?? repositionableinputstream.java
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/* RepositionableInputStream.java * * $Id: RepositionableInputStream.java,v 1.3 2006/01/19 02:05:33 stack-sf Exp $ * * Created Dec 20, 2005 * * Copyright (C) 2005 Internet Archive. * * This file is part of the Heritrix web crawler (crawler.archive.org). * * Heritrix is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser Public License as published by * the Free Software Foundation; either version 2.1 of the License, or * any later version. * * Heritrix 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 Lesser Public License for more details. * * You should have received a copy of the GNU Lesser Public License * along with Heritrix; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */package org.archive.io;import it.unimi.dsi.fastutil.io.RepositionableStream;import java.io.BufferedInputStream;import java.io.IOException;import java.io.InputStream;/** * Wrapper around an {@link InputStream} to make a primitive Repositionable * stream. Uses a {@link BufferedInputStream}. Has limitations as we come * across buffer boundaries. At least if the access is over the top end of * the buffer, could be fixed by calling a buffer fill. Going back is * probably not possible. Mitigate against buffer boundary problems by * having the inflater buffer -- if stream is gzipped -- be at least half * size of the backing buffer used here. * <p>TODO: More robust implementation. Tried to use the it.unimi.dsi.io * FastBufferdInputStream but relies on FileChannel ByteBuffers and if not * present -- as would be the case reading from a network stream, the main * application for this instance -- then it expects the underlying stream * implements RepositionableStream interface. * @author stack */public class RepositionableInputStream extends BufferedInputStream implements RepositionableStream { private long position = 0; private long markPosition = 0; public RepositionableInputStream(InputStream in) { super(in); } public RepositionableInputStream(InputStream in, int size) { super(in, size); } public int read(byte[] b) throws IOException { int read = super.read(b); if (read != -1) { position += read; } return read; } public synchronized int read(byte[] b, int offset, int ct) throws IOException { int read = super.read(b, offset, ct); if (read != -1) { position += read; } return read; } public int read() throws IOException { int c = super.read(); if (c != -1) { position++; } return c; } /** * @param offset Offset is ignored. We call reset on underlying stream. Use * sparingly and only after a call to position. */ public void position(final long offset) { if (this.position == offset) { return; } int diff = (int)(offset - this.position); long lowerBound = this.position - this.pos; long upperBound = lowerBound + this.count; if (offset < lowerBound || offset >= upperBound) { throw new IllegalAccessError("Offset outside goes outside " + "current this.buf (TODO: At least do fills if positive)"); } this.position = offset; this.pos += diff; } public void mark(int readlimit) { this.markPosition = this.position; super.mark(readlimit); } public void reset() throws IOException { super.reset(); this.position = this.markPosition; } public long position() { return this.position; }}
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