Double linked list - Remove node when node contents/value given

[kingparthi]

This is a program to add, display & delete an item from the double linked list ...
Here the add & display works correctly... where my delete is having some
problem, when ever I delete an item, it also deletes the tails..
kindly can someone help out...



Here is my data types used in my program

typedef struct
{
char data[MAX_PRID_LEN];
int OidLen;
}Data_Type;
 
//structure for global data
typedef struct TAG_DATA
{
    Data_Type Data;
    int Status;
    struct TAG_DATA *next;
    struct TAG_DATA *prev;
}__stGData;
 
 
typedef struct TAG_LIST
{
    __stGData *head;
    __stGData *tail;
    int count;
}__stGList;
 
__stGList g_PridList;
 
 
// my main() function
{
    GData=(__stGData *)malloc(sizeof(__stGData));
    len=sizeof(int);
    printf("\nEnter the Prid value: ");
    scanf("%d",&prid);
 
    memcpy(GData->Data.data,&prid,len);
    GData->Data.OidLen = len;
    res=AddtoGList(&g_PridList, GData);
    if(res!=0)
    {
      printf("Adding created PRID to list failed");
      free(GData);
    }
    DisplayPridGList(g_PridList);
 
    printf("\nEnter the Prid value u wish to remove: ");
    scanf("%d",&prid);
    memcpy(GData->Data.data,&prid,(len));
 
   res =RemovefromGList(&g_PridList, GData);
}
 
 
//Function to add element
{   __stGData *temp=list->head;
    if (list->head == NULL)
    {
        /* no list items right now */
        list->head = list->tail=GData;
        GData->next=NULL;
        GData->prev=NULL;
    }
    else
    {
        while(temp->next!=NULL)
        {
            temp=temp->next;
        }
        /* there are one or more item */
        temp->next = GData;
        GData->prev=temp;
        GData->next=NULL;
        list->tail=GData;
    }
    /* increment number of items */
    list->count ++;
}    
 
//Function to display the list elements
{
  __stGData *temp=list.head;
    int i=1,j,val;
        while(temp)
        {
            printf("%d>",i);
            memcpy(&val,temp->Data.data,temp->Data.OidLen);
            printf("%d",val);
            i++;
            temp=temp->next;
            printf("\n");
        }
}    
// Function to remove 
int RemovefromGList(__stGList *list,__stGData *GData)
{
     int printval;
    __stGData *temp=list->head;
    if(list->head==NULL)
    {
        printf("Global Table is Empty");
        return -1;
    }
    if(temp->next==NULL)
    {
        if(strncmp(temp->Data.data,GData->Data.data,temp->Data.OidLen)==0)
        {
            temp->prev=NULL;
            temp->next=NULL;
            free(temp);
            list->head=NULL;
        }
    }
    else
    {
    while(temp)
        {
        if(strncmp(temp->Data.data,GData->Data.data,temp->Data.OidLen)==0)
         {
           if(temp->prev == NULL)
            {
        list->head=temp->next;
                    list->head->prev=NULL;
             }
                else
                {
                    temp->prev->next=temp->next;
                }
                if(temp->next == NULL)
                {
                    list->tail=temp->prev;
                }
                else
    {
                    temp->next->prev=temp->prev;
    }
    break;    
            }
            temp=temp->next;
        }
    }
    list->count--;
    return 0;
}

[weaknessforcats]

You have way, way too much code in your remove function.

Your linked list has only one scenario

A--->B--->C
A<---B<---C

To remove B:
1) Set B->prev->next to B-->next
Note: B->prev->next is A and B->next is C so you are setting A->next to C

2) Set B->next->prev to B->prev
Note: B->next->prev is C->prev and B->prev is A so you are setting C->prev to A

3) Node B is disconnected. Disconnecting A or C follows the same pattern but a nex/prev pointer will be zero, so skip that part.

This is about 5 lines of code.

[kingparthi]

Sir,
Obviously I am doing the same wht you have said... already.. please do look at the code..
//============================================
if(temp->prev == NULL)
{
list->head=temp->next;
list->head->prev=NULL;
}
else
{
temp->prev->next=temp->next;
}
if(temp->next == NULL)
{
list->tail=temp->prev;
list->tail->next=NULL;
}
else
{
temp->next->prev=temp->prev;
}
free(temp);
//========================================

Here the problem is I need to find the exact node to remove.... so in a while loop I am iterating to compare the node contents... and then removing..
by doing this even when I give a node content which not existing.. the tail of list gets altered...kindly give ur suggestions on this issue...

[Banfa]

In your code to remove an item you decrement list->count regardless of whether you actually did or didn't remove an item.

In your code to insert an item you needlessly use a loop to find the final item in the list when you could use list->tail.