C arrays of structs

arrays_of_structs.c

/*
 * Populate and process arrays of structs in C, with error handling.
 *
 * Zero-Clause BSD (0BSD)
 * ---------------------------------------------------------------------
 * Permission to use, copy, modify, and/or distribute this software for
 * any purpose with or without fee is hereby granted.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
 * AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 * ---------------------------------------------------------------------
 */

#ifndef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 200809L
#endif

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

struct tag {
        uint32_t id;
        char *value;
};

void populate(struct tag **, size_t *);

void process(struct tag *, size_t);

void
populate(struct tag **tags, size_t *ntags)
{
        if (tags == NULL || ntags == NULL) {
                errno = EINVAL;
                return;
        }

        *tags = calloc(3, sizeof(struct tag));
        if (*tags == NULL)
                return;

        *ntags = 3;
        (*tags)[0] = (struct tag){79, "spam"};
        (*tags)[1] = (struct tag){97, "eggs"};
        (*tags)[2] = (struct tag){101, "crap"};
}

void
process(struct tag *tags, size_t ntags)
{
        size_t n;

        if (tags == NULL || ntags <= 0) {
                errno = EINVAL;
                return;
        }

        for (n = 0; n < ntags; ++n) {
                struct tag *t = &tags[n];
                if (t != NULL)
                        printf("%3d %s\n", t->id, t->value);
        }
}

int
main(void)
{
        struct tag *tags = NULL;
        size_t ntags;

        populate(&tags, &ntags);
        process(tags, ntags);

        free(tags);

        return 0;
}