private void fillBuf() throws IOException {
    int result = in.read(buf, 0, buf.length);
    if (result == -1) {
      throw new EOFException();
    }
    pos = 0;
    end = result;
  }
Reads new input data into the buffer. Call only with pos == end or end == -1,
depending on the desired outcome if the function throws.
core/src/main/java/com/bumptech/glide/disklrucache/StrictLineReader.java