C#:
private ulong[] IsFriendOf(ulong playerId)
private ulong[] GetFriendList(ulong playerId)
private string[] GetFriendList(string playerId)
private ulong[] GetFriends(ulong playerId)
private int GetMaxFriends()
private bool IsFriend(ulong playerId, ulong friendId)
private bool RemoveFriend(ulong playerId, ulong friendId)
private bool AddFriend(ulong playerId, ulong friendId)
private bool AreFriends(ulong playerId, ulong friendId)
private bool HasFriend(ulong playerId, ulong friendId)