C++ Primer Plus

• Write a Store functor that writes string information to a file. The Store constructor should specify an ifstream object, and the overloaded operator()(const string &) should indicate the string to write. A workable plan is to first write the string’s size to the file and then write the string contents. For example, if len holds the string size, you could use this:

os.write((char *)&len, sizeof(std::size_t)); // store length

os.write(s.data(), len); // store characters

The data() member returns a pointer to an array that holds the characters in the string. It’s similar to the c_str() member except that the latter appends a null character.

• Write a GetStrs() function that recovers information from the file. It can use read() to obtain the size of a string and then use a loop to read that many characters from the file, appending them to an initially empty temporary string. Because a string’s data is private, you have to use a class method to get data into the string rather than read directly into it.