yacy_search_server/source/de/anomic/kelondro/kelondroBLOBArray.java

// kelondroBLOBArray.java
// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 19.08.2008 on http://yacy.net
//
// This is a part of YaCy, a peer-to-peer based web search engine
//
// $LastChangedDate: 2006-04-02 22:40:07 +0200 (So, 02 Apr 2006) $
// $LastChangedRevision: 1986 $
// $LastChangedBy: orbiter $
//
// LICENSE
// 
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package de.anomic.kelondro;

import java.io.File;
import java.io.IOException;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.TreeMap;
import java.util.concurrent.CopyOnWriteArrayList;

import de.anomic.server.serverDate;

public class kelondroBLOBArray implements kelondroBLOB {

    /*
     * This class implements a BLOB using a set of kelondroBLOBHeap objects
     * In addition to a kelondroBLOBHeap this BLOB can delete large amounts of data using a given time limit.
     * This is realized by creating separate BLOB files. New Files are created when either
     * - a given time limit is reached
     * - a given space limit is reached
     * To organize such an array of BLOB files, the following file name structure is used:
     * <BLOB-Name>/<YYYYMMDDhhmm>.blob
     * That means all BLOB files are inside a directory that has the name of the BLOBArray.
     * To delete content that is out-dated, one special method is implemented that deletes content by a given
     * time-out. Deletions are not made automatically, they must be triggered using this method.
     */
    
    private int keylength;
    private kelondroByteOrder ordering;
    private File heapLocation;
    private long maxage;
    private long maxsize;
    private List<blobItem> blobs;
    
    public kelondroBLOBArray(
            final File heapLocation,
            final int keylength, final kelondroByteOrder ordering,
            long maxage, long maxsize
            ) throws IOException {
        this.keylength = keylength;
        this.ordering = ordering;
        this.heapLocation = heapLocation;
        this.maxage = maxage;
        this.maxsize = maxsize;

        // check existence of the heap directory
        if (heapLocation.exists()) {
            if (!heapLocation.isDirectory()) throw new IOException("the BLOBArray directory " + heapLocation.toString() + " does not exist (is blocked by a file with same name)");
        } else {
            if(!heapLocation.mkdirs()) throw new IOException("the BLOBArray directory " + heapLocation.toString() + " does not exist (can not be created)");
        }

        // register all blob files inside this directory
        String[] files = heapLocation.list();
        Date d;
        TreeMap<Long, blobItem> sortedItems = new TreeMap<Long, blobItem>();
        kelondroBLOB oneBlob;
        File f;
        for (int i = 0; i < files.length; i++) {
            if (files[i].length() == 17 && files[i].endsWith("blob")) {
               try {
                   d = serverDate.parseShortSecond(files[i].substring(0, 12));
               } catch (ParseException e) {continue;}
               f = new File(heapLocation, files[i]);
               oneBlob = new kelondroBLOBHeap(f, keylength, ordering);
               sortedItems.put(Long.valueOf(d.getTime()), new blobItem(d, f, oneBlob));
            }
        }
        
        // read the blob tree in a sorted way and write them into an array
        blobs = new CopyOnWriteArrayList<blobItem>();
        for (blobItem bi : sortedItems.values()) {
            blobs.add(bi);
        }
    }
    
    private class blobItem {
        Date creation;
        File location;
        kelondroBLOB blob;
        public blobItem(Date creation, File location, kelondroBLOB blob) {
            this.creation = creation;
            this.location = location;
            this.blob = blob;
        }
        public blobItem() throws IOException {
            // make a new blob file and assign it in this item
            this.creation = new Date();
            this.location = new File(heapLocation, serverDate.formatShortSecond(creation) + ".blob");
            this.blob = new kelondroBLOBHeap(location, keylength, ordering);;
        }
    }
    
    /**
     * ask for the length of the primary key
     * @return the length of the key
     */
    public int keylength() {
        return this.keylength;
    }
    
    /**
     * clears the content of the database
     * @throws IOException
     */
    public void clear() throws IOException {
        for (blobItem bi: blobs) bi.blob.clear();
        blobs.clear();
    }
    
    /**
     * ask for the number of entries
     * @return the number of entries in the table
     */
    public int size() {
        int s = 0;
        for (blobItem bi: blobs) s += bi.blob.size();
        return s;
    }
    
    /**
     * iterator over all keys
     * @param up
     * @param rotating
     * @return
     * @throws IOException
     */
    public kelondroCloneableIterator<byte[]> keys(boolean up, boolean rotating) throws IOException {
        assert rotating = false;
        final List<kelondroCloneableIterator<byte[]>> c = new ArrayList<kelondroCloneableIterator<byte[]>>(blobs.size());
        final Iterator<blobItem> i = blobs.iterator();
        while (i.hasNext()) {
            c.add(i.next().blob.keys(up, rotating));
        }
        return kelondroMergeIterator.cascade(c, this.ordering, kelondroMergeIterator.simpleMerge, up);
    }
    
    /**
     * iterate over all keys
     * @param up
     * @param firstKey
     * @return
     * @throws IOException
     */
    public kelondroCloneableIterator<byte[]> keys(boolean up, byte[] firstKey) throws IOException {
        final List<kelondroCloneableIterator<byte[]>> c = new ArrayList<kelondroCloneableIterator<byte[]>>(blobs.size());
        final Iterator<blobItem> i = blobs.iterator();
        while (i.hasNext()) {
            c.add(i.next().blob.keys(up, firstKey));
        }
        return kelondroMergeIterator.cascade(c, this.ordering, kelondroMergeIterator.simpleMerge, up);
    }
    
    /**
     * check if a specific key is in the database
     * @param key  the primary key
     * @return
     * @throws IOException
     */
    public boolean has(byte[] key) throws IOException {
        for (blobItem bi: blobs) if (bi.blob.has(key)) return true;
        return false;
    }
    
    /**
     * retrieve the whole BLOB from the table
     * @param key  the primary key
     * @return
     * @throws IOException
     */
    public byte[] get(byte[] key) throws IOException {
        byte[] b;
        for (blobItem bi: blobs) {
            b = bi.blob.get(key);
            if (b != null) return b;
        }
        return null;
    }
    
    /**
     * write a whole byte array as BLOB to the table
     * @param key  the primary key
     * @param b
     * @throws IOException
     */
    public void put(byte[] key, byte[] b) throws IOException {
        blobItem bi = (blobs.size() == 0) ? null : blobs.get(blobs.size() - 1);
        if ((bi == null) || (bi.creation.getTime() - System.currentTimeMillis() > this.maxage) || (bi.location.length() > this.maxsize)) {
            // add a new blob to the array
            bi = new blobItem();
            blobs.add(bi);
        }
        bi.blob.put(key, b);
    }
    
    /**
     * remove a BLOB
     * @param key  the primary key
     * @throws IOException
     */
    public void remove(byte[] key) throws IOException {
        for (blobItem bi: blobs) bi.blob.remove(key);
    }
    
    /**
     * close the BLOB
     */
    public void close() {
        for (blobItem bi: blobs) bi.blob.close();
        blobs.clear();
        blobs = null;
    }
    
}