| /* |
| * The Apache Software License, Version 1.1 |
| * |
| * Copyright (c) 2002 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 "The Jakarta Project", "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.filters; |
| |
| import java.io.IOException; |
| import java.io.Reader; |
| |
| import org.apache.tools.ant.types.Parameter; |
| |
| /** |
| * Reads the first <code>n</code> lines of a stream. |
| * (Default is first 10 lines.) |
| * <p> |
| * Example: |
| * <pre><headfilter lines="3"/></pre> |
| * Or: |
| * <pre><filterreader classname="org.apache.tools.ant.filters.HeadFilter"> |
| * <param name="lines" value="3"/> |
| * </filterreader></pre> |
| * |
| * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a> |
| */ |
| public final class HeadFilter |
| extends BaseParamFilterReader |
| implements ChainableReader { |
| /** Parameter name for the number of lines to be returned. */ |
| private static final String LINES_KEY = "lines"; |
| |
| /** Number of lines currently read in. */ |
| private long linesRead = 0; |
| |
| /** Number of lines to be returned in the filtered stream. */ |
| private long lines = 10; |
| |
| /** |
| * Constructor for "dummy" instances. |
| * |
| * @see BaseFilterReader#BaseFilterReader() |
| */ |
| public HeadFilter() { |
| super(); |
| } |
| |
| /** |
| * Creates a new filtered reader. |
| * |
| * @param in A Reader object providing the underlying stream. |
| * Must not be <code>null</code>. |
| */ |
| public HeadFilter(final Reader in) { |
| super(in); |
| } |
| |
| /** |
| * Returns the next character in the filtered stream. If the desired |
| * number of lines have already been read, the resulting stream is |
| * effectively at an end. Otherwise, the next character from the |
| * underlying stream is read and returned. |
| * |
| * @return the next character in the resulting stream, or -1 |
| * if the end of the resulting stream has been reached |
| * |
| * @exception IOException if the underlying stream throws an IOException |
| * during reading |
| */ |
| public final int read() throws IOException { |
| if (!getInitialized()) { |
| initialize(); |
| setInitialized(true); |
| } |
| |
| int ch = -1; |
| |
| if (linesRead < lines) { |
| |
| ch = in.read(); |
| |
| if (ch == '\n') { |
| linesRead++; |
| } |
| } |
| |
| return ch; |
| } |
| |
| /** |
| * Sets the number of lines to be returned in the filtered stream. |
| * |
| * @param lines the number of lines to be returned in the filtered stream |
| */ |
| public final void setLines(final long lines) { |
| this.lines = lines; |
| } |
| |
| /** |
| * Returns the number of lines to be returned in the filtered stream. |
| * |
| * @return the number of lines to be returned in the filtered stream |
| */ |
| private final long getLines() { |
| return lines; |
| } |
| |
| /** |
| * Creates a new HeadFilter using the passed in |
| * Reader for instantiation. |
| * |
| * @param rdr A Reader object providing the underlying stream. |
| * Must not be <code>null</code>. |
| * |
| * @return a new filter based on this configuration, but filtering |
| * the specified reader |
| */ |
| public final Reader chain(final Reader rdr) { |
| HeadFilter newFilter = new HeadFilter(rdr); |
| newFilter.setLines(getLines()); |
| newFilter.setInitialized(true); |
| return newFilter; |
| } |
| |
| /** |
| * Scans the parameters list for the "lines" parameter and uses |
| * it to set the number of lines to be returned in the filtered stream. |
| */ |
| private final void initialize() { |
| Parameter[] params = getParameters(); |
| if (params != null) { |
| for (int i = 0; i < params.length; i++) { |
| if (LINES_KEY.equals(params[i].getName())) { |
| lines = new Long(params[i].getValue()).longValue(); |
| break; |
| } |
| } |
| } |
| } |
| } |