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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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