com.guardtime.ksi.hashing

Class DataHasher

java.lang.Object

com.guardtime.ksi.hashing.DataHasher

public class DataHasher
extends Object

Functionality for hashing data.

Data hasher is stateful, all new data added is added to the same hash calculation, if this class needs to be reused for separate entities, for example hashing multiple files, the reset() method must be called to reset hash calculation.

Example for hashing a file

 
 // create hasher for default hash algorithm
 DataHasher hasher = new DataHasher();
 // add file to hasher for hashing
 hasher.addFile(new File("test.txt"));
 // get the hash code
 DataHash hash = hasher.getHash();
 
 

Call chaining

DataHasher addData() functions always return the same hasher so it is possible to chain call to the hasher, if needed.

For example

 
 DataHasher hasher = new DataHasher();
 DataHash hash = hasher.addData("Header").addData(bodyBytes).addData(signatureBytes).getHash();
 
 

Constructor Summary

Constructors

Constructor and Description
DataHasher() Creates new data hasher for the default algorithm (SHA-256).
DataHasher(HashAlgorithm algorithm) Creates new data hasher for specified algorithm.
DataHasher(HashAlgorithm algorithm, boolean checkExpiration) Creates new data hasher for specified algorithm.

Method Summary

Modifier and Type	Method and Description
DataHasher	addData(byte[] data) Adds data to the digest using the specified array of bytes, starting at an offset of 0.
DataHasher	addData(byte[] data, int offset, int length) Updates the digest using the specified array of bytes, starting at the specified offset.
DataHasher	addData(DataHash dataHash) Adds DataHash.getImprint() to the digest.
DataHasher	addData(File file) Adds data to the digest using the specified file, starting at the offset 0.
DataHasher	addData(File file, int bufferSize) Adds data to the digest using the specified file, starting at the offset 0.
DataHasher	addData(InputStream inStream) Adds data to the digest using the specified input stream of bytes, starting at an offset of 0.
DataHasher	addData(InputStream inStream, int bufferSize) Adds data to the digest using the specified input stream of bytes, starting at an offset of 0.
DataHash	getHash() Gets the final hash value for the digest.
DataHasher	reset() Resets the hash calculation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DataHasher

public DataHasher(HashAlgorithm algorithm)

Creates new data hasher for specified algorithm.

Parameters:

algorithm - HashAlgorithm describing the algorithm to be used in hashing.

Throws:

IllegalArgumentException - when hash algorithm is unknown or the algorithm isn't implemented.

NullPointerException - when input algorithm is null.

DataHasher

public DataHasher(HashAlgorithm algorithm,
                  boolean checkExpiration)

Creates new data hasher for specified algorithm.

Parameters:

algorithm - HashAlgorithm describing the algorithm to be used in hashing.

checkExpiration - boolean flag to check, if algorithm is deprecated or obsolete.

Throws:

IllegalArgumentException - when hash algorithm is unknown, isn't implemented, is deprecated or is obsolete.

NullPointerException - when input algorithm is null.

DataHasher

public DataHasher()

Creates new data hasher for the default algorithm (SHA-256).

Throws:

IllegalArgumentException - when hash algorithm is unknown or the algorithm isn't implemented.

Method Detail

addData

public final DataHasher addData(byte[] data,
                                int offset,
                                int length)

Updates the digest using the specified array of bytes, starting at the specified offset.

Parameters:

data - the array of bytes.

offset - the offset to start from in the array of bytes.

length - the number of bytes to use, starting at the offset.

Returns:

The same DataHasher object for chaining calls.

Throws:

IllegalStateException - when hash is already been calculated.

addData

public final DataHasher addData(byte[] data)

Adds data to the digest using the specified array of bytes, starting at an offset of 0.

Parameters:

data - the array of bytes.

Returns:

The same DataHasher object for chaining calls.

Throws:

NullPointerException - when input data is null.

addData

public final DataHasher addData(InputStream inStream)

Adds data to the digest using the specified input stream of bytes, starting at an offset of 0.

Parameters:

inStream - input stream of bytes.

Returns:

The same DataHasher object for chaining calls.

Throws:

HashException - when hash calculation fails.

addData

public final DataHasher addData(File file)

Adds data to the digest using the specified file, starting at the offset 0.

Parameters:

file - input file.

Returns:

The same DataHasher object for chaining calls.

Throws:

HashException - when hash calculation fails.

addData

public final DataHasher addData(DataHash dataHash)

Adds DataHash.getImprint() to the digest.

Parameters:

dataHash - input digest.

Returns:

The same DataHasher object for chaining calls.

Throws:

NullPointerException - when input value is null.

addData

public final DataHasher addData(InputStream inStream,
                                int bufferSize)

Adds data to the digest using the specified input stream of bytes, starting at an offset of 0.

Parameters:

inStream - input stream of bytes.

bufferSize - maximum allowed buffer size for reading data.

Returns:

The same DataHasher object for chaining calls.

Throws:

HashException - when hash calculation fails.

NullPointerException - when input stream is null.

addData

public final DataHasher addData(File file,
                                int bufferSize)

Adds data to the digest using the specified file, starting at the offset 0.

Parameters:

file - input file.

bufferSize - size of buffer for reading data.

Returns:

The same DataHasher object for chaining calls.

Throws:

HashException - when hash calculation fails.

NullPointerException - when input file is null.

getHash

public final DataHash getHash()

Gets the final hash value for the digest.

This will not reset hash calculation.

Returns:

hashValue with computed hash value.

Throws:

HashException - when exception occurs during hash calculation.

reset

public final DataHasher reset()

Resets the hash calculation.

Returns:

The same DataHasher object for chaining calls.