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#include<stdio.h>
#include<stdlib.h>
struct prefix {
   unsigned int IP ;
   unsigned char len ;
  struct prefix *next ;
 };
typedef struct prefix Prefix ;
int cal(int d){
   int i , sum ;
   sum = 2 ;
   for( i = 0 ; i < d-1 ; i++)
     sum = sum * 2 ;
      return sum+1 ; }
 
Prefix *insert_a_node(Prefix *head,Prefix *node ){
    Prefix *cur ;
      cur = head ;
    if(head == NULL)
        return node ;
    if( node == NULL )
       return head ;
    if( node->IP < head->IP)
      { node->next = head ;
          return node ;  }
    while( cur->next != NULL && cur->next->IP <= node->IP)
        cur = cur->next ;
       node->next = cur->next ;
       cur->next = node ;
      return head ;
                       }
 
void insert_prefix(Prefix *group_head,Prefix *node,int index){
  int i = 0;
  Prefix *t;
 
  if(node == NULL) return;
  if(group_head->next == NULL)
        {
         group_head->next=node;
         t = group_head;
         return ;
        }
  if(node->IP <= group_head->next->IP)
        {
        node->next = group_head->next ;
        group_head->next=node;
        return ;
        }
 t = group_head->next ;
 if(t->next==NULL)
   {  t->next=node;
      return;}
  while(t->next!=NULL && t->next->IP < node->IP)
        t=t->next;
    node->next=t->next;
    t->next=node;
    return;
}
Prefix *build_list_no_order(Prefix *head,Prefix *node){
 
     if (head == NULL)
         return node ;
     if (node == NULL)
        return head ;
   Prefix *cur ;
     cur = head ;
   while ( cur->next != NULL)
    cur = cur->next ;
    cur->next = node ;
  return head ;
 
 }
 
Prefix *build_routing_table(){
    int a[5],i ;
   int ip = 0 ;
  Prefix *head ;
      head =  NULL ;
 FILE *ofp ;
 ofp = fopen("routing_table","r") ;
 while( fscanf(ofp,"%d.%d.%d.%d/%d",&a[0],&a[1],&a[2],&a[3],&a[4]) != EOF){
       Prefix *node = (Prefix*)malloc(sizeof(Prefix)) ;
   for ( i =0 ; i < 4 ; i++)
   {  ip = ip + a[i] ;
    if ( i != 3 )
      ip = ip<<8 ;  }
        node->IP = ip ;
        ip = 0 ;
        node->len=a[4];
      head = build_list_no_order(head,node);  }
    return head ;
 
    }
 
void segment(int d,Prefix *rout ,Prefix group[]){
   int index=0,i;
 
   for(i=31 ; i>31-d ; i--){
    if(rout->len<d)
         index=cal(d)-1;
    if( ( rout->IP & 1<<i ) && ( i!=32-d))
        {index++;
        index=index<<1;}
    if( (rout->IP & 1<<i) && i==32-d)
        index++;
    if( !(rout->IP & 1<<i) && i!=32-d)
        index=index<<1;
      }
   insert_prefix(&group[index],rout,index);
 
   }
int main ( int argc , char *argv[]){
  Prefix *head ;
  Prefix *routing_head;
  Prefix *trace_head;
  Prefix *temp_rout ;
  int d = 2 ; //need use argc finally
  int group_num;
  group_num = cal(d);
  Prefix group[group_num] ;
  trace_head = build_trace();
  routing_head = build_routing_table();
 
 while(routing_head != NULL ){
  segment(d,routing_head,group);
  routing_head = routing_head->next;
  }
 
     return 0 ;
}
 

prog.c: In function ‘insert_prefix’:
prog.c:34:7: warning: unused variable ‘i’ [-Wunused-variable]
   int i = 0;
       ^
prog.c: In function ‘build_list_no_order’:
prog.c:64:4: warning: this ‘while’ clause does not guard... [-Wmisleading-indentation]
    while ( cur->next != NULL)
    ^~~~~
prog.c:66:5: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘while’
     cur->next = node ;
     ^~~
prog.c: In function ‘main’:
prog.c:118:16: warning: implicit declaration of function ‘build_trace’ [-Wimplicit-function-declaration]
   trace_head = build_trace();
                ^~~~~~~~~~~
prog.c:118:14: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
   trace_head = build_trace();
              ^
prog.c:113:11: warning: unused variable ‘temp_rout’ [-Wunused-variable]
   Prefix *temp_rout ;
           ^~~~~~~~~
prog.c:112:11: warning: variable ‘trace_head’ set but not used [-Wunused-but-set-variable]
   Prefix *trace_head;
           ^~~~~~~~~~
prog.c:110:11: warning: unused variable ‘head’ [-Wunused-variable]
   Prefix *head ;
           ^~~~
prog.c: In function ‘insert_prefix’:
prog.c:50:10: warning: ‘t’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   while(t->next!=NULL && t->next->IP < node->IP)
         ~^~~~~~
prog.c: In function ‘segment’:
prog.c:50:10: warning: ‘t’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   while(t->next!=NULL && t->next->IP < node->IP)
         ~^~~~~~
prog.c:35:11: note: ‘t’ was declared here
   Prefix *t;
           ^
/home/Dp5Ur3/ccXMxJGT.o: In function `main':
prog.c:(.text.startup+0x9): undefined reference to `build_trace'
collect2: error: ld returned 1 exit status

Standard output is empty