HDTHeader.java
/*******************************************************************************
* Copyright (c) 2020 Eclipse RDF4J contributors.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Distribution License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*******************************************************************************/
package org.eclipse.rdf4j.rio.hdt;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.zip.CheckedInputStream;
import org.eclipse.rdf4j.common.io.UncloseableInputStream;
/**
* HDT Header Part.
* <p>
* This part starts with <code>$HDT</code>, followed by a byte indicating the type of the part, the NULL-terminated
* string for the format, and optionally one or more <code>key=value;</code> properties.
* <p>
* Then a <code>NULL</code> byte, followed by the 16-bit CRC (<code>$HDT</code> and <code>NULL</code> included).
* <p>
* Structure:
*
* <pre>
* +------+------+--------+------+------------+------+-------+
* | $HDT | type | format | NULL | key=value; | NULL | CRC16 |
* +------+------+--------+------+------------+------+-------+
* </pre>
*
* @author Bart Hanssens
*/
class HDTHeader extends HDTPart {
final static byte[] HEADER_FORMAT = "ntriples".getBytes(StandardCharsets.US_ASCII);
final static String HEADER_LENGTH = "length";
private byte[] headerData;
@Override
void parse(InputStream is) throws IOException {
// don't close CheckedInputStream, as it will close the underlying inputstream
try (UncloseableInputStream uis = new UncloseableInputStream(is);
CheckedInputStream cis = new CheckedInputStream(uis, new CRC16())) {
checkControl(cis, HDTPart.Type.HEADER);
checkFormat(cis, HEADER_FORMAT);
properties = getProperties(cis);
checkCRC(cis, is, 2);
}
int hlen = getIntegerProperty(properties, HEADER_LENGTH, "Header length");
headerData = parseHeaderData(is, hlen);
}
/**
* Get raw header data (byte array data stored as NTriples)
*
* @return byte array
*/
byte[] getHeaderData() {
return headerData;
}
/**
* Parse header data with metadata in NTriples format.
*
* @param is
* @param len
* @throws IOException
*/
private byte[] parseHeaderData(InputStream is, int len) throws IOException {
byte[] b = new byte[len];
is.read(b);
return b;
}
}