skiplist/examples/slm.c
2024-03-18 21:19:26 -04:00

136 lines
3.4 KiB
C

#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include "../include/sl.h"
/*
* SKIPLIST EXAMPLE:
*
* This example creates a Skiplist keys and values are integers.
* 'slex' - meaning: SkipList EXample
*/
/*
* To start, you must create a type node that will contain the
* fields you'd like to maintain in your Skiplist. In this case
* we map int -> int, but what you put here is up to you. You
* don't even need a "key", just a way to compare one node against
* another, logic you'll provide in SKIP_DECL as a block below.
*/
struct slex_node {
int key;
int value;
SKIP_ENTRY(slex_node) entries;
};
/*
* Generate all the access functions for our type of Skiplist.
* The last argument to this macro is a block of code used to
* compare the nodes you defined above.
* This block can expect four arguments:
* - a reference to the Skiplist, `slist`
* - the two nodes to compare, `a` and `b`
* - and `aux`, which you can use to pass into this function
* any additional information required to compare objects.
* `aux` is passed from the value in the Skiplist, you can
* modify that value at any time to suit your needs.
*
* Your block should result in a return statement:
* a < b : return -1
* a == b : return 0
* a > b : return 1
*
* This result provides the ordering within the Skiplist. Sometimes
* your block of code will not be used when comparing nodes. This
* happens when `a` or `b` are references to the head or tail of the
* list or when `a == b`. In those cases the comparison function
* returns before using the code in your block, don't panic. :)
*/
SKIPLIST_DECL(slex, api_, entries)
int
__slm_key_compare(slex_t *list, slex_node_t *a, slex_node_t *b, void *aux)
{
(void)list;
(void)aux;
if (a->key < b->key)
return -1;
if (a->key > b->key)
return 1;
return 0;
}
#define DOT
#ifdef DOT
/* Also declare the functions used to visualize a Sliplist (DOT/Graphviz) */
SKIPLIST_DECL_DOT(slex, api_, entries)
void
sprintf_slex_node(slex_node_t *node, char *buf)
{
sprintf(buf, "%d:%d", node->key, node->value);
}
#endif
int
main()
{
int rc = 0;
/* Allocate and initialize a Skiplist. */
slex_t *list = (slex_t *)malloc(sizeof(slex_t));
if (list == NULL) {
rc = ENOMEM;
goto fail;
}
rc = api_skip_init_slex(list, 12, 4, __slm_key_compare);
struct slex_node *n;
/* Insert 7 key/value pairs into the list. */
for (int i = -2; i <= 2; i++) {
SKIP_ALLOC_NODE(list, n, slex_node, entries);
n->key = i;
n->value = i;
api_skip_insert_slex(list, n);
}
FILE *of = fopen("/tmp/slm.dot", "w");
if (!of) {
perror("Failed to open file /tmp/slm.dot");
return EXIT_FAILURE;
}
api_skip_dot_slex(of, list, sprintf_slex_node);
fclose(of);
#if 0
/* Delete a specific element in the list. */
struct slex_node query;
query.key = 4;
struct slex_node *removed = SKIP_REMOVE(list, q, entries);
free(removed);
/* Forward traversal. */
SKIP_FOREACH(np, &head, entries)
np-> ...
/* Reverse traversal. */
SKIP_FOREACH_REVERSE(np, &head, skiphead, entries)
np-> ...
/* Skiplist Deletion. */
while (!SKIP_EMPTY(&head)) {
n1 = SKIP_FIRST(&head);
SKIP_REMOVE(&head, n1, entries);
free(n1);
}
/* Faster Skiplist Deletion. */
n1 = SKIP_FIRST(&head);
while (n1 != NULL) {
n2 = SKIP_NEXT(n1, entries);
free(n1);
n1 = n2;
}
SKIP_INIT(&head);
#endif
fail:;
return rc;
}