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/*
 * Copyright 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.commons.net.ftp;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;


/**
 * This class handles the entire process of parsing a listing of
 * file entries from the server.
 * 

* This object defines a two-part parsing mechanism. *

* The first part is comprised of reading the raw input into an internal * list of strings. Every item in this list corresponds to an actual * file. All extraneous matter emitted by the server will have been * removed by the end of this phase. This is accomplished in conjunction * with the FTPFileEntryParser associated with this engine, by calling * its methods readNextEntry() - which handles the issue of * what delimits one entry from another, usually but not always a line * feed and preParse() - which handles removal of * extraneous matter such as the preliminary lines of a listing, removal * of duplicates on versioning systems, etc. *

* The second part is composed of the actual parsing, again in conjunction * with the particular parser used by this engine. This is controlled * by an iterator over the internal list of strings. This may be done * either in block mode, by calling the getNext() and * getPrevious() methods to provide "paged" output of less * than the whole list at one time, or by calling the * getFiles() method to return the entire list. *

* Examples: *

* Paged access: *

 *    FTPClient f=FTPClient();
 *    f.connect(server);
 *    f.login(username, password);
 *    FTPListParseEngine engine = f.initiateListParsing(directory);
 *
 *    while (engine.hasNext()) {
 *       FTPFile[] files = engine.getNext(25);  // "page size" you want
 *       //do whatever you want with these files, display them, etc.
 *       //expensive FTPFile objects not created until needed.
 *    }
 * 
*

* For unpaged access, simply use FTPClient.listFiles(). That method * uses this class transparently. * @version $Id: FTPListParseEngine.java,v 1.7 2004/04/22 00:48:07 scohen Exp $ */ public class FTPListParseEngine { private List entries = new LinkedList(); private ListIterator _internalIterator = entries.listIterator(); FTPFileEntryParser parser = null; public FTPListParseEngine(FTPFileEntryParser parser) { this.parser = parser; } /** * handle the iniitial reading and preparsing of the list returned by * the server. After this method has completed, this object will contain * a list of unparsed entries (Strings) each referring to a unique file * on the server. * * @param stream input stream provided by the server socket. * * @exception IOException * thrown on any failure to read from the sever. */ public void readServerList(InputStream stream) throws IOException { this.entries = new LinkedList(); readStream(stream); this.parser.preParse(this.entries); resetIterator(); } /** * Internal method for reading the input into the entries list. * After this method has completed, entries will contain a * collection of entries (as defined by * FTPFileEntryParser.readNextEntry()), but this may contain * various non-entry preliminary lines from the server output, duplicates, * and other data that will not be part of the final listing. * * @param stream The socket stream on which the input will be read. * * @exception IOException * thrown on any failure to read the stream */ private void readStream(InputStream stream) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(stream)); String line = this.parser.readNextEntry(reader); while (line != null) { this.entries.add(line); line = this.parser.readNextEntry(reader); } reader.close(); } /** * Returns an array of at most quantityRequested FTPFile * objects starting at this object's internal iterator's current position. * If fewer than quantityRequested such * elements are available, the returned array will have a length equal * to the number of entries at and after after the current position. * If no such entries are found, this array will have a length of 0. * * After this method is called this object's internal iterator is advanced * by a number of positions equal to the size of the array returned. * * @param quantityRequested * the maximum number of entries we want to get. * * @return an array of at most quantityRequested FTPFile * objects starting at the current position of this iterator within its * list and at least the number of elements which exist in the list at * and after its current position. */ public FTPFile[] getNext(int quantityRequested) { List tmpResults = new LinkedList(); int count = quantityRequested; while (count > 0 && this._internalIterator.hasNext()) { String entry = (String) this._internalIterator.next(); FTPFile temp = this.parser.parseFTPEntry(entry); tmpResults.add(temp); count--; } return (FTPFile[]) tmpResults.toArray(new FTPFile[0]); } /** * Returns an array of at most quantityRequested FTPFile * objects starting at this object's internal iterator's current position, * and working back toward the beginning. * * If fewer than quantityRequested such * elements are available, the returned array will have a length equal * to the number of entries at and after after the current position. * If no such entries are found, this array will have a length of 0. * * After this method is called this object's internal iterator is moved * back by a number of positions equal to the size of the array returned. * * @param quantityRequested * the maximum number of entries we want to get. * * @return an array of at most quantityRequested FTPFile * objects starting at the current position of this iterator within its * list and at least the number of elements which exist in the list at * and after its current position. This array will be in the same order * as the underlying list (not reversed). */ public FTPFile[] getPrevious(int quantityRequested) { List tmpResults = new LinkedList(); int count = quantityRequested; while (count > 0 && this._internalIterator.hasPrevious()) { String entry = (String) this._internalIterator.previous(); FTPFile temp = this.parser.parseFTPEntry(entry); tmpResults.add(0,temp); count--; } return (FTPFile[]) tmpResults.toArray(new FTPFile[0]); } /** * Returns an array of FTPFile objects containing the whole list of * files returned by the server as read by this object's parser. * * @return an array of FTPFile objects containing the whole list of * files returned by the server as read by this object's parser. * @exception IOException */ public FTPFile[] getFiles() throws IOException { List tmpResults = new LinkedList(); Iterator iter = this.entries.iterator(); while (iter.hasNext()) { String entry = (String) iter.next(); FTPFile temp = this.parser.parseFTPEntry(entry); tmpResults.add(temp); } return (FTPFile[]) tmpResults.toArray(new FTPFile[0]); } /** * convenience method to allow clients to know whether this object's * internal iterator's current position is at the end of the list. * * @return true if internal iterator is not at end of list, false * otherwise. */ public boolean hasNext() { return _internalIterator.hasNext(); } /** * convenience method to allow clients to know whether this object's * internal iterator's current position is at the beginning of the list. * * @return true if internal iterator is not at beginning of list, false * otherwise. */ public boolean hasPrevious() { return _internalIterator.hasPrevious(); } /** * resets this object's internal iterator to the beginning of the list. */ public void resetIterator() { this._internalIterator = this.entries.listIterator(); } }

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