source: josm/src/org/openstreetmap/josm/io/ProgressInputStream.java@ 153

package org.openstreetmap.josm.io;

import java.io.IOException;
import java.io.InputStream;
import java.net.URLConnection;

import org.openstreetmap.josm.Main;

/**
 * Read from an other reader and increment an progress counter while on the way.
 * @author Imi
 */
public class ProgressInputStream extends InputStream {

        private final InputStream in;
        private int readSoFar = 0;
        private int lastDialogUpdate = 0;
        private final URLConnection connection;

        public ProgressInputStream(URLConnection con) throws IOException {
                this.connection = con;
                this.in = con.getInputStream();
                int contentLength = con.getContentLength();
                if (contentLength > 0)
                        Main.pleaseWaitDlg.progress.setMaximum(contentLength);
                else
                        Main.pleaseWaitDlg.progress.setMaximum(0);
                Main.pleaseWaitDlg.progress.setValue(0);
        }

        @Override public void close() throws IOException {
                in.close();
        }

        @Override public int read(byte[] b, int off, int len) throws IOException {
                int read = in.read(b, off, len);
                if (read != -1)
                        advanceTicker(read);
                return read;
        }

        @Override public int read() throws IOException {
                int read = in.read();
                if (read != -1)
                        advanceTicker(1);
                return read;
        }

        /**
         * Increase ticker (progress counter and displayed text) by the given amount.
         * @param amount
         */
        private void advanceTicker(int amount) {
                if (Main.pleaseWaitDlg.progress.getMaximum() == 0 && connection.getContentLength() != -1)
                        Main.pleaseWaitDlg.progress.setMaximum(connection.getContentLength());

                readSoFar += amount;

                if (readSoFar / 1024 != lastDialogUpdate) {
                        lastDialogUpdate++;
                        String progStr = " "+readSoFar/1024+"/";
                        progStr += (Main.pleaseWaitDlg.progress.getMaximum()==0) ? "??? KB" : (Main.pleaseWaitDlg.progress.getMaximum()/1024)+" KB";
                        Main.pleaseWaitDlg.progress.setValue(readSoFar);

                        String cur = Main.pleaseWaitDlg.currentAction.getText();
                        int i = cur.indexOf(' ');
                        if (i != -1)
                                cur = cur.substring(0, i) + progStr;
                        else
                                cur += progStr;
                        Main.pleaseWaitDlg.currentAction.setText(cur);
                }
        }
}