001 /*
002 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
003 *
004 * Copyright (c) 1997-2010 Oracle and/or its affiliates. All rights reserved.
005 *
006 * The contents of this file are subject to the terms of either the GNU
007 * General Public License Version 2 only ("GPL") or the Common Development
008 * and Distribution License("CDDL") (collectively, the "License"). You
009 * may not use this file except in compliance with the License. You can
010 * obtain a copy of the License at
011 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
012 * or packager/legal/LICENSE.txt. See the License for the specific
013 * language governing permissions and limitations under the License.
014 *
015 * When distributing the software, include this License Header Notice in each
016 * file and include the License file at packager/legal/LICENSE.txt.
017 *
018 * GPL Classpath Exception:
019 * Oracle designates this particular file as subject to the "Classpath"
020 * exception as provided by Oracle in the GPL Version 2 section of the License
021 * file that accompanied this code.
022 *
023 * Modifications:
024 * If applicable, add the following below the License Header, with the fields
025 * enclosed by brackets [] replaced by your own identifying information:
026 * "Portions Copyright [year] [name of copyright owner]"
027 *
028 * Contributor(s):
029 * If you wish your version of this file to be governed by only the CDDL or
030 * only the GPL Version 2, indicate your decision by adding "[Contributor]
031 * elects to include this software in this distribution under the [CDDL or GPL
032 * Version 2] license." If you don't indicate a single choice of license, a
033 * recipient has the option to distribute your version of this file under
034 * either the CDDL, the GPL Version 2 or to extend the choice of license to
035 * its licensees as provided above. However, if you add GPL Version 2 code
036 * and therefore, elected the GPL Version 2 license, then the option applies
037 * only if the new code is made subject to such option by the copyright
038 * holder.
039 */
040
041 package com.sun.enterprise.admin.cli;
042
043 import java.io.BufferedReader;
044 import java.io.BufferedWriter;
045 import java.io.IOException;
046 import java.io.Reader;
047 import java.io.Writer;
048
049 /**
050 * Pager.java
051 *
052 * @author <a href="mailto:toby.h.ferguson@sun.com">Toby H Ferguson</a>
053 */
054
055 class Pager {
056 private BufferedReader in;
057 private BufferedWriter out;
058 private int pageLength;
059 private String line;
060
061 /**
062 * Construct an object which will copy one pages worth of lines
063 * at a time from the input to the
064 * the output.
065 *
066 * No attempt is made under any circumstances to close the input
067 * or output.
068 *
069 * @param lines the number of lines in a page. A number less
070 * than 0 means copy all the input to the output.
071 * @param in the source of the copy operation
072 * @param out the destination of the copy operation
073 * @throws IOException if there's a problem reading from, or
074 * writing to, the source or destination
075 */
076 Pager(int lines, Reader in, Writer out) throws IOException {
077 this.in = new BufferedReader(in);
078 this.out = new BufferedWriter(out);
079 pageLength = lines;
080 nextLine();
081 }
082
083 /**
084 * Copy the next page worth of lines from input to output
085 */
086 void nextPage() throws IOException {
087 for (int i = 0; (pageLength < 0 || i < pageLength) && hasNext(); i++) {
088 out.write(line);
089 out.newLine();
090 nextLine();
091 }
092 out.flush();
093 }
094
095 /**
096 * Indicate if there are lines left to be copied
097 * @return true iff there is at least one line left to be copied
098 */
099 boolean hasNext() {
100 return line != null;
101 }
102
103 /**
104 * Get the next line and copy it inot the internal buffer so's
105 * we can answer the hasNext() question
106 */
107 private void nextLine() throws IOException {
108 line = in.readLine();
109 }
110 }