blob.h

#ifndef BLOB_H
#define BLOB_H
#include <memory>
#include <vector>

template<typename T> class Blob
{
public:
	typedef T value_type;
	typedef typename std::vector<T>::size_type size_type;

	// constructors
	Blob();
	Blob(std::initializer_list<T> il);

	// number of elements in the Blob
	size_type size() const { return data->size(); }
	bool      empty() const { return data->empty(); }

	void push_back(const T& t) { data->push_back(t); }
	void push_back(T&& t) { data->push_back(std::move(t)); }
	void pop_back();

	// element access
	T& back();
	T& operator[](size_type i);

	const T& back() const;
	const T& operator [](size_type i) const;

private:
	std::shared_ptr<std::vector<T>> data;
	// throw msg if data[i] isn't valid
	void check(size_type i, const std::string &msg) const;
};

// constructors
template<typename T>
Blob<T>::Blob() : data(std::make_shared<std::vector<T>>())
{}

template<typename T>
Blob<T>::Blob(std::initializer_list<T> il) :
data(std::make_shared<std::vector<T>>(il))
{}

template<typename T>
void Blob<T>::check(size_type i, const std::string &msg) const
{
	if (i >= data->size())
		throw std::out_of_range(msg);
}

template<typename T>
T& Blob<T>::back()
{
	check(0, "back on empty Blob");
	return data->back();
}

template<typename T>
const T& Blob<T>::back() const
{
	check(0, "back on empty Blob");
	return data->back();
}


template<typename T>
T& Blob<T>::operator [](size_type i)
{
	// if i is too big, check function will throw, preventing access to a nonexistent element
	check(i, "subscript out of range");
	return (*data)[i];
}


template<typename T>
const T& Blob<T>::operator [](size_type i) const
{
	// if i is too big, check function will throw, preventing access to a nonexistent element
	check(i, "subscript out of range");
	return (*data)[i];
}

template<typename T>
void Blob<T>::pop_back()
{
	check(0, "pop_back on empty Blob");
	data->pop_back();
}

#endif // BLOB_H