/**
* Returns an instance of a specific checksum algorithm for caching.
*
* @param instance of the algorithm
*/
public void returnAlgorithm(ChecksumAlgorithm algorithm) {
ConcurrentLinkedQueue<ChecksumAlgorithm> cache = pool.get(algorithm.getName());
if (cache.size() < MAX_CACHE_SIZE) {
algorithm.reset();
cache.add(algorithm);
}
}
public Checksum(ChecksumAlgorithm checksumAlgorithm) {
this.checksumAlgorithm = checksumAlgorithm;
try {
md = MessageDigest.getInstance(checksumAlgorithm.getAlgorithm());
} catch (NoSuchAlgorithmException e) {
// Not really possible, but here none-the-less
throw new IllegalStateException(
"Unable to initialize MessageDigest algorithm "
+ checksumAlgorithm.getAlgorithm()
+ " : "
+ e.getMessage(),
e);
}
}
/**
* Sets the checksum values ahead of the transfer
*
* @param algorithm the checksume algorithm
* @param value the checksum value as hexadecimal number
* @return nothing
* @throws ServerException if an error occured.
*/
public void setChecksum(ChecksumAlgorithm algorithm, String value)
throws IOException, ServerException {
String arguments = algorithm.toFtpCmdArgument() + " " + value;
Command cmd = new Command("SCKS", arguments);
try {
controlChannel.execute(cmd);
} catch (UnexpectedReplyCodeException urce) {
throw ServerException.embedUnexpectedReplyCodeException(urce);
} catch (FTPReplyParseException rpe) {
throw ServerException.embedFTPReplyParseException(rpe);
}
}
/**
* Computes and returns a checksum of a file. transferred.
*
* @param algorithm the checksume algorithm
* @param offset the offset
* @param length the length
* @param file file to compute checksum of
* @return the computed checksum
* @throws ServerException if an error occured.
*/
public String checksum(ChecksumAlgorithm algorithm, long offset, long length, String file)
throws IOException, ServerException {
String arguments =
algorithm.toFtpCmdArgument()
+ " "
+ String.valueOf(offset)
+ " "
+ String.valueOf(length)
+ " "
+ file;
Command cmd = new Command("CKSM", arguments);
Reply reply = null;
try {
reply = controlChannel.execute(cmd);
return reply.getMessage();
} catch (UnexpectedReplyCodeException urce) {
throw ServerException.embedUnexpectedReplyCodeException(urce);
} catch (FTPReplyParseException rpe) {
throw ServerException.embedFTPReplyParseException(rpe);
}
}
/**
* Adds a new Algorithm to factory. NOTE: The same existing algorithm will be overridden.
*
* @param algorithm
*/
public void addAlgorithm(ChecksumAlgorithm algorithm) {
algorithms.put(algorithm.getName(), algorithm);
pool.put(algorithm.getName(), new ConcurrentLinkedQueue<ChecksumAlgorithm>());
}
public RunningChecksum(ChecksumAlgorithm algorithm) throws NoSuchAlgorithmException {
this.algorithm = algorithm;
this.offset = 0;
this.digest = MessageDigest.getInstance(algorithm.getDigestName());
}
