Package org.saidone.misc

Class AnvDigestInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

org.saidone.misc.AnvDigestInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class AnvDigestInputStream
extends FilterInputStream

AnvDigestInputStream wraps another InputStream and computes a message digest while the data is read.

The digest algorithm is provided at construction time and each read operation updates the underlying MessageDigest. When the stream has been consumed the final hash value can be obtained via getHash(). This utility is typically used when a checksum or fingerprint of the streamed content is required without buffering the entire input in memory.

Field Summary

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

Constructors

Constructor	Description
AnvDigestInputStream(InputStream inputStream)	Creates a digesting stream that performs no hashing.
AnvDigestInputStream(InputStream inputStream, String algorithm)	Creates a new digesting stream using the supplied algorithm.

Method Summary

Modifier and Type	Method	Description
String	getHash()	Returns the computed hash as a lowercase hexadecimal string.
int	read()
int	read(byte[] b)
int	read(byte[] b, int off, int len)

Methods inherited from class java.io.FilterInputStream

available, close, mark, markSupported, reset, skip

Methods inherited from class java.io.InputStream

nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Methods inherited from class java.lang.Object

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

Constructor Details

AnvDigestInputStream

public AnvDigestInputStream(InputStream inputStream,
 String algorithm)
                     throws NoSuchAlgorithmException

Creates a new digesting stream using the supplied algorithm.

Parameters:

inputStream - the underlying stream to read

algorithm - name of the MessageDigest algorithm

Throws:

NoSuchAlgorithmException - if the algorithm is not available

AnvDigestInputStream

public AnvDigestInputStream(InputStream inputStream)
                     throws NoSuchAlgorithmException

Creates a digesting stream that performs no hashing. This constructor is mainly useful when the same type is required but hashing is disabled.

Parameters:

inputStream - the underlying stream

Throws:

NoSuchAlgorithmException - if the algorithm is not available

Method Details

read

public int read()
         throws IOException

Overrides:

read in class FilterInputStream

Throws:

IOException

read

public int read(byte[] b)
         throws IOException

Overrides:

read in class FilterInputStream

Throws:

IOException

read

public int read(byte[] b,
 int off,
 int len)
         throws IOException

Overrides:

read in class FilterInputStream

Throws:

IOException

getHash

public String getHash()

Returns the computed hash as a lowercase hexadecimal string. This method should be called once the stream has been fully consumed. If hashing was disabled via AnvDigestInputStream(InputStream), this method returns null.

Returns:

the digest of the read bytes or null if hashing is disabled