Java example source code file (MeteredStream.java)

This example Java source code file (MeteredStream.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

chunkedinputstream, filterinputstream, http, ioexception, meteredstream, net, network, progresssource, resetting, throwable, util

The MeteredStream.java Java example source code

/*
 * Copyright (c) 1994, 2004, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.net.www;

import java.net.URL;
import java.util.*;
import java.io.*;
import sun.net.ProgressSource;
import sun.net.www.http.ChunkedInputStream;


public class MeteredStream extends FilterInputStream {

    // Instance variables.
    /* if expected != -1, after we've read >= expected, we're "closed" and return -1
     * from subsequest read() 's
     */
    protected boolean closed = false;
    protected long expected;
    protected long count = 0;
    protected long markedCount = 0;
    protected int markLimit = -1;
    protected ProgressSource pi;

    public MeteredStream(InputStream is, ProgressSource pi, long expected)
    {
        super(is);

        this.pi = pi;
        this.expected = expected;

        if (pi != null) {
            pi.updateProgress(0, expected);
        }
    }

    private final void justRead(long n) throws IOException   {
        if (n == -1) {

            /*
             * don't close automatically when mark is set and is valid;
             * cannot reset() after close()
             */
            if (!isMarked()) {
                close();
            }
            return;
        }

        count += n;

        /**
         * If read beyond the markLimit, invalidate the mark
         */
        if (count - markedCount > markLimit) {
            markLimit = -1;
        }

        if (pi != null)
            pi.updateProgress(count, expected);

        if (isMarked()) {
            return;
        }

        // if expected length is known, we could determine if
        // read overrun.
        if (expected > 0)   {
            if (count >= expected) {
                close();
            }
        }
    }

    /**
     * Returns true if the mark is valid, false otherwise
     */
    private boolean isMarked() {

        if (markLimit < 0) {
            return false;
        }

        // mark is set, but is not valid anymore
        if (count - markedCount > markLimit) {
           return false;
        }

        // mark still holds
        return true;
    }

    public synchronized int read() throws java.io.IOException {
        if (closed) {
            return -1;
        }
        int c = in.read();
        if (c != -1) {
            justRead(1);
        } else {
            justRead(c);
        }
        return c;
    }

    public synchronized int read(byte b[], int off, int len)
                throws java.io.IOException {
        if (closed) {
            return -1;
        }
        int n = in.read(b, off, len);
        justRead(n);
        return n;
    }

    public synchronized long skip(long n) throws IOException {

        // REMIND: what does skip do on EOF????
        if (closed) {
            return 0;
        }

        if (in instanceof ChunkedInputStream) {
            n = in.skip(n);
        }
        else {
            // just skip min(n, num_bytes_left)
            long min = (n > expected - count) ? expected - count: n;
            n = in.skip(min);
        }
        justRead(n);
        return n;
    }

    public void close() throws IOException {
        if (closed) {
            return;
        }
        if (pi != null)
            pi.finishTracking();

        closed = true;
        in.close();
    }

    public synchronized int available() throws IOException {
        return closed ? 0: in.available();
    }

    public synchronized void mark(int readLimit) {
        if (closed) {
            return;
        }
        super.mark(readLimit);

        /*
         * mark the count to restore upon reset
         */
        markedCount = count;
        markLimit = readLimit;
    }

    public synchronized void reset() throws IOException {
        if (closed) {
            return;
        }

        if (!isMarked()) {
            throw new IOException ("Resetting to an invalid mark");
        }

        count = markedCount;
        super.reset();
    }

    public boolean markSupported() {
        if (closed) {
            return false;
        }
        return super.markSupported();
    }

    protected void finalize() throws Throwable {
        try {
            close();
            if (pi != null)
                pi.close();
        }
        finally {
            // Call super class
            super.finalize();
        }
    }
}