Simple vector

simple_vector.cpp

#include <iostream>
#include <vector>
using namespace std;

const int trunk_size = 8 * 1024 * 1024;

class A {
public:
	static int counter;
	A() { id = counter++; cout << "alloc " << id << " @ " << this << endl; trunk.resize(trunk_size); }
	A(int size) { id = counter++; cout << "alloc " << id << " @ " << this << endl; trunk.resize(size); }
	A(const A& other) : trunk(other.trunk) { id = counter++; cout << "cpy " << id << endl; }
	A& operator=(const A& other) { id = counter++; trunk = other.trunk; cout << "assign " << id << " @ " << this << endl; }
	~A() { cout << "dealloc " << id << " @ " << this << endl; }

private:
	int id;
	vector<char> trunk;
};

int A::counter = 0;

template <typename T>
struct simple_vector {
	simple_vector() : cap(0), sz(0), t(nullptr) {}

	simple_vector(int n) : cap(n*2), sz(0) {
		t = static_cast<T*>(std::malloc(sizeof(T)*cap));
	}

	~simple_vector() {
		for(int i=0;i<sz;++i) { t[i].~T(); }
		std::free(t);
	}

	void push_back(const T& e) {
		if(sz==cap) {
			reserve(cap*2);
		}

		new(t+sz) T(e);
		++sz;
	}

	void pop_back() {
		if (sz > 0) {
			back().~T();
			--sz;
		}
	}

	T& front() { return t[0]; }
	T& back() { return t[sz-1]; }
	void reserve(int n) {
		if(n>cap) {
			T* new_t = static_cast<T*>(std::malloc(sizeof(T)*n));
			if(new_t != nullptr) {
				t = new_t;
				std::copy(t, t+sz, new_t);
			} else {
				cerr << "Out of memory." << endl;
				exit(-1);
			}
		}
	}

private:
	int cap;
	int sz;
	T* t;
};

int main() {
	cout << "begin" << endl;
	{
		vector<A> v(3);
	}

	{
		A a[3] = {A(), A(), A()};
	}

	{
		simple_vector<A> v(10);
		for(int i=0;i<8;++i)
			v.push_back(A(trunk_size));

		cout << "before pop back" << endl;
		char dummy;
		cin >> dummy;

		for(int i=0;i<5;++i)
			v.pop_back();

		cout << "after pop back" << endl;
		cin >> dummy;
	}
	cout << "out of scope." << endl;

	char dummy;
	cin >> dummy;
	cout << "end" << endl;
	return 0;
}