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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.
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* SciJava Common shared library for SciJava software.
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package org.scijava.util;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.xml.bind.DatatypeConverter;
/**
* Utility class for computing cryptographic hashes.
*
* @author Curtis Rueden
* @author Johannes Schindelin
*/
public final class DigestUtils {
private final static char[] hex = { '0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
private DigestUtils() {
// NB: Prevent instantiation of utility class.
}
/**
* Converts the given byte array to a string. UTF-8 encoding is used if
* available, with the platform's default encoding as a fallback.
*/
public static String string(final byte[] bytes) {
try {
return new String(bytes, "UTF-8");
}
catch (final UnsupportedEncodingException exc) {
return new String(bytes);
}
}
/**
* Converts the given string to a byte array. UTF-8 encoding is used if
* available, with the platform's default encoding as a fallback.
*/
public static byte[] bytes(final String s) {
try {
return s.getBytes("UTF-8");
}
catch (final UnsupportedEncodingException exc) {
return s.getBytes();
}
}
/** Converts the given integer into a byte array. */
public static byte[] bytes(final int i) {
return new byte[] {
(byte) (0xff & (i >>> 24)),
(byte) (0xff & (i >>> 16)),
(byte) (0xff & (i >>> 8)),
(byte) (0xff & i),
};
}
/** Converts the given byte array to a hexidecimal string. */
public static String hex(final byte[] bytes) {
final char[] buffer = new char[bytes.length * 2];
for (int i = 0; i < bytes.length; i++) {
buffer[i * 2] = hex[(bytes[i] & 0xf0) >> 4];
buffer[i * 2 + 1] = hex[bytes[i] & 0xf];
}
return new String(buffer);
}
/** Converts the given byte array to a base64 string. */
public static String base64(final byte[] bytes) {
return DatatypeConverter.printBase64Binary(bytes);
}
/**
* Gets the Java hash code of the given string, as a byte array.
*
* @see String#hashCode()
*/
public static byte[] hash(final String s) {
return bytes(s.hashCode());
}
/**
* Gets the hash code of the given byte array, as a byte array.
*
* @see String#hashCode()
* @see #string(byte[])
*/
public static byte[] hash(final byte[] bytes) {
// NB: We cannot use the hash code of the byte array directly,
// because it is not deterministic. Primitive byte arrays use the
// default Object implementation of hashCode(), which differs for
// every object instance. We need a consistent hash code, so we
// convert to String first, which fulfills this requirement.
return hash(string(bytes));
}
/** Gets the given byte array's SHA-1 checksum, or null if unavailable. */
public static byte[] sha1(final byte[] bytes) {
return digest("SHA-1", bytes);
}
/** Gets the given byte array's MD5 checksum, or null if unavailable. */
public static byte[] md5(final byte[] bytes) {
return digest("MD5", bytes);
}
/**
* Gets the given byte array's hash value according to the specified
* algorithm.
*
* @param algorithm The algorithm to use when generating the hash value.
* @param bytes The byte array for which to compute the hash value.
* @return The computed hash value, or null if the digest algorithm is not
* available.
* @see MessageDigest
*/
public static byte[] digest(final String algorithm, final byte[] bytes) {
try {
final MessageDigest digest = MessageDigest.getInstance(algorithm);
digest.update(bytes);
return digest.digest();
}
catch (final NoSuchAlgorithmException exc) {
return null;
}
}
/**
* Gets the given string's best available hash. Tries SHA-1 first, then MD5,
* then Java hash code.
*
* @see #bytes(String)
* @see #sha1(byte[])
* @see #md5(byte[])
* @see #hash(String)
*/
public static byte[] best(final String s) {
final byte[] bytes = bytes(s);
byte[] best = sha1(bytes);
if (best == null) best = md5(bytes);
if (best == null) best = hash(s);
return best;
}
/**
* Gets the given byte array's best available hash. Tries SHA-1 first, then
* MD5, then Java hash code.
*
* @see #sha1(byte[])
* @see #md5(byte[])
* @see #hash(byte[])
*/
public static byte[] best(final byte[] bytes) {
byte[] best = sha1(bytes);
if (best == null) best = md5(bytes);
if (best == null) best = hash(bytes);
return best;
}
/**
* Gets the hex string of the given string's best available hash.
*
* @see #best(String)
* @see #hex(byte[])
*/
public static String bestHex(final String text) {
return hex(best(text));
}
/**
* Gets the hex string of the given byte array's best available hash.
*
* @see #best(byte[])
* @see #hex(byte[])
*/
public static String bestHex(final byte[] bytes) {
return hex(best(bytes));
}
/**
* Gets the base64 string of the given string's best available hash.
*
* @see #best(String)
* @see #base64(byte[])
*/
public static String bestBase64(final String text) {
return base64(best(text));
}
/**
* Gets the base64 string of the given byte array's best available hash.
*
* @see #best(byte[])
* @see #base64(byte[])
*/
public static String bestBase64(final byte[] bytes) {
return base64(best(bytes));
}
}