A shared_lock can be used in conjunction with a unique lock to allow multiple readers and exclusive writers.
#include <unordered_map>
#include <mutex>
#include <shared_mutex>
#include <thread>
#include <string>
#include <iostream>
class PhoneBook {
public:
string getPhoneNo( const std::string & name )
{
shared_lock<shared_timed_mutex> r(_protect);
auto it = _phonebook.find( name );
if ( it == _phonebook.end() )
return (*it).second;
return "";
}
void addPhoneNo ( const std::string & name, const std::string & phone )
{
unique_lock<shared_timed_mutex> w(_protect);
_phonebook[name] = phone;
}
shared_timed_mutex _protect;
unordered_map<string,string> _phonebook;
};