sclass JE_RepByte implements I_JECompressor {
  public S compress(byte[] data) {
    if (empty(data)) null;
    byte b = data[0];
    int n = data.length;
    for (int i = 1; i < n; i++)
      if (data[i] != b)
        null;
    ret formatFunctionCall repByte(n, b);
  }
}