skiplist/examples/slm.c

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#include <assert.h>
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#include <errno.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <stdio.h>
#include <stdlib.h>
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#include "../include/sl.h"
/*
* SKIPLIST EXAMPLE:
*
* This example creates a Skiplist keys and values are integers.
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* 'slex' - meaning: SkipList EXample
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*/
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/*
* 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.
*/
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struct slex_node {
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int key;
int value;
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SKIP_ENTRY(slex_node) entries;
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};
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/*
* Generate all the access functions for our type of Skiplist.
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*/
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SKIPLIST_DECL(
slex, api_, entries,
/* free node */ { (void)node; },
/* update node */ { node->value = new->value; })
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/*
* Getter
* It can be useful to have simple get/put-style API, but to
* do that you'll have to supply some blocks of code used to
* extract data from within your nodes.
*/
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SKIPLIST_GETTERS(
slex, api_, int, int, { query.key = key; }, { return node->value; })
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/*
* Now we need a way to compare the nodes you defined above.
* Let's create a function with four arguments:
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* - 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.
*
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* Your function should result in a return statement:
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* a < b : return -1
* a == b : return 0
* a > b : return 1
*
* This result provides the ordering within the Skiplist. Sometimes
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* your function will not be used when comparing nodes. This will
* happen when `a` or `b` are references to the head or tail of the
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* list or when `a == b`. In those cases the comparison function
* returns before using the code in your block, don't panic. :)
*/
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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;
}
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#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);
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}
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#endif
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int
main()
{
int rc = 0;
/* Allocate and initialize a Skiplist. */
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slex_t *list = (slex_t *)malloc(sizeof(slex_t));
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if (list == NULL) {
rc = ENOMEM;
goto fail;
}
rc = api_skip_init_slex(list, 12, 4, __slm_key_compare);
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if (rc)
return rc;
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struct slex_node *n;
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/* Insert 7 key/value pairs into the list. */
for (int i = -2; i <= 2; i++) {
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int v;
slex_node_t new;
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rc = api_skip_alloc_node_slex(list, &n);
if (rc)
return rc;
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n->key = i;
n->value = i;
api_skip_insert_slex(list, n);
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v = api_skip_get_slex(list, i);
((void)v);
new.key = n->key;
new.value = n->value * 10;
api_skip_update_slex(list, &new);
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}
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slex_node_t q;
q.key = 0;
api_skip_remove_slex(list, &q);
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assert(api_skip_gte_slex(list, -3) == -20);
assert(api_skip_gte_slex(list, -2) == -20);
assert(api_skip_gte_slex(list, 0) == 10);
assert(api_skip_gte_slex(list, 2) == 20);
assert(api_skip_gte_slex(list, 3) == 0);
assert(api_skip_lte_slex(list, -3) == 0);
assert(api_skip_lte_slex(list, -2) == -20);
assert(api_skip_lte_slex(list, 0) == -10);
assert(api_skip_lte_slex(list, 2) == 20);
assert(api_skip_lte_slex(list, 3) == 20);
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FILE *of = fopen("/tmp/slm.dot", "w");
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if (!of) {
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perror("Failed to open file /tmp/slm.dot");
return EXIT_FAILURE;
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}
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api_skip_dot_slex(of, list, 0, sprintf_slex_node);
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fclose(of);
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api_skip_destroy_slex(list);
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fail:;
return rc;
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}