Hash table for ip addreses

hi guys,

I need to store IP addresses in a hash table and count the number of messages they send.
(Unknown number of IPs or messages)

I don't know what is the fastest data structure in this case (an array, a tree...).

Also i need a good hash function for the IP addresses.

Thanks in advance...

If you are using C++ just use std::map. If you do it in C (and don't use a library) you are going to be writing 100's of lines of code that all has to work perfectly, not simple or easy even for experts.

On a *nix system with a C compiler, you can use hcreate(), hsearch() and hfree(). Alternatively, you could use a third party library such as Apache's APR library (specifically, the apr_hash_xx routines), which is portable across multiple platforms.

For C++, you could use std::unordered_map instead of std::map if you have a C++ 0x standard compliant compiler. For older C++ compilers, most of them support a std::hash_map template even though it wasn't part of the standard . std::hash_map is faster than std::map (because std::map sorts on every item insert)