地图加锁

map加锁
for (std::map<int, ST_TRANS_INFO>::iterator iter = m_TransInfo.begin(); iter != m_TransInfo.end(); )
{
  time_t tCurrent = time(NULL);
  if (difftime(tCurrent, iter->second.tRtcpArrived) >= 30.0f)
  {
  m_TransInfo.erase(iter++);
  }
  else
  {
  ++iter;
  }
}

我仅需要在difftime为true的时候对map进行write，请问如何加锁啊，加在最外层，如果迭代很频繁又不进difftime就感觉很浪费资源，请问有什么好办法吗

[解决办法]

C/C++ code

if (difftime(tCurrent, iter->second.tRtcpArrived) >= 30.0f)  {  Lock();  m_TransInfo.erase(iter++);  UnLock();  }