src/main/org/apache/tools/ant/util/LazyFileOutputStream.java

/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "Ant" and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.tools.ant.util;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Class that delays opening the output file until the first bytes
 * shall be written or the method {@link #open open} has been invoked
 * explicitly.
 *
 * @since Ant 1.6
 */
public class LazyFileOutputStream extends OutputStream {

    private FileOutputStream fos;
    private File file;
    private boolean append;
    private boolean opened = false;
    private boolean closed = false;

    /**
     * Creates a stream that will eventually write to the file with
     * the given name and replace it.
     */
    public LazyFileOutputStream(String name) {
        this(name, false);
    }

    /**
     * Creates a stream that will eventually write to the file with
     * the given name and optionally append to instead of replacing
     * it.
     */
    public LazyFileOutputStream(String name, boolean append) {
        this(new File(name), append);
    }

    /**
     * Creates a stream that will eventually write to the file with
     * the given name and replace it.
     */
    public LazyFileOutputStream(File f) {
        this(f, false);
    }

    /**
     * Creates a stream that will eventually write to the file with
     * the given name and optionally append to instead of replacing
     * it.
     */
    public LazyFileOutputStream(File file, boolean append) {
        this.file = file;
        this.append = append;
    }

    /**
     * Explicitly open the file for writing.
     *
     * <p>Returns silently if the file has already been opened.</p>
     */
    public void open() throws IOException {
        ensureOpened();
    }

    public synchronized void close() throws IOException {
        if (opened) {
            fos.close();
        }
        closed = true;
    }

    /**
     * Delegates to the three arg version.
     */
    public void write(byte[] b) throws IOException {
        write(b, 0, b.length);
    }

    public synchronized void write(byte[] b, int offset, int len) 
        throws IOException {
        ensureOpened();
        fos.write(b, offset, len);
    }

    public synchronized void write(int b) throws IOException {
        ensureOpened();
        fos.write(b);
    }

    private synchronized void ensureOpened() throws IOException {
        if (closed) {
            throw new IOException(file + " has already been closed.");
        }

        if (!opened) {
            fos = new FileOutputStream(file.getAbsolutePath(), append);
            opened = true;
        }
    }
}