printstream.java

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/*
 * @(#)PrintStream.java	1.29 06/10/13
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program 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.   
 *   
 * This program 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 at /legal/license.txt).   
 *   
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.io;


/**
 * A <code>PrintStream</code> adds functionality to another output stream,
 * namely the ability to print representations of various data values
 * conveniently.  Two other features are provided as well.  Unlike other output
 * streams, a <code>PrintStream</code> never throws an
 * <code>IOException</code>; instead, exceptional situations merely set an
 * internal flag that can be tested via the <code>checkError</code> method.
 * Optionally, a <code>PrintStream</code> can be created so as to flush
 * automatically; this means that the <code>flush</code> method is
 * automatically invoked after a byte array is written, one of the
 * <code>println</code> methods is invoked, or a newline character or byte
 * (<code>'\n'</code>) is written.
 *
 * <p> All characters printed by a <code>PrintStream</code> are converted into
 * bytes using the platform's default character encoding.  The <code>{@link
 * PrintWriter}</code> class should be used in situations that require writing
 * characters rather than bytes.
 *
 * @version    1.21, 00/02/02
 * @author     Mark Reinhold
 * @since      JDK1.0
 */

public class PrintStream extends FilterOutputStream {

    private boolean autoFlush = false;
    private boolean trouble = false;

    /**
     * Track both the text- and character-output streams, so that their buffers
     * can be flushed without flushing the entire stream.
     */
    private BufferedWriter textOut;
    private OutputStreamWriter charOut;

    /**
     * Create a new print stream.  This stream will not flush automatically.
     *
     * @param  out        The output stream to which values and objects will be
     *                    printed
     *
     * @see java.io.PrintWriter#PrintWriter(java.io.OutputStream)
     */
    public PrintStream(OutputStream out) {
	this(out, false);
    }

    /* Initialization is factored into a private constructor (note the swapped
     * parameters so that this one isn't confused with the public one) and a
     * separate init method so that the following two public constructors can
     * share code.  We use a separate init method so that the constructor that
     * takes an encoding will throw an NPE for a null stream before it throws
     * an UnsupportedEncodingException for an unsupported encoding.
     */

    private PrintStream(boolean autoFlush, OutputStream out)
    {
	super(out);
	if (out == null)
	    throw new NullPointerException("Null output stream");
	this.autoFlush = autoFlush;
    }

    private void init(OutputStreamWriter osw) {
	this.charOut = osw;
	this.textOut = new BufferedWriter(osw);
    }

    /**
     * Create a new print stream.
     *
     * @param  out        The output stream to which values and objects will be
     *                    printed
     * @param  autoFlush  A boolean; if true, the output buffer will be flushed
     *                    whenever a byte array is written, one of the
     *                    <code>println</code> methods is invoked, or a newline
     *                    character or byte (<code>'\n'</code>) is written
     *
     * @see java.io.PrintWriter#PrintWriter(java.io.OutputStream, boolean)
     */
    public PrintStream(OutputStream out, boolean autoFlush) {
	this(autoFlush, out);
	init(new OutputStreamWriter(this));
    }

    /**
     * Create a new print stream.
     *
     * @param  out        The output stream to which values and objects will be
     *                    printed
     * @param  autoFlush  A boolean; if true, the output buffer will be flushed
     *                    whenever a byte array is written, one of the
     *                    <code>println</code> methods is invoked, or a newline
     *                    character or byte (<code>'\n'</code>) is written
     * @param  encoding   The name of a supported
     *                    <a href="../lang/package-summary.html#charenc">
     *                    character encoding</a>
     *
     * @exception  UnsupportedEncodingException
     *             If the named encoding is not supported
     */
    public PrintStream(OutputStream out, boolean autoFlush, String encoding)
        throws UnsupportedEncodingException
    {
	this(autoFlush, out);
	init(new OutputStreamWriter(this, encoding));
    }

    /** Check to make sure that the stream has not been closed */
    private void ensureOpen() throws IOException {
	if (out == null)
	    throw new IOException("Stream closed");
    }

    /**
     * Flush the stream.  This is done by writing any buffered output bytes to
     * the underlying output stream and then flushing that stream.
     *
     * @see        java.io.OutputStream#flush()
     */
    public void flush() {
	synchronized (this) {
	    try {
		ensureOpen();
		out.flush();
	    }
	    catch (IOException x) {
		trouble = true;
	    }
	}
    }

    private boolean closing = false; /* To avoid recursive closing */

    /**
     * Close the stream.  This is done by flushing the stream and then closing
     * the underlying output stream.
     *
     * @see        java.io.OutputStream#close()
     */
    public void close() {
	synchronized (this) {
	    if (! closing) {
		closing = true;
		try {
		    textOut.close();
		    out.close();
		}
		catch (IOException x) {
		    trouble = true;
		}
		textOut = null;
		charOut = null;
		out = null;
	    }
	}
    }

    /**
     * Flush the stream and check its error state.  The internal error state
     * is set to <code>true</code> when the underlying output stream throws an
     * <code>IOException</code> other than <code>InterruptedIOException</code>,
     * and when the <code>setError</code> method is invoked.  If an operation
     * on the underlying output stream throws an
     * <code>InterruptedIOException</code>, then the <code>PrintStream</code>
     * converts the exception back into an interrupt by doing:
     * <pre>
     *     Thread.currentThread().interrupt();
     * </pre>
     * or the equivalent.
     *
     * @return True if and only if this stream has encountered an
     *         <code>IOException</code> other than
     *         <code>InterruptedIOException</code>, or the
     *         <code>setError</code> method has been invoked
     */
    public boolean checkError() {
	if (out != null)
	    flush();
	return trouble;
    }

    /**
     * Set the error state of the stream to <code>true</code>.
     *
     * @since JDK1.1
     */
    protected void setError() {
	trouble = true;
    }


    /*
     * Exception-catching, synchronized output operations,
     * which also implement the write() methods of OutputStream
     */

    /**
     * Write the specified byte to this stream.  If the byte is a newline and
     * automatic flushing is enabled then the <code>flush</code> method will be
     * invoked.
     *
     * <p> Note that the byte is written as given; to write a character that
     * will be translated according to the platform's default character
     * encoding, use the <code>print(char)</code> or <code>println(char)</code>
     * methods.
     *
     * @param  b  The byte to be written
     * @see #print(char)
     * @see #println(char)
     */
    public void write(int b) {
	try {
	    synchronized (this) {
		ensureOpen();
		out.write(b);
		if ((b == '\n') && autoFlush)
		    out.flush();
	    }
	}
	catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	}
	catch (IOException x) {
	    trouble = true;
	}
    }

    /**
     * Write <code>len</code> bytes from the specified byte array starting at
     * offset <code>off</code> to this stream.  If automatic flushing is
     * enabled then the <code>flush</code> method will be invoked.
     *
     * <p> Note that the bytes will be written as given; to write characters
     * that will be translated according to the platform's default character
     * encoding, use the <code>print(char)</code> or <code>println(char)</code>
     * methods.
     *
     * @param  buf   A byte array
     * @param  off   Offset from which to start taking bytes
     * @param  len   Number of bytes to write
     */
    public void write(byte buf[], int off, int len) {
	try {
	    synchronized (this) {
		ensureOpen();
		out.write(buf, off, len);
		if (autoFlush)
		    out.flush();
	    }
	}
	catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	}
	catch (IOException x) {
	    trouble = true;
	}
    }

    /*
     * The following private methods on the text- and character-output streams
     * always flush the stream buffers, so that writes to the underlying byte
     * stream occur as promptly as with the original PrintStream.
     */

    private void write(char buf[]) {
	try {
	    synchronized (this) {
		ensureOpen();
		textOut.write(buf);
		textOut.flushBuffer();
		charOut.flushBuffer();
		if (autoFlush) {
		    for (int i = 0; i < buf.length; i++)
			if (buf[i] == '\n')
			    out.flush();
		}
	    }
	}
	catch (InterruptedIOException x) {
	    Thread.currentThread().interrupt();
	}