dict.c

#include <stdio.h>
#include <stdlib.h>

#include "debug.h"

/*
  Dictionary based on code by Morten Eriksen <mortene@sim.no>.
*/

#include "dict.h"

struct dict_entry {
	unsigned int hash;
	void * key;
	void * value;
	struct dict_entry * next;
};

/* #define DICTTABLESIZE 97 */
#define DICTTABLESIZE 997 /* Semi-randomly selected prime number. */
/* #define DICTTABLESIZE 9973 */
/* #define DICTTABLESIZE 99991 */
/* #define DICTTABLESIZE 999983 */

struct dict {
	struct dict_entry * buckets[DICTTABLESIZE];
	unsigned int (*key2hash)(void *);
	int (*key_cmp)(void *, void *);
};

struct dict *
dict_init(unsigned int (*key2hash)(void *), int (*key_cmp)(void *, void *)) {
	struct dict * d;
	int i;

	d = malloc(sizeof(struct dict));
	if (!d) {
		perror("malloc()");
		exit(1);
	}
	for (i = 0; i < DICTTABLESIZE; i++) { /* better use memset()? */
		d->buckets[i] = NULL;
	}
	d->key2hash = key2hash;
	d->key_cmp = key_cmp;
	return d;
}

void
dict_clear(struct dict * d) {
	int i;
	struct dict_entry * entry, * nextentry;

	for (i = 0; i < DICTTABLESIZE; i++) {
		for (entry = d->buckets[i]; entry != NULL; entry = nextentry) {
			nextentry = entry->next;
			free(entry);
		}
		d->buckets[i] = NULL;
	}
	free(d);
}

int
dict_enter(struct dict * d, void * key, void * value) {
	struct dict_entry * entry, * newentry;
	unsigned int hash = d->key2hash(key);
	unsigned int bucketpos = hash % DICTTABLESIZE;

	newentry = malloc(sizeof(struct dict_entry));
	if (!newentry) {
		perror("malloc");
		exit(1);
	}

	newentry->hash  = hash;
	newentry->key   = key;
	newentry->value = value;
	newentry->next  = NULL;

	entry = d->buckets[bucketpos];
	while (entry && entry->next) entry = entry->next;

	if (entry) entry->next = newentry;
	else d->buckets[bucketpos] = newentry;

	debug(3, "new dict entry at %p[%d]: (%p,%p)\n", d, bucketpos, key, value);
	return 0;
}

void *
dict_find_entry(struct dict * d, void * key) {
	unsigned int hash = d->key2hash(key);
	unsigned int bucketpos = hash % DICTTABLESIZE;
	struct dict_entry * entry;

	for (entry = d->buckets[bucketpos]; entry; entry = entry->next) {
		if (hash != entry->hash) {
			continue;
		}
		if (!d->key_cmp(key, entry->key)) {
			break;
		}
	}
	return entry ? entry->value : NULL;
}

void
dict_apply_to_all(struct dict * d, void (*func)(void *key, void *value, void *data), void *data) {
	int i;

	for (i = 0; i < DICTTABLESIZE; i++) {
		struct dict_entry * entry = d->buckets[i];
		while (entry) {
			func(entry->key, entry->value, data);
			entry = entry->next;
		}
	}
}

/*****************************************************************************/

unsigned int
dict_key2hash_string(void * key) {
	const char * s = (const char *)key;
	unsigned int total = 0, shift = 0;

	while (*s) {
		total = total ^ ((*s) << shift);
		shift += 5;
		if (shift > 24) shift -= 24;
		s++;
	}
	return total;
}

int
dict_key_cmp_string(void * key1, void * key2) {
	return strcmp((const char *)key1, (const char *)key2);
}

unsigned int
dict_key2hash_int(void * key) {
	return (unsigned int)key;
}

int
dict_key_cmp_int(void * key1, void * key2) {
	return key1 - key2;
}