Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

https://github.com/nbulischeck/list.h

Linear Linked List Library
https://github.com/nbulischeck/list.h

c header linked-list

Last synced: 1 day ago
JSON representation

Linear Linked List Library

Lists

README 

        
# list.h



Implementations for singly-linked and doubly-linked list functions.



## Basic Working Example



```C

#include 

#include 

#include "list.h"



typedef struct node {

    int key;

    struct node *next;

} node_t;



node_t *head = NULL;

 

int main(){

    node_t *item, *tmp;



    item = malloc(sizeof(node_t));

    item->key = 5;

    item->next = NULL;

    SL_APPEND(head, item);



    SL_FOREACH(head, item) printf("%d\n", item->key);



    SL_FOREACH_SAFE(head, item, tmp){

        SL_DELETE(head, item);

        free(item);

    }



    return 0;

}

```



## Functions Available



**Every function has a doubly-linked list counterpart.** The doubly-linked list

version takes the exact same arguments. They are referred to as `DL_` and the function name. For example, `DL_EMPTY` and `DL_APPEND`.



|  Function Name  | Arg 1 | Arg 2  | Arg 3 | Arg 4 |

|  -------------  | ----- | ------ | ----- | ----- |

| SL_EMPTY        | head  | int    |       |       |

| SL_APPEND       | head  | node   |       |       |

| SL_PREPEND      | head  | node   |       |       |

| SL_SORT         | head  | fn *   |       |       |

| SL_LAST         | head  | node   |       |       |

| SL_REVERSE      | head  |        |       |       |

| SL_CONCAT       | head  | head   |       |       |

| SL_LENGTH       | head  | int    |       |       |

| SL_FOREACH      | head  | node   |       |       |

| SL_FOREACH_SAFE | head  | node   | node  |       |

| SL_INDEX        | head  | node   | int   |       |

| SL_SEARCH       | head  | fn *   | query | node  |

| SL_DELETE       | head  | node   |       |       |



### SL_APPEND



This function appends a node to the end of a linked list.



Argument 1: The head node of the list



Argument 2: The node to be appended to the list



Call:

```C

SL_APPEND(head, node);

```



### SL_PREPEND



This function prepends a node to the start of a linked list.



Argument 1: The head node of the list



Argument 2: The node to be prepended to the list



Call:

```C

SL_PREPEND(head, node);

```



### SL_SORT



This function sorts a linked list in O(n log n) time.



Argument 1: The head node of the list



Argument 2: A function pointer to a compare function



Call:

```C

SL_SORT(head, fn *);

```



>**Note**: The function pointer must be able to identify if one key is less than or equal to another and return a value accordingly. The check to swap is if the return value of the compare function is less than or equal to zero. For strings, you can use `strcmp()` and for integers you can simply return the difference.



### SL_REVERSE



This function reverses a linked list. For example, `a->b->c->d` becomes `d->c->b->a`.



Argument 1: The head node of the list



Call:

```C

SL_REVERSE(head);

```



### SL_CONCAT



This function concatenates two linked lists. For example, list1: `a->b` and list2: `c->d` becomes `a->b->c->d`.



Argument 1: The head node of the first list



Argument 2: The head node of the second list



Call:

```C

SL_CONCAT(head, head);

```



### SL_LENGTH



This function stores the length of a linked list in the second argument.



Argument 1: The head node of the list



Argument 2: An integer to store the length of the list



Call:

```C

SL_LENGTH(head, length);

```



>**Note**: The second argument **will** be clobbered!



### SL_FOREACH



This function iterates over the length of the list and returns the node at each step. This is helpful when operating on every node in the list (printing the list or altering each node).



Argument 1: The head node of the list



Argument 2: A temporary node to store each intermediary node



Call:

```C

SL_FOREACH(head, node);

```



### SL_FOREACH_SAFE



This function iterates over the length of the list and returns the node at each step. This is helpful when operating on every node in the list (printing the list, altering each node, or destroying the list).



Argument 1: The head node of the list



Argument 2: A temporary node to store each intermediary node



Argument 3: A temporary node to safely store the next node



Call:

```C

SL_FOREACH_SAFE(head, node, tmp);

```



### SL_INDEX



This function returns a node at the nth position in the list. The list is zero-indexed, so if you ask for the 0th node, you'll get the head.



Argument 1: The head node of the list



Argument 2: A temporary node to store the returned node



Argument 3: An integer index value



Call:

```C

SL_INDEX(head, node, index);

```



>**Note**: Check for a proper return value after a function call to SL_INDEX. If your index is out of range, a NULL node will be returned.



### SL_SEARCH



This function searches the list and compares each node to the query using the function pointer argument. If a valid match is found, the matching node is placed in the fourth argument `node`. This is one of the most versatile functions due to the nature of the function pointer. You're given the ability to search for nodes, keys (int, char *, ...), etc. The limit to which you can search the list is your ability to write a proper compare function.



Argument 1: The head node of the list



Argument 2: A function pointer to a compare function



Argument 3: The item you want to query



Argument 4: A temporary node to store the returned node



Call:

```C

SL_SEARCH(head, cmp, query, node);

```



>**Note**: Check for a proper return value after a function call to SL_SEARCH. If a node is not found, a NULL node will be returned.



### SL_DELETE



This function removes a node from the linked list. **SL_DELETE only unlinks the node!** The memory **must** be freed to avoid a memory leak.



Argument 1: The head node of the list



Argument 2: The node to be removed



Call:

```C

SL_DELETE(head, node);

```



## Recipes



Below are some common use cases for the above functions.



### SL_FOREACH



#### Print an entire list



```C

SL_FOREACH(head, node) printf("%d\n", node->key);

```



### SL_FOREACH_SAFE



#### Delete an entire list



See [SL_DELETE](#sl_delete-1).



### SL_SEARCH



#### Search by key



```C

/* For integers */

int cmp(node_t *a, int key){

    return a->key - key;

}

SL_SEARCH(head, cmp, 5, node);



/* For strings */

int cmp(node_t *a, char *key){

    return strcmp(a->key, key);

}

SL_SEARCH(head, cmp, "Hello, world!", node);



/* For pointers */

int cmp(node_t *a, void *ptr){

    return (a->data.ptr == ptr) ? 0 : 1;

}

SL_SEARCH(head, cmp, ptr, node);

```



### SL_DELETE



#### Delete a single node



```C

SL_DELETE(head, node);

free(node);

```



#### Delete an entire list



```C

SL_FOREACH_SAFE(head, node, tmp){

    SL_DELETE(head, node);

    free(node);

}

```