reference_count_string.hh

#include <cassert>
#include <cstring>

#include <iostream>

namespace reference_counted_string {

// The ctor increments ref_cnt_, but the dtor does not decrement it.
struct StringObject {
  StringObject() : len_(0), ref_cnt_(1), s_(new char[1]) {
    assert(s_ != 0);
    s_[0] = '\0';
  }
  StringObject(int n) : len_(n), ref_cnt_(1), s_(new char[len_ + 1]) {
    assert(s_ != 0);
    s_[0] = '\0';
  }
  StringObject(const char *p)
      : len_(strlen(p)), ref_cnt_(1), s_(new char[len_ + 1]) {
    assert(s_ != 0);
    strncpy(s_, p, len_);
    s_[len_] = '\0';
    std::cout << s_ << std::endl;
  }
  ~StringObject() {
#ifdef DEBUG
    ::std::cout << "Deleting StringObject " << s_ << ::std::endl;
#endif
    delete[] s_;
  }

  size_t len_;
  int ref_cnt_;
  char *s_;
};

// The CountedString constructor never increments ref_cnt_, as the StringObject
// constructor does that.  It decrements ref_cnt_ upon manual StringObject
// deletion.
class CountedString {
public:
  CountedString() {
    str_ = new StringObject;
    assert(str_ != 0);
  }
  CountedString(const char *p) {
    str_ = new StringObject(p);
    assert(str_ != 0);
#ifdef DEBUG
    ::std::cout << "Char* constructor " << str_->s_ << ::std::endl;
#endif
  }
  CountedString(const ::std::string str) {
    str_ = new StringObject(str.c_str());
    assert(str_ != 0);
#ifdef DEBUG
    ::std::cout << "String constructor " << str_->s_ << ::std::endl;
#endif
  }
  CountedString(const CountedString &str) {
    // Because ref_cnt_ is not mutex-protected and could be decremented in
    // another thread.
    assert(0 != str.str_->ref_cnt_);
    str_ = new StringObject(str.str_->s_);
    assert(str_ != 0);
#ifdef DEBUG
    ::std::cout << "Copy constructor " << str_->s_ << ::std::endl;
#endif
  }
  CountedString(int n) {
    assert(n >= 0);
    str_ = new StringObject(n);
    assert(str_ != 0);
  }
  ~CountedString() {
    // Because ref_cnt_ is not mutex-protected and could be decremented in
    // another thread.
    assert(str_->ref_cnt_ >= 0);
    if (0 == --str_->ref_cnt_) {
#ifdef DEBUG
      ::std::cout << "Deleting CountedString " << str_->s_ << ::std::endl;
#endif
      delete str_;
    }
  }
  size_t length() const { return str_->len_; }
  friend void Swap(CountedString &str1, CountedString &str2);
  friend CountedString operator+(const CountedString &str1,
                                 const CountedString &str2);
  bool operator==(const CountedString &str1) const;
  bool operator==(const char *str) const;
  void operator=(const CountedString &str);
  char operator[](const int i) const;
  CountedString operator()(int from, int to) const;
  bool Search(const char *str) const;
  operator char *() const;
  friend void operator<<(std::ostream &out, const CountedString &cs);

private:
  StringObject *str_ = nullptr;
};

void operator<<(std::ostream &out, const CountedString &cs);
CountedString operator+(const CountedString &str1, const CountedString &str2);
void Swap(CountedString &str1, CountedString &str2);
} // namespace reference_counted_string