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254 lines
8.9 KiB
254 lines
8.9 KiB
// kelondroBufferedRA.java
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// -----------------------
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// part of The Kelondro Database
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// (C) by Michael Peter Christen; mc@anomic.de
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// first published on http://www.anomic.de
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// Frankfurt, Germany, 2005
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// last major change: 13.09.2005
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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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//
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// Using this software in any meaning (reading, learning, copying, compiling,
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// running) means that you agree that the Author(s) is (are) not responsible
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// for cost, loss of data or any harm that may be caused directly or indirectly
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// by usage of this softare or this documentation. The usage of this software
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// is on your own risk. The installation and usage (starting/running) of this
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// software may allow other people or application to access your computer and
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// any attached devices and is highly dependent on the configuration of the
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// software which must be done by the user of the software; the author(s) is
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// (are) also not responsible for proper configuration and usage of the
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// software, even if provoked by documentation provided together with
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// the software.
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//
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// Any changes to this file according to the GPL as documented in the file
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// gpl.txt aside this file in the shipment you received can be done to the
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// lines that follows this copyright notice here, but changes must not be
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// done inside the copyright notive above. A re-distribution must contain
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// the intact and unchanged copyright notice.
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// Contributions and changes to the program code must be marked as such.
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package de.anomic.kelondro;
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import java.io.IOException;
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public class kelondroBufferedRA extends kelondroAbstractRA implements kelondroRA {
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// FIXME: a lot of synchronization of ra is needed here
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protected kelondroRA ra;
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protected byte[] buffer;
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protected int bufferPage;
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protected boolean bufferWritten;
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private long seekpos;
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private int bufferSizeExp;
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private int bufferSize;
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private int bufferOffsetFilter;
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private int bufferStart;
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public kelondroBufferedRA(kelondroRA ra, int minBufferSize, int bufferStartMin) {
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// calculate buffer organization parameters
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this.bufferSizeExp = 0;
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minBufferSize--;
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while (minBufferSize > 0) {minBufferSize = minBufferSize >> 1; this.bufferSizeExp++;}
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this.bufferSize = 1 << this.bufferSizeExp;
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this.bufferOffsetFilter = this.bufferSize - 1;
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this.bufferStart = 0;
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while (this.bufferStart < bufferStartMin) this.bufferStart += this.bufferSize;
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// init buffer
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this.ra = ra;
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this.name = ra.name();
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this.buffer = new byte[bufferSize];
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this.seekpos = 0;
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this.bufferPage = -1;
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this.bufferWritten = true;
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}
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public long length() throws IOException {
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return ra.length();
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}
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public long available() throws IOException {
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synchronized (ra) {
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ra.seek(seekpos);
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return ra.available();
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}
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}
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private void readBuffer(int newPageNr) throws IOException {
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if (newPageNr == bufferPage) return;
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bufferPage = newPageNr;
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ra.seek(bufferPage << bufferSizeExp);
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ra.readFully(buffer, 0, bufferSize);
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bufferWritten = true;
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}
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/*
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private void writeBuffer() throws IOException {
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if ((bufferWritten) || (bufferPage < 0)) return;
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ra.seek(bufferPage << bufferSizeExp);
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ra.write(buffer, 0, bufferSize);
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bufferWritten = true;
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}
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*/
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private void updateToBuffer(int newPageNr) throws IOException {
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if (newPageNr != bufferPage) {
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//writeBuffer();
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readBuffer(newPageNr);
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}
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}
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// pseudo-native method read
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public int read() throws IOException {
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if (seekpos < bufferStart) {
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// do not use buffer
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ra.seek(seekpos);
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int r = ra.read();
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seekpos++;
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return r;
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}
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int bn = (int) seekpos >> bufferSizeExp; // buffer page number
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int offset = (int) seekpos & bufferOffsetFilter; // buffer page offset
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seekpos++;
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updateToBuffer(bn);
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return 0xFF & buffer[offset];
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}
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// pseudo-native method write
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public void write(int b) throws IOException {
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if (seekpos < bufferStart) {
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// do not use buffer
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ra.seek(seekpos);
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ra.write(b);
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seekpos++;
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} else {
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// write to ra direkt
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ra.seek(seekpos);
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ra.write(b);
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// and write also to buffer
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int bn = (int) seekpos >> bufferSizeExp; // buffer page number
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int offset = (int) seekpos & bufferOffsetFilter; // buffer page offset
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updateToBuffer(bn);
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buffer[offset] = (byte) b;
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bufferWritten = false;
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// update seek pos
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seekpos++;
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}
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}
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public int read(byte[] b, int off, int len) throws IOException {
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// check buffer size
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if (seekpos < bufferStart) {
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// do not use buffer
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ra.seek(seekpos);
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int r = ra.read(b, off, len);
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seekpos += len;
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return r;
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}
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// check simple case
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int bn1 = (int) seekpos >> bufferSizeExp; // buffer page number, first position
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int bn2 = (int) (seekpos + len - 1) >> bufferSizeExp; // buffer page number, last position
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int offset = (int) seekpos & bufferOffsetFilter; // buffer page offset
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updateToBuffer(bn1);
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if (bn1 == bn2) {
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// simple case
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System.arraycopy(buffer, offset, b, off, len);
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seekpos += len;
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return len;
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}
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// do recursively
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int thislen = bufferSize - offset;
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System.arraycopy(buffer, offset, b, off, thislen);
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seekpos += thislen;
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return thislen + read(b, off + thislen, len - thislen);
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}
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public void write(byte[] b, int off, int len) throws IOException {
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if (seekpos < bufferStart) {
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// do not use buffer
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ra.seek(seekpos);
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ra.write(b, off, len);
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seekpos += len;
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} else {
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int bn1 = (int) seekpos >> bufferSizeExp; // buffer page number, first position
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int bn2 = (int) (seekpos + len - 1) >> bufferSizeExp; // buffer page number, last position
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int offset = (int) seekpos & bufferOffsetFilter; // buffer page offset
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updateToBuffer(bn1);
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if (bn1 == bn2) {
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// simple case
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ra.seek(seekpos);
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ra.write(b, off, len);
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System.arraycopy(b, off, buffer, offset, len);
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bufferWritten = false;
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seekpos += len;
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} else {
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// do recursively
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int thislen = bufferSize - offset;
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ra.seek(seekpos);
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ra.write(b, off, thislen);
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System.arraycopy(b, off, buffer, offset, thislen);
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bufferWritten = false;
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seekpos += thislen;
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write(b, off + thislen, len - thislen);
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}
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}
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}
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public void seek(long pos) throws IOException {
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seekpos = pos;
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}
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public void close() throws IOException {
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// write unwritten buffer
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if (buffer == null) return;
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//writeBuffer();
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ra.close();
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buffer = null;
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}
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/*
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public void finalize() {
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try {
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close();
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} catch (IOException e) {}
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}
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*/
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public static void main(String[] args) {
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try {
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kelondroRA file = new kelondroBufferedRA(new kelondroFileRA("testx"), 64, 30);
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file.seek(1024 - 2);
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byte[] b = new byte[]{65, 66, 77, 88};
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file.write(b);
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file.seek(1024 * 2 - 30);
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for (int i = 65; i < 150; i++) file.write(i);
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file.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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