StrVec_ex40.h

#ifndef STRVEC_H_
#define STRVEC_H_

#include <string>
#include <utility>
#include <memory>

class StrVec
{
public:
	StrVec() : elements(nullptr), first_free(nullptr), cap(nullptr) { }
	StrVec(std::initializer_list<std::string>);
	StrVec(const StrVec&);
	StrVec &operator=(const StrVec&);
	~StrVec();
	void push_back(const std::string&);
	size_t size() const { return first_free - elements; }
	size_t capacity() const { return cap - elements; }
	std::string *begin() const { return elements; }
	std::string *end() const { return first_free; }
	void reserve(size_t n);
	void resize(size_t n);
	void resize(size_t n, const std::string &s);
private:
	std::allocator<std::string> alloc;
	void chk_n_alloc() { if(size() == capacity()) reallocate(); }
	std::pair<std::string*, std::string*> alloc_n_copy(const std::string*, const std::string*);
	void free();
	void reallocate();
	std::string *elements;
	std::string *first_free;
	std::string *cap;
};

StrVec::StrVec(std::initializer_list<std::string> il)
{
	auto newdata = alloc_n_copy(il.begin(), il.end());
	elements = newdata.first;
	first_free = cap = newdata.second;
}

void StrVec::push_back(const std::string &s)
{
	chk_n_alloc();
	alloc.construct(first_free++, s);
}

std::pair<std::string*,std::string*> StrVec::alloc_n_copy(const std::string *b, const std::string *e)
{
	auto data = alloc.allocate(e-b);
	return {data, uninitialized_copy(b, e, data)};
}

void StrVec::free()
{
	if(elements)
	{
		for(auto p = first_free; p != elements; )
			alloc.destroy(--p);
		alloc.deallocate(elements, cap-elements);
	}
}

StrVec::StrVec(const StrVec &s)
{
	auto newdata = alloc_n_copy(s.begin(), s.end());
	elements = newdata.first;
	first_free = cap = newdata.second;
}

StrVec::~StrVec()
{
	free();
}

void StrVec::reserve(size_t n)
{
	if(n <= capacity()) return;
	auto newdata = alloc.allocate(n);
	auto dest = newdata;
	auto elem = elements;
	for(size_t i = 0; i != size(); ++i)
		alloc.construct(dest++, std::move(*elem++));
	free();
	elements = newdata;
	first_free = dest;
	cap = elements + n;
}

void StrVec::resize(size_t n)
{
	resize(n,std::string());
}

void StrVec::resize(size_t n, const std::string &s)
{
	if(n < size())
	{
		while(n < size())
			alloc.destroy(--first_free);
	}else if(n > size())
	{
		while(n > size())
			push_back(s);
			// alloc.construct(first_free, s);
	}
}

StrVec &StrVec::operator=(const StrVec &rhs)
{
	auto data = alloc_n_copy(rhs.begin(), rhs.end());
	free();
	elements = data.first;
	first_free = cap = data.second;
	return *this;
}

void StrVec::reallocate()
{
	auto newcapacity = size() ? 2 * size() : 1;
	auto newdata = alloc.allocate(newcapacity);
	auto dest = newdata;
	auto elem = elements;
	for(size_t i = 0; i != size(); ++i)
		alloc.construct(dest++, std::move(*elem++));
	free();
	elements = newdata;
	first_free = dest;
	cap = elements + newcapacity;
}

#endif