/*
 *  call-seq:
 *     thr.keys   => array
 *
 *  Returns an an array of the names of the thread-local variables (as Symbols).
 *
 *     thr = Thread.new do
 *       Thread.current[:cat] = 'meow'
 *       Thread.current["dog"] = 'woof'
 *     end
 *     thr.join   #=> #<Thread:0x401b3f10 dead>
 *     thr.keys   #=> [:dog, :cat]
 */

static VALUE
rb_thread_keys(VALUE self)
{
    rb_thread_t *th;
    VALUE ary = rb_ary_new();
    GetThreadPtr(self, th);

    if (th->local_storage) {
        st_foreach(th->local_storage, thread_keys_i, ary);
    }
    return ary;
}