unordered_map与IP地址作为键

Question

我想在我的应用程序中建立链表的列表。该列表将包含唯一的IP地址，并且对于每个IP地址，我都有一个应用程序列表。我试图用unordered_map采取的boost ::升压:: ASIO ::知识产权来构建它::地址作为重点和std ::列表作为值：

#include <boost/unordered/unordered_map.hpp> 
#include <iostream> 
#include <list> 

using namespace boost::asio::ip; 
using namespace std; 

typedef int  ApplicationID; 
typedef address IPAddress; 
typedef list <ApplicationID> APP_LIST; 
typedef boost::unordered::unordered_map <IPAddress, APP_LIST> USER_MAP; 

USER_MAP user_map; 

后来我试图让该列表相关联与IP地址如下：

APP_LIST *list = &user_map[ip]; 

但我得到的编译错误，所以你可以请注明什么问题？

1. 是否可以使用Boost：IPaddress作为关键功能？

2. 另一个问题是有可能使用char [some_size]作为关键值？

错误输出：

In file included from /boost/functional/hash/hash.hpp:535:0, 
       from /boost/functional/hash.hpp:6, 
       from /boost/unordered/unordered_map.hpp:21, 
       from ipc_module.cpp:18: 
/boost/functional/hash/extensions.hpp: In member function ‘std::size_t boost::hash<T>::operator()(const T&) const [with T = boost::asio::ip::address, std::size_t = long unsigned int]’: 
/boost/unordered/detail/unique.hpp:331:55: instantiated from ‘boost::unordered::detail::table_impl<Types>::value_type& boost::unordered::detail::table_impl<Types>::operator[](const key_type&) [with Types = boost::unordered::detail::map<std::allocator<std::pair<const boost::asio::ip::address, std::list<int> > >, boost::asio::ip::address, std::list<int>, boost::hash<boost::asio::ip::address>, std::equal_to<boost::asio::ip::address> >, boost::unordered::detail::table_impl<Types>::value_type = std::pair<const boost::asio::ip::address, std::list<int> >, boost::unordered::detail::table_impl<Types>::key_type = boost::asio::ip::address]’ 
/boost/unordered/unordered_map.hpp:1192:26: instantiated from ‘boost::unordered::unordered_map<K, T, H, P, A>::mapped_type& boost::unordered::unordered_map<K, T, H, P, A>::operator[](const key_type&) [with K = boost::asio::ip::address, T = std::list<int>, H = boost::hash<boost::asio::ip::address>, P = std::equal_to<boost::asio::ip::address>, A = std::allocator<std::pair<const boost::asio::ip::address, std::list<int> > >, boost::unordered::unordered_map<K, T, H, P, A>::mapped_type = std::list<int>, boost::unordered::unordered_map<K, T, H, P, A>::key_type = boost::asio::ip::address]’ 
ipc_module.cpp:175:40: instantiated from here 
/boost/functional/hash/extensions.hpp:176:34: error: no matching function for call to ‘hash_value(const boost::asio::ip::address&)’ 
/boost/functional/hash/extensions.hpp:176:34: note: candidates are: 
/boost/smart_ptr/shared_ptr.hpp:708:33: note: template<class T> std::size_t boost::hash_value(const boost::shared_ptr<T>&) 
/boost/functional/hash/hash.hpp:144:24: note: std::size_t boost::hash_value(bool) 
/boost/functional/hash/hash.hpp:144:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘bool’ 
/boost/functional/hash/hash.hpp:149:24: note: std::size_t boost::hash_value(char) 
/boost/functional/hash/hash.hpp:149:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘char’ 
/boost/functional/hash/hash.hpp:154:24: note: std::size_t boost::hash_value(unsigned char) 
/boost/functional/hash/hash.hpp:154:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘unsigned char’ 
/boost/functional/hash/hash.hpp:159:24: note: std::size_t boost::hash_value(signed char) 
/boost/functional/hash/hash.hpp:159:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘signed char’ 
/boost/functional/hash/hash.hpp:164:24: note: std::size_t boost::hash_value(short int) 
/boost/functional/hash/hash.hpp:164:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘short int’ 
/boost/functional/hash/hash.hpp:169:24: note: std::size_t boost::hash_value(short unsigned int) 
/boost/functional/hash/hash.hpp:169:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘short unsigned int’ 
/boost/functional/hash/hash.hpp:174:24: note: std::size_t boost::hash_value(int) 
/boost/functional/hash/hash.hpp:174:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘int’ 
/boost/functional/hash/hash.hpp:179:24: note: std::size_t boost::hash_value(unsigned int) 
/boost/functional/hash/hash.hpp:179:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘unsigned int’ 
/boost/functional/hash/hash.hpp:184:24: note: std::size_t boost::hash_value(long int) 
/boost/functional/hash/hash.hpp:184:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘long int’ 
/boost/functional/hash/hash.hpp:189:24: note: std::size_t boost::hash_value(long unsigned int) 
/boost/functional/hash/hash.hpp:189:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘long unsigned int’ 
/boost/functional/hash/hash.hpp:195:24: note: std::size_t boost::hash_value(wchar_t) 
/boost/functional/hash/hash.hpp:195:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘wchar_t’ 
/boost/functional/hash/hash.hpp:202:24: note: std::size_t boost::hash_value(boost::long_long_type) 
/boost/functional/hash/hash.hpp:202:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘boost::long_long_type {aka long long int}’ 
/boost/functional/hash/hash.hpp:207:24: note: std::size_t boost::hash_value(boost::ulong_long_type) 
/boost/functional/hash/hash.hpp:207:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘boost::ulong_long_type {aka long long unsigned int}’ 
/boost/functional/hash/hash.hpp:215:36: note: template<class T> std::size_t boost::hash_value(T* const&) 
/boost/functional/hash/hash.hpp:308:24: note: template<class T, unsigned int N> std::size_t boost::hash_value(const T (&)[N]) 
/boost/functional/hash/hash.hpp:314:24: note: template<class T, unsigned int N> std::size_t boost::hash_value(T (&)[N]) 
/boost/functional/hash/hash.hpp:327:24: note: std::size_t boost::hash_value(float) 
/boost/functional/hash/hash.hpp:327:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘float’ 
/boost/functional/hash/hash.hpp:332:24: note: std::size_t boost::hash_value(double) 
/boost/functional/hash/hash.hpp:332:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘double’ 
/boost/functional/hash/hash.hpp:337:24: note: std::size_t boost::hash_value(long double) 
/boost/functional/hash/hash.hpp:337:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘long double’ 
/boost/functional/hash/hash.hpp:321:24: note: template<class Ch, class A> std::size_t boost::hash_value(const std::basic_string<Ch, std::char_traits<_CharT>, A>&) 
/boost/functional/hash/hash.hpp:343:24: note: std::size_t boost::hash_value(std::type_index) 
/boost/functional/hash/hash.hpp:343:24: note: no known conversion for argument 1 from ‘const boost::asio::ip::address’ to ‘std::type_index’ 
/boost/functional/hash/extensions.hpp:54:17: note: template<class A, class B> std::size_t boost::hash_value(const std::pair<_T1, _T2>&) 
/boost/functional/hash/extensions.hpp:63:17: note: template<class T, class A> std::size_t boost::hash_value(const std::vector<_Tp, _Alloc>&) 
/boost/functional/hash/extensions.hpp:69:17: note: template<class T, class A> std::size_t boost::hash_value(const std::list<_Tp, _Alloc>&) 
/boost/functional/hash/extensions.hpp:75:17: note: template<class T, class A> std::size_t boost::hash_value(const std::deque<_Tp, _Alloc>&) 
/boost/functional/hash/extensions.hpp:81:17: note: template<class K, class C, class A> std::size_t boost::hash_value(const std::set<_Key, _Compare, _Alloc>&) 
/boost/functional/hash/extensions.hpp:87:17: note: template<class K, class C, class A> std::size_t boost::hash_value(const std::multiset<_Key, _Compare, _Alloc>&) 
/boost/functional/hash/extensions.hpp:93:17: note: template<class K, class T, class C, class A> std::size_t boost::hash_value(const std::map<_Key, _Tp, _Compare, _Alloc>&) 
/boost/functional/hash/extensions.hpp:99:17: note: template<class K, class T, class C, class A> std::size_t boost::hash_value(const std::multimap<_Key, _Tp, _Compare, _Alloc>&) 
/boost/functional/hash/extensions.hpp:105:17: note: template<class T> std::size_t boost::hash_value(const std::complex<_Tp>&) 
/boost/functional/hash/extensions.hpp:177:9: warning: control reaches end of non-void function [-Wreturn-type] 
/boost/asio/error.hpp: At global scope: 
/boost/asio/error.hpp:244:45: warning: ‘boost::asio::error::system_category’ defined but not used [-Wunused-variable] 
/boost/asio/error.hpp:246:45: warning: ‘boost::asio::error::netdb_category’ defined but not used [-Wunused-variable] 
/boost/asio/error.hpp:248:45: warning: ‘boost::asio::error::addrinfo_category’ defined but not used [-Wunused-variable] 
/boost/asio/error.hpp:250:45: warning: ‘boost::asio::error::misc_category’ defined but not used [-Wunused-variable] 

Answer 1

下面是我在对ip::address的类接口进行简要检查后得出的结论。

我想说明的是，使用它非常浪费。特别是如果你碰巧知道所有地址都是ipv4，例如那么我宁愿输入ulong。

namespace boost 
{ 
    template <> 
     struct hash<IPAddress> 
     { 
      size_t operator()(IPAddress const& v) const { 
       if (v.is_v4()) 
        return v.to_v4().to_ulong(); 
       if (v.is_v6()) 
       { 
        auto const& range = v.to_v6().to_bytes(); 
        return hash_range(range.begin(), range.end()); 
       } 
       if (v.is_unspecified()) 
       { 
        // guaranteed to be random: chosen by fair dice roll 
        return static_cast<size_t>(0x4751301174351161ul); 
       } 
       return hash_value(v.to_string()); 
      } 
     }; 
} 

看到它Live on Coliru：

#include <boost/asio.hpp> 
#include <boost/unordered/unordered_map.hpp> 
#include <iostream> 
#include <list> 

typedef int             ApplicationID; 
typedef boost::asio::ip::address        IPAddress; 
typedef std::list<ApplicationID>        APP_LIST; 
typedef boost::unordered::unordered_map<IPAddress, APP_LIST> USER_MAP; 

namespace boost 
{ 
    template <> 
     struct hash<IPAddress> 
     { 
      size_t operator()(IPAddress const& v) const { 
       if (v.is_v4()) 
        return v.to_v4().to_ulong(); 
       if (v.is_v6()) 
       { 
        auto const& range = v.to_v6().to_bytes(); 
        return hash_range(range.begin(), range.end()); 
       } 
       if (v.is_unspecified()) 
        return 0x4751301174351161ul; 
       return hash_value(v.to_string()); 
      } 
     }; 
} 

int main() 
{ 
    USER_MAP map; 
    map.insert({ {}, {} }); 
} 

Answer 2

，如果你写的名称IP地址的哈希函数，它将正常工作。