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139 lines
3.7 KiB
C++
139 lines
3.7 KiB
C++
#pragma once
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#include <boost/noncopyable.hpp>
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#include <DB/Common/ProfileEvents.h>
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#include <DB/Common/Allocator.h>
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#include <DB/Common/Exception.h>
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#include <DB/Core/ErrorCodes.h>
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#include <DB/Core/Defines.h>
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namespace DB
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{
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/** Замена std::vector<char> для использования в буферах.
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* Отличается тем, что не делает лишний memset. (И почти ничего не делает.)
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* Также можно попросить выделять выровненный кусок памяти.
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*/
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struct Memory : boost::noncopyable, Allocator<false>
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{
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size_t m_capacity = 0;
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size_t m_size = 0;
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char * m_data = nullptr;
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size_t alignment = 0;
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Memory() {}
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/// Если alignment != 0, то будет выделяться память, выровненная на alignment.
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Memory(size_t size_, size_t alignment_ = 0) : m_capacity(size_), m_size(m_capacity), alignment(alignment_)
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{
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alloc();
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}
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~Memory()
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{
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dealloc();
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}
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Memory(Memory && rhs)
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{
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*this = std::move(rhs);
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}
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Memory & operator=(Memory && rhs)
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{
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std::swap(m_capacity, rhs.m_capacity);
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std::swap(m_size, rhs.m_size);
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std::swap(m_data, rhs.m_data);
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std::swap(alignment, rhs.alignment);
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return *this;
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}
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size_t size() const { return m_size; }
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const char & operator[](size_t i) const { return m_data[i]; }
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char & operator[](size_t i) { return m_data[i]; }
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void resize(size_t new_size)
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{
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if (0 == m_capacity)
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{
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m_size = m_capacity = new_size;
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alloc();
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}
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else if (new_size < m_capacity)
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{
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m_size = new_size;
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return;
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}
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else
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{
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new_size = align(new_size, alignment);
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/// @todo pointer to void can be converted to pointer to any type with static_cast by ISO C++, reinterpret_cast has no advantages
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m_data = reinterpret_cast<char *>(Allocator::realloc(m_data, m_capacity, new_size, alignment));
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m_capacity = new_size;
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m_size = m_capacity;
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}
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}
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static size_t align(const size_t value, const size_t alignment)
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{
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if (!alignment)
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return value;
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return (value + alignment - 1) / alignment * alignment;
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}
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private:
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void alloc()
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{
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if (!m_capacity)
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{
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m_data = nullptr;
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return;
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}
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ProfileEvents::increment(ProfileEvents::IOBufferAllocs);
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ProfileEvents::increment(ProfileEvents::IOBufferAllocBytes, m_capacity);
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size_t new_capacity = align(m_capacity, alignment);
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/// @todo pointer to void can be converted to pointer to any type with static_cast by ISO C++, reinterpret_cast has no advantages
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m_data = reinterpret_cast<char *>(Allocator::alloc(new_capacity, alignment));
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m_capacity = new_capacity;
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m_size = m_capacity;
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}
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void dealloc()
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{
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if (!m_data)
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return;
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/// @todo pointer to any type can be implicitly converted to pointer to void, no cast required
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Allocator::free(reinterpret_cast<void *>(m_data), m_capacity);
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m_data = nullptr; /// Чтобы избежать double free, если последующий вызов alloc кинет исключение.
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}
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};
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/** Буфер, который может сам владеть своим куском памяти для работы.
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* Аргумент шаблона - ReadBuffer или WriteBuffer
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*/
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template <typename Base>
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class BufferWithOwnMemory : public Base
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{
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protected:
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Memory memory;
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public:
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/// Если передать не-NULL existing_memory, то буфер не будет создавать свой кусок памяти, а будет использовать существующий (и не будет им владеть).
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BufferWithOwnMemory(size_t size = DBMS_DEFAULT_BUFFER_SIZE, char * existing_memory = nullptr, size_t alignment = 0) : Base(nullptr, 0), memory(existing_memory ? 0 : size, alignment)
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{
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Base::set(existing_memory ? existing_memory : &memory[0], size);
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}
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};
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}
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