Linked List retriving problems

[c0w]

I have these two functions that will add a link to a list and will also get a particular part of the linked data. When the array is filled with the getuser function it fills it with junk data.

// Add user to the linked list
void adduser(char *ipaddr, char username[], LINK first)
{
	LINK newE;
	LINK tmp; 
	LINK prev;
	
	if ( (newE = (LINK)malloc(sizeof(LIST))) == NULL)
	{
		cout << "Not enough memory";
		exit(0);
	}
	
	strcpy(newE->ip, ipaddr);
	strcpy(newE->user, username);

	if ( first == NULL )
	{
		first=newE;
		newE->next=NULL;
	}
	else 
	{
		tmp = first->next;
		prev=first;
		while( tmp->next != NULL )
		{
			newE->next = tmp;
			if (newE->next != prev->next)
			{
   				cout << "ERROR";
    				exit(0);
			}
			prev->next = newE;
			
		}
		if (tmp->next == NULL )
		{
			tmp->next = newE;
			newE->next = NULL;
		}
	}
}


// Retrieve a user from the list
void getuser(char name[], char *ipaddr, LINK first)
{
	LINK cur_ptr, next;
	cur_ptr = first;

	while ( cur_ptr != NULL )
	{
		next = cur_ptr->next;
		if ( strcmp( ipaddr, cur_ptr->ip) == 0 )
               strcpy( name, cur_ptr->user );
		cur_ptr = next;
     }
}

ip is a char array of 20 and user is a char array of 30
typedef struct data LIST;
typedef LIST *LINK;
and first is a value that is initialised in the main source to NULL.

[Scarlet7]

> void adduser(char *ipaddr, char username[], LINK first)

The 'first' parameter needs to be the address of a pointer in order to update its pointer, otherwise only the local stack pointer will be updated, which will be lost on return.

main()
{
     LINK first = NULL;

     adduser("1.1.1.1", "BATMAN", &first);
    ...  
}

void adduser(char *ipaddr, char username[], LINK *first)
{
     if ( *first == NULL )
     {
          *first=newE;
          newE->next=NULL;
     }   
}

[c0w]

I recieved errors of argument three in adduser cannot be of
LIST**.

[Scarlet7]

This is compiles ok

  
#include <stdlib.h> 
#include <malloc.h>
#include <string.h>
#include <iostream.h>

struct data;
typedef struct data LIST;
typedef LIST *LINK;

struct data
{
     char ip[20];
     char user[30];
     LIST *next ;
};


// Add user to the linked list
void adduser(char *ipaddr, char username[], LINK *first)
{
     LINK newE;
     LINK tmp; 
     LINK prev;
     
     if ( (newE = (LINK)malloc(sizeof(LIST))) == NULL)
     {
          cout << "Not enough memory";
          exit(0);
     }
     
     strcpy(newE->ip, ipaddr);
     strcpy(newE->user, username);

     if ( *first == NULL )
     {
          *first=newE;
          newE->next=NULL;
     }
     else 
     {
          tmp = (*first)->next;
          prev=*first;
          while( tmp->next != NULL )
          {
               newE->next = tmp;
               if (newE->next != prev->next)
               {
                       cout << "ERROR";
                        exit(0);
               }
               prev->next = newE;
               
          }
          if (tmp->next == NULL )
          {
               tmp->next = newE;
               newE->next = NULL;
          }
     }
}

// Retrieve a user from the list
void getuser(char name[], char *ipaddr, LINK first)
{
     LINK cur_ptr, next;
     cur_ptr = first;

     while ( cur_ptr != NULL )
     {
          next = cur_ptr->next;
          if ( strcmp( ipaddr, cur_ptr->ip) == 0 )
               strcpy( name, cur_ptr->user );
          cur_ptr = next;
     }
}

main()
{
     LINK first = NULL;
     char name[30];

     adduser("1.1.1.1", "BATMAN", &first);
     getuser( name, "1.1.1.1", first);

     cout <<  name << endl;

     return 0;
}