/* call-seq: define_function(name) { |args,...| }
 *
 * Define a function named +name+ with +args+.  The arity of the block
 * will be used as the arity for the function defined.
 */
static VALUE define_function(VALUE self, VALUE name)
{
  sqlite3RubyPtr ctx;
  VALUE block;
  int status;

  Data_Get_Struct(self, sqlite3Ruby, ctx);
  REQUIRE_OPEN_DB(ctx);

  block = rb_block_proc();

  status = sqlite3_create_function(
    ctx->db,
    StringValuePtr(name),
    rb_proc_arity(block),
    SQLITE_UTF8,
    (void *)block,
    rb_sqlite3_func,
    NULL,
    NULL
  );

  CHECK(ctx->db, status);

  rb_hash_aset(rb_iv_get(self, "@functions"), name, block);

  return self;
}