plume

Class Digest

java.lang.Object

plume.Digest

public final class Digest
extends java.lang.Object

Computes a message digest for a file. The primary entry point into this class is getFileDigest(String,MessageDigest).

Method Summary

Modifier and Type	Method and Description
static byte[]	getFileDigest(java.lang.String filename, java.security.MessageDigest md) This convenience method is used by both create() and verify().
static byte[]	hexDecode(java.lang.String s) A convenience method to convert from a string of hexadecimal digits to an array of bytes.
static java.lang.String	hexEncode(byte[] bytes) A convenience method to convert an array of bytes to a String.

Methods inherited from class java.lang.Object

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

Method Detail

getFileDigest

public static byte[] getFileDigest(java.lang.String filename,
                                   java.security.MessageDigest md)
                            throws java.io.IOException

This convenience method is used by both create() and verify(). It reads the contents of a named file and computes a message digest for it, using the specified MessageDigest object.

Parameters:

filename - the file to read

md - the MessageDigest

Returns:

the message digest

Throws:

java.io.IOException - if there is a problem reading the file

hexEncode

public static java.lang.String hexEncode(byte[] bytes)

A convenience method to convert an array of bytes to a String. We do this simply by converting each byte to two hexadecimal digits. Something like Base 64 encoding is more compact, but harder to encode.

Parameters:

bytes - the bytes to convert to a String

Returns:

a String representation of the input bytes

hexDecode

public static byte[] hexDecode(java.lang.String s)
                        throws java.lang.IllegalArgumentException

A convenience method to convert from a string of hexadecimal digits to an array of bytes. This method is the reverse of hexEncode(byte[]).

Parameters:

s - the String to convert to an array of bytes

Returns:

the bytes equivalent to the input String

Throws:

java.lang.IllegalArgumentException