public int getStartxref() throws IOException {
int size = Math.min(1024, file.length());
int pos = file.length() - size;
file.seek(pos);
String str = readString(1024);
int idx = str.lastIndexOf("startxref");
if (idx < 0) throw new IOException("PDF startxref not found.");
return pos + idx;
}
public int length() throws IOException {
return file.length();
}