memory-performance

# 内存管理与性能 ## 智能指针 cpp #include // unique_ptr - 独占所有权 auto create_resource() { return std::make_unique("data"); } // shared_ptr - 引用计数 std::shared_ptr shared = std::make_shared(42); std::weak_ptr weak = shared; // 非拥有引用 // 自定义删除器 auto file_deleter = [](FILE* fp) { if (fp) fclose(fp); }; std::unique_ptr file( fopen("data.txt", "r"), file_deleter ); // enable_shared_from_this class Node : public std::enable_shared_from_this { public: std::shared_ptr get_shared() { return shared_from_this(); } }; ## 自定义分配器 cpp #include #include // 用于固定大小对象的池分配器 template class PoolAllocator { struct Block { alignas(T) std::byte data[sizeof(T)]; Block* next; }; Block pool_[PoolSize]; Block* free_list_ = nullptr; public: using value_type = T; PoolAllocator() { // 初始化空闲链表 for (size_t i = 0; i next; return reinterpret_cast(block->data); } void deallocate(T* p, size_t n) { if (n != 1) return; Block* block = reinterpret_cast(p); block->next = free_list_; free_list_ = block; } }; // 用法 std::vector<int, PoolAllocator> vec; // Arena 分配器 - 线性分配器 class Arena { std::byte* buffer_; size_t size_; size_t offset_ = 0; public: Arena(size_t size) : size_(size) { buffer_ = new std::byte[size]; } ~Arena() { delete[] buffer_; } template T* allocate(size_t n = 1) { size_t alignment = alignof(T); size_t space = size_ - offset_; void* ptr = buffer_ + offset_; if (std::align(alignment, sizeof(T) * n, ptr, space)) { offset_ = size_ - space + sizeof(T) * n; return static_cast(ptr); } throw std::bad_alloc(); } void reset() { offset_ = 0; } }; ## 移动语义