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/*******************************************************************************
* Copyright (c) 2000, 2003 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Common Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/cpl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.swt.internal.image;
import java.io.*;
final class TIFFRandomFileAccess {
LEDataInputStream inputStream;
int start, current, next;
byte[][] buffers;
static final int CHUNK_SIZE = 8192;
static final int LIST_SIZE = 128;
public TIFFRandomFileAccess(LEDataInputStream stream) {
inputStream = stream;
start = current = next = inputStream.getPosition();
buffers = new byte[LIST_SIZE][];
}
void seek(int pos) throws IOException {
if (pos == current) return;
if (pos < start) throw new IOException();
current = pos;
if (current > next) {
int n = current - next;
/* store required bytes */
int index = next / CHUNK_SIZE;
int offset = next % CHUNK_SIZE;
while (n > 0) {
if (index >= buffers.length) {
byte[][] oldBuffers = buffers;
buffers = new byte[Math.max(index + 1, oldBuffers.length + LIST_SIZE)][];
System.arraycopy(oldBuffers, 0, buffers, 0, oldBuffers.length);
}
if (buffers[index] == null) buffers[index] = new byte[CHUNK_SIZE];
int cnt = inputStream.read(buffers[index], offset, Math.min(n, CHUNK_SIZE - offset));
n -= cnt;
next += cnt;
index++;
offset = 0;
}
}
}
void read(byte b[]) throws IOException {
int size = b.length;
int nCached = Math.min(size, next - current);
int nMissing = size - next + current;
int destNext = 0;
if (nCached > 0) {
/* Get cached bytes */
int index = current / CHUNK_SIZE;
int offset = current % CHUNK_SIZE;
while (nCached > 0) {
int cnt = Math.min(nCached, CHUNK_SIZE - offset);
System.arraycopy(buffers[index], offset, b, destNext, cnt);
nCached -= cnt;
destNext += cnt;
index++;
offset = 0;
}
}
if (nMissing > 0) {
/* Read required bytes */
int index = next / CHUNK_SIZE;
int offset = next % CHUNK_SIZE;
while (nMissing > 0) {
if (index >= buffers.length) {
byte[][] oldBuffers = buffers;
buffers = new byte[Math.max(index, oldBuffers.length + LIST_SIZE)][];
System.arraycopy(oldBuffers, 0, buffers, 0, oldBuffers.length);
}
if (buffers[index] == null) buffers[index] = new byte[CHUNK_SIZE];
int cnt = inputStream.read(buffers[index], offset, Math.min(nMissing, CHUNK_SIZE - offset));
System.arraycopy(buffers[index], offset, b, destNext, cnt);
nMissing -= cnt;
next += cnt;
destNext += cnt;
index++;
offset = 0;
}
}
current += size;
}
}
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