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1   /*
2    * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
3    * and other copyright owners as documented in the project's IP log.
4    *
5    * This program and the accompanying materials are made available
6    * under the terms of the Eclipse Distribution License v1.0 which
7    * accompanies this distribution, is reproduced below, and is
8    * available at http://www.eclipse.org/org/documents/edl-v10.php
9    *
10   * All rights reserved.
11   *
12   * Redistribution and use in source and binary forms, with or
13   * without modification, are permitted provided that the following
14   * conditions are met:
15   *
16   * - Redistributions of source code must retain the above copyright
17   *   notice, this list of conditions and the following disclaimer.
18   *
19   * - Redistributions in binary form must reproduce the above
20   *   copyright notice, this list of conditions and the following
21   *   disclaimer in the documentation and/or other materials provided
22   *   with the distribution.
23   *
24   * - Neither the name of the Eclipse Foundation, Inc. nor the
25   *   names of its contributors may be used to endorse or promote
26   *   products derived from this software without specific prior
27   *   written permission.
28   *
29   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30   * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42   */
43  package org.eclipse.jgit.lfs.lib;
44  
45  import java.security.MessageDigest;
46  import java.security.NoSuchAlgorithmException;
47  import java.text.MessageFormat;
48  
49  import org.eclipse.jgit.lfs.internal.LfsText;
50  
51  /**
52   * Misc. constants used throughout JGit LFS extension.
53   *
54   * @since 4.3
55   **/
56  @SuppressWarnings("nls")
57  public final class Constants {
58  	/** Hash function used natively by Git LFS extension for large objects. */
59  	private static final String LONG_HASH_FUNCTION = "SHA-256";
60  
61  	/**
62  	 * A Git LFS large object hash is 256 bits, i.e. 32 bytes.
63  	 * <p>
64  	 * Changing this assumption is not going to be as easy as changing this
65  	 * declaration.
66  	 */
67  	public static final int LONG_OBJECT_ID_LENGTH = 32;
68  
69  	/**
70  	 * A Git LFS large object can be expressed as a 64 character string of
71  	 * hexadecimal digits.
72  	 *
73  	 * @see #LONG_OBJECT_ID_LENGTH
74  	 */
75  	public static final int LONG_OBJECT_ID_STRING_LENGTH = LONG_OBJECT_ID_LENGTH
76  			* 2;
77  
78  	/**
79  	 * Create a new digest function for objects.
80  	 *
81  	 * @return a new digest object.
82  	 * @throws RuntimeException
83  	 *             this Java virtual machine does not support the required hash
84  	 *             function. Very unlikely given that JGit uses a hash function
85  	 *             that is in the Java reference specification.
86  	 */
87  	public static MessageDigest newMessageDigest() {
88  		try {
89  			return MessageDigest.getInstance(LONG_HASH_FUNCTION);
90  		} catch (NoSuchAlgorithmException nsae) {
91  			throw new RuntimeException(MessageFormat.format(
92  					LfsText.get().requiredHashFunctionNotAvailable,
93  					LONG_HASH_FUNCTION), nsae);
94  		}
95  	}
96  
97  	static {
98  		if (LONG_OBJECT_ID_LENGTH != newMessageDigest().getDigestLength())
99  			throw new LinkageError(
100 					LfsText.get().incorrectLONG_OBJECT_ID_LENGTH);
101 	}
102 
103 	/**
104 	 * Content type used by LFS REST API as defined in
105 	 * {@link "https://github.com/github/git-lfs/blob/master/docs/api/http-v1-batch.md"}
106 	 */
107 	public static String CONTENT_TYPE_GIT_LFS_JSON = "application/vnd.git-lfs+json";
108 
109 	/**
110 	 * "arbitrary binary data" as defined in RFC 2046
111 	 * {@link "https://www.ietf.org/rfc/rfc2046.txt"}
112 	 */
113 	public static String HDR_APPLICATION_OCTET_STREAM = "application/octet-stream";
114 }