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/*
* This file is part of *** M y C o R e ***
* See http://www.mycore.de/ for details.
*
* MyCoRe 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 3 of the License, or
* (at your option) any later version.
*
* MyCoRe 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.
*
* You should have received a copy of the GNU General Public License
* along with MyCoRe. If not, see .
*/
package org.mycore.datamodel.ifs;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import org.mycore.common.MCRException;
import org.mycore.common.config.MCRConfigurationException;
import org.mycore.common.content.streams.MCRBlockingInputStream;
/**
* This input stream is used by the MyCoRe filesystem classes to read the
* content of a file and import it into the System. MCRContentInputStream
* provides the header of the file that is read (the first 64k) for content type
* detection purposes, counts the number of bytes read and builds an MD5
* checksum String while content goes through this input stream.
*
* @author Frank Lützenkirchen
* @version $Revision$ $Date$
*/
public class MCRContentInputStream extends FilterInputStream {
/** The number of bytes that will be read for content type detection */
protected static final int HEADER_SIZE = 65536;
/** The MD5 checksum of all bytes read through this stream */
protected byte[] md5 = null;
/** The message digest to build the MD5 checksum */
protected MessageDigest digest = null;
/** The total number of bytes read so far */
protected long length;
/** The header of the file read */
protected byte[] header;
/**
* Constructs a new MCRContentInputStream
*
* @param in
* the InputStream to read from
* @throws MCRConfigurationException
* if java classes supporting MD5 checksums are not found
*/
public MCRContentInputStream(InputStream in) throws MCRException {
super(null);
digest = buildMD5Digest();
DigestInputStream dis = new DigestInputStream(in, digest);
MCRBlockingInputStream bis = new MCRBlockingInputStream(dis, HEADER_SIZE);
byte[] buffer = new byte[HEADER_SIZE];
try {
int num = bis.read(buffer, 0, buffer.length);
header = new byte[Math.max(0, num)];
if (num > 0) {
System.arraycopy(buffer, 0, header, 0, num);
}
} catch (IOException ex) {
String msg = "Error while reading content input stream header";
throw new MCRException(msg, ex);
}
this.in = bis;
}
public int consume() throws IOException {
byte[] buffer = new byte[4096];
int numRead, totalRead = 0;
do {
numRead = read(buffer);
if (numRead > 0) {
totalRead += numRead;
}
} while (numRead != -1);
return totalRead;
}
@Override
public int read() throws IOException {
int b;
// if current position is in header buffer, return value from there
if (header.length > 0 && length < header.length) {
b = header[(int) length];
length++;
} else {
b = super.read();
if (b != -1) {
length++;
}
}
return b;
}
@Override
public int read(byte[] buf, int off, int len) throws IOException {
// if current position is in header buffer, return bytes from there
if (header.length > 0 && length < header.length) {
int numAvail = header.length - (int) length;
len = Math.min(len, numAvail);
System.arraycopy(header, (int) length, buf, off, len);
length += len;
return len;
} else {
len = super.read(buf, off, len);
if (len != -1) {
length += len;
}
return len;
}
}
/**
* Returns the first 64 k of the underlying input stream. This is used for
* content type detection during file import into MyCoRe.
*
* @return the first 64 k of the input stream
*/
public byte[] getHeader() {
return header;
}
/**
* Returns the number of bytes read so far
*
* @return the number of bytes read
*/
public long getLength() {
return length;
}
/**
* Returns the MD5 message digest that has been built during reading of the
* underlying input stream.
*
* @return the MD5 message digest checksum of all bytes that have been read
*/
public byte[] getMD5() {
if (md5 == null) {
md5 = digest.digest();
}
return md5;
}
/**
* Returns the MD5 checksum as a String
*
* @return the MD5 checksum as a String of hex digits
*/
public String getMD5String() {
return getMD5String(getMD5());
}
/**
* Given an MD5 message digest, returns the MD5 checksum as a String
*
* @return the MD5 checksum as a String of hex digits
*/
public static String getMD5String(byte[] digest) {
StringBuilder md5SumBuilder = new StringBuilder();
for (byte b : digest) {
md5SumBuilder.append(Integer.toString((b & 0xff) + 0x100, 16).substring(1));
}
return md5SumBuilder.toString();
}
/**
* Builds a MessageDigest instance for MD5 checksum computation.
*
* @throws MCRConfigurationException
* if no java classes that support MD5 algorithm could be found
*/
private static MessageDigest buildMD5Digest() {
try {
return MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException exc) {
String msg = "Could not find java classes that support MD5 checksum algorithm";
throw new MCRConfigurationException(msg, exc);
}
}
}
