- /*
- * Copyright 2002-2004 The Apache Software Foundation
- *
- * Licensed 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 org.apache.tools.ant.util.LineTokenizer;
- 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>
- *
- */
- 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";
-
- /** Parameter name for the number of lines to be skipped. */
- private static final String SKIP_KEY = "skip";
-
- /** Number of lines currently read in. */
- private long linesRead = 0;
-
- /** 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;
-
- /** 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;
-
- /**
- * 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);
- lineTokenizer = new LineTokenizer();
- lineTokenizer.setIncludeDelims(true);
- }
-
- /**
- * 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);
- }
-
- while (line == null || line.length() == 0) {
- line = lineTokenizer.getToken(in);
- if (line == null) {
- return -1;
- }
- line = headFilter(line);
- 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 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;
- }
-
- /**
- * 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 final 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 final long getSkip() {
- return skip;
- }
-
- /**
- * 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.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 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();
- continue;
- }
- if (SKIP_KEY.equals(params[i].getName())) {
- skip = new Long(params[i].getValue()).longValue();
- continue;
- }
- }
- }
- }
-
- /**
- * implements a head filter on the input stream
- */
- private String headFilter(String line) {
- linesRead++;
- if (skip > 0) {
- if ((linesRead - 1) < skip) {
- return null;
- }
- }
-
- if (lines > 0) {
- if (linesRead > (lines + skip)) {
- return null;
- }
- }
- return line;
- }
- }