gistfile1.h

#define rb_jgParticleWrap(particle)                                     \
     Data_Wrap_Struct(c_jgParticle, NULL, NULL, (particle))

VALUE rb_jgAreaWrap(jgArea *area)
{
     VALUE wrappedArea = Data_Wrap_Struct(c_jgArea, NULL, NULL, area);
     
     VALUE *particles = malloc(area->particles->length * sizeof(VALUE));
     for(int i = 0; i < area->particles->length; i++)
          particles[i] = rb_jgParticleWrap(area->particles->arr[i]);

     VALUE particlesArray = rb_ary_new4(area->particles->length, particles);
     free(particles);

     rb_iv_set(wrappedArea, "particles", particlesArray);

     return wrappedArea;
}

VALUE rb_jgCollisionWrap(jgCollision *collision)
{     
     VALUE wrappedCollision = Data_Wrap_Struct(c_jgCollision, NULL, jgCollisionFree, collision);
     
     rb_iv_set(wrappedCollision, "particle",        rb_jgParticleWrap(collision->particle));
     rb_iv_set(wrappedCollision, "area",            rb_jgAreaWrap(collision->area));
     rb_iv_set(wrappedCollision, "area_particle_a", rb_jgParticleWrap(collision->areaParticleA));
     rb_iv_set(wrappedCollision, "area_particle_b", rb_jgParticleWrap(collision->areaParticleB));
     
     return wrappedCollision;
}

static VALUE rb_jgWorldCollisions(VALUE self)
{
     jgWorld *world = WORLD(self);

     VALUE *collisions = malloc(world->collisions->length * sizeof(VALUE));
     for(int i = 0; i < world->collisions->length; i++)
          collisions[i] = rb_jgCollisionWrap(world->collisions->arr[i]);

     return rb_ary_new4(world->collisions->length, collisions);
}

     rb_define_method(c_jgWorld, "collisions", rb_jgWorldCollisions, 0);