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Diffstat (limited to 'framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/filters/TailFilter.java')
| -rw-r--r-- | framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/filters/TailFilter.java | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/filters/TailFilter.java b/framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/filters/TailFilter.java new file mode 100644 index 00000000..fcc84d16 --- /dev/null +++ b/framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/filters/TailFilter.java @@ -0,0 +1,243 @@ +/* + * 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<String> lineList = new LinkedList<String>(); + + /** + * 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 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 lineList.removeFirst(); + } + return null; + } +} |