字符数组作为C ++映射中的值 [英] Character Array as a value in C++ map

问题描述

我要定义

  Map< int，char [5]> myMap; 
  

上述声明被c ++编译器接受，并且不会抛出错误， / p>

  int main（）
 {
 char arr [5] =sdf; 
 map< int，char [5]> myMap; 
 myMap.insert（pair< int，char [5]>（0，arr））; 
 return 0; 
} 
  

我得到错误：

 在/usr/include/c++/4.6/bits/stl_algobase.h:65:0中包含的文件中，
来自/usr/include/c++/4.6/位/ char_traits.h：41，
从/usr/include/c++/4.6/ios:41，
从/usr/include/c++/4.6/ostream:40，
从/ usr / include / c ++ / 4.6 / iostream：40，
来自charMap.cpp：1：
 /usr/include/c++/4.6/bits/stl_pair.h：在构造函数'std :: pair< _T1，_T2> :: pair（const _T1& const _T2&）[with _T1 = int，_T2 = char [5]]'：
 charMap.cpp：9：42：从这里实例化
 /usr/include/c++/4.6/bits/stl_pair.h:104:31：error：array用作初始化器
 /usr/include/c++/4.6/bits/stl_pair.h：在构造函数'std :: [...] [with _U1 = int，_U2 = char [5]，_T1 = const int，_T2 = char [5]]'：'_T1，_T2> :: pair（const std :: pair <_U1，_U2& 
 charMap.cpp：9：43：从这里实例化
 /usr/include/c++/4.6/bits/stl_pair.h:109:39：error：array用作初始化器
  

重要的是我定义一个固定大小的字符数组，因为它优化了我的网络流操作。有没有办法实现呢？我不想使用 char * 或 std :: string 。

 <$ c 
 $ c> struct FiveChar 
 {
 FiveChar（char in [5]）{memcpy（data，in，5）; } 
 char& operator []（unsigned int idx）{return data [idx]; } 
 char data [5]; 
}; 
 
 int main（void）
 {
 char arr [5] =sdf; 
 map< int，FiveChar> myMap; 
 myMap.insert（pair< int，FiveChar>（0，arr））; 
 return 0; 
} 
  

I want to define something like

Map<int, char[5] > myMap;

The above declaration is accepted by c++ compiler and no error is thrown but when I do something like this

int main()
{
    char arr[5] ="sdf";
    map <int, char[5]> myMap;
    myMap.insert(pair<int, char[5]>(0,arr));
    return 0;
}

I get error as:

In file included from /usr/include/c++/4.6/bits/stl_algobase.h:65:0,
                 from /usr/include/c++/4.6/bits/char_traits.h:41,
                 from /usr/include/c++/4.6/ios:41,
                 from /usr/include/c++/4.6/ostream:40,
                 from /usr/include/c++/4.6/iostream:40,
                 from charMap.cpp:1:
/usr/include/c++/4.6/bits/stl_pair.h: In constructor ‘std::pair<_T1, _T2>::pair(const _T1&, const _T2&) [with _T1 = int, _T2 = char [5]]’:
charMap.cpp:9:42:   instantiated from here
/usr/include/c++/4.6/bits/stl_pair.h:104:31: error: array used as initializer
/usr/include/c++/4.6/bits/stl_pair.h: In constructor ‘std::pair<_T1, _T2>::pair(const std::pair<_U1, _U2>&) [with _U1 = int, _U2 = char [5], _T1 = const int, _T2 = char [5]]’:
charMap.cpp:9:43:   instantiated from here
/usr/include/c++/4.6/bits/stl_pair.h:109:39: error: array used as initializer

It is important for me to define a fixed size character array because it optimizes my network stream operation. Is there any way to achieve it? I do not want to use char * or std::string.

解决方案

One way is to wrap the fixed size character array as a struct.

struct FiveChar
{
   FiveChar(char in[5]) { memcpy(data, in, 5); }
   char& operator[](unsigned int idx) { return data[idx]; }
   char data[5];
};

int main(void)
{
   char arr[5] = "sdf";
   map<int, FiveChar> myMap;
   myMap.insert(pair<int, FiveChar>(0, arr));
   return 0;
}

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