PL/pgSQL function to convert a hexadecimal string to a bit varying

hex_to_bit_varying.sql

DROP FUNCTION IF EXISTS hex_to_bit_varying(hex_string text);
CREATE FUNCTION hex_to_bit_varying(hex_string text) RETURNS bit varying AS $$
DECLARE
  bytes bytea = decode(hex_string, 'hex');
  n int = length(bytes) * 8 - 1;
  bits bit varying := B''::bit varying;
BEGIN
  -- RAISE NOTICE 'bytes=%, n=%', bytes, n;
  -- RAISE NOTICE 'bits=%', bits;
  FOR i IN 0 .. n BY 8 LOOP
    FOR j IN REVERSE 7 .. 0 LOOP
      bits := bits || get_bit(bytes, i+j)::bit;
      -- RAISE NOTICE 'offset=% (i=%, j=%), b=%, bits=%', i+j, i, j, get_bit(bytes, i+j), bits;
    END LOOP;
  END LOOP;
  RETURN bits;
END;
$$ LANGUAGE plpgsql;