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273 lines
7.8 KiB
C++
273 lines
7.8 KiB
C++
#pragma once
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#include <string.h>
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#include <malloc.h>
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#include <cstddef>
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#include <algorithm>
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#include <memory>
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#include <boost/noncopyable.hpp>
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#include <Yandex/likely.h>
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#include <Yandex/strong_typedef.h>
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#include <DB/Core/Exception.h>
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#include <DB/Core/ErrorCodes.h>
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namespace DB
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{
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/** Динамический массив для POD-типов.
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* Предназначен для небольшого количества больших массивов (а не большого количества маленьких).
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* А точнее - для использования в ColumnVector.
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* Отличается от std::vector тем, что не инициализирует элементы.
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* Сделано noncopyable, чтобы не было случайных копий. Скопировать данные можно с помощью метода assign.
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* Поддерживается только часть интерфейса std::vector.
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*
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* Если вставлять элементы push_back-ом, не делая reserve, то PODArray примерно в 2.5 раза быстрее std::vector.
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*/
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template <typename T>
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class PODArray : private boost::noncopyable, private std::allocator<char> /// empty base optimization
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{
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private:
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typedef std::allocator<char> Allocator;
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static const size_t initial_size;
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char * c_start;
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char * c_end;
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char * c_end_of_storage;
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bool use_libc_realloc;
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T * t_start() { return reinterpret_cast<T *>(c_start); }
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T * t_end() { return reinterpret_cast<T *>(c_end); }
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T * t_end_of_storage() { return reinterpret_cast<T *>(c_end_of_storage); }
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const T * t_start() const { return reinterpret_cast<const T *>(c_start); }
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const T * t_end() const { return reinterpret_cast<const T *>(c_end); }
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const T * t_end_of_storage() const { return reinterpret_cast<const T *>(c_end_of_storage); }
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size_t storage_size() const { return c_end_of_storage - c_start; }
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static size_t byte_size(size_t n) { return n * sizeof(T); }
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static size_t round_up_to_power_of_two(size_t n)
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{
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--n;
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n |= n >> 1;
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n |= n >> 2;
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n |= n >> 4;
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n |= n >> 8;
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n |= n >> 16;
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n |= n >> 32;
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++n;
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return n;
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}
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static size_t to_size(size_t n) { return byte_size(std::max(initial_size, round_up_to_power_of_two(n))); }
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void alloc(size_t n)
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{
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size_t bytes_to_alloc = to_size(n);
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c_start = c_end = Allocator::allocate(bytes_to_alloc);
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c_end_of_storage = c_start + bytes_to_alloc;
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//memset(c_start, 0, bytes_to_alloc);
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}
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void dealloc()
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{
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if (use_libc_realloc)
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::free(c_start);
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else
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Allocator::deallocate(c_start, storage_size());
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}
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void realloc(size_t n)
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{
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// std::cerr << "realloc" << std::endl;
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ptrdiff_t end_diff = c_end - c_start;
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size_t bytes_to_alloc = to_size(n);
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char * old_c_start = c_start;
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char * old_c_end_of_storage = c_end_of_storage;
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if (use_libc_realloc)
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{
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c_start = reinterpret_cast<char *>(::realloc(c_start, bytes_to_alloc));
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if (NULL == c_start)
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throwFromErrno("PODArray: cannot realloc", ErrorCodes::CANNOT_ALLOCATE_MEMORY);
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}
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else
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{
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c_start = reinterpret_cast<char *>(malloc(bytes_to_alloc));
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if (NULL == c_start)
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throwFromErrno("PODArray: cannot realloc", ErrorCodes::CANNOT_ALLOCATE_MEMORY);
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memcpy(c_start, old_c_start, old_c_end_of_storage - old_c_start);
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Allocator::deallocate(old_c_start, old_c_end_of_storage - old_c_start);
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}
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//memset(c_start + (old_c_end_of_storage - old_c_start), 0, bytes_to_alloc - (old_c_end_of_storage - old_c_start));
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c_end = c_start + end_diff;
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c_end_of_storage = c_start + bytes_to_alloc;
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use_libc_realloc = true;
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}
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public:
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typedef T value_type;
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/// Просто typedef нельзя, так как возникает неоднозначность для конструкторов и функций assign.
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class iterator
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{
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private:
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T * ptr;
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public:
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iterator() {}
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iterator(T * ptr_) : ptr(ptr_) {}
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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++() { ++ptr; return *this; }
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T & operator* () const { return *ptr; }
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T * operator->() const { return ptr; }
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iterator operator+ (ptrdiff_t diff) const { return ptr + diff; }
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iterator operator- (ptrdiff_t diff) const { return ptr - diff; }
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ptrdiff_t operator- (const iterator & rhs) const { return ptr - rhs.ptr; }
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};
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class const_iterator
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{
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private:
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const T * ptr;
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public:
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const_iterator() {}
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const_iterator(const T * ptr_) : ptr(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++() { ++ptr; return *this; }
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const T & operator* () const { return *ptr; }
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const T * operator->() const { return ptr; }
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const_iterator operator+ (ptrdiff_t diff) const { return ptr + diff; }
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const_iterator operator- (ptrdiff_t diff) const { return ptr - diff; }
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ptrdiff_t operator- (const const_iterator & rhs) const { return ptr - rhs.ptr; }
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};
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PODArray() : use_libc_realloc(false) { alloc(initial_size); }
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PODArray(size_t n) : use_libc_realloc(false) { alloc(n); c_end += byte_size(n); }
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PODArray(size_t n, const T & x) : use_libc_realloc(false) { alloc(n); assign(n, x); }
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PODArray(const_iterator from_begin, const_iterator from_end) : use_libc_realloc(false) { alloc(from_end - from_begin); insert(from_begin, from_end); }
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~PODArray() { dealloc(); }
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size_t size() const { return t_end() - t_start(); }
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bool empty() const { return t_end() == t_start(); }
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size_t capacity() const { return t_end_of_storage() - t_start(); }
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T & operator[] (size_t n) { return t_start()[n]; }
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const T & operator[] (size_t n) const { return t_start()[n]; }
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T & front() { return t_start()[0]; }
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T & back() { return t_end()[-1]; }
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const T & front() const { return t_start()[0]; }
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const T & back() const { return t_end()[-1]; }
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iterator begin() { return t_start(); }
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iterator end() { return t_end(); }
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const_iterator begin() const { return t_start(); }
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const_iterator end() const { return t_end(); }
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void reserve(size_t n)
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{
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if (n > capacity())
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realloc(n);
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}
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void reserve()
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{
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realloc(size() * 2);
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}
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void resize(size_t n)
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{
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reserve(n);
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c_end = c_start + byte_size(n);
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}
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void clear()
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{
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c_end = c_start;
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}
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void push_back(const T & x)
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{
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if (unlikely(c_end == c_end_of_storage))
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reserve();
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*t_end() = x;
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c_end += byte_size(1);
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}
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/// Не вставляйте в массив кусок самого себя. Потому что при ресайзе, итераторы на самого себя могут инвалидироваться.
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void insert(const_iterator from_begin, const_iterator from_end)
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{
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size_t required_capacity = size() + (from_end - from_begin);
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if (required_capacity > capacity())
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reserve(round_up_to_power_of_two(required_capacity));
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size_t bytes_to_copy = byte_size(from_end - from_begin);
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memcpy(c_end, reinterpret_cast<const void *>(&*from_begin), bytes_to_copy);
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c_end += bytes_to_copy;
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}
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void swap(PODArray<T> & rhs)
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{
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std::swap(c_start, rhs.c_start);
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std::swap(c_end, rhs.c_end);
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std::swap(c_end_of_storage, rhs.c_end_of_storage);
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}
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void assign(size_t n, const T & x)
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{
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resize(n);
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std::fill(begin(), end(), x);
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}
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void assign(const_iterator from_begin, const_iterator from_end)
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{
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size_t required_capacity = from_end - from_begin;
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if (required_capacity > capacity())
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reserve(round_up_to_power_of_two(required_capacity));
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size_t bytes_to_copy = byte_size(required_capacity);
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memcpy(c_start, reinterpret_cast<const void *>(from_begin), bytes_to_copy);
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c_end = c_start + bytes_to_copy;
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}
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void assign(const PODArray<T> & from)
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{
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assign(from.begin(), from.end());
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}
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};
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template <typename T>
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const size_t PODArray<T>::initial_size = 4096;
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}
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