001/* 002 * Licensed to DuraSpace under one or more contributor license agreements. 003 * See the NOTICE file distributed with this work for additional information 004 * regarding copyright ownership. 005 * 006 * DuraSpace licenses this file to you under the Apache License, 007 * Version 2.0 (the "License"); you may not use this file except in 008 * compliance with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.fcrepo.kernel.api.utils; 019 020import static com.google.common.base.Throwables.propagate; 021import static java.util.Collections.singletonMap; 022import static org.apache.commons.codec.binary.Hex.encodeHexString; 023import static org.slf4j.LoggerFactory.getLogger; 024 025import java.net.URI; 026import java.net.URISyntaxException; 027import java.util.Map; 028 029import org.slf4j.Logger; 030 031import com.google.common.collect.ImmutableMap; 032 033/** 034 * Digest helpers to convert digests (checksums) into URI strings 035 * (based loosely on Magnet URIs) 036 * @author Chris Beer 037 * @since Mar 6, 2013 038 */ 039public final class ContentDigest { 040 041 private static final Logger LOGGER = getLogger(ContentDigest.class); 042 043 public static final Map<String, String> algorithmToScheme = ImmutableMap 044 .of("SHA-1", "urn:sha1", "SHA1", "urn:sha1"); 045 046 public static final Map<String, String> schemeToAlgorithm = 047 singletonMap("urn:sha1", "SHA-1"); 048 049 public static final String DEFAULT_ALGORITHM = "SHA-1"; 050 051 private ContentDigest() { 052 } 053 054 /** 055 * Convert a MessageDigest algorithm and checksum value to a URN 056 * @param algorithm the message digest algorithm 057 * @param value the checksum value 058 * @return URI 059 */ 060 public static URI asURI(final String algorithm, final String value) { 061 try { 062 final String scheme = algorithmToScheme.get(algorithm); 063 064 return new URI(scheme, value, null); 065 } catch (final URISyntaxException unlikelyException) { 066 LOGGER.warn("Exception creating checksum URI: {}", 067 unlikelyException); 068 throw propagate(unlikelyException); 069 } 070 } 071 072 /** 073 * Convert a MessageDigest algorithm and checksum byte-array data to a URN 074 * @param algorithm the message digest algorithm 075 * @param data the checksum byte-array data 076 * @return URI 077 */ 078 public static URI asURI(final String algorithm, final byte[] data) { 079 return asURI(algorithm, asString(data)); 080 } 081 082 /** 083 * Given a digest URI, get the corresponding MessageDigest algorithm 084 * @param digestUri the digest uri 085 * @return MessageDigest algorithm 086 */ 087 public static String getAlgorithm(final URI digestUri) { 088 if (digestUri == null) { 089 return DEFAULT_ALGORITHM; 090 } 091 return schemeToAlgorithm 092 .get(digestUri.getScheme() + ":" + 093 digestUri.getSchemeSpecificPart().split(":", 2)[0]); 094 } 095 096 private static String asString(final byte[] data) { 097 return encodeHexString(data); 098 } 099 100 /** 101 * Placeholder checksum value. 102 * @return URI 103 */ 104 public static URI missingChecksum() { 105 return asURI("SHA-1", "missing"); 106 } 107 108}