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/* ZipInputStreamSectionLoader.java
* =========================================================================
* This file is part of the GrInvIn project - http://www.grinvin.org
*
* Copyright (C) 2005-2008 Universiteit Gent
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program 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
* General Public License for more details.
*
* A copy of the GNU General Public License can be found in the file
* LICENSE.txt provided with the source distribution of this program (see
* the META-INF directory in the source jar). This license can also be
* found on the GNU website at http://www.gnu.org/licenses/gpl.html.
*
* If you did not receive a copy of the GNU General Public License along
* with this program, contact the lead developer, or write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
package org.grinvin.io;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
/**
* Loads sections from a {@link ZipInputStream}. Note that each section
* on the input strean can be accessed at most once.
*/
public class ZipInputStreamSectionLoader implements SectionLoader {
//
private ZipInputStream in;
//
private byte[] buffer;
//
private int offset;
//
private static final int DEFAULT_SIZE = 4096;
//
private static final double GROWTH_FACTOR = 1.5;
//
private void checkBufferSize (int pos) {
if (pos >= buffer.length) {
int newSize = (int)(buffer.length * GROWTH_FACTOR);
byte[] newBuffer = new byte[newSize];
System.arraycopy (buffer, 0, newBuffer, 0, buffer.length);
buffer = newBuffer;
}
}
/**
* Maps section names to offset/length-pairs
*/
private Map<String,int[]> map;
/**
* Default constructor.
*/
public ZipInputStreamSectionLoader(ZipInputStream in) {
this.in = in;
this.buffer = new byte[DEFAULT_SIZE];
this.offset = 0;
this.map = new HashMap<String,int[]>();
}
/**
* Read the next section from the inputstream, add it to the map and
* return the name of the section read. Returns {@code null} when
* the input stream has no more sections.
*/
private String readNextSection () throws IOException {
ZipEntry entry = in.getNextEntry();
if (entry == null)
return null;
String name = entry.getName();
// read the entire entry
int pos = offset;
checkBufferSize (pos);
int size = in.read (buffer, pos, buffer.length - pos);
while (size > 0) {
pos += size;
checkBufferSize (pos);
size = in.read (buffer, pos, buffer.length - pos);
}
in.closeEntry ();
map.put (name, new int[] { offset, pos - offset});
offset = pos;
return name;
}
//
public InputStream openSection(String name) throws IOException{
if (! map.containsKey(name)) {
String section = readNextSection ();
while (section != null && ! section.equals (name))
section = readNextSection ();
if (section == null)
return null;
}
int[] info = map.get(name);
InputStream stream = new ByteArrayInputStream (buffer, info[0], info[1]);
return stream;
}
}
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