C++ primer 13.5 动态内存管理类示例程序

#include <iostream>
#include <sstream>
#include <fstream>
#include <cstdlib>
#include <set>
#include <memory>
#include <vector>

using namespace std;
class strVec{
public:
    strVec():elements(nullptr),first_free(nullptr),cap(nullptr){};
    strVec(const strVec &);
    strVec & operator=(const strVec &);
    ~strVec();
    void push_back(const string &);
    size_t size() const {return first_free - elements;}
    size_t capacity() const {return cap - elements;}
    string * begin() const {return elements;}
    string * end() const {return first_free;}

private:
    static allocator<string> alloc;
    void chk_n_alloc(){if(size() == capacity()) reallocate();}
    pair<string *,string *> alloc_n_copy(const string *,const string *);
    void free();
    void reallocate();
    string * elements;
    string * first_free;
    string * cap;
};
allocator<string> strVec::alloc;
void strVec::push_back(const string & s) {
    chk_n_alloc();
    alloc.construct(first_free++,s);
}
pair<string *,string *>
strVec::alloc_n_copy(const string * b, const string * e) {
    auto data = alloc.allocate(e - b);
    return {data,uninitialized_copy(b,e,data)};
}
void
strVec::free(){
    if(elements){
        for(auto i = first_free; i != elements; ){
            alloc.destroy(i--);
        }
        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();
}
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 p = alloc.allocate(newcapacity);
    auto ele = elements;
    auto dest = p;
    for(int i = 0; i < size(); ++i)
        alloc.construct(dest ++,std::move(*ele++));
    free();
    elements = p;
    first_free = dest;
    cap = elements + newcapacity;
}

int
main() {







    return 0;
}