Unordered_map using pointer address as key - c++

Question

I'm trying to create a map with a custom key, which is an object's pointer address, as mentioned.
I need the address because for now it's the only relevant way to compare between two objects.
from what i understood, the proper way of doing this is by using const char* as key
here is the typedef :
typedef __gnu_cxx::unordered_map<const char*, std::string> TargetsTags;
I'm a bit confused about the following:
how do I create the operator() ?
This is what i used for std::string:
namespace __gnu_cxx {
template<>
struct hash<std::string>
{
hash<const char*> h;
size_t operator()(const std::string &s) const
{
return h(s.c_str());
};
};
}
What about const char*?
And is this the correct way of doing this?

Answer 1

The working example using c++11:
#include <iostream>
#include <unordered_map>
#include <string>
#include <functional>
using namespace std;
class myhash {
public:
size_t operator() (const char *val) const {
return std::hash<std::string>()(val);
}
};
class myequal {
public:
bool operator()(const char *val1, const char *val2) const{
return std::string(val1) == std::string(val2);
}
};
int main() {
std::unordered_map<const char*, string, myhash, myequal> mymap;
mymap["abc"] = "abcd";
mymap["cba"] = "dcba";
std::cout << mymap["abc"] << std::endl;
return 0;
}