| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| package org.apache.tools.ant.filters; |
| |
| import java.io.IOException; |
| import java.io.Reader; |
| import java.util.LinkedList; |
| import org.apache.tools.ant.types.Parameter; |
| import org.apache.tools.ant.util.LineTokenizer; |
| |
| /** |
| * Reads the last <code>n</code> lines of a stream. (Default is last10 lines.) |
| * |
| * Example: |
| * |
| * <pre><tailfilter lines="3"/></pre> |
| * |
| * Or: |
| * |
| * <pre><filterreader classname="org.apache.tools.ant.filters.TailFilter"> |
| * <param name="lines" value="3"/> |
| * </filterreader></pre> |
| * |
| */ |
| public final class TailFilter extends BaseParamFilterReader |
| implements ChainableReader { |
| /** Parameter name for the number of lines to be returned. */ |
| private static final String LINES_KEY = "lines"; |
| |
| /** Parameter name for the number of lines to be skipped. */ |
| private static final String SKIP_KEY = "skip"; |
| |
| /** Default number of lines to show */ |
| private static final int DEFAULT_NUM_LINES = 10; |
| |
| /** Number of lines to be returned in the filtered stream. */ |
| private long lines = DEFAULT_NUM_LINES; |
| |
| /** Number of lines to be skipped. */ |
| private long skip = 0; |
| |
| /** Whether or not read-ahead been completed. */ |
| private boolean completedReadAhead = false; |
| |
| /** A line tokenizer */ |
| private LineTokenizer lineTokenizer = null; |
| |
| /** the current line from the input stream */ |
| private String line = null; |
| /** the position in the current line */ |
| private int linePos = 0; |
| |
| private LinkedList lineList = new LinkedList(); |
| |
| /** |
| * Constructor for "dummy" instances. |
| * |
| * @see BaseFilterReader#BaseFilterReader() |
| */ |
| public TailFilter() { |
| super(); |
| } |
| |
| /** |
| * Creates a new filtered reader. |
| * |
| * @param in A Reader object providing the underlying stream. |
| * Must not be <code>null</code>. |
| */ |
| public TailFilter(final Reader in) { |
| super(in); |
| lineTokenizer = new LineTokenizer(); |
| lineTokenizer.setIncludeDelims(true); |
| } |
| |
| /** |
| * Returns the next character in the filtered stream. If the read-ahead |
| * has been completed, the next character in the buffer is returned. |
| * Otherwise, the stream is read to the end and buffered (with the buffer |
| * growing as necessary), then the appropriate position in the buffer is |
| * set to read from. |
| * |
| * @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 int read() throws IOException { |
| if (!getInitialized()) { |
| initialize(); |
| setInitialized(true); |
| } |
| |
| while (line == null || line.length() == 0) { |
| line = lineTokenizer.getToken(in); |
| line = tailFilter(line); |
| if (line == null) { |
| return -1; |
| } |
| linePos = 0; |
| } |
| |
| int ch = line.charAt(linePos); |
| linePos++; |
| if (linePos == line.length()) { |
| line = null; |
| } |
| 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 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 long getLines() { |
| return lines; |
| } |
| |
| /** |
| * Sets the number of lines to be skipped in the filtered stream. |
| * |
| * @param skip the number of lines to be skipped in the filtered stream |
| */ |
| public void setSkip(final long skip) { |
| this.skip = skip; |
| } |
| |
| /** |
| * Returns the number of lines to be skipped in the filtered stream. |
| * |
| * @return the number of lines to be skipped in the filtered stream |
| */ |
| private long getSkip() { |
| return skip; |
| } |
| |
| /** |
| * Creates a new TailFilter 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 Reader chain(final Reader rdr) { |
| TailFilter newFilter = new TailFilter(rdr); |
| newFilter.setLines(getLines()); |
| newFilter.setSkip(getSkip()); |
| 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. |
| * also scan for "skip" parameter. |
| */ |
| private void initialize() { |
| Parameter[] params = getParameters(); |
| if (params != null) { |
| for (int i = 0; i < params.length; i++) { |
| if (LINES_KEY.equals(params[i].getName())) { |
| setLines(Long.parseLong(params[i].getValue())); |
| continue; |
| } |
| if (SKIP_KEY.equals(params[i].getName())) { |
| skip = Long.parseLong(params[i].getValue()); |
| continue; |
| } |
| } |
| } |
| } |
| |
| /** |
| * implement a tail filter on a stream of lines. |
| * line = null is the end of the stream. |
| * @return "" while reading in the lines, |
| * line while outputting the lines |
| * null at the end of outputting the lines |
| */ |
| private String tailFilter(String line) { |
| if (!completedReadAhead) { |
| if (line != null) { |
| lineList.add(line); |
| if (lines == -1) { |
| if (lineList.size() > skip) { |
| return (String) lineList.removeFirst(); |
| } |
| } else { |
| long linesToKeep = lines + (skip > 0 ? skip : 0); |
| if (linesToKeep < lineList.size()) { |
| lineList.removeFirst(); |
| } |
| } |
| return ""; |
| } |
| completedReadAhead = true; |
| if (skip > 0) { |
| for (int i = 0; i < skip; ++i) { |
| lineList.removeLast(); |
| } |
| } |
| if (lines > -1) { |
| while (lineList.size() > lines) { |
| lineList.removeFirst(); |
| } |
| } |
| } |
| if (lineList.size() > 0) { |
| return (String) lineList.removeFirst(); |
| } |
| return null; |
| } |
| } |