//-*-java-*-

FileCheck {
  (@
    private static Hashtable checksums;
    private Checksum ck;
    private File output, old;
    private PrintWriter out;
  @)

  /** Read in the checksum list from the file. */
  static void readChecksums(File file) (@
    try {
      checksums = (Hashtable)
	(new ObjectInputStream(new FileInputStream(file))).readObject();
    } catch (IOException e) {
      checksums = new Hashtable();
    } catch (ClassNotFoundException e) {
      throw new RuntimeException(e.toString());
    }
  @)
  /** Write the current checksum list to the file. */
  static void writeChecksums(File file) (@
    try {
      (new ObjectOutputStream(new FileOutputStream(file))).writeObject(checksums);
    } catch (IOException e) {
      throw new RuntimeException(e.toString());
    }
  @)

  /** Open the file */
  PrintWriter openOutputFile(File file) (@
    output = file;
    old = new File(output + "~");
    if (output.exists()) output.renameTo(old);
    try {
      ck = new Adler32();
      out = new PrintWriter
	(new CheckedOutputStream(new FileOutputStream(output), ck));
    } catch (IOException e) {
      throw new RuntimeException(e.toString());
    }
    return out;
  @)

  /** Close and flush the current output file.  If the file hasn't
      changed, move the old one back so the timestamp doesn't change. */
  void closeOutputFile() (@
    out.flush();
    out.close();
    Long oldck = (Long) checksums.get(output);
    //System.err.println(output + ": " + ck.getValue() + " " +
    //		       old + ": " + oldck);
    if (oldck != null && oldck.longValue() == ck.getValue() && old.exists()) {
      output.delete();	// not needed on Unix, but it is on Windows...
      old.renameTo(output);
    } else {
      checksums.put(output, new Long(ck.getValue()));
      old.delete();
    }
  @)

}