localnewsdb.java

java高级使用教程 全书一共分六章

// LocalNewsDb - local netnews database
//
// Copyright (C)1996,1998 by Jef Poskanzer <[e-mail]>. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme.Nnrpd;

import java.io.*;
import java.util.*;
import java.net.*;
import Acme.Utils;
import Acme.UnixUser;

/// Local netnews database.
// <P>
// This is a news database that uses the local filesystem.
// <P>
// <A HREF="/resources/classes/Acme/Nnrpd/LocalNewsDb.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>

public class LocalNewsDb extends NewsDb
    {

    // Typical places to look for local netnews files.

    private static final String SPOOLDIR_1 = "/usr/spool/news";
    private static final String SPOOLDIR_2 = "/var/spool/news";

    private static final String LIBDIR_1 = "/usr/lib/news";
    private static final String LIBDIR_USER_1 = "usenet";
    private static final String LIBDIR_USER_2 = "news";

    private static final String AUXLIBDIR_1 = "/var/news";

    /// The directory where articles live.
    private static String SPOOLDIR;

    /// The directory with most auxiliary files.
    private static String LIBDIR;

    /// The directory with the other auxiliary files.
    private static String AUXLIBDIR;

    /// The active file.
    private static File ACTIVE;

    /// The history file.
    private static File HISTORY;

    /// The active.times file, or null.
    private static File ACTIVE_TIMES;

    /// The distrib.pats file, or null.
    private static File DISTRIB_PATS;

    /// The distributions file, or null.
    private static File DISTRIBUTIONS;

    /// The newsgroups file, or null.
    private static File NEWSGROUPS;

    /// The nnrp.access file, or null.
    private static File NNRP_ACCESS;

    /// The overview.fmt file, or null.
    private static File OVERVIEW_FMT;

    private String[] overviewFmt = null;
    private OverviewCache overviewCache;

    // Group cache.
    private Hashtable groupTable = null;
    private long groupsFetched;
 
    // Group descriptions cache.
    private Hashtable groupDescsTable = null;
    private long groupDescsFetched;


    /// Constructor.
    // @param oCacheSize how many overview entries to save in the cach
    // @exception NewsDbException if something goes wrong
    public LocalNewsDb( int oCacheSize ) throws NewsDbException
	{
	initializePaths();

	// See if there's an overview database.
	if ( OVERVIEW_FMT != null )
	    {
	    try
		{
		BufferedReader br =
		    new BufferedReader( new FileReader( OVERVIEW_FMT ) );
		String[] lines = new String[100];
		int count = 0;
		while ( true )
		    {
		    String line = br.readLine();
		    if ( line == null )
			break;
		    line = line.trim();
		    if ( line.startsWith( "#" ) )
			continue;
		    if ( line.endsWith( ":" ) )
			line = line.substring( 0, line.length() - 1 );
		    lines[count++] = line;
		    }
		br.close();
		overviewFmt = new String[count];
		System.arraycopy( lines, 0, overviewFmt, 0, count );
		overviewCache = new OverviewCache( oCacheSize );
		}
	    catch ( IOException ignore ) {}
	    }
	}

    /// Attempt authorization.
    // @exception NewsDbException if something goes wrong
    public boolean authorize( String user, String password ) throws NewsDbException
	{
	// !!!
	throw new NewsDbException( "not implemented yet" );
	}

    /// Whether posting is allowed.
    // @exception NewsDbException if something goes wrong
    public boolean getPostingOk() throws NewsDbException
	{
	// !!!
	return true;
	}

    /// Get a group by name.
    // @exception NewsDbException if something goes wrong
    public NewsDbGroup getGroup( String groupName ) throws NewsDbException
	{
	// Check group cache.
	checkGroups();
	// And return results directly from the cache.  If it's not in
	// there, we don't have any place else to look.
	return (NewsDbGroup) groupTable.get( groupName );
	}

    /// Get an article by group and number.
    // @exception NewsDbException if something goes wrong
    public NewsDbArticle getArticle( NewsDbGroup group, int artNum ) throws NewsDbException
	{
	if ( group.getDbStamp() != dbStamp )
	    throw new NewsDbException( "mismatched database stamps" );
	return getArticleFromFile(
	    group.getName().replace( '.', '/' ) + "/" +
	    Integer.toString( artNum ) );
	}

    /// Get an article by message-id.
    // @exception NewsDbException if something goes wrong
    public NewsDbArticle getArticle( String messageId ) throws NewsDbException
	{
	// !!!
	throw new NewsDbException( "not implemented yet" );
	}

    /// Get an article by relative filename
    // @exception NewsDbException if something goes wrong
    private NewsDbArticle getArticleFromFile( String filename ) throws NewsDbException
	{
	filename = SPOOLDIR + "/" + filename;
	File file = new File( filename );
	if ( ! ( file.exists() && file.isFile() && file.canRead() ) )
	    return null;
	try
	    {
	    InputStream is = new FileInputStream( file );
	    byte[] bytes = new byte[(int) file.length()];
	    Utils.readFully( is, bytes, 0, bytes.length );
	    is.close();
	    return new NewsDbArticle( dbStamp, new String( bytes ) );
	    }
	catch ( IOException e )
	    {
	    throw new NewsDbException( "problem reading article: " + e );
	    }
	}

    // Remember the most recent names array that matched, so we can do
    // a quick address compare instead of a more expensive content compare.
    private String[] lastOkNames = null;

    /// Get specified headers from a range of articles by group and number.
    // Some implementations have special faster methods for getting
    // headers from articles, e.g. an XOVER command to a remote server
    // or a local overview database.  If no such fast method is available,
    // this returns null and the caller should fall back on conventional
    // means.
    // @exception NewsDbException if something goes wrong
    public String[][] getHeaders( String[] names, NewsDbGroup group, int firstArtNum, int lastArtNum ) throws NewsDbException
	{
	// Do we have an XOVER database?
	if ( overviewFmt == null )
	    return null;
	// Is the names list the same as overviewFmt?
	if ( names != lastOkNames )
	    {
	    if ( ! Utils.equalsStrings( names, overviewFmt ) )
		return null;
	    lastOkNames = names;
	    }
	// Check that this group is one of ours.
	if ( group.getDbStamp() != dbStamp )
	    throw new NewsDbException( "mismatched database stamps" );
	// Do we need to refresh overview data for this group?
	long now = System.currentTimeMillis();
	long time = overviewCache.getLastTime( group );
	if ( time == -1 || now - time >= NnrpdUtils.INT_CHECKOVERVIEW )
	    {
	    readOverview( group );
	    overviewCache.setLastTime( group );
	    }
	// Now just get articles from the cache.
	int numArts = lastArtNum - firstArtNum + 1;
	String[][] results = new String[numArts][];
	for ( int i = 0; i < numArts; ++i )
	    {
	    int artNum = firstArtNum + i;
	    results[i] = overviewCache.getEntry( group, artNum );
	    }
	return results;
	}

    private void readOverview( NewsDbGroup group ) throws NewsDbException
	{
	try
	    {