/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you under
* the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.common.hash;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Objects;
/**
* This MessageDigests class provides convenience methods for obtaining
* thread local {@link MessageDigest} instances for MD5, SHA-1, and
* SHA-256 message digests.
*/
public final class MessageDigests {
private static ThreadLocal<MessageDigest> createThreadLocalMessageDigest(String digest) {
return ThreadLocal.withInitial(() -> {
try {
return MessageDigest.getInstance(digest);
} catch (NoSuchAlgorithmException e) {
throw new IllegalStateException("unexpected exception creating MessageDigest instance for [" + digest + "]", e);
}
});
}
private static final ThreadLocal<MessageDigest> MD5_DIGEST = createThreadLocalMessageDigest("MD5");
private static final ThreadLocal<MessageDigest> SHA_1_DIGEST = createThreadLocalMessageDigest("SHA-1");
private static final ThreadLocal<MessageDigest> SHA_256_DIGEST = createThreadLocalMessageDigest("SHA-256");
/**
* Returns a {@link MessageDigest} instance for MD5 digests; note
* that the instance returned is thread local and must not be
* shared amongst threads.
*
* @return a thread local {@link MessageDigest} instance that
* provides MD5 message digest functionality.
*/
public static MessageDigest md5() {
return get(MD5_DIGEST);
}
/**
* Returns a {@link MessageDigest} instance for SHA-1 digests; note
* that the instance returned is thread local and must not be
* shared amongst threads.
*
* @return a thread local {@link MessageDigest} instance that
* provides SHA-1 message digest functionality.
*/
public static MessageDigest sha1() {
return get(SHA_1_DIGEST);
}
/**
* Returns a {@link MessageDigest} instance for SHA-256 digests;
* note that the instance returned is thread local and must not be
* shared amongst threads.
*
* @return a thread local {@link MessageDigest} instance that
* provides SHA-256 message digest functionality.
*/
public static MessageDigest sha256() {
return get(SHA_256_DIGEST);
}
private static MessageDigest get(ThreadLocal<MessageDigest> messageDigest) {
MessageDigest instance = messageDigest.get();
instance.reset();
return instance;
}
private static final char[] HEX_DIGITS = "0123456789abcdef".toCharArray();
/**
* Format a byte array as a hex string.
*
* @param bytes the input to be represented as hex.
* @return a hex representation of the input as a String.
*/
public static String toHexString(byte[] bytes) {
Objects.requireNonNull(bytes);
StringBuilder sb = new StringBuilder(2 * bytes.length);
for (int i = 0; i < bytes.length; i++) {
byte b = bytes[i];
sb.append(HEX_DIGITS[b >> 4 & 0xf]).append(HEX_DIGITS[b & 0xf]);
}
return sb.toString();
}
}