检查给定的 IP 是否在给定的网络范围内或不在 C 中

如何解决检查给定的 IP 是否在给定的网络范围内或不在 C 中

我在一次面试中被问到这个问题，我被严格要求使用 C/C++ 进行编程。我不太喜欢 C++，我试过用 C 编写代码，谁能帮我改进我的代码，它工作得很好，但我认为这不是最好的解决方法。

问题：检查给定的 IP 是否在网络范围内或不使用 C。例如：IP 地址：192.168.0.1 和网络：192.168.0.0/24 => 答案应该是，它在网络范围内。

我的回答如下，但我们可以改进吗？ 谁能分享他们对这个问题的答案？

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *int_to_bin(unsigned short n){

  char *result = malloc(n);
  int c,k;
  char ch = '1';
  char ch1 = '0';
  for (c=7; c>=0; c--){
    k = n >> c; //Convert Integer to Binary by Right Shift Operation
    if(k & 1){
      strncat(result,&ch,1);
    }
    else{
      strncat(result,&ch1,1);
    }
  }
  return result;
}

int main(){
  unsigned short n1,n2,n3,n4;
  unsigned short m1,m2,m3,m4,m5;
  char ip[33];
  char sub[49];

  printf("Enter an IP address\n");
  scanf("%s",ip);
  sscanf(ip,"%hu.%hu.%hu.%hu",&n1,&n2,&n3,&n4);

  printf("Enter a Subnet address\n");
  scanf("%s",sub);
  sscanf(sub,"%hu.%hu.%hu.%hu/%hu",&m1,&m2,&m3,&m4,&m5);

  char target[ 33 ];  //This variable will store the 1s and 0s after converting IP address into binary
  char target1[ 49 ]; //This variable will store the 1s and 0s after converting Subnet address into binary
  char *a = int_to_bin(n1);
  char *b = int_to_bin(n2);
  char *c = int_to_bin(n3);
  char *d = int_to_bin(n4);

  char *o = int_to_bin(m1);
  char *p = int_to_bin(m2);
  char *q = int_to_bin(m3);
  char *r = int_to_bin(m4);

  strcat(target,a);
  strcat(target,b);
  strcat(target,c);
  strcat(target,d);

  strcat(target1,o);
  strcat(target1,p);
  strcat(target1,q);
  strcat(target1,r);
  //printf("%s\n",target);
  //printf("%s\n",target1);

  int i;
  for (i=0; i<m5; i++){
    if(target[i] != target1[i]){
      printf("IP is not in Subnet range\n");
      exit(0);
    }
  }
  printf("IP is in Subnet range\n");

  return 0;
}

解决方法

我做了一些更改，我的代码如下所示。如果您认为其中有任何错误，请告诉我：

1. 我正在接受输入并使用 sscanf 函数，将每个八位字节存储为整数格式。
2. 然后使用int_to_bin函数，使用右移操作将整数转换为二进制并存储到字符数组中。
3. 然后我在最后做 strcat 以组合数组。
4. 最后，我使用 'for' 循环进行前缀匹配。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *int_to_bin(unsigned short n){

  char *result;
  int c,d,t;
  t=0;
  result = (char*)malloc(32+1);
  

  if (result == NULL)
    exit(EXIT_FAILURE);
  
  for (c=7; c>=0; c--){
    d = n >> c; //Convert Integer to Binary by Right Shift Operation
    if(d & 1){
      *(result+t) = 1 + '0';
    }
    else{
      *(result+t) = 0 + '0';
    }
    t++;
  }
  *(result+t) = '\0';
  return result;
}

int main(){
  unsigned short n1,n2,n3,n4;
  unsigned short m1,m2,m3,m4,m5;
  char ip[33];
  char sub[49];

  printf("Enter an IP address\n");
  scanf("%s",ip);
  sscanf(ip,"%hu.%hu.%hu.%hu",&n1,&n2,&n3,&n4); //This will store each octet in integer format

  printf("Enter a Network address\n");
  scanf("%s",sub);
  sscanf(sub,"%hu.%hu.%hu.%hu/%hu",&m1,&m2,&m3,&m4,&m5); //This will store each octet in integer format

  char target[ 33 ];  //This variable will store the 1s and 0s after converting IP address into binary
  char target1[ 49 ]; //This variable will store the 1s and 0s after converting Subnet address into binary
  char *a = int_to_bin(n1);
  char *b = int_to_bin(n2);
  char *c = int_to_bin(n3);
  char *d = int_to_bin(n4);

  char *o = int_to_bin(m1);
  char *p = int_to_bin(m2);
  char *q = int_to_bin(m3);
  char *r = int_to_bin(m4);

  strcat(target,a);
  strcat(target,b);
  strcat(target,c);
  strcat(target,d);

  strcat(target1,o);
  strcat(target1,p);
  strcat(target1,q);
  strcat(target1,r);
  //printf("%s\n",target);
  //printf("%s\n",target1);

  int i;
  for (i=0; i<m5; i++){
    if(target[i] != target1[i]){
      printf("IP is not in given Network range\n");
      exit(0);
    }
  }
  printf("IP is in given Network range\n");

  return 0;
}