cache_friendly.c

#include <stdint.h>
#include <glib.h>
#include <gmodule.h>

struct entity {
    int32_t value;          // 4 bytes
    char name[12];      // 12 bytes
};


struct manager {
    char            name[256];
    GArray          *entities;
};


void manager_entity_add (struct manager *manager, struct entity entity);


void
manager_entity_add (struct manager *self, struct entity entity)
{
    g_array_append_val(self->entities, entity);
}


int main(int argc, char *argv[])
{

    struct manager *mgr = malloc(sizeof *mgr);
    g_strlcpy(mgr->name, "MANAGER", 256);

    mgr->entities = g_array_sized_new(TRUE, TRUE, sizeof(struct entity), 512);

    // Method 1: Anonymous struct
    manager_entity_add(mgr, (struct entity){ .name = "name1", .value = 42});

    // Method 2: Stack struct
    struct entity t2;
    g_strlcpy(t2.name, "name2", sizeof(t2.name));
    t2.value = 23;
    manager_entity_add(mgr, t2);

    // Method 3: Heap struct
    struct entity *t3 = malloc(sizeof *t3);
    g_strlcpy(t3->name, "name3", sizeof(t3->name));
    t3->value = 1;
    manager_entity_add(mgr, *t3);

    // Print entities
    g_print("# entities: %d\n", mgr->entities->len);
    struct entity *t;
    for(size_t i=0; i< mgr->entities->len; i++)
    {
        t = &g_array_index((mgr->entities), struct entity, i);
        g_print("Object %s @ %p\n", t->name, (void*)&(*t));
    }

    free(t3);
    g_array_free(mgr->entities, TRUE);
    free(mgr);
    return EXIT_SUCCESS;
}