k/v lists in C

iter.c

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

/**
 * this code has been placed into the public domain
 */

/**
 * ideally you'd have a hashmap (or lately i've been pretty happy with
 * binary-trie-backed dicts), but in a pinch this sort of thing can be
 * faster and is always simpler.
 */

struct kvpair {
	char *key;
	void *value;
};

struct kvpair pairs[] = {
	{"k1", "value"},
	{"k2", "another value"},
	{"etc", "just goes on"},

	{NULL}
};

/* equivalent to: */
char *cpairs[] = {
	"k1", "value",
	"k2", "another value",
	"etc", "just goes on",

	NULL
};

/***/

void iter_over(struct kvpair *pairs)
{
	/**
	 * since pairs->value is a `void *` we'll just print the memory
	 * address as a hex number. the `z` format qualifier says `this number
	 * is a size_t`.
	 */

	for (; pairs->key; pairs++)
		printf("%s => %zX\n", pairs->key, (size_t) pairs->value);
}

int main(int argc, char **argv)
{
	puts("pairs:");
	iter_over(pairs);

	puts("");
	puts("cpairs:");
	iter_over((struct kvpair *) cpairs);
}