text: #include <iostream>
  #include <fstream>
  #include <string>
  #include "addressbook/addressbook.pb.h"
  
  using namespace std;
  
  // Iterates though all people in the AddressBook and prints info about them.
  void ListPeople(const tutorial::AddressBook& address_book) {
    for (int i = 0; i < address_book.person_size(); i++) {
      const tutorial::Person& person = address_book.person(i);
  
      cout << "Person ID: " << person.id() << endl;
      cout << "  Name: " << person.name() << endl;
      if (person.has_email()) {
        cout << "  E-mail address: " << person.email() << endl;
      }
  
      for (int j = 0; j < person.phone_size(); j++) {
        const tutorial::Person::PhoneNumber& phone_number = person.phone(j);
  
        switch (phone_number.type()) {
          case tutorial::Person::MOBILE:
            cout << "  Mobile phone #: ";
            break;
          case tutorial::Person::HOME:
            cout << "  Home phone #: ";
            break;
          case tutorial::Person::WORK:
            cout << "  Work phone #: ";
            break;
        }
        cout << phone_number.number() << endl;
      }
    }
  }
  
  // Main function:  Reads the entire address book from a file and prints all
  //   the information inside.
  int main(int argc, char* argv[]) {
    // Verify that the version of the library that we linked against is
    // compatible with the version of the headers we compiled against.
    GOOGLE_PROTOBUF_VERIFY_VERSION;
  
    if (argc != 2) {
      cerr << "Usage:  " << argv[0] << " ADDRESS_BOOK_FILE" << endl;
      return -1;
    }
  
    tutorial::AddressBook address_book;
  
    {
      // Read the existing address book.
      fstream input(argv[1], ios::in | ios::binary);
      if (!address_book.ParseFromIstream(&input)) {
        cerr << "Failed to parse address book." << endl;
        return -1;
      }
    }
  
    ListPeople(address_book);
  
    // Optional:  Delete all global objects allocated by libprotobuf.
    google::protobuf::ShutdownProtobufLibrary();
  
    return 0;
  }
  