c++添加swich case string 的支持

    #pragma once      // ----------------------------------------------------------------------------      // string_switch_case.h      //      // These macros together implement switch-case functionality for C strings and      // std::string.  When first encountered, the switch-case structure does two      // passes.  The first pass is a one-time initialization of a std::map with the      // strings as keys, and line numbers as values, to get the unique keys needed       // for a numeric switch-case.  All subsequent passes use the std::map to      // retrieve an unsigned integer for a given string, that was mapped during the      // first pass, to use for a numeric switch case.  This switch-case approach can      // be used repeatedly and even nested.  An example of the usage is as follows:      //      // switch_string(a)      // {      // case_string("first string")      //    printf("first string");      //    break;      // case_string("second string")      //    printf("second string");      // case_string("third string")      //    printf("falls through to third string");      //    break;      // default_case_string      //    printf("default");      // }      // end_switch_string      //      // The end_switch_string macro is required after the closing brace of the      // switch-case structure.  Each case_string statement must be on a unique line.      // Each case_string has its own local scope.  A case_string statement is      // ignored if declared within scope brackets beneath a sibling case statement.      // ----------------------------------------------------------------------------            #include <map>      #include <string>                  // switch macro      #define switch_string(a) while (true) {     static std::map<std::string, unsigned int> _string_lookup_;   static bool _init_ = true;  unsigned int _val_ = 0;     if (!_init_) {      std::map<std::string, unsigned int>::iterator _iter_ =            _string_lookup_.find(a);            if (_iter_ != _string_lookup_.end()) {              _val_ = (*_iter_).second; }             else {              _val_ = 0xffffffff;             }   }   switch(_val_) {     case 0:                  // case macro      #define case_string(a)      }   case __LINE__:      if (_init_)             _string_lookup_.insert              (std::pair<std::string, unsigned int>(a, __LINE__));      else {                  // default case macro      #define default_case_string         }   default:        if (!_init_) {                  // required macro for the end of the switch-case      #define end_switch_string   }   if (_init_) {       _init_ = false;     }   else {      break;  } }