C语言解析,解释一下执行步骤

发布网友 发布时间：2022-04-30 04:07

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懂视网 时间：2022-04-30 08:28

官方给的链接打不开，而且里面的逻辑，每次都会打开文件，所以自己做了点个修改，发上来，借大家参考：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <vector>
#include <fstream>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>

class IP17MON {
public:
 static bool init(const std::string strPathToDataFile = "./17monipdb.dat") {
		if(is_init) {
			return true;
		}

 printf("Opening %s
", strPathToDataFile.c_str());
 std::ifstream ifDataFile(strPathToDataFile.c_str(), std::ios::binary);
 if (ifDataFile.is_open() == false) {
  printf("%m
");
  return false;
 }
 // std vector reserve
		vecDataFile.assign(std::istreambuf_iterator<char>(ifDataFile), std::istreambuf_iterator<char>());
 printf("Load %lu bytes success
", vecDataFile.size());
  
 unsigned int uiIndexLen = 0;
 memcpy(&uiIndexLen, &vecDataFile[0], 4);
 uiIndexLen = ntohl(uiIndexLen);
 printf("uiIndexLen = %d
", uiIndexLen);
 pIPIndex = &vecDataFile[4];
 pIPData = &vecDataFile[uiIndexLen];
		is_init = 1;
 return true;
 }

 static std::string find(const std::string strIP) { 
 struct sockaddr_in stSockAddrInet;

		memset(&stSockAddrInet, 0, sizeof(struct sockaddr_in));
 if(inet_aton(strIP.c_str(), &stSockAddrInet.sin_addr) == 0) {
  printf("convert error
");
  return "";
 }
 unsigned int uiIP = ntohl(stSockAddrInet.sin_addr.s_addr);
 
 // atoi The string can contain additional characters after those 
 // that form the integral number, which are ignored and have no 
 // effect on the behavior of this function.
 int iFirst = atoi(strIP.c_str());
 int iStart = 0;
 memcpy(&iStart, pIPIndex+(iFirst*4), 4);
		printf("iStart = %d
", iStart);
 int iMaxComLen = pIPData - pIPIndex - 1024 - 4;
  
 int iIndexOffset = -1;
 unsigned char ucIndexLength = 0;
 for (iStart = iStart * 8 + 1024; iStart < iMaxComLen; iStart += 8) {
  unsigned int uiCurrIP = 0;
  memcpy(&uiCurrIP, pIPIndex+iStart, 4);
  uiCurrIP = ntohl(uiCurrIP);
  if (uiCurrIP >= uiIP) {
  iIndexOffset = 0;
  memcpy(&iIndexOffset, pIPIndex+iStart+4, 3); 
  memcpy(&ucIndexLength, pIPIndex+iStart+7, 1); 
  break;
  }
 }
  
 if (iIndexOffset == -1) {
  return "";
 }
  
 std::string strRegion(pIPData + iIndexOffset - 1024, ucIndexLength);
 return strRegion;
 }
public:
 static std::vector<char> vecDataFile;
 static char *pIPIndex, *pIPData;
	static int is_init;
};
char *IP17MON::pIPIndex;
char *IP17MON::pIPData;
int IP17MON::is_init = 0;
std::vector<char> IP17MON::vecDataFile;
 
extern "C" const char *find_monip(const char *ip)
{
 if (IP17MON::init() == false) {
		return "";
	}
 return IP17MON::find(ip).c_str(); 
}

C语言解析17monipdb.dat(http://www.ipip.net/)免费数据库

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热心网友 时间：2022-04-30 05:36

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