对象池模板

概述

对象池的引入也是嵌入式开发的常用方法，也是内存预分配的一种，主要是用来隐藏全局对象的跟踪，通常预内存分配是通过数组来实现。

CMake配置

cmake_minimum_required(VERSION 3.5.1)project(objpool)add_executable(objpool objpool.cpp)set(CMAKE_SYSTEM_NAME Linux)SET(CMAKE_CXX_FLAGS "--std=c++11")

完整Demo

#include <iostream>template<class T, size_t N>
class ObjectPool {private:T objects[N];size_t available[N];size_t top = 0;public:ObjectPool(): top(0) {for (size_t i = 0; i < N; i++) {available[i] = i;}}T& get() {if (top < N) {size_t idx = available[top++];return objects[idx];} else {throw std::runtime_error("All objects are in use");}}void free(const T& obj) {const T* ptr = &obj;size_t idx = (ptr - objects) / sizeof(T);if (idx < N) {if (top) {objects[idx].deinit();top--;available[top] = idx;} else {throw std::runtime_error("Some object was freed more than once");}} else {throw std::runtime_error("Freeing object that does not belong to the pool");}}size_t requested() const { return top; }
};struct Point {int x, y;void deinit() { std::cout << "Hello " << x << ", " << y << "\n"; }
};int main() {ObjectPool<Point, 10> points;Point& a = points.get(); a.x = 10; a.y=20;std::cout << "Point a (" << a.x << ", " << a.y << ") initialized, requested " <<points.requested() << std::endl;Point& b = points.get(); std::cout << "Point b (" << b.x << ", " << b.y << ") not initialized, requested " <<points.requested() << std::endl;points.free(a);std::cout << "Point a(" << a.x << ", " << a.y << ") returned, requested " <<points.requested() << std::endl;Point& c = points.get();std::cout << "Point c(" << c.x << ", " << c.y << ") not intialized, requested " <<points.requested() << std::endl;Point local;try {points.free(local);} catch (std::runtime_error e) {std::cout << "Exception caught: " << e.what() << std::endl;}
}