501 lines
18 KiB
Java
501 lines
18 KiB
Java
// Records.java
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// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
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// first published 14.01.2008 on http://yacy.net
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//
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// $LastChangedDate$
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// $LastChangedRevision$
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// $LastChangedBy$
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//
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// LICENSE
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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package net.yacy.kelondro.io;
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import java.io.File;
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import java.io.FileNotFoundException;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import net.yacy.cora.document.encoding.UTF8;
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import net.yacy.cora.util.ConcurrentLog;
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import net.yacy.kelondro.util.FileUtils;
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import net.yacy.kelondro.util.MemoryControl;
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/**
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* The Records data structure is a flat file with records of fixed length.
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* The file does not contain any meta information and the first record starts
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* right at file position 0.
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* The access rules are in such a way that a minimum of IO operations are necessary
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* Two caches provide a mirror to content in the file: a read cache and a write buffer
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* The read cache contains a number of entries from the file; a mirror that moves
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* whenever information outside the mirror is requested.
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* The write buffer always exists only at the end of the file. It contains only records
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* that have never been written to the file before. When the write buffer is flushed,
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* the file grows
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* The record file may also shrink when the last entry of the file is removed.
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* Removal of Entries inside the file is not possible, but such entries can be erased
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* by overwriting the data with zero bytes
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* All access to the file is made with byte[] that are generated outside of this class
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* This class only references byte[] that are handed over to methods of this class.
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*/
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public final class Records {
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private RandomAccessFile raf;
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private final File tablefile;
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/**
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* number of bytes in one record
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*/
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protected final int recordsize;
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/**
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* number of entries in buffer
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*/
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private int buffercount;
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private byte[] buffer;
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private final byte[] zero;
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/**
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* stay below hard disc cache (is that necessary?)
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*/
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private static final int maxWriteBuffer = 16 * 1024;
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public Records(final File tablefile, final int recordsize) {
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this.tablefile = tablefile;
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this.recordsize = recordsize;
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// initialize zero buffer
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this.zero = new byte[recordsize];
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for (int i = 0; i < recordsize; i++) this.zero[i] = 0;
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// initialize table file
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if (!tablefile.exists()) {
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// make new file
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FileOutputStream fos = null;
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try {
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fos = new FileOutputStream(tablefile);
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} catch (final FileNotFoundException e) {
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// should not happen
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ConcurrentLog.logException(e);
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}
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try { if (fos != null) fos.close(); } catch (final IOException e) {}
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}
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// open an existing table file
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try {
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this.raf = new RandomAccessFile(tablefile,"rw");
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} catch (final FileNotFoundException e) {
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// should never happen
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ConcurrentLog.logException(e);
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}
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// initialize write buffer
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int buffersize = Math.max(1, (maxWriteBuffer / recordsize)) * recordsize;
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if (!MemoryControl.request(buffersize + 1024 * 1024 * 20, true)) {
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// not enough memory there, take less
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long lessmem = Math.min(maxWriteBuffer / 8, MemoryControl.available() - (1024 * 1024 * 6) / 6);
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//System.out.println("newmem vorher: cachesize = " + cachesize + ", buffersize = " + buffersize + ", available = " + serverMemory.available() + ", lessmem = " + lessmem);
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buffersize = Math.max(1, (int) (lessmem / recordsize)) * recordsize;
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//System.out.println("newmem nachher: cachesize = " + cachesize + ", buffersize = " + buffersize);
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}
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this.buffer = new byte[buffersize];
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this.buffercount = 0;
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}
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public void clear() {
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try {
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this.raf.setLength(0);
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int buffersize = Math.max(1, (maxWriteBuffer / recordsize)) * recordsize;
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this.buffer = new byte[buffersize];
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this.buffercount = 0;
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} catch (IOException e) {
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ConcurrentLog.logException(e);
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}
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}
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/**
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* @param tablefile
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* @param recordsize
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* @return number of records in table
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*/
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public final static long tableSize(final File tablefile, final long recordsize) throws IOException {
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if (!tablefile.exists()) return 0;
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final long size = tablefile.length();
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if (size % recordsize != 0) throw new IOException("wrong file size: file = " + tablefile + ", size = " + size + ", recordsize = " + recordsize);
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return size / recordsize;
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}
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public final static void fixTableSize(final File tablefile, final long recordsize) throws IOException {
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if (!tablefile.exists()) return;
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final long size = tablefile.length();
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long cut = size % recordsize;
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if (cut > 0) {
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RandomAccessFile raf = new RandomAccessFile(tablefile, "rw");
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raf.setLength(size - cut);
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raf.close();
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}
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}
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/**
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* @return the number of records in file plus number of records in buffer
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* @throws IOException
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*/
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public final synchronized long size() throws IOException {
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return filesize() + this.buffercount;
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}
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public final File filename() {
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return this.tablefile;
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}
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/**
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* @return records in file
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* @throws IOException
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*/
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private final long filesize() throws IOException {
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long records = 0;
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try {
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records = this.raf.length() / this.recordsize;
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} catch (final NullPointerException e) {
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// This may happen on shutdown while still something is moving on
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ConcurrentLog.logException(e);
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}
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return records;
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}
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/**
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* checks if the index is inside the buffer
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*
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* @param index
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* @return the index offset inside the buffer or -1 if the index is not in the buffer
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* @throws IOException
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*/
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private final int inBuffer(final long index, final long filesize) throws IOException {
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if (index >= filesize && index < filesize + this.buffercount) {
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return (int) (index - filesize);
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}
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return -1;
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}
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/**
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* write buffer to end of file
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*/
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protected final synchronized void flushBuffer() {
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if (this.raf == null) return;
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try {
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this.raf.seek(this.raf.length());
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this.raf.write(this.buffer, 0, this.recordsize * this.buffercount);
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} catch (final IOException e) {
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ConcurrentLog.logException(e);
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}
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this.buffercount = 0;
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}
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public final synchronized void close() {
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// close the file
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if (this.raf != null) try {
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flushBuffer();
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this.raf.close();
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} catch (final IOException e) {
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ConcurrentLog.logException(e);
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}
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this.raf = null;
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this.buffer = null;
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}
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/**
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* @param index record which should be read
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* @param b destination array
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* @param start offset in b to store data
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* @throws IOException
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*/
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public final synchronized void get(final long index, final byte[] b, final int start) throws IOException {
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assert b.length - start >= this.recordsize;
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final long filesize = filesize();
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final long s = filesize + this.buffercount;
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if (index >= s) throw new IndexOutOfBoundsException("kelondroEcoFS.get(" + index + ") outside bounds (" + s + ")");
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// check if index is inside of cache
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final int q = inBuffer(index, filesize);
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if (q < 0) {
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// copy records from file to given buffer
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this.raf.seek(this.recordsize * index);
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this.raf.readFully(b, start, this.recordsize);
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return;
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}
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// read entry from the buffer
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System.arraycopy(this.buffer, q * this.recordsize, b, start, this.recordsize);
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}
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public final synchronized void put(final long index, final byte[] b, final int start) throws IOException {
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assert b.length - start >= this.recordsize;
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long filesize = filesize();
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final long s = filesize + this.buffercount;
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if (index > s) throw new IndexOutOfBoundsException("kelondroEcoFS.put(" + index + ") outside bounds (" + s + ")");
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// check if this is an empty entry
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if (isClean(b , start, this.recordsize)) {
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clean(index);
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return;
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}
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// check if index is inside of cache
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final int q = inBuffer(index, filesize);
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if (q >= 0) {
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// write entry to the buffer
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System.arraycopy(b, start, this.buffer, q * this.recordsize, this.recordsize);
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return;
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}
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if (index == s) {
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// append the record to the end of the file;
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// look if there is space in the buffer
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if (this.buffercount >= this.buffer.length / this.recordsize) {
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assert this.buffercount == this.buffer.length / this.recordsize;
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// the record does not fit in current buffer
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// write buffer
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flushBuffer();
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// write new entry to buffer
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System.arraycopy(b, start, this.buffer, 0, this.recordsize);
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this.buffercount = 1;
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} else {
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System.arraycopy(b, start, this.buffer, this.buffercount * this.recordsize, this.recordsize);
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this.buffercount++;
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}
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assert this.buffercount <= this.buffer.length / this.recordsize;
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} else {
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// write the record directly to the file,
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// do not care about the cache; this case was checked before
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this.raf.seek(index * this.recordsize);
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this.raf.write(b, start, this.recordsize);
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}
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}
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public final synchronized void add(final byte[] b, final int start) throws IOException {
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assert b.length - start >= this.recordsize;
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// check if this is an empty entry
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if (isClean(b , start, this.recordsize)) {
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// it is not possible to add a clean record at the end of a EcoFS, because
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// such records should cause the record to shrink
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throw new IOException("add: record at end is clean");
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}
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// append the record to the end of the file;
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// look if there is space in the buffer
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if (this.buffercount >= this.buffer.length / this.recordsize) {
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assert this.buffercount == this.buffer.length / this.recordsize;
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// the record does not fit in current buffer
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// write buffer
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flushBuffer();
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// write new entry to buffer
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System.arraycopy(b, start, this.buffer, 0, this.recordsize);
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this.buffercount = 1;
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} else {
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System.arraycopy(b, start, this.buffer, this.buffercount * this.recordsize, this.recordsize);
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this.buffercount++;
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}
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assert this.buffercount <= this.buffer.length / this.recordsize;
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}
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private final static boolean isClean(final byte[] b, final int offset, final int length) {
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for (int i = 0; i < length; i++) {
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if (b[i + offset] != 0) return false;
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}
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return true;
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}
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private final boolean isClean(final long index) throws IOException {
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long filesize = filesize();
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long size = filesize + this.buffercount;
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assert index < size;
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// check if index is inside of buffer
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final int q = inBuffer(index, filesize);
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if (q >= 0) {
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// check entry from the buffer
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return isClean(this.buffer, q * this.recordsize, this.recordsize);
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}
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byte[] b = new byte[this.recordsize];
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this.raf.seek(index * this.recordsize);
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this.raf.readFully(b, 0, this.recordsize);
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return isClean(b, 0, this.recordsize);
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}
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/**
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* @see clean(long, byte[], int)
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* @param index
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* @throws IOException
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*/
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private final void clean(final long index) throws IOException {
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long filesize = filesize();
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final long s = filesize + this.buffercount;
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if (index >= s) throw new IndexOutOfBoundsException("kelondroEcoFS.clean(" + index + ") outside bounds (" + s + ")");
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if (index == s - 1) {
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cleanLast();
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return;
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}
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// check if index is inside of cache
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final int q = inBuffer(index, filesize);
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if (q >= 0) {
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// write zero to the buffer
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System.arraycopy(this.zero, 0, this.buffer, q * this.recordsize, this.recordsize);
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return;
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}
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this.raf.seek(index * this.recordsize);
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this.raf.write(this.zero, 0, this.recordsize);
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}
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/**
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* @see clean(long, byte[], int)
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* @param b
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* @param start
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* @throws IOException
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*/
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public final synchronized void cleanLast(final byte[] b, final int start) throws IOException {
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cleanLast0(b, start);
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long i;
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while ((i = size()) > 0 && isClean(i - 1)) {
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//System.out.println("Extra clean/1: before size = " + size());
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cleanLast0();
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//System.out.println(" after size = " + size());
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}
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}
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/**
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* this is like
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* <code>clean(this.size() - 1, b, start);</code>
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*
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* @see clean(long, byte[], int)
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* @param b
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* @param start
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* @throws IOException
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*/
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private final void cleanLast0(final byte[] b, final int start) throws IOException {
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assert b.length - start >= this.recordsize;
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// check if index is inside of buffer
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if (this.buffercount > 0) {
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// read entry from the buffer
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System.arraycopy(this.buffer, (this.buffercount - 1) * this.recordsize, b, start, this.recordsize);
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// shrink buffer
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this.buffercount--;
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return;
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}
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// read entry from the file
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long endpos = this.raf.length() - this.recordsize;
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if (endpos >= 0) { // prevent seek error for 0 size file
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this.raf.seek(endpos);
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this.raf.readFully(b, start, this.recordsize);
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} else {
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endpos = 0;
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System.arraycopy(this.zero, 0, b, start, this.recordsize);
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}
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// write zero bytes to the cache and to the file
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this.raf.seek(endpos);
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this.raf.write(this.zero, 0, this.recordsize);
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// shrink file
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this.raf.setLength(endpos);
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}
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/**
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* @see clean(long, byte[], int)
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* @throws IOException
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*/
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public final synchronized void cleanLast() throws IOException {
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cleanLast0();
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long i;
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while (((i = size()) > 0) && (isClean(i - 1))) {
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//System.out.println("Extra clean/0: before size = " + size());
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cleanLast0();
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//System.out.println(" after size = " + size());
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}
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}
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private final void cleanLast0() throws IOException {
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// check if index is inside of cache
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if (this.buffercount > 0) {
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// shrink buffer
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this.buffercount--;
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return;
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}
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// shrink file
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if (this.raf.length() > 0) // already 0 length, nothing to shrink (prevent seek io error)
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this.raf.setLength(this.raf.length() - this.recordsize);
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}
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public final void deleteOnExit() {
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this.tablefile.deleteOnExit();
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}
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/**
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* main - writes some data and checks the tables size (with time measureing)
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* @param args
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*/
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public static void main(final String[] args) {
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// open a file, add one entry and exit
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final File f = new File(args[0]);
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if (f.exists()) FileUtils.deletedelete(f);
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try {
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final Records t = new Records(f, 8);
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final byte[] b = new byte[8];
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t.add("01234567".getBytes(), 0);
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t.add("ABCDEFGH".getBytes(), 0);
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t.add("abcdefgh".getBytes(), 0);
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t.add("--------".getBytes(), 0);
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t.add("********".getBytes(), 0);
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for (int i = 0; i < 1000; i++) t.add("++++++++".getBytes(), 0);
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t.add("=======0".getBytes(), 0);
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t.add("=======1".getBytes(), 0);
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t.add("=======2".getBytes(), 0);
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t.cleanLast(b, 0);
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System.out.println(UTF8.String(b));
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t.cleanLast(b, 0);
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//t.clean(2, b, 0);
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System.out.println(UTF8.String(b));
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t.get(1, b, 0);
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System.out.println(UTF8.String(b));
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t.put(1, "AbCdEfGh".getBytes(), 0);
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t.get(1, b, 0);
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System.out.println(UTF8.String(b));
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t.get(3, b, 0);
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System.out.println(UTF8.String(b));
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t.get(4, b, 0);
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System.out.println(UTF8.String(b));
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System.out.println("size = " + t.size());
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//t.clean(t.size() - 2);
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t.cleanLast();
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final long start = System.currentTimeMillis();
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long c = 0;
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for (int i = 0; i < 100000; i++) {
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c = t.size();
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}
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System.out.println("size() needs " + ((System.currentTimeMillis() - start) / 100) + " nanoseconds");
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System.out.println("size = " + c);
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t.close();
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} catch (final IOException e) {
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ConcurrentLog.logException(e);
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}
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}
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}
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