ex13_47.cpp

#include "headers.h"

class String {
    friend void print(String& s);

   public:
    // Normal constructors
    String() : begin(nullptr), end(nullptr){};
    String(const string& s);
    String(const char* pc);

    // Copy constructor
    String(const String& s);

    // Copy assgnment operator
    String& operator=(const String& rhs);

    // destructor
    ~String();

    size_t length() const;

   private:
    allocator<char> alloc;
    char* begin;
    char* end;
    void free();
    pair<char*, char*> allocate_n_copy(const char* begin, const char* end);
};

String::String(const string& s) {
    auto size = s.length();
    begin = alloc.allocate(size);
    end = uninitialized_copy(s.begin(), s.end(), begin);
}

String::String(const char* pc) {
    int len = 0;
    auto p = pc;
    while (*p != '\0') {
        len++;
        p++;
    }

    auto pair = allocate_n_copy(pc, pc + len);
    begin = pair.first;
    end = pair.second;
}

String::String(const String& s) {
    cout << "String(const String& s)" << endl;
    auto pair = allocate_n_copy(s.begin, s.end);
    begin = pair.first;
    end = pair.second;
}

String& String::operator=(const String& rhs) {
    cout << "operator=(const String & rhs)" << endl;

    // construction
    auto new_begin = alloc.allocate(rhs.length());
    auto new_end = uninitialized_copy(rhs.begin, rhs.end, new_begin);

    // destuction
    free();

    begin = new_begin;
    end = new_end;
    return *this;
}

String::~String() {
    cout << "~String()" << endl;
    free();
}

size_t String::length() const { return end - begin; }

void String::free() {
    for_each(begin, end, [this](char& c) { alloc.destroy(&c); });
    alloc.deallocate(begin, length());
}

pair<char*, char*> String::allocate_n_copy(const char* b, const char* e) {
    auto size = e - b;
    auto begin = alloc.allocate(size);
    auto end = uninitialized_copy(b, e, begin);
    return {begin, end};
}

void print(String& s) {
    cout << "\"";
    for (auto p = s.begin; p != s.end; p++) {
        cout << *p;
    }
    cout << "\", " << s.length() << endl;
}

int main() {
    char cstyle[] = "Hello World!";
    String s0(cstyle);
    print(s0);
    cout << endl;

    String s1("AAA");
    String s2(s1);
    print(s1);
    print(s2);
    cout << endl;

    // String s3("BBB");
    // print(s3);
    // s1 = s3;
    // print(s1);
    // print(s2);
    // print(s3);
}