I wrote a server program, and there is a class called "apInfoMutex",
which can store client's file descriptor info and what messages they sent;
the class code is as below:
---
class apInfoTable{
   public:
      apInfoTable();
      boost::shared_mutex rwMutex;
      void   addFD(int apfd, char *srvceType, vector<string> *codeList);
      void   delFD(int apfd);
      bool   getFD(list<int> *des, char *srvceType, char *srvceCode);

   private:
      boost::unordered_map<int, boost::unordered_set<pair<string, string> > >
tableFD;
      boost::unordered_map<pair<string, string>, boost::unordered_set<int> >
tablePush;
};
---
there is just one apInfoTable as global declaration in my program,
but there would be two or more threads to calling these public
method at the same time, and there is a method called "getFD()" in this class,
the code is as below:
---
bool apInfoTable::getFD(list<int> *des, char *type, char *code){
   bool flag=false;
   boost::shared_lock<boost::shared_mutex> lock(rwMutex);
   for(boost::unordered_set<int>::iterator it=tablePush[pair<string, string>
(type, code)].begin();it!=tablePush[pair<string, string>(type, code)].end
();it++){
      flag=true;
      des->push_back(*it);
   }
   return flag;
}
---
I found if I calling getFD() method like this:
char type[12];
char code[32];
list<int> fdList;
memset(type, 0x00, sizeof(type));
memset(code, 0x00, sizeof(code));
memcpy(type, "My Type", sizeof("My Type"));
memcpy(code, "My Code", sizeof("My Code"));
fdList.clear();
bool rc=getFD(&fdList, type, code);