（转）有一组从IP范围到地理位置信息的数据，不同地点的IP范围没有重叠，实现从单个IP地址查到相应的地理位置。

get_loc_in_ip_range.cc

#include <iostream>
#include <algorithm>
#include <stdint.h>
#include <string>
#include <map>
#include <cassert>

using namespace std;

// ip range is expressed as [startIP, endIP)
// thus the MAX_IP is not available 
struct Data
{
  uint32_t startIP;
  string   geoLoc;	
};

typedef map<uint32_t, Data> ipmap_t; // <endIP, Data>

bool getLocInIPRange(const ipmap_t& ipmap, uint32_t ip, string& loc)
{
  ipmap_t::const_iterator it = ipmap.upper_bound(ip);
  if(it != ipmap.end() && it->second.startIP <= ip)
  {
    loc = it->second.geoLoc;
    return true;
  }
  return false;
}

void addMapItem(ipmap_t& ipmap, uint32_t startIP, uint32_t endIP, const char* loc)
{
  Data data = {startIP, string(loc)};
  pair<ipmap_t::iterator, bool> res = ipmap.insert(pair<uint32_t, Data>(endIP,data));
  assert(res.second);
}

int main(int argc, const char* argv[])
{
  ipmap_t ipmap;
  addMapItem(ipmap, 0, 100, "Shanghai");
  addMapItem(ipmap, 101, 303, "Xi'an");
  addMapItem(ipmap, 406, 700, "Nanchang");
  addMapItem(ipmap, 800, 900, "Nanjing");
  addMapItem(ipmap, 1000, 1008, "Yuyao");


  // search
  while(true)
  {
    uint32_t ip;
    cout << "please input ip: ";
    cin >> ip;
    string foundLoc;
    bool exist = getLocInIPRange(ipmap, ip, foundLoc);
    if(exist)
      cout << foundLoc.c_str() << endl;
    else
      cout << "out of range!" << endl;
  }
}

原来如此:)
BTW, 你blog的文章挺有价值的。