sll
Singly Linked List Library
Muhammad A Muquit
Introduction
Sll is a Singly Linked List library. The functions takes pointer to a void data type, so you can make a linked list from any kind of data. It's required that you have to write your own function to free your data. You will pass a pointer to your function while calling sll free routines. Please look at the Examples section for code sample. I hope You will find the library useful. Note, this library is not object oriented, nothing is abstracted, I wrote it this way. I wanted to see clearly what's going on. I wrote it because I was tired of many object oriented linked list libraries out there.

Download sll.tar.gz

sll Data Structure 

    typedef struct _Sll
    {
        void
            *data;          /* void pointer for user data */

        struct _Sll
            *next;          /* pointer to next node */
    } Sll;

sll Function reference 
    void initlist         (Sll **list)
    Sll  *allocateNode    (void *data)
    void appendNode       (Sll **head,Sll **new)
    void appendNodeSorted (Sll **head,Sll **new,int (*compFunc) (void *,void *))
    void insertNode       (Sll **head,Sll **new)
    Bool emptyList        (Sll *list)
    void delNode          (Sll **head,Sll *node)
    void freeNode         (Sll **list)
    Sll  *getNthNode      (Sll *head,int n)
    void destroyNode      (Sll **head, void (*freeFunc)(void **))
    void destroyNodes     (Sll **head, void (*freeFunc)(void **))
    int  numNodes         (Sll **head)

  • void initList (Sll **list)
    Initializes *list by setting the list pointer to NULL.

  • Sll *allocateNode (void *data)
    Allocates space for a new node and initializes the data fields. The user is responsible for passing a valid pointer to data. The pointer to data can be anything. If a large amount data needs to be used use a structure.

  • void appendNode (Sll **head,Sll **new)
    Appends a node to the end of a list. head list gets modified and new is the node to be appended.

  • void appendNodeSorted(Sll **head,Sll **new,int (*compFunc)(void *,void *)
    Appends a node to the end of a list sorted. The data of two lists are passed to the user defined function compFunction for sorting. The function returns an integer 0 or > 0.

  • void insertNode(Sll **head,Sll **new)
    Inserts a node at the beginning of a list. Insert node new at the beginning of list head. Note, the list head gets modified.

  • Bool emptyList(Sll *list)
    Checks if a list is empty. returns TRUE if the list is empty, FALSE otherwise.

  • void delNode(Sll **head,Sll *node)
    Deletes a node from the list. head is the list to modify and node is the node to remove. Note, the user data is not freed by this routine. See also freeNode.

  • void freeNode(Sll **list)
    Frees a node. It does not do free the data. It checks before freeing if the list is NULL or not. If not NULL, it will be freed. Therefore, list must point to a valid location in memory. See also destroyNode.

  • Sll *getNthNode(Sll *head,int n)
    Returns the nth node in a list. Note a node starts at 1. If there is no such node, NULL is returned.

  • void destroyNode(Sll **head,Sll *node,void (*freeFunc)(void **))
    Frees memory allocated for a node and the data associated with the node. The caller is responsible to write the function to free the memory for the data. The caller function frees the user data and the function delnode is used to delete the node. delNode calls freeNode to free the memory associated with the node.

  • void destroyNodes(Sll **head,void (*freeFunc)(void **))
    Frees the entire list and the data. The caller is responsible to write the function to free data and pass it in the function.

  • int numNodes(Sll **head)
    Returns number of nodes in the list.
    • Examples
  • Example 1 - Insert a node at the beginning of the list
  • Example 2 - Append a node at the end of the list.
  • Example 3 - Append a node at the end of the list sorted.
  • Example 4 - Delete a node.

    Example 1: Insert a node at the beginning of the list. The code is available in examples/insert directory. 

    /*
**  test inserting a node at the beginning of the list. print the result
**  and then free the memory. a user defined function is called to free
**  the data.
**
**  Development History:
**      who                  when           why
**      ma_muquit@fccc.edu   Aug-09-1998    first cut
*/


#include <config.h>
#include <sll.h>

typedef struct _addr
{
    char
        *name,
        *city,
        *state;
} Addr;

static void freeData(void **data);

int main (int argc,char **argv) 
{
    Sll
        *l,
        *head=NULL,
        *new=NULL;
    Addr
        *addr;

    int
        n=0;

    (void) fprintf(stderr,
"=========================================================================\n");
    (void) fprintf(stderr," Testing Insert a node at the beginning of a list\n");
    (void) fprintf(stderr,
"=========================================================================\n");

    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }

    /*
    ** it will be the last node
    */
    addr->name=strdup("Muhammad A Muquit");
    addr->city=strdup("Philadelphia");
    addr->state=strdup("PA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }

    new=allocateNode((void *) addr);
    insertNode(&head,&new);
    (void) fprintf(stderr,"Inserting Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** insert node before the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Janet Hunter");
    addr->city=strdup("Santa Clara");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    insertNode(&head,&new);
    (void) fprintf(stderr,"Inserting Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);


    /*
    ** insert node before the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Babs Jensen");
    addr->city=strdup("Cupertino");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    insertNode(&head,&new);
    (void) fprintf(stderr,"Inserting Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** print
    */
    (void) fprintf(stderr,"\n\nPrinting........\n");
    n=0;
    for (l=head; l; l=l->next)
    {
        addr=(Addr *) l->data;
        (void) fprintf(stderr,"Node: %d\n",++n);
        (void) fprintf(stderr,"  %s\n",addr->name);
        (void) fprintf(stderr,"  %s\n",addr->city);
        (void) fprintf(stderr,"  %s\n\n",addr->state);
    }

    /*
    ** free nodes
    */
    destroyNodes(&head,freeData);

    exit(0);
}


/*
** routine to free the user data
*/

static void freeData(void **data)
{
    Addr
        **addr=(Addr **) data;

    static int
        n=0;

    n++;
    if (*addr)
    {
        if ((*addr)->name)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->name);
            (void) free((char *) (*addr)->name);
        }
        if ((*addr)->city)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->city);
            (void) free ((char *) (*addr)->city);
        }
        if ((*addr)->state)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->state);
            (void) free ((char *) (*addr)->state);
        }

        (void) fprintf(stderr,"Freeing the node %d itself\n\n",n);
        (void) free((char *) (*addr));
        (*addr)=NULL;
    }
}

    Example 2: Append a node at the end of the list. The code is available in examples/append directory. 

    /*
**  test appending a node at the end of the list. print the result
**  and then free the memory. a user defined function is called to free
**  the data.
**
**  Development History:
**      who                  when           why
**      ma_muquit@fccc.edu   Aug-09-1998    first cut
*/


#include <config.h>
#include <sll.h>

typedef struct _addr
{
    char
        *name,
        *city,
        *state;
} Addr;

static void freeData(void **data);

int main (int argc,char **argv) 
{
    Sll
        *l,
        *head=NULL,
        *new=NULL;
    Addr
        *addr;

    int
        n=0;

    (void) fprintf(stderr,
"=========================================================================\n");
    (void) fprintf(stderr," Testing Append a node at the beginning of a list\n");
    (void) fprintf(stderr,
"=========================================================================\n");

    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }

    (void) fprintf(stderr,"\n---------------[ appending ]----------\n");
    /*
    ** it will be the last node
    */
    addr->name=strdup("Muhammad A Muquit");
    addr->city=strdup("Philadelphia");
    addr->state=strdup("PA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }

    new=allocateNode((void *) addr);
    appendNode(&head,&new);
    (void) fprintf(stderr,"Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** append node after the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Janet Hunter");
    addr->city=strdup("Santa Clara");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    appendNode(&head,&new);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);


    /*
    ** append node after the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Babs Jensen");
    addr->city=strdup("Cupertino");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    appendNode(&head,&new);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** print
    */
    (void) fprintf(stderr,"\n---------------[ printing ]----------\n");
    n=0;
    for (l=head; l; l=l->next)
    {
        addr=(Addr *) l->data;
        (void) fprintf(stderr,"Node: %d\n",++n);
        (void) fprintf(stderr,"  %s\n",addr->name);
        (void) fprintf(stderr,"  %s\n",addr->city);
        (void) fprintf(stderr,"  %s\n",addr->state);
    }

    /*
    ** free nodes
    */
    (void) fprintf(stderr,"\n---------------[ freeing ]----------\n");
    destroyNodes(&head,freeData);

    exit(0);
}


/*
** routine to free the user data
*/

static void freeData(void **data)
{
    Addr
        **addr=(Addr **) data;

    static int
        n=0;

    n++;
    if (*addr)
    {
        if ((*addr)->name)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->name);
            (void) free((char *) (*addr)->name);
        }
        if ((*addr)->city)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->city);
            (void) free ((char *) (*addr)->city);
        }
        if ((*addr)->state)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->state);
            (void) free ((char *) (*addr)->state);
        }

        (void) fprintf(stderr,"Freeing the node %d itself\n\n",n);
        (void) free((char *) (*addr));
        (*addr)=NULL;
    }
}
    Example 3: Appends a node to the end of a list sorted. 
    /*
**  Appends a node to the end of a list sorted. The data of two lists are
**  passed to the user defined function compFunction for sorting. 
**
**  Development History:
**      who                  when           why
**      ma_muquit@fccc.edu   Aug-09-1998    first cut
*/


#include <config.h>
#include <sll.h>

typedef struct _addr
{
    char
        *name,
        *city,
        *state;
} Addr;

static void freeData(void **data);
static int compFunc(void *a1,void *a2);

int main (int argc,char **argv) 
{
    Sll
        *l,
        *head=NULL,
        *new=NULL;
    Addr
        *addr;

    int
        n=0;

    (void) fprintf(stderr,
"=========================================================================\n");
    (void) fprintf(stderr," Testing Append a node at the beginning of a list\n");
    (void) fprintf(stderr,
"=========================================================================\n");

    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }

    (void) fprintf(stderr,"\n---------------[ appending ]----------\n");
    /*
    ** it will be the last node
    */
    addr->name=strdup("Cindy Muquit");
    addr->city=strdup("Philadelphia");
    addr->state=strdup("PA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }

    new=allocateNode((void *) addr);
    appendNodeSorted(&head,&new,compFunc);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** append node before the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Janet Hunter");
    addr->city=strdup("Santa Clara");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    appendNodeSorted(&head,&new,compFunc);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);


    /*
    ** append node before the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Babs Jensen");
    addr->city=strdup("Cupertino");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    appendNodeSorted(&head,&new,compFunc);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** print
    */
    (void) fprintf(stderr,"\n---------------[ printing ]----------\n");
    n=0;
    for (l=head; l; l=l->next)
    {
        addr=(Addr *) l->data;
        (void) fprintf(stderr,"Node: %d\n",++n);
        (void) fprintf(stderr,"  %s\n",addr->name);
        (void) fprintf(stderr,"  %s\n",addr->city);
        (void) fprintf(stderr,"  %s\n",addr->state);
    }

    /*
    ** free nodes
    */
    (void) fprintf(stderr,"\n---------------[ freeing ]----------\n");
    destroyNodes(&head,freeData);

    exit(0);
}


/*
** routine to free the user data
*/

static void freeData(void **data)
{
    Addr
        **addr=(Addr **) data;

    static int
        n=0;

    n++;
    if (*addr)
    {
        if ((*addr)->name)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->name);
            (void) free((char *) (*addr)->name);
        }
        if ((*addr)->city)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->city);
            (void) free ((char *) (*addr)->city);
        }
        if ((*addr)->state)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->state);
            (void) free ((char *) (*addr)->state);
        }

        (void) fprintf(stderr,"Freeing the node %d itself\n\n",n);
        (void) free((char *) (*addr));
        (*addr)=NULL;
    }
}


static int compFunc(void *a1,void *a2)
{
    Addr
        *addr1=(Addr *) a1,
        *addr2=(Addr *) a2;

/*
    (void) fprintf(stderr,"name1=%s\n",addr1->name);
    (void) fprintf(stderr,"name2=%s\n",addr2->name);
*/
    return (strcasecmp(addr1->name,addr2->name));
}
    Example 4: Delete a node. 
    /*
**  first append a node at the end of a list. then dele a node and free the
**  memory associated with data.
**
**  Development History:
**      who                  when           why
**      ma_muquit@fccc.edu   Aug-09-1998    first cut
*/


#include <config.h>
#include <sll.h>

typedef struct _addr
{
    char
        *name,
        *city,
        *state;
} Addr;

static void freeData(void **data);

int main (int argc,char **argv) 
{
    Sll
        *node,
        *l,
        *head=NULL,
        *new=NULL;
    Addr
        *addr;

    int
        n=0;

    (void) fprintf(stderr,
"=========================================================================\n");
    (void) fprintf(stderr," Append a node at the beginning of a list\n");
    (void) fprintf(stderr,
"=========================================================================\n");

    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }

    (void) fprintf(stderr,"\n---------------[ appending ]----------\n");
    /*
    ** it will be the last node
    */
    addr->name=strdup("Muhammad A Muquit");
    addr->city=strdup("Philadelphia");
    addr->state=strdup("PA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }

    new=allocateNode((void *) addr);
    appendNode(&head,&new);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** append node before the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Janet Hunter");
    addr->city=strdup("Santa Clara");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    appendNode(&head,&new);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);


    /*
    ** append node before the last one
    */
    addr=(Addr *) malloc(sizeof(Addr));
    if (addr == NULL)
    {
        (void) fprintf(stderr," malloc failed\n");
        exit(-1);
    }
    addr->name=strdup("Babs Jensen");
    addr->city=strdup("Cupertino");
    addr->state=strdup("CA");

    if ((addr->name == NULL) ||
        (addr->city == NULL) ||
        (addr->state == NULL))
    {
        (void) fprintf(stderr,"malloc failed\n");
        exit(-1);
    }   
    new=allocateNode((void *) addr);
    appendNode(&head,&new);
    (void) fprintf(stderr,"Appending Node: %d\n", ++n);
    (void) fprintf(stderr,"  %s\n",addr->name);
    (void) fprintf(stderr,"  %s\n",addr->city);
    (void) fprintf(stderr,"  %s\n",addr->state);

    /*
    ** print
    */
    (void) fprintf(stderr,"\n---------------[ printing ]----------\n");
    n=0;
    for (l=head; l; l=l->next)
    {
        addr=(Addr *) l->data;
        (void) fprintf(stderr,"Node: %d\n",++n);
        (void) fprintf(stderr,"  %s\n",addr->name);
        (void) fprintf(stderr,"  %s\n",addr->city);
        (void) fprintf(stderr,"  %s\n",addr->state);
    }

    (void) fprintf(stderr,"\n-----------[ delete Node 2 ]---------\n");
    node=getNthNode(head,2);
    if (node != NULL)
        destroyNode(&head,node,freeData);
    else
        (void) fprintf(stderr,"No node found at position 2\n");
    (void) fprintf(stderr,"\n-----------[ printing all the nodes again ]--------\n");
    n=0;
    for (l=head; l; l=l->next)
    {
        addr=(Addr *) l->data;
        (void) fprintf(stderr,"Node: %d\n",++n);
        (void) fprintf(stderr,"  %s\n",addr->name);
        (void) fprintf(stderr,"  %s\n",addr->city);
        (void) fprintf(stderr,"  %s\n",addr->state);
    }


    /*
    ** free nodes
    */
    (void) fprintf(stderr,"\n---------------[ freeing ]----------\n");
    destroyNodes(&head,freeData);

    exit(0);
}


/*
** routine to free the user data
*/

static void freeData(void **data)
{
    Addr
        **addr=(Addr **) data;

    if (*addr)
    {
        if ((*addr)->name)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->name);
            (void) free((char *) (*addr)->name);
        }
        if ((*addr)->city)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->city);
            (void) free ((char *) (*addr)->city);
        }
        if ((*addr)->state)
        {
            (void) fprintf(stderr," Freeing: %s\n",(*addr)->state);
            (void) free ((char *) (*addr)->state);
        }

        (void) fprintf(stderr,"Freeing the node itself\n\n");
        (void) free((char *) (*addr));
        (*addr)=NULL;
    }
}
    Copyright - GNU GPL

    ChangeLog

  • First cut, Aug-09-1999
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