org.sf.rhash

Class RHash

java.lang.Object

org.sf.rhash.RHash

public final class RHash
extends Object

Incremental hasher. This class allows you to do incremental hashing for set of hashing algorithms.

To do hashing RHash instance is first created and then filled with message chunks using update() methods. Finally, finish() should be called to end all calculations and generate digests, which then can be obtained with getDigest() method. Note, that trying to update finished RHash has no effect other than throwing IllegalStateException though you can reuse this class by calling reset() method, returning it to the state which was immediately after creating.

To quickly produce message digest for a single message/file and a single algorithm you may use convenience methods RHash.computeHash().

This class is thread safe.

Constructor Summary

Constructors

Constructor and Description
RHash(HashType... types) Creates new RHash to compute message digests for given types.
RHash(Set<HashType> types) Creates new RHash to compute message digests for given types.

Method Summary

Methods

Modifier and Type	Method and Description
static Digest	computeHash(HashType type, byte[] data) Computes hash of given data.
static Digest	computeHash(HashType type, byte[] data, int ofs, int len) Computes hash of given range in data.
static Digest	computeHash(HashType type, File file) Computes hash of given string.
static Digest	computeHash(HashType type, String str) Computes hash of given string.
static Digest	computeHash(HashType type, String str, String encoding) Computes hash of given string.
protected void	finalize() Called by garbage collector to free native resources.
void	finish() Finishes calculation of hash codes.
Digest	getDigest() Returns digest for processed data.
Digest	getDigest(HashType type) Returns digest for given hash type.
String	getMagnet(String filename) Returns magnet link for given filename.
String	getMagnet(String filename, HashType... types) Returns magnet link that includes specified filename and hashes for given algorithms.
static String	getMagnetFor(String filename, HashType... types) Produces magnet link for specified file with given hashes.
static String	getMagnetFor(String filename, Set<HashType> types) Produces magnet link for specified file with given hashes.
boolean	isFinished() Tests whether this RHash is finished or not.
void	reset() Resets this RHash to initial state.
RHash	update(byte[] data) Updates this RHash with new data chunk.
RHash	update(byte[] data, int ofs, int len) Updates this RHash with new data chunk.
RHash	update(File file) Updates this RHash with data from given file.
RHash	update(String str) Updates this RHash with new data chunk.

Methods inherited from class java.lang.Object

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

Constructor Detail

RHash

public RHash(HashType... types)

Creates new RHash to compute message digests for given types.

Parameters:

types - types of hashing algorithms

Throws:

NullPointerException - if any of arguments is null

IllegalArgumentException - if zero hash types specified

RHash

public RHash(Set<HashType> types)

Creates new RHash to compute message digests for given types.

Parameters:

types - set of hashing types

Throws:

NullPointerException - if argument is null

IllegalArgumentException - if argument is empty set

Method Detail

computeHash

public static Digest computeHash(HashType type,
                 byte[] data,
                 int ofs,
                 int len)

Computes hash of given range in data. This method calculates message digest for byte subsequence in array data starting from data[ofs] and ending at data[ofs+len-1].

Parameters:

type - type of hash algorithm

data - the bytes to process

ofs - index of the first byte in array to process

len - count of bytes to process

Returns:

message digest for specified subarray

Throws:

NullPointerException - if either type or data is null

IndexOutOfBoundsException - if ofs < 0, len < 0 or ofs+len > data.length

computeHash

public static Digest computeHash(HashType type,
                 byte[] data)

Computes hash of given data.

Parameters:

type - type of hash algorithm

data - the bytes to process

Returns:

message digest for specified array

Throws:

NullPointerException - if either type or data is null

computeHash

public static Digest computeHash(HashType type,
                 String str,
                 String encoding)
                          throws UnsupportedEncodingException

Computes hash of given string. String is encoded into a sequence of bytes using the specified charset.

Parameters:

type - type of hash algorithm

str - the string to process

encoding - encoding to use

Returns:

message digest for specified string

Throws:

NullPointerException - if any of arguments is null

UnsupportedEncodingException - if specified encoding is not supported

computeHash

public static Digest computeHash(HashType type,
                 String str)

Computes hash of given string. String is encoded into a sequence of bytes using the default platform encoding.

Parameters:

type - type of hash algorithm

str - the string to process

Returns:

message digest for specified string

Throws:

NullPointerException - if any of arguments is null

computeHash

public static Digest computeHash(HashType type,
                 File file)
                          throws IOException

Computes hash of given string.

Parameters:

type - type of hash algorithm

file - the file to process

Returns:

data hash

Throws:

NullPointerException - if any of arguments is null

IOException - if an I/O error occurs while hashing

getMagnetFor

public static String getMagnetFor(String filename,
                  HashType... types)
                           throws IOException

Produces magnet link for specified file with given hashes.

Parameters:

filename - the file to generate magnet for

types - types of hashing algorithms

Throws:

IOException

getMagnetFor

public static String getMagnetFor(String filename,
                  Set<HashType> types)
                           throws IOException

Produces magnet link for specified file with given hashes.

Parameters:

filename - the file to generate magnet for

types - set of hashing types

Throws:

IOException

update

public RHash update(byte[] data,
           int ofs,
           int len)

Updates this RHash with new data chunk. This method hashes bytes from data[ofs] through data[ofs+len-1].

Parameters:

data - data to be hashed

ofs - index of the first byte to hash

len - number of bytes to hash

Returns:

this object

Throws:

NullPointerException - if data is null

IndexOutOfBoundsException - if ofs < 0, len < 0 or ofs+len > data.length

IllegalStateException - if finish() was called and there were no subsequent calls of reset()

update

public RHash update(byte[] data)

Updates this RHash with new data chunk. This method has the same effect as

update(data, 0, data.length)

Parameters:

data - data to be hashed

Returns:

this object

Throws:

NullPointerException - if data is null

IllegalStateException - if finish() was called and there were no subsequent calls of reset()

update

public RHash update(String str)

Updates this RHash with new data chunk. String is encoded into a sequence of bytes using the default platform encoding.

Parameters:

str - string to be hashed

Returns:

this object

Throws:

NullPointerException - if str is null

IllegalStateException - if finish() was called and there were no subsequent calls of reset()

update

public RHash update(File file)
             throws IOException

Updates this RHash with data from given file.

Parameters:

file - file to be hashed

Returns:

this object

Throws:

IOException - if an I/O error occurs

NullPointerException - if file is null

IllegalStateException - if finish() was called and there were no subsequent calls of reset()

finish

public void finish()

Finishes calculation of hash codes. Does nothing if RHash is already finished.

reset

public void reset()

Resets this RHash to initial state. The RHash becomes available to process new data chunks. Note, that this method returns RHash to the state after creating the object, NOT the state when hashing continues. Therefore, all previously calculated hashes are lost and process starts from the very beginning.

isFinished

public boolean isFinished()

Tests whether this RHash is finished or not.

Returns:

false if this RHash is ready to receive new data for hashing; true if hash calculations are finished

getDigest

public Digest getDigest(HashType type)

Returns digest for given hash type.

Parameters:

type - hash type

Returns:

Digest for processed data

Throws:

NullPointerException - if type is null

IllegalStateException - if this RHash is not finished

IllegalArgumentException - if this RHash was not created to calculate hash for specified algorithm

getDigest

public Digest getDigest()

Returns digest for processed data. If more than one hashing type was passed to the RHash constructor, then the least hash type (in the order induced by compareTo()) is used.

Returns:

Digest for processed data

Throws:

IllegalStateException - if this RHash is not finished

getMagnet

public String getMagnet(String filename,
               HashType... types)

Returns magnet link that includes specified filename and hashes for given algorithms. Only hashes that were computed by this RHash are included.

Parameters:

filename - file name to include in magnet, may be null

Returns:

magnet link

Throws:

IllegalStateException - if this RHash is not finished

getMagnet

public String getMagnet(String filename)

Returns magnet link for given filename. Magnet includes all hashes that were computed by this RHash.

Parameters:

filename - file name to include in magnet, may be null

Returns:

magnet link

Throws:

IllegalStateException - if this RHash is not finished

finalize

protected void finalize()

Called by garbage collector to free native resources.

Overrides:

finalize in class Object