place_value]) : end();
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}
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const_iterator find(Key x) const
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{
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if (ZeroTraits::check(x))
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return has_zero ? begin() : end();
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size_t place_value = place(hash(x));
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while (!ZeroTraits::check(buf[place_value]) && buf[place_value] != x)
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{
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++place_value;
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place_value &= mask();
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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++collisions;
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#endif
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}
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return !ZeroTraits::check(buf[place_value]) ? const_iterator(this, &buf[place_value]) : end();
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}
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size_t size() const
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{
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return m_size;
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}
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bool empty() const
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{
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return 0 == m_size;
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}
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size_t getBufferSizeInBytes() const
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{
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return buf_size_bytes();
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}
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#ifdef DBMS_HASH_MAP_COUNT_COLLISIONS
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size_t getCollisions() const
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{
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return collisions;
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}
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#endif
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};
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}
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