git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@5387 6c8d7289-2bf4-0310-a012-ef5d649a1542pull/1/head
orbiter
16 years ago
parent
1779c3c507
commit
5b94498643
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// kelondroCachedFileRA.java
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// -----------------------
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// part of The Kelondro Database
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// (C) by Michael Peter Christen; mc@yacy.net
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// first published on http://yacy.net
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// Frankfurt, Germany, 2004-2008
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// last major change: 09.12.2008
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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 de.anomic.kelondro;
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import java.io.File;
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import java.io.FileNotFoundException;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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public final class kelondroCachedFileRA extends kelondroAbstractRA implements kelondroRA {
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private RandomAccessFile RAFile;
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private byte[] cache;
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private long cachestart;
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private int cachelen;
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public kelondroCachedFileRA(final File file) throws IOException, FileNotFoundException {
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this.name = file.getName();
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this.file = file;
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RAFile = new RandomAccessFile(file, "rw");
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cache = new byte[8192];
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cachestart = 0;
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cachelen = 0;
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}
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public synchronized long length() throws IOException {
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return this.RAFile.length();
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}
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public synchronized void setLength(long length) throws IOException {
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cachelen = 0;
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RAFile.setLength(length);
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}
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public synchronized long available() throws IOException {
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return this.length() - RAFile.getFilePointer();
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}
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public synchronized final void readFully(final byte[] b, final int off, int len) throws IOException {
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long seek = RAFile.getFilePointer();
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if (cache != null && cachestart <= seek && cachelen - seek + cachestart >= len) {
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// read from cache
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//System.out.println("*** DEBUG FileRA " + this.file.getName() + ": CACHE HIT at " + seek);
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System.arraycopy(cache, (int) (seek - cachestart), b, off, len);
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RAFile.seek(seek + len);
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return;
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}
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if (cache == null || cache.length < len) {
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// cannot fill cache here
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RAFile.readFully(b, off, len);
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return;
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}
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// we fill the cache here
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int available = (int) (this.RAFile.length() - seek);
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if (available < len) throw new IOException("EOF, available = " + available + ", requested = " + len);
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if (cachestart + cachelen == seek && cache.length - cachelen >= len) {
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RAFile.readFully(cache, cachelen, len);
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//System.out.println("*** DEBUG FileRA " + this.file.getName() + ": append fill " + len + " bytes");
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System.arraycopy(cache, cachelen, b, off, len);
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cachelen += len;
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} else {
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// fill the cache as much as possible
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int m = Math.min(available, cache.length);
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RAFile.readFully(cache, 0, m);
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cachestart = seek;
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cachelen = m;
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if (m != len) RAFile.seek(seek + len);
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//System.out.println("*** DEBUG FileRA " + this.file.getName() + ": replace fill " + len + " bytes");
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System.arraycopy(cache, 0, b, off, len);
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}
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}
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public synchronized void write(final byte[] b, final int off, final int len) throws IOException {
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//assert len > 0;
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// write to file
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if (this.cache.length > 512) this.cache = new byte[512]; // the large cache is only useful during an initialization phase
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long seekpos = this.RAFile.getFilePointer();
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if (this.cachelen + len <= this.cache.length && this.cachestart + this.cachelen == seekpos) {
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// append to cache
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System.arraycopy(b, off, this.cache, this.cachelen, len);
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//System.out.println("*** DEBUG FileRA " + this.file.getName() + ": write append " + len + " bytes");
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this.cachelen += len;
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} else if (len <= this.cache.length) {
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// copy to cache
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System.arraycopy(b, off, this.cache, 0, len);
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//System.out.println("*** DEBUG FileRA " + this.file.getName() + ": write copy " + len + " bytes");
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this.cachelen = len;
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this.cachestart = seekpos;
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} else {
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// delete cache
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this.cachelen = 0;
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}
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RAFile.write(b, off, len);
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}
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public synchronized void seek(final long pos) throws IOException {
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RAFile.seek(pos);
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}
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public synchronized void close() throws IOException {
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if (RAFile != null) RAFile.close();
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this.cache = null;
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this.RAFile = null;
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}
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protected void finalize() throws Throwable {
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if (RAFile != null) {
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this.close();
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}
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super.finalize();
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}
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}
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