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DSS CRL Parser with stream is an implementation of DSS CRL Parser API which streams the CRL to validate it and extract revocation data. This implementation is experimental but offers better performances.

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/**
 * DSS - Digital Signature Services
 * Copyright (C) 2015 European Commission, provided under the CEF programme
 * 
 * This file is part of the "DSS - Digital Signature Services" project.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package eu.europa.esig.dss.crl.stream.impl;

import org.bouncycastle.asn1.ASN1InputStream;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * This class is used to access to static methods of ASN1InputStream
 */
final class DERUtil {

	private DERUtil() {
	}

	/**
	 * Reads the next tag if {@code InputStream}
	 *
	 * @param is {@link InputStream} to read
	 * @return integer
	 * @throws IOException if an exception occurs
	 */
	public static int readTag(InputStream is) throws IOException {
		return is.read();
	}

	/**
	 * Reads length of {@code InputStream}
	 *
	 * @param is {@link InputStream} to read
	 * @return length
	 * @throws IOException if an exception occurs
	 */
	public static int readLength(InputStream is) throws IOException {
		try (ASN1InputStreamDSS dssIS = new ASN1InputStreamDSS(is, Integer.MAX_VALUE)) {
			return dssIS.readLength();
		}
	}

	/**
	 * Adaptation from org.bouncycastle.asn1.ASN1OutputStream.writeLength(int)
	 * 
	 * @param os     {@link OutputStream}
	 * @param length the length to add
	 * @throws IOException if an error occurs during the OutputStream creation
	 */
	public static void writeLength(OutputStream os, int length) throws IOException {
		if (length > 127) {
			int size = 1;
			int val = length;

			while ((val >>>= 8) != 0) {
				size++;
			}

			os.write((byte) (size | 0x80));

			for (int i = (size - 1) * 8; i >= 0; i -= 8) {
				os.write((byte) (length >> i));
			}
		} else {
			os.write((byte) length);
		}
	}

	/**
	 * Reads the tag number
	 *
	 * Copied from
	 * https://github.com/bcgit/bc-java/blob/r1rv63/core/src/main/java/org/bouncycastle/asn1/ASN1InputStream.java
	 *
	 * @param is {@link InputStream}
	 * @param tag the tag number to read
	 * @return tag number
	 * @throws IOException if an excsption occurs
	 */
	public static int readTagNumber(InputStream is, int tag) throws IOException {
		int tagNo = tag & 0x1f;

		//
		// with tagged object tag number is bottom 5 bits, or stored at the start of the
		// content
		//
		if (tagNo == 0x1f) {
			tagNo = 0;

			int b = is.read();

			// X.690-0207 8.1.2.4.2
			// "c) bits 7 to 1 of the first subsequent octet shall not all be zero."
			if ((b & 0x7f) == 0) // Note: -1 will pass
			{
				throw new IOException("corrupted stream - invalid high tag number found");
			}

			while ((b >= 0) && ((b & 0x80) != 0)) {
				tagNo |= (b & 0x7f);
				tagNo <<= 7;
				b = is.read();
			}

			if (b < 0) {
				throw new EOFException("EOF found inside tag value.");
			}

			tagNo |= (b & 0x7f);
		}

		return tagNo;
	}

	private static class ASN1InputStreamDSS extends ASN1InputStream {
		
		public ASN1InputStreamDSS(InputStream input, int limit) {
			super(input, limit);
		}
		
		@Override
		protected int readLength() throws IOException {
			return super.readLength();
		}

		@Override
		public void close() throws IOException {
			// not our job
		}

	}

}