/*
 * Copyright (C) 2008, Google Inc.
 * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2006-2017, Shawn O. Pearce <spearce@spearce.org>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.lib;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.MessageFormat;

import org.eclipse.jgit.errors.CorruptObjectException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.util.MutableInteger;

Misc. constants and helpers used throughout JGit.
/**
 * Misc. constants and helpers used throughout JGit.
 */
@SuppressWarnings("nls")
public final class Constants {
	
Hash function used natively by Git for all objects. /** Hash function used natively by Git for all objects. */
	private static final String HASH_FUNCTION = "SHA-1";

	
A Git object hash is 160 bits, i.e. 20 bytes.

Changing this assumption is not going to be as easy as changing this
declaration.
/**
	 * A Git object hash is 160 bits, i.e. 20 bytes.
	 * <p>
	 * Changing this assumption is not going to be as easy as changing this
	 * declaration.
	 */
	public static final int OBJECT_ID_LENGTH = 20;

	
A Git object can be expressed as a 40 character string of hexadecimal
digits.
See Also:
OBJECT_ID_LENGTH/**
	 * A Git object can be expressed as a 40 character string of hexadecimal
	 * digits.
	 *
	 * @see #OBJECT_ID_LENGTH
	 */
	public static final int OBJECT_ID_STRING_LENGTH = OBJECT_ID_LENGTH * 2;

	
Special name for the "HEAD" symbolic-ref. /** Special name for the "HEAD" symbolic-ref. */
	public static final String HEAD = "HEAD";

	
Special name for the "FETCH_HEAD" symbolic-ref. /** Special name for the "FETCH_HEAD" symbolic-ref. */
	public static final String FETCH_HEAD = "FETCH_HEAD";

	
Text string that identifies an object as a commit.

Commits connect trees into a string of project histories, where each
commit is an assertion that the best way to continue is to use this other
tree (set of files).
/**
	 * Text string that identifies an object as a commit.
	 * <p>
	 * Commits connect trees into a string of project histories, where each
	 * commit is an assertion that the best way to continue is to use this other
	 * tree (set of files).
	 */
	public static final String TYPE_COMMIT = "commit";

	
Text string that identifies an object as a blob.

Blobs store whole file revisions. They are used for any user file, as
well as for symlinks. Blobs form the bulk of any project's storage space.
/**
	 * Text string that identifies an object as a blob.
	 * <p>
	 * Blobs store whole file revisions. They are used for any user file, as
	 * well as for symlinks. Blobs form the bulk of any project's storage space.
	 */
	public static final String TYPE_BLOB = "blob";

	
Text string that identifies an object as a tree.

Trees attach object ids (hashes) to names and file modes. The normal use
for a tree is to store a version of a directory and its contents.
/**
	 * Text string that identifies an object as a tree.
	 * <p>
	 * Trees attach object ids (hashes) to names and file modes. The normal use
	 * for a tree is to store a version of a directory and its contents.
	 */
	public static final String TYPE_TREE = "tree";

	
Text string that identifies an object as an annotated tag.

Annotated tags store a pointer to any other object, and an additional
message. It is most commonly used to record a stable release of the
project.
/**
	 * Text string that identifies an object as an annotated tag.
	 * <p>
	 * Annotated tags store a pointer to any other object, and an additional
	 * message. It is most commonly used to record a stable release of the
	 * project.
	 */
	public static final String TYPE_TAG = "tag";

	private static final byte[] ENCODED_TYPE_COMMIT = encodeASCII(TYPE_COMMIT);

	private static final byte[] ENCODED_TYPE_BLOB = encodeASCII(TYPE_BLOB);

	private static final byte[] ENCODED_TYPE_TREE = encodeASCII(TYPE_TREE);

	private static final byte[] ENCODED_TYPE_TAG = encodeASCII(TYPE_TAG);

	
An unknown or invalid object type code. /** An unknown or invalid object type code. */
	public static final int OBJ_BAD = -1;

	
In-pack object type: extended types.

This header code is reserved for future expansion. It is currently
undefined/unsupported.
/**
	 * In-pack object type: extended types.
	 * <p>
	 * This header code is reserved for future expansion. It is currently
	 * undefined/unsupported.
	 */
	public static final int OBJ_EXT = 0;

	
In-pack object type: commit.

Indicates the associated object is a commit.

This constant is fixed and is defined by the Git packfile format.
See Also:
TYPE_COMMIT/**
	 * In-pack object type: commit.
	 * <p>
	 * Indicates the associated object is a commit.
	 * <p>
	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
	 *
	 * @see #TYPE_COMMIT
	 */
	public static final int OBJ_COMMIT = 1;

	
In-pack object type: tree.

Indicates the associated object is a tree.

This constant is fixed and is defined by the Git packfile format.
See Also:
TYPE_BLOB/**
	 * In-pack object type: tree.
	 * <p>
	 * Indicates the associated object is a tree.
	 * <p>
	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
	 *
	 * @see #TYPE_BLOB
	 */
	public static final int OBJ_TREE = 2;

	
In-pack object type: blob.

Indicates the associated object is a blob.

This constant is fixed and is defined by the Git packfile format.
See Also:
TYPE_BLOB/**
	 * In-pack object type: blob.
	 * <p>
	 * Indicates the associated object is a blob.
	 * <p>
	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
	 *
	 * @see #TYPE_BLOB
	 */
	public static final int OBJ_BLOB = 3;

	
In-pack object type: annotated tag.

Indicates the associated object is an annotated tag.

This constant is fixed and is defined by the Git packfile format.
See Also:
TYPE_TAG/**
	 * In-pack object type: annotated tag.
	 * <p>
	 * Indicates the associated object is an annotated tag.
	 * <p>
	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
	 *
	 * @see #TYPE_TAG
	 */
	public static final int OBJ_TAG = 4;

	
In-pack object type: reserved for future use. /** In-pack object type: reserved for future use. */
	public static final int OBJ_TYPE_5 = 5;

	
In-pack object type: offset delta

Objects stored with this type actually have a different type which must
be obtained from their delta base object. Delta objects store only the
changes needed to apply to the base object in order to recover the
original object.

An offset delta uses a negative offset from the start of this object to
refer to its delta base. The base object must exist in this packfile
(even in the case of a thin pack).

This constant is fixed and is defined by the Git packfile format.
/**
	 * In-pack object type: offset delta
	 * <p>
	 * Objects stored with this type actually have a different type which must
	 * be obtained from their delta base object. Delta objects store only the
	 * changes needed to apply to the base object in order to recover the
	 * original object.
	 * <p>
	 * An offset delta uses a negative offset from the start of this object to
	 * refer to its delta base. The base object must exist in this packfile
	 * (even in the case of a thin pack).
	 * <p>
	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
	 */
	public static final int OBJ_OFS_DELTA = 6;

	
In-pack object type: reference delta

Objects stored with this type actually have a different type which must
be obtained from their delta base object. Delta objects store only the
changes needed to apply to the base object in order to recover the
original object.

A reference delta uses a full object id (hash) to reference the delta
base. The base object is allowed to be omitted from the packfile, but
only in the case of a thin pack being transferred over the network.

This constant is fixed and is defined by the Git packfile format.
/**
	 * In-pack object type: reference delta
	 * <p>
	 * Objects stored with this type actually have a different type which must
	 * be obtained from their delta base object. Delta objects store only the
	 * changes needed to apply to the base object in order to recover the
	 * original object.
	 * <p>
	 * A reference delta uses a full object id (hash) to reference the delta
	 * base. The base object is allowed to be omitted from the packfile, but
	 * only in the case of a thin pack being transferred over the network.
	 * <p>
	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
	 */
	public static final int OBJ_REF_DELTA = 7;

	
Pack file signature that occurs at file header - identifies file as Git
packfile formatted.

This constant is fixed and is defined by the Git packfile format.
/**
	 * Pack file signature that occurs at file header - identifies file as Git
	 * packfile formatted.
	 * <p>
	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
	 */
	public static final byte[] PACK_SIGNATURE = { 'P', 'A', 'C', 'K' };

	
Native character encoding for commit messages, file names...
Deprecated:
Use StandardCharsets.UTF_8 directly instead./**
	 * Native character encoding for commit messages, file names...
	 *
	 * @deprecated Use {@link java.nio.charset.StandardCharsets#UTF_8} directly
	 *             instead.
	 */
	@Deprecated
	public static final Charset CHARSET;

	
Native character encoding for commit messages, file names...
Deprecated:
Use StandardCharsets.UTF_8 directly instead./**
	 * Native character encoding for commit messages, file names...
	 *
	 * @deprecated Use {@link java.nio.charset.StandardCharsets#UTF_8} directly
	 *             instead.
	 */
	@Deprecated
	public static final String CHARACTER_ENCODING;

	
Default main branch name /** Default main branch name */
	public static final String MASTER = "master";

	
Default stash branch name /** Default stash branch name */
	public static final String STASH = "stash";

	
Prefix for branch refs /** Prefix for branch refs */
	public static final String R_HEADS = "refs/heads/";

	
Prefix for remotes refs /** Prefix for remotes refs */
	public static final String R_REMOTES = "refs/remotes/";

	
Prefix for tag refs /** Prefix for tag refs */
	public static final String R_TAGS = "refs/tags/";

	
Prefix for notes refs /** Prefix for notes refs */
	public static final String R_NOTES = "refs/notes/";

	
Standard notes ref /** Standard notes ref */
	public static final String R_NOTES_COMMITS = R_NOTES + "commits";

	
Prefix for any ref /** Prefix for any ref */
	public static final String R_REFS = "refs/";

	
Standard stash ref /** Standard stash ref */
	public static final String R_STASH = R_REFS + STASH;

	
Logs folder name /** Logs folder name */
	public static final String LOGS = "logs";

	
Objects folder name
Since:
5.5/**
	 * Objects folder name
	 * @since 5.5
	 */
	public static final String OBJECTS = "objects";

	
Info refs folder /** Info refs folder */
	public static final String INFO_REFS = "info/refs";

	
Info alternates file (goes under OBJECTS)
Since:
5.5/**
	 * Info alternates file (goes under OBJECTS)
	 * @since 5.5
	 */
	public static final String INFO_ALTERNATES = "info/alternates";

	
HTTP alternates file (goes under OBJECTS)
Since:
5.5/**
	 * HTTP alternates file (goes under OBJECTS)
	 * @since 5.5
	 */
	public static final String INFO_HTTP_ALTERNATES = "info/http-alternates";

	
Packed refs file /** Packed refs file */
	public static final String PACKED_REFS = "packed-refs";

	
Excludes-file
Since:
3.0/**
	 * Excludes-file
	 *
	 * @since 3.0
	 */
	public static final String INFO_EXCLUDE = "info/exclude";

	
Attributes-override-file
Since:
4.2/**
	 * Attributes-override-file
	 *
	 * @since 4.2
	 */
	public static final String INFO_ATTRIBUTES = "info/attributes";

	
The system property that contains the system user name
Since:
3.6/**
	 * The system property that contains the system user name
	 *
	 * @since 3.6
	 */
	public static final String OS_USER_DIR = "user.dir";

	
The system property that contains the system user name /** The system property that contains the system user name */
	public static final String OS_USER_NAME_KEY = "user.name";

	
The environment variable that contains the author's name /** The environment variable that contains the author's name */
	public static final String GIT_AUTHOR_NAME_KEY = "GIT_AUTHOR_NAME";

	
The environment variable that contains the author's email /** The environment variable that contains the author's email */
	public static final String GIT_AUTHOR_EMAIL_KEY = "GIT_AUTHOR_EMAIL";

	
The environment variable that contains the commiter's name /** The environment variable that contains the commiter's name */
	public static final String GIT_COMMITTER_NAME_KEY = "GIT_COMMITTER_NAME";

	
The environment variable that contains the commiter's email /** The environment variable that contains the commiter's email */
	public static final String GIT_COMMITTER_EMAIL_KEY = "GIT_COMMITTER_EMAIL";

	
The environment variable that blocks use of the system config file
Since:
3.3/**
	 * The environment variable that blocks use of the system config file
	 *
	 * @since 3.3
	 */
	public static final String GIT_CONFIG_NOSYSTEM_KEY = "GIT_CONFIG_NOSYSTEM";

	
The environment variable that limits how close to the root of the file
systems JGit will traverse when looking for a repository root.
/**
	 * The environment variable that limits how close to the root of the file
	 * systems JGit will traverse when looking for a repository root.
	 */
	public static final String GIT_CEILING_DIRECTORIES_KEY = "GIT_CEILING_DIRECTORIES";

	
The environment variable that tells us which directory is the ".git"
directory
/**
	 * The environment variable that tells us which directory is the ".git"
	 * directory
	 */
	public static final String GIT_DIR_KEY = "GIT_DIR";

	
The environment variable that tells us which directory is the working
directory.
/**
	 * The environment variable that tells us which directory is the working
	 * directory.
	 */
	public static final String GIT_WORK_TREE_KEY = "GIT_WORK_TREE";

	
The environment variable that tells us which file holds the Git index.
/**
	 * The environment variable that tells us which file holds the Git index.
	 */
	public static final String GIT_INDEX_FILE_KEY = "GIT_INDEX_FILE";

	
The environment variable that tells us where objects are stored
/**
	 * The environment variable that tells us where objects are stored
	 */
	public static final String GIT_OBJECT_DIRECTORY_KEY = "GIT_OBJECT_DIRECTORY";

	
The environment variable that tells us where to look for objects, besides
the default objects directory.
/**
	 * The environment variable that tells us where to look for objects, besides
	 * the default objects directory.
	 */
	public static final String GIT_ALTERNATE_OBJECT_DIRECTORIES_KEY = "GIT_ALTERNATE_OBJECT_DIRECTORIES";

	
Default value for the user name if no other information is available /** Default value for the user name if no other information is available */
	public static final String UNKNOWN_USER_DEFAULT = "unknown-user";

	
Beginning of the common "Signed-off-by: " commit message line /** Beginning of the common "Signed-off-by: " commit message line */
	public static final String SIGNED_OFF_BY_TAG = "Signed-off-by: ";

	
A gitignore file name /** A gitignore file name */
	public static final String GITIGNORE_FILENAME = ".gitignore";

	
Default remote name used by clone, push and fetch operations /** Default remote name used by clone, push and fetch operations */
	public static final String DEFAULT_REMOTE_NAME = "origin";

	
Default name for the Git repository directory /** Default name for the Git repository directory */
	public static final String DOT_GIT = ".git";

	
Default name for the Git repository configuration /** Default name for the Git repository configuration */
	public static final String CONFIG = "config";

	
A bare repository typically ends with this string /** A bare repository typically ends with this string */
	public static final String DOT_GIT_EXT = ".git";

	
Name of the attributes file
Since:
3.7/**
	 * Name of the attributes file
	 *
	 * @since 3.7
	 */
	public static final String DOT_GIT_ATTRIBUTES = ".gitattributes";

	
Key for filters in .gitattributes
Since:
4.2/**
	 * Key for filters in .gitattributes
	 *
	 * @since 4.2
	 */
	public static final String ATTR_FILTER = "filter";

	
clean command name, used to call filter driver
Since:
4.2/**
	 * clean command name, used to call filter driver
	 *
	 * @since 4.2
	 */
	public static final String ATTR_FILTER_TYPE_CLEAN = "clean";

	
smudge command name, used to call filter driver
Since:
4.2/**
	 * smudge command name, used to call filter driver
	 *
	 * @since 4.2
	 */
	public static final String ATTR_FILTER_TYPE_SMUDGE = "smudge";

	
Builtin filter commands start with this prefix
Since:
4.6/**
	 * Builtin filter commands start with this prefix
	 *
	 * @since 4.6
	 */
	public static final String BUILTIN_FILTER_PREFIX = "jgit://builtin/";

	
Name of the ignore file /** Name of the ignore file */
	public static final String DOT_GIT_IGNORE = ".gitignore";

	
Name of the submodules file /** Name of the submodules file */
	public static final String DOT_GIT_MODULES = ".gitmodules";

	
Name of the .git/shallow file /** Name of the .git/shallow file */
	public static final String SHALLOW = "shallow";

	
Prefix of the first line in a ".git" file
Since:
3.6/**
	 * Prefix of the first line in a ".git" file
	 *
	 * @since 3.6
	 */
	public static final String GITDIR = "gitdir: ";

	
Name of the folder (inside gitDir) where submodules are stored
Since:
3.6/**
	 * Name of the folder (inside gitDir) where submodules are stored
	 *
	 * @since 3.6
	 */
	public static final String MODULES = "modules";

	
Name of the folder (inside gitDir) where the hooks are stored.
Since:
3.7/**
	 * Name of the folder (inside gitDir) where the hooks are stored.
	 *
	 * @since 3.7
	 */
	public static final String HOOKS = "hooks";

	
Merge attribute.
Since:
4.9/**
	 * Merge attribute.
	 *
	 * @since 4.9
	 */
	public static final String ATTR_MERGE = "merge"; //$NON-NLS-1$

	
Diff attribute.
Since:
4.11/**
	 * Diff attribute.
	 *
	 * @since 4.11
	 */
	public static final String ATTR_DIFF = "diff"; //$NON-NLS-1$

	
Binary value for custom merger.
Since:
4.9/**
	 * Binary value for custom merger.
	 *
	 * @since 4.9
	 */
	public static final String ATTR_BUILTIN_BINARY_MERGER = "binary"; //$NON-NLS-1$

	
Create a new digest function for objects.
Throws:
RuntimeException – 
            this Java virtual machine does not support the required hash
            function. Very unlikely given that JGit uses a hash function
            that is in the Java reference specification.
Returns:
a new digest object./**
	 * Create a new digest function for objects.
	 *
	 * @return a new digest object.
	 * @throws java.lang.RuntimeException
	 *             this Java virtual machine does not support the required hash
	 *             function. Very unlikely given that JGit uses a hash function
	 *             that is in the Java reference specification.
	 */
	public static MessageDigest newMessageDigest() {
		try {
			return MessageDigest.getInstance(HASH_FUNCTION);
		} catch (NoSuchAlgorithmException nsae) {
			throw new RuntimeException(MessageFormat.format(
					JGitText.get().requiredHashFunctionNotAvailable, HASH_FUNCTION), nsae);
		}
	}

	
Convert an OBJ_* type constant to a TYPE_* type constant.
Params:
typeCode – the type code, from a pack representation.
Returns:
the canonical string name of this type./**
	 * Convert an OBJ_* type constant to a TYPE_* type constant.
	 *
	 * @param typeCode the type code, from a pack representation.
	 * @return the canonical string name of this type.
	 */
	public static String typeString(int typeCode) {
		switch (typeCode) {
		case OBJ_COMMIT:
			return TYPE_COMMIT;
		case OBJ_TREE:
			return TYPE_TREE;
		case OBJ_BLOB:
			return TYPE_BLOB;
		case OBJ_TAG:
			return TYPE_TAG;
		default:
			throw new IllegalArgumentException(MessageFormat.format(
					JGitText.get().badObjectType, Integer.valueOf(typeCode)));
		}
	}

	
Convert an OBJ_* type constant to an ASCII encoded string constant.

The ASCII encoded string is often the canonical representation of
the type within a loose object header, or within a tag header.
Params:
typeCode – the type code, from a pack representation.
Returns:
the canonical ASCII encoded name of this type./**
	 * Convert an OBJ_* type constant to an ASCII encoded string constant.
	 * <p>
	 * The ASCII encoded string is often the canonical representation of
	 * the type within a loose object header, or within a tag header.
	 *
	 * @param typeCode the type code, from a pack representation.
	 * @return the canonical ASCII encoded name of this type.
	 */
	public static byte[] encodedTypeString(int typeCode) {
		switch (typeCode) {
		case OBJ_COMMIT:
			return ENCODED_TYPE_COMMIT;
		case OBJ_TREE:
			return ENCODED_TYPE_TREE;
		case OBJ_BLOB:
			return ENCODED_TYPE_BLOB;
		case OBJ_TAG:
			return ENCODED_TYPE_TAG;
		default:
			throw new IllegalArgumentException(MessageFormat.format(
					JGitText.get().badObjectType, Integer.valueOf(typeCode)));
		}
	}

	
Parse an encoded type string into a type constant.
Params:
id – 
           object id this type string came from; may be null if that is
           not known at the time the parse is occurring.
typeString – 
           string version of the type code.
endMark – 
           character immediately following the type string. Usually ' '
           (space) or '\n' (line feed).
offset – 
           position within typeString where the parse
           should start. Updated with the new position (just past
           endMark when the parse is successful.
Throws:
CorruptObjectException – 
            there is no valid type identified by typeString.
Returns:
a type code constant (one of OBJ_BLOB, OBJ_COMMIT, OBJ_TAG, OBJ_TREE./**
	 * Parse an encoded type string into a type constant.
	 *
	 * @param id
	 *            object id this type string came from; may be null if that is
	 *            not known at the time the parse is occurring.
	 * @param typeString
	 *            string version of the type code.
	 * @param endMark
	 *            character immediately following the type string. Usually ' '
	 *            (space) or '\n' (line feed).
	 * @param offset
	 *            position within <code>typeString</code> where the parse
	 *            should start. Updated with the new position (just past
	 *            <code>endMark</code> when the parse is successful.
	 * @return a type code constant (one of {@link #OBJ_BLOB},
	 *         {@link #OBJ_COMMIT}, {@link #OBJ_TAG}, {@link #OBJ_TREE}.
	 * @throws org.eclipse.jgit.errors.CorruptObjectException
	 *             there is no valid type identified by <code>typeString</code>.
	 */
	public static int decodeTypeString(final AnyObjectId id,
			final byte[] typeString, final byte endMark,
			final MutableInteger offset) throws CorruptObjectException {
		try {
			int position = offset.value;
			switch (typeString[position]) {
			case 'b':
				if (typeString[position + 1] != 'l'
						|| typeString[position + 2] != 'o'
						|| typeString[position + 3] != 'b'
						|| typeString[position + 4] != endMark)
					throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
				offset.value = position + 5;
				return Constants.OBJ_BLOB;

			case 'c':
				if (typeString[position + 1] != 'o'
						|| typeString[position + 2] != 'm'
						|| typeString[position + 3] != 'm'
						|| typeString[position + 4] != 'i'
						|| typeString[position + 5] != 't'
						|| typeString[position + 6] != endMark)
					throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
				offset.value = position + 7;
				return Constants.OBJ_COMMIT;

			case 't':
				switch (typeString[position + 1]) {
				case 'a':
					if (typeString[position + 2] != 'g'
							|| typeString[position + 3] != endMark)
						throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
					offset.value = position + 4;
					return Constants.OBJ_TAG;

				case 'r':
					if (typeString[position + 2] != 'e'
							|| typeString[position + 3] != 'e'
							|| typeString[position + 4] != endMark)
						throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
					offset.value = position + 5;
					return Constants.OBJ_TREE;

				default:
					throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
				}

			default:
				throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
			}
		} catch (ArrayIndexOutOfBoundsException bad) {
			throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
		}
	}

	
Convert an integer into its decimal representation.
Params:
s – 
           the integer to convert.
Returns:
a decimal representation of the input integer. The returned array
        is the smallest array that will hold the value./**
	 * Convert an integer into its decimal representation.
	 *
	 * @param s
	 *            the integer to convert.
	 * @return a decimal representation of the input integer. The returned array
	 *         is the smallest array that will hold the value.
	 */
	public static byte[] encodeASCII(long s) {
		return encodeASCII(Long.toString(s));
	}

	
Convert a string to US-ASCII encoding.
Params:
s – 
           the string to convert. Must not contain any characters over
           127 (outside of 7-bit ASCII).
Throws:
IllegalArgumentException – 
            the input string contains one or more characters outside of
            the 7-bit ASCII character space.
Returns:
a byte array of the same length as the input string, holding the
        same characters, in the same order./**
	 * Convert a string to US-ASCII encoding.
	 *
	 * @param s
	 *            the string to convert. Must not contain any characters over
	 *            127 (outside of 7-bit ASCII).
	 * @return a byte array of the same length as the input string, holding the
	 *         same characters, in the same order.
	 * @throws java.lang.IllegalArgumentException
	 *             the input string contains one or more characters outside of
	 *             the 7-bit ASCII character space.
	 */
	public static byte[] encodeASCII(String s) {
		final byte[] r = new byte[s.length()];
		for (int k = r.length - 1; k >= 0; k--) {
			final char c = s.charAt(k);
			if (c > 127)
				throw new IllegalArgumentException(MessageFormat.format(JGitText.get().notASCIIString, s));
			r[k] = (byte) c;
		}
		return r;
	}

	
Convert a string to a byte array in the standard character encoding.
Params:
str – 
           the string to convert. May contain any Unicode characters.
See Also:
CHARACTER_ENCODING
Returns:
a byte array representing the requested string, encoded using the
        default character encoding (UTF-8)./**
	 * Convert a string to a byte array in the standard character encoding.
	 *
	 * @param str
	 *            the string to convert. May contain any Unicode characters.
	 * @return a byte array representing the requested string, encoded using the
	 *         default character encoding (UTF-8).
	 * @see #CHARACTER_ENCODING
	 */
	public static byte[] encode(String str) {
		final ByteBuffer bb = UTF_8.encode(str);
		final int len = bb.limit();
		if (bb.hasArray() && bb.arrayOffset() == 0) {
			final byte[] arr = bb.array();
			if (arr.length == len)
				return arr;
		}

		final byte[] arr = new byte[len];
		bb.get(arr);
		return arr;
	}

	static {
		if (OBJECT_ID_LENGTH != newMessageDigest().getDigestLength())
			throw new LinkageError(JGitText.get().incorrectOBJECT_ID_LENGTH);
		CHARSET = UTF_8;
		CHARACTER_ENCODING = UTF_8.name();
	}

	
name of the file containing the commit msg for a merge commit /** name of the file containing the commit msg for a merge commit */
	public static final String MERGE_MSG = "MERGE_MSG";

	
name of the file containing the IDs of the parents of a merge commit /** name of the file containing the IDs of the parents of a merge commit */
	public static final String MERGE_HEAD = "MERGE_HEAD";

	
name of the file containing the ID of a cherry pick commit in case of conflicts /** name of the file containing the ID of a cherry pick commit in case of conflicts */
	public static final String CHERRY_PICK_HEAD = "CHERRY_PICK_HEAD";

	
name of the file containing the commit msg for a squash commit /** name of the file containing the commit msg for a squash commit */
	public static final String SQUASH_MSG = "SQUASH_MSG";

	
name of the file containing the ID of a revert commit in case of conflicts /** name of the file containing the ID of a revert commit in case of conflicts */
	public static final String REVERT_HEAD = "REVERT_HEAD";

	
name of the ref ORIG_HEAD used by certain commands to store the original
value of HEAD
/**
	 * name of the ref ORIG_HEAD used by certain commands to store the original
	 * value of HEAD
	 */
	public static final String ORIG_HEAD = "ORIG_HEAD";

	
Name of the file in which git commands and hooks store and read the
message prepared for the upcoming commit.
Since:
4.0/**
	 * Name of the file in which git commands and hooks store and read the
	 * message prepared for the upcoming commit.
	 *
	 * @since 4.0
	 */
	public static final String COMMIT_EDITMSG = "COMMIT_EDITMSG";

	
Well-known object ID for the empty blob.
Since:
0.9.1/**
	 * Well-known object ID for the empty blob.
	 *
	 * @since 0.9.1
	 */
	public static final ObjectId EMPTY_BLOB_ID = ObjectId
			.fromString("e69de29bb2d1d6434b8b29ae775ad8c2e48c5391");

	
Well-known object ID for the empty tree.
Since:
5.1/**
	 * Well-known object ID for the empty tree.
	 *
	 * @since 5.1
	 */
	public static final ObjectId EMPTY_TREE_ID = ObjectId
			.fromString("4b825dc642cb6eb9a060e54bf8d69288fbee4904");

	
Suffix of lock file name
Since:
4.7/**
	 * Suffix of lock file name
	 *
	 * @since 4.7
	 */
	public static final String LOCK_SUFFIX = ".lock"; //$NON-NLS-1$

	private Constants() {
		// Hide the default constructor
	}
}