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  /*
   * 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.commons.net.ftp;
 
 import java.util.List;
 
 import  org.apache.commons.net.util.Charsets;


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 1414510 2012-11-28 02:40:39Z ggregory $
 
 public class FTPListParseEngine {
     private List<Stringentries = new LinkedList<String>();
 
     private final FTPFileEntryParser parser;
 
     public FTPListParseEngine(FTPFileEntryParser parser) {
         this. = parser;
     }

    
handle the initial 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.

Parameters:
stream input stream provided by the server socket.
encoding the encoding to be used for reading the stream
Throws:
IOException thrown on any failure to read from the sever.
 
    public void readServerList(InputStream streamString encoding)
    throws IOException
    {
        this. = new LinkedList<String>();
        readStream(streamencoding);
        this..preParse(this.);
        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.

Parameters:
stream The socket stream on which the input will be read.
encoding The encoding to use.
Throws:
IOException thrown on any failure to read the stream
    private void readStream(InputStream streamString encodingthrows IOException
    {
        BufferedReader reader = new BufferedReader(
                new InputStreamReader(stream, Charsets.toCharset(encoding)));
        String line = this..readNextEntry(reader);
        while (line != null)
        {
            this..add(line);
            line = this..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.

Parameters:
quantityRequested the maximum number of entries we want to get.
Returns:
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.

NOTE: This array may contain null members if any of the individual file listings failed to parse. The caller should check each entry for null before referencing it.

    public FTPFile[] getNext(int quantityRequested) {
        List<FTPFiletmpResults = new LinkedList<FTPFile>();
        int count = quantityRequested;
        while (count > 0 && this..hasNext()) {
            String entry = this..next();
            FTPFile temp = this..parseFTPEntry(entry);
            tmpResults.add(temp);
            count--;
        }
        return tmpResults.toArray(new FTPFile[tmpResults.size()]);
    }

    
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.

Parameters:
quantityRequested the maximum number of entries we want to get.
Returns:
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).

NOTE: This array may contain null members if any of the individual file listings failed to parse. The caller should check each entry for null before referencing it.

    public FTPFile[] getPrevious(int quantityRequested) {
        List<FTPFiletmpResults = new LinkedList<FTPFile>();
        int count = quantityRequested;
        while (count > 0 && this..hasPrevious()) {
            String entry = this..previous();
            FTPFile temp = this..parseFTPEntry(entry);
            tmpResults.add(0,temp);
            count--;
        }
        return tmpResults.toArray(new FTPFile[tmpResults.size()]);
    }

    
Returns an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser.

Returns:
an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser. None of the entries will be null
Throws:
IOException - not ever thrown, may be removed in a later release
    public FTPFile[] getFiles()
    throws IOException // TODO remove; not actually thrown
    {
        return getFiles(.);
    }

    
Returns an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser. The files are filtered before being added to the array.

Parameters:
filter FTPFileFilter, must not be null.
Returns:
an array of FTPFile objects containing the whole list of files returned by the server as read by this object's parser.

NOTE: This array may contain null members if any of the individual file listings failed to parse. The caller should check each entry for null before referencing it, or use the a filter such as FTPFileFilters.NON_NULL which does not allow null entries.

Throws:
IOException - not ever thrown, may be removed in a later release
Since:
2.2
    public FTPFile[] getFiles(FTPFileFilter filter)
    throws IOException // TODO remove; not actually thrown
    {
        List<FTPFiletmpResults = new ArrayList<FTPFile>();
        Iterator<Stringiter = this..iterator();
        while (iter.hasNext()) {
            String entry = iter.next();
            FTPFile temp = this..parseFTPEntry(entry);
            if (filter.accept(temp)){
                tmpResults.add(temp);
            }
        }
        return tmpResults.toArray(new FTPFile[tmpResults.size()]);
    }

    
convenience method to allow clients to know whether this object's internal iterator's current position is at the end of the list.

Returns:
true if internal iterator is not at end of list, false otherwise.
    public boolean hasNext() {
        return .hasNext();
    }

    
convenience method to allow clients to know whether this object's internal iterator's current position is at the beginning of the list.

Returns:
true if internal iterator is not at beginning of list, false otherwise.
    public boolean hasPrevious() {
        return .hasPrevious();
    }

    
resets this object's internal iterator to the beginning of the list.
    public void resetIterator() {
        this. = this..listIterator();
    }
    // DEPRECATED METHODS - for API compatibility only - DO NOT USE

    
Do not use.

Deprecated:
use readServerList(InputStream, String) instead
    @Deprecated
    public void readServerList(InputStream stream)
    throws IOException
    {
        readServerList(streamnull);
    }
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