/* call-seq: db.collation(name, comparator)
 *
 * Add a collation with name +name+, and a +comparator+ object.  The
 * +comparator+ object should implement a method called "compare" that takes
 * two parameters and returns an integer less than, equal to, or greater than
 * 0.
 */
static VALUE collation(VALUE self, VALUE name, VALUE comparator)
{
  sqlite3RubyPtr ctx;
  Data_Get_Struct(self, sqlite3Ruby, ctx);
  REQUIRE_OPEN_DB(ctx);

  CHECK(ctx->db, sqlite3_create_collation_v2(
        ctx->db,
        StringValuePtr(name),
        SQLITE_UTF8,
        (void *)comparator,
        NIL_P(comparator) ? NULL : rb_comparator_func,
        NULL));

  /* Make sure our comparator doesn't get garbage collected. */
  rb_hash_aset(rb_iv_get(self, "@collations"), name, comparator);

  return self;
}