Implement SHA-256 abstraction

The Large File Storage extension specified by GitHub [1] uses SHA-256 to
compute the ID of large files stored by the extension. Hence implement a
SHA-256 abstraction similar to the SHA-1 abstraction used by JGit.

[1] https://git-lfs.github.com/

Bug: 470333
Change-Id: I3a95954543c8570d73929e55f4a884b55dbf1b7a
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

7 files changed, 1752 insertions, 0 deletions

diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/InvalidLongObjectIdException.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/InvalidLongObjectIdException.java
new file mode 100644
index 0000000000..1f6e2d174f
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/errors/InvalidLongObjectIdException.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2009, Jonas Fonseca <fonseca@diku.dk>
+ * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
+ * Copyright (C) 2008, 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.lfs.errors;
+
+import java.io.UnsupportedEncodingException;
+import java.text.MessageFormat;
+
+import org.eclipse.jgit.lfs.internal.LfsText;
+
+/**
+ * Thrown when an invalid long object id is passed in as an argument.
+ *
+ * @since 4.3
+ */
+public class InvalidLongObjectIdException extends IllegalArgumentException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * Create exception with bytes of the invalid object id.
+	 *
+	 * @param bytes containing the invalid id.
+	 * @param offset in the byte array where the error occurred.
+	 * @param length of the sequence of invalid bytes.
+	 */
+	public InvalidLongObjectIdException(byte[] bytes, int offset, int length) {
+		super(MessageFormat.format(LfsText.get().invalidLongId,
+				asAscii(bytes, offset, length)));
+	}
+
+	/**
+	 * @param idString
+	 *            String containing the invalid id
+	 */
+	public InvalidLongObjectIdException(String idString) {
+		super(MessageFormat.format(LfsText.get().invalidLongId, idString));
+	}
+
+	private static String asAscii(byte[] bytes, int offset, int length) {
+		try {
+			return ": " + new String(bytes, offset, length, "US-ASCII"); //$NON-NLS-1$ //$NON-NLS-2$
+		} catch (UnsupportedEncodingException e2) {
+			return ""; //$NON-NLS-1$
+		} catch (StringIndexOutOfBoundsException e2) {
+			return ""; //$NON-NLS-1$
+		}
+	}
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java
new file mode 100644
index 0000000000..eaffcc9047
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/LfsText.java
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
+ * 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.lfs.internal;
+
+import org.eclipse.jgit.nls.NLS;
+import org.eclipse.jgit.nls.TranslationBundle;
+
+/**
+ * Translation bundle for JGit LFS server
+ */
+public class LfsText extends TranslationBundle {
+
+	/**
+	 * @return an instance of this translation bundle
+	 */
+	public static LfsText get() {
+		return NLS.getBundleFor(LfsText.class);
+	}
+
+	// @formatter:off
+	/***/ public String incorrectLONG_OBJECT_ID_LENGTH;
+	/***/ public String invalidLongId;
+	/***/ public String invalidLongIdLength;
+	/***/ public String requiredHashFunctionNotAvailable;
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/AbbreviatedLongObjectId.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/AbbreviatedLongObjectId.java
new file mode 100644
index 0000000000..e9eb0e3850
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/AbbreviatedLongObjectId.java
@@ -0,0 +1,375 @@
+/*
+ * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
+ * 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.lfs.lib;
+
+import java.io.Serializable;
+import java.text.MessageFormat;
+
+import org.eclipse.jgit.lfs.errors.InvalidLongObjectIdException;
+import org.eclipse.jgit.lfs.internal.LfsText;
+import org.eclipse.jgit.lib.AbbreviatedObjectId;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.util.NB;
+import org.eclipse.jgit.util.RawParseUtils;
+
+/**
+ * A prefix abbreviation of an {@link LongObjectId}.
+ * <p>
+ * Enable abbreviating SHA-256 strings used by Git LFS, using sufficient leading
+ * digits from the LongObjectId name to still be unique within the repository
+ * the string was generated from. These ids are likely to be unique for a useful
+ * period of time, especially if they contain at least 6-10 hex digits.
+ * <p>
+ * This class converts the hex string into a binary form, to make it more
+ * efficient for matching against an object.
+ *
+ * Ported to SHA-256 from {@link AbbreviatedObjectId}
+ *
+ * @since 4.3
+ */
+public final class AbbreviatedLongObjectId implements Serializable {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * Test a string of characters to verify it is a hex format.
+	 * <p>
+	 * If true the string can be parsed with {@link #fromString(String)}.
+	 *
+	 * @param id
+	 *            the string to test.
+	 * @return true if the string can converted into an AbbreviatedObjectId.
+	 */
+	public static final boolean isId(final String id) {
+		if (id.length() < 2
+				|| Constants.LONG_OBJECT_ID_STRING_LENGTH < id.length())
+			return false;
+		try {
+			for (int i = 0; i < id.length(); i++)
+				RawParseUtils.parseHexInt4((byte) id.charAt(i));
+			return true;
+		} catch (ArrayIndexOutOfBoundsException e) {
+			return false;
+		}
+	}
+
+	/**
+	 * Convert an AbbreviatedObjectId from hex characters (US-ASCII).
+	 *
+	 * @param buf
+	 *            the US-ASCII buffer to read from.
+	 * @param offset
+	 *            position to read the first character from.
+	 * @param end
+	 *            one past the last position to read (<code>end-offset</code> is
+	 *            the length of the string).
+	 * @return the converted object id.
+	 */
+	public static final AbbreviatedLongObjectId fromString(final byte[] buf,
+			final int offset, final int end) {
+		if (end - offset > Constants.LONG_OBJECT_ID_STRING_LENGTH)
+			throw new IllegalArgumentException(MessageFormat.format(
+							LfsText.get().invalidLongIdLength,
+					Integer.valueOf(end - offset),
+					Integer.valueOf(Constants.LONG_OBJECT_ID_STRING_LENGTH)));
+		return fromHexString(buf, offset, end);
+	}
+
+	/**
+	 * Convert an AbbreviatedObjectId from an {@link AnyObjectId}.
+	 * <p>
+	 * This method copies over all bits of the Id, and is therefore complete
+	 * (see {@link #isComplete()}).
+	 *
+	 * @param id
+	 *            the {@link ObjectId} to convert from.
+	 * @return the converted object id.
+	 */
+	public static final AbbreviatedLongObjectId fromLongObjectId(
+			AnyLongObjectId id) {
+		return new AbbreviatedLongObjectId(
+				Constants.LONG_OBJECT_ID_STRING_LENGTH, id.w1, id.w2, id.w3,
+				id.w4);
+	}
+
+	/**
+	 * Convert an AbbreviatedLongObjectId from hex characters.
+	 *
+	 * @param str
+	 *            the string to read from. Must be &lt;= 64 characters.
+	 * @return the converted object id.
+	 */
+	public static final AbbreviatedLongObjectId fromString(final String str) {
+		if (str.length() > Constants.LONG_OBJECT_ID_STRING_LENGTH)
+			throw new IllegalArgumentException(
+					MessageFormat.format(LfsText.get().invalidLongId, str));
+		final byte[] b = org.eclipse.jgit.lib.Constants.encodeASCII(str);
+		return fromHexString(b, 0, b.length);
+	}
+
+	private static final AbbreviatedLongObjectId fromHexString(final byte[] bs,
+			int ptr, final int end) {
+		try {
+			final long a = hexUInt64(bs, ptr, end);
+			final long b = hexUInt64(bs, ptr + 16, end);
+			final long c = hexUInt64(bs, ptr + 32, end);
+			final long d = hexUInt64(bs, ptr + 48, end);
+			return new AbbreviatedLongObjectId(end - ptr, a, b, c, d);
+		} catch (ArrayIndexOutOfBoundsException e1) {
+			throw new InvalidLongObjectIdException(bs, ptr, end - ptr);
+		}
+	}
+
+	private static final long hexUInt64(final byte[] bs, int p, final int end) {
+		if (16 <= end - p)
+			return RawParseUtils.parseHexInt64(bs, p);
+
+		long r = 0;
+		int n = 0;
+		while (n < 16 && p < end) {
+			r <<= 4;
+			r |= RawParseUtils.parseHexInt4(bs[p++]);
+			n++;
+		}
+		return r << (16 - n) * 4;
+	}
+
+	static long mask(final int nibbles, final long word, final long v) {
+		final long b = (word - 1) * 16;
+		if (b + 16 <= nibbles) {
+			// We have all of the bits required for this word.
+			//
+			return v;
+		}
+
+		if (nibbles <= b) {
+			// We have none of the bits required for this word.
+			//
+			return 0;
+		}
+
+		final long s = 64 - (nibbles - b) * 4;
+		return (v >>> s) << s;
+	}
+
+	/** Number of half-bytes used by this id. */
+	final int nibbles;
+
+	final long w1;
+
+	final long w2;
+
+	final long w3;
+
+	final long w4;
+
+	AbbreviatedLongObjectId(final int n, final long new_1, final long new_2,
+			final long new_3, final long new_4) {
+		nibbles = n;
+		w1 = new_1;
+		w2 = new_2;
+		w3 = new_3;
+		w4 = new_4;
+	}
+
+	/** @return number of hex digits appearing in this id */
+	public int length() {
+		return nibbles;
+	}
+
+	/** @return true if this ObjectId is actually a complete id. */
+	public boolean isComplete() {
+		return length() == Constants.LONG_OBJECT_ID_STRING_LENGTH;
+	}
+
+	/** @return a complete ObjectId; null if {@link #isComplete()} is false */
+	public LongObjectId toLongObjectId() {
+		return isComplete() ? new LongObjectId(w1, w2, w3, w4) : null;
+	}
+
+	/**
+	 * Compares this abbreviation to a full object id.
+	 *
+	 * @param other
+	 *            the other object id.
+	 * @return &lt;0 if this abbreviation names an object that is less than
+	 *         <code>other</code>; 0 if this abbreviation exactly matches the
+	 *         first {@link #length()} digits of <code>other.name()</code>;
+	 *         &gt;0 if this abbreviation names an object that is after
+	 *         <code>other</code>.
+	 */
+	public final int prefixCompare(final AnyLongObjectId other) {
+		int cmp;
+
+		cmp = NB.compareUInt64(w1, mask(1, other.w1));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w2, mask(2, other.w2));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w3, mask(3, other.w3));
+		if (cmp != 0)
+			return cmp;
+
+		return NB.compareUInt64(w4, mask(4, other.w4));
+	}
+
+	/**
+	 * Compare this abbreviation to a network-byte-order LongObjectId.
+	 *
+	 * @param bs
+	 *            array containing the other LongObjectId in network byte order.
+	 * @param p
+	 *            position within {@code bs} to start the compare at. At least
+	 *            32 bytes, starting at this position are required.
+	 * @return &lt;0 if this abbreviation names an object that is less than
+	 *         <code>other</code>; 0 if this abbreviation exactly matches the
+	 *         first {@link #length()} digits of <code>other.name()</code>;
+	 *         &gt;0 if this abbreviation names an object that is after
+	 *         <code>other</code>.
+	 */
+	public final int prefixCompare(final byte[] bs, final int p) {
+		int cmp;
+
+		cmp = NB.compareUInt64(w1, mask(1, NB.decodeInt64(bs, p)));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w2, mask(2, NB.decodeInt64(bs, p + 8)));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w3, mask(3, NB.decodeInt64(bs, p + 16)));
+		if (cmp != 0)
+			return cmp;
+
+		return NB.compareUInt64(w4, mask(4, NB.decodeInt64(bs, p + 24)));
+	}
+
+	/**
+	 * Compare this abbreviation to a network-byte-order LongObjectId.
+	 *
+	 * @param bs
+	 *            array containing the other LongObjectId in network byte order.
+	 * @param p
+	 *            position within {@code bs} to start the compare at. At least 4
+	 *            longs, starting at this position are required.
+	 * @return &lt;0 if this abbreviation names an object that is less than
+	 *         <code>other</code>; 0 if this abbreviation exactly matches the
+	 *         first {@link #length()} digits of <code>other.name()</code>;
+	 *         &gt;0 if this abbreviation names an object that is after
+	 *         <code>other</code>.
+	 */
+	public final int prefixCompare(final long[] bs, final int p) {
+		int cmp;
+
+		cmp = NB.compareUInt64(w1, mask(1, bs[p]));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w2, mask(2, bs[p + 1]));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w3, mask(3, bs[p + 2]));
+		if (cmp != 0)
+			return cmp;
+
+		return NB.compareUInt64(w4, mask(4, bs[p + 3]));
+	}
+
+	/** @return value for a fan-out style map, only valid of length &gt;= 2. */
+	public final int getFirstByte() {
+		return (int) (w1 >>> 56);
+	}
+
+	private long mask(final long word, final long v) {
+		return mask(nibbles, word, v);
+	}
+
+	@Override
+	public int hashCode() {
+		return (int) (w1 >> 32);
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (o instanceof AbbreviatedLongObjectId) {
+			final AbbreviatedLongObjectId b = (AbbreviatedLongObjectId) o;
+			return nibbles == b.nibbles && w1 == b.w1 && w2 == b.w2
+					&& w3 == b.w3 && w4 == b.w4;
+		}
+		return false;
+	}
+
+	/**
+	 * @return string form of the abbreviation, in lower case hexadecimal.
+	 */
+	public final String name() {
+		final char[] b = new char[Constants.LONG_OBJECT_ID_STRING_LENGTH];
+
+		AnyLongObjectId.formatHexChar(b, 0, w1);
+		if (nibbles <= 16)
+			return new String(b, 0, nibbles);
+
+		AnyLongObjectId.formatHexChar(b, 16, w2);
+		if (nibbles <= 32)
+			return new String(b, 0, nibbles);
+
+		AnyLongObjectId.formatHexChar(b, 32, w3);
+		if (nibbles <= 48)
+			return new String(b, 0, nibbles);
+
+		AnyLongObjectId.formatHexChar(b, 48, w4);
+		return new String(b, 0, nibbles);
+	}
+
+	@SuppressWarnings("nls")
+	@Override
+	public String toString() {
+		return "AbbreviatedLongObjectId[" + name() + "]"; //$NON-NLS-1$
+	}
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/AnyLongObjectId.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/AnyLongObjectId.java
new file mode 100644
index 0000000000..1f0df882d2
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/AnyLongObjectId.java
@@ -0,0 +1,555 @@
+/*
+ * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
+ * 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.lfs.lib;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.Writer;
+import java.nio.ByteBuffer;
+
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.util.NB;
+
+/**
+ * A (possibly mutable) SHA-256 abstraction.
+ * <p>
+ * If this is an instance of {@link MutableLongObjectId} the concept of equality
+ * with this instance can alter at any time, if this instance is modified to
+ * represent a different object name.
+ *
+ * Ported to SHA-256 from {@link AnyObjectId}
+ *
+ * @since 4.3
+ */
+public abstract class AnyLongObjectId implements Comparable<AnyLongObjectId> {
+
+	/**
+	 * Compare two object identifier byte sequences for equality.
+	 *
+	 * @param firstObjectId
+	 *            the first identifier to compare. Must not be null.
+	 * @param secondObjectId
+	 *            the second identifier to compare. Must not be null.
+	 * @return true if the two identifiers are the same.
+	 */
+	public static boolean equals(final AnyLongObjectId firstObjectId,
+			final AnyLongObjectId secondObjectId) {
+		if (firstObjectId == secondObjectId)
+			return true;
+
+		// We test word 2 first as odds are someone already used our
+		// word 1 as a hash code, and applying that came up with these
+		// two instances we are comparing for equality. Therefore the
+		// first two words are very likely to be identical. We want to
+		// break away from collisions as quickly as possible.
+		//
+		return firstObjectId.w2 == secondObjectId.w2
+				&& firstObjectId.w3 == secondObjectId.w3
+				&& firstObjectId.w4 == secondObjectId.w4
+				&& firstObjectId.w1 == secondObjectId.w1;
+	}
+
+	long w1;
+
+	long w2;
+
+	long w3;
+
+	long w4;
+
+	/**
+	 * Get the first 8 bits of the LongObjectId.
+	 *
+	 * This is a faster version of {@code getByte(0)}.
+	 *
+	 * @return a discriminator usable for a fan-out style map. Returned values
+	 *         are unsigned and thus are in the range [0,255] rather than the
+	 *         signed byte range of [-128, 127].
+	 */
+	public final int getFirstByte() {
+		return (int) (w1 >>> 56);
+	}
+
+	/**
+	 * Get the second 8 bits of the LongObjectId.
+	 *
+	 * @return a discriminator usable for a fan-out style map. Returned values
+	 *         are unsigned and thus are in the range [0,255] rather than the
+	 *         signed byte range of [-128, 127].
+	 */
+	public final int getSecondByte() {
+		return (int) ((w1 >>> 48) & 0xff);
+	}
+
+	/**
+	 * Get any byte from the LongObjectId.
+	 *
+	 * Callers hard-coding {@code getByte(0)} should instead use the much faster
+	 * special case variant {@link #getFirstByte()}.
+	 *
+	 * @param index
+	 *            index of the byte to obtain from the raw form of the
+	 *            LongObjectId. Must be in range [0,
+	 *            {@link Constants#LONG_OBJECT_ID_LENGTH}).
+	 * @return the value of the requested byte at {@code index}. Returned values
+	 *         are unsigned and thus are in the range [0,255] rather than the
+	 *         signed byte range of [-128, 127].
+	 * @throws ArrayIndexOutOfBoundsException
+	 *             {@code index} is less than 0, equal to
+	 *             {@link Constants#LONG_OBJECT_ID_LENGTH}, or greater than
+	 *             {@link Constants#LONG_OBJECT_ID_LENGTH}.
+	 */
+	public final int getByte(int index) {
+		long w;
+		switch (index >> 3) {
+		case 0:
+			w = w1;
+			break;
+		case 1:
+			w = w2;
+			break;
+		case 2:
+			w = w3;
+			break;
+		case 3:
+			w = w4;
+			break;
+		default:
+			throw new ArrayIndexOutOfBoundsException(index);
+		}
+
+		return (int) ((w >>> (8 * (15 - (index & 15)))) & 0xff);
+	}
+
+	/**
+	 * Compare this LongObjectId to another and obtain a sort ordering.
+	 *
+	 * @param other
+	 *            the other id to compare to. Must not be null.
+	 * @return &lt; 0 if this id comes before other; 0 if this id is equal to
+	 *         other; &gt; 0 if this id comes after other.
+	 */
+	public final int compareTo(final AnyLongObjectId other) {
+		if (this == other)
+			return 0;
+
+		int cmp;
+
+		cmp = NB.compareUInt64(w1, other.w1);
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w2, other.w2);
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w3, other.w3);
+		if (cmp != 0)
+			return cmp;
+
+		return NB.compareUInt64(w4, other.w4);
+	}
+
+	/**
+	 * Compare this LongObjectId to a network-byte-order LongObjectId.
+	 *
+	 * @param bs
+	 *            array containing the other LongObjectId in network byte order.
+	 * @param p
+	 *            position within {@code bs} to start the compare at. At least
+	 *            32 bytes, starting at this position are required.
+	 * @return a negative integer, zero, or a positive integer as this object is
+	 *         less than, equal to, or greater than the specified object.
+	 */
+	public final int compareTo(final byte[] bs, final int p) {
+		int cmp;
+
+		cmp = NB.compareUInt64(w1, NB.decodeInt64(bs, p));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w2, NB.decodeInt64(bs, p + 8));
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w3, NB.decodeInt64(bs, p + 16));
+		if (cmp != 0)
+			return cmp;
+
+		return NB.compareUInt64(w4, NB.decodeInt64(bs, p + 24));
+	}
+
+	/**
+	 * Compare this LongObjectId to a network-byte-order LongObjectId.
+	 *
+	 * @param bs
+	 *            array containing the other LongObjectId in network byte order.
+	 * @param p
+	 *            position within {@code bs} to start the compare at. At least 4
+	 *            longs, starting at this position are required.
+	 * @return a negative integer, zero, or a positive integer as this object is
+	 *         less than, equal to, or greater than the specified object.
+	 */
+	public final int compareTo(final long[] bs, final int p) {
+		int cmp;
+
+		cmp = NB.compareUInt64(w1, bs[p]);
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w2, bs[p + 1]);
+		if (cmp != 0)
+			return cmp;
+
+		cmp = NB.compareUInt64(w3, bs[p + 2]);
+		if (cmp != 0)
+			return cmp;
+
+		return NB.compareUInt64(w4, bs[p + 3]);
+	}
+
+	/**
+	 * Tests if this LongObjectId starts with the given abbreviation.
+	 *
+	 * @param abbr
+	 *            the abbreviation.
+	 * @return true if this LongObjectId begins with the abbreviation; else
+	 *         false.
+	 */
+	public boolean startsWith(final AbbreviatedLongObjectId abbr) {
+		return abbr.prefixCompare(this) == 0;
+	}
+
+	public final int hashCode() {
+		return (int) (w1 >> 32);
+	}
+
+	/**
+	 * Determine if this LongObjectId has exactly the same value as another.
+	 *
+	 * @param other
+	 *            the other id to compare to. May be null.
+	 * @return true only if both LongObjectIds have identical bits.
+	 */
+	public final boolean equals(final AnyLongObjectId other) {
+		return other != null ? equals(this, other) : false;
+	}
+
+	public final boolean equals(final Object o) {
+		if (o instanceof AnyLongObjectId)
+			return equals((AnyLongObjectId) o);
+		else
+			return false;
+	}
+
+	/**
+	 * Copy this LongObjectId to an output writer in raw binary.
+	 *
+	 * @param w
+	 *            the buffer to copy to. Must be in big endian order.
+	 */
+	public void copyRawTo(final ByteBuffer w) {
+		w.putLong(w1);
+		w.putLong(w2);
+		w.putLong(w3);
+		w.putLong(w4);
+	}
+
+	/**
+	 * Copy this LongObjectId to a byte array.
+	 *
+	 * @param b
+	 *            the buffer to copy to.
+	 * @param o
+	 *            the offset within b to write at.
+	 */
+	public void copyRawTo(final byte[] b, final int o) {
+		NB.encodeInt64(b, o, w1);
+		NB.encodeInt64(b, o + 8, w2);
+		NB.encodeInt64(b, o + 16, w3);
+		NB.encodeInt64(b, o + 24, w4);
+	}
+
+	/**
+	 * Copy this LongObjectId to an long array.
+	 *
+	 * @param b
+	 *            the buffer to copy to.
+	 * @param o
+	 *            the offset within b to write at.
+	 */
+	public void copyRawTo(final long[] b, final int o) {
+		b[o] = w1;
+		b[o + 1] = w2;
+		b[o + 2] = w3;
+		b[o + 3] = w4;
+	}
+
+	/**
+	 * Copy this LongObjectId to an output writer in raw binary.
+	 *
+	 * @param w
+	 *            the stream to write to.
+	 * @throws IOException
+	 *             the stream writing failed.
+	 */
+	public void copyRawTo(final OutputStream w) throws IOException {
+		writeRawLong(w, w1);
+		writeRawLong(w, w2);
+		writeRawLong(w, w3);
+		writeRawLong(w, w4);
+	}
+
+	private static void writeRawLong(final OutputStream w, long v)
+			throws IOException {
+		w.write((int) (v >>> 56));
+		w.write((int) (v >>> 48));
+		w.write((int) (v >>> 40));
+		w.write((int) (v >>> 32));
+		w.write((int) (v >>> 24));
+		w.write((int) (v >>> 16));
+		w.write((int) (v >>> 8));
+		w.write((int) v);
+	}
+
+	/**
+	 * Copy this LongObjectId to an output writer in hex format.
+	 *
+	 * @param w
+	 *            the stream to copy to.
+	 * @throws IOException
+	 *             the stream writing failed.
+	 */
+	public void copyTo(final OutputStream w) throws IOException {
+		w.write(toHexByteArray());
+	}
+
+	/**
+	 * Copy this LongObjectId to a byte array in hex format.
+	 *
+	 * @param b
+	 *            the buffer to copy to.
+	 * @param o
+	 *            the offset within b to write at.
+	 */
+	public void copyTo(byte[] b, int o) {
+		formatHexByte(b, o + 0, w1);
+		formatHexByte(b, o + 16, w2);
+		formatHexByte(b, o + 32, w3);
+		formatHexByte(b, o + 48, w4);
+	}
+
+	/**
+	 * Copy this LongObjectId to a ByteBuffer in hex format.
+	 *
+	 * @param b
+	 *            the buffer to copy to.
+	 */
+	public void copyTo(ByteBuffer b) {
+		b.put(toHexByteArray());
+	}
+
+	private byte[] toHexByteArray() {
+		final byte[] dst = new byte[Constants.LONG_OBJECT_ID_STRING_LENGTH];
+		formatHexByte(dst, 0, w1);
+		formatHexByte(dst, 16, w2);
+		formatHexByte(dst, 32, w3);
+		formatHexByte(dst, 48, w4);
+		return dst;
+	}
+
+	private static final byte[] hexbyte = { '0', '1', '2', '3', '4', '5', '6',
+			'7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
+
+	private static void formatHexByte(final byte[] dst, final int p, long w) {
+		int o = p + 15;
+		while (o >= p && w != 0) {
+			dst[o--] = hexbyte[(int) (w & 0xf)];
+			w >>>= 4;
+		}
+		while (o >= p)
+			dst[o--] = '0';
+	}
+
+	/**
+	 * Copy this LongObjectId to an output writer in hex format.
+	 *
+	 * @param w
+	 *            the stream to copy to.
+	 * @throws IOException
+	 *             the stream writing failed.
+	 */
+	public void copyTo(final Writer w) throws IOException {
+		w.write(toHexCharArray());
+	}
+
+	/**
+	 * Copy this LongObjectId to an output writer in hex format.
+	 *
+	 * @param tmp
+	 *            temporary char array to buffer construct into before writing.
+	 *            Must be at least large enough to hold 2 digits for each byte
+	 *            of object id (64 characters or larger).
+	 * @param w
+	 *            the stream to copy to.
+	 * @throws IOException
+	 *             the stream writing failed.
+	 */
+	public void copyTo(final char[] tmp, final Writer w) throws IOException {
+		toHexCharArray(tmp);
+		w.write(tmp, 0, Constants.LONG_OBJECT_ID_STRING_LENGTH);
+	}
+
+	/**
+	 * Copy this LongObjectId to a StringBuilder in hex format.
+	 *
+	 * @param tmp
+	 *            temporary char array to buffer construct into before writing.
+	 *            Must be at least large enough to hold 2 digits for each byte
+	 *            of object id (64 characters or larger).
+	 * @param w
+	 *            the string to append onto.
+	 */
+	public void copyTo(final char[] tmp, final StringBuilder w) {
+		toHexCharArray(tmp);
+		w.append(tmp, 0, Constants.LONG_OBJECT_ID_STRING_LENGTH);
+	}
+
+	char[] toHexCharArray() {
+		final char[] dst = new char[Constants.LONG_OBJECT_ID_STRING_LENGTH];
+		toHexCharArray(dst);
+		return dst;
+	}
+
+	private void toHexCharArray(final char[] dst) {
+		formatHexChar(dst, 0, w1);
+		formatHexChar(dst, 16, w2);
+		formatHexChar(dst, 32, w3);
+		formatHexChar(dst, 48, w4);
+	}
+
+	private static final char[] hexchar = { '0', '1', '2', '3', '4', '5', '6',
+			'7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
+
+	static void formatHexChar(final char[] dst, final int p, long w) {
+		int o = p + 15;
+		while (o >= p && w != 0) {
+			dst[o--] = hexchar[(int) (w & 0xf)];
+			w >>>= 4;
+		}
+		while (o >= p)
+			dst[o--] = '0';
+	}
+
+	@SuppressWarnings("nls")
+	@Override
+	public String toString() {
+		return "AnyLongObjectId[" + name() + "]";
+	}
+
+	/**
+	 * @return string form of the SHA-256, in lower case hexadecimal.
+	 */
+	public final String name() {
+		return new String(toHexCharArray());
+	}
+
+	/**
+	 * @return string form of the SHA-256, in lower case hexadecimal.
+	 */
+	public final String getName() {
+		return name();
+	}
+
+	/**
+	 * Return an abbreviation (prefix) of this object SHA-256.
+	 * <p>
+	 * This implementation does not guarantee uniqueness. Callers should instead
+	 * use {@link ObjectReader#abbreviate(AnyObjectId, int)} to obtain a unique
+	 * abbreviation within the scope of a particular object database.
+	 *
+	 * @param len
+	 *            length of the abbreviated string.
+	 * @return SHA-256 abbreviation.
+	 */
+	public AbbreviatedLongObjectId abbreviate(final int len) {
+		final long a = AbbreviatedLongObjectId.mask(len, 1, w1);
+		final long b = AbbreviatedLongObjectId.mask(len, 2, w2);
+		final long c = AbbreviatedLongObjectId.mask(len, 3, w3);
+		final long d = AbbreviatedLongObjectId.mask(len, 4, w4);
+		return new AbbreviatedLongObjectId(len, a, b, c, d);
+	}
+
+	/**
+	 * Obtain an immutable copy of this current object.
+	 * <p>
+	 * Only returns <code>this</code> if this instance is an unsubclassed
+	 * instance of {@link LongObjectId}; otherwise a new instance is returned
+	 * holding the same value.
+	 * <p>
+	 * This method is useful to shed any additional memory that may be tied to
+	 * the subclass, yet retain the unique identity of the object id for future
+	 * lookups within maps and repositories.
+	 *
+	 * @return an immutable copy, using the smallest memory footprint possible.
+	 */
+	public final LongObjectId copy() {
+		if (getClass() == LongObjectId.class)
+			return (LongObjectId) this;
+		return new LongObjectId(this);
+	}
+
+	/**
+	 * Obtain an immutable copy of this current object.
+	 * <p>
+	 * See {@link #copy()} if <code>this</code> is a possibly subclassed (but
+	 * immutable) identity and the application needs a lightweight identity
+	 * <i>only</i> reference.
+	 *
+	 * @return an immutable copy. May be <code>this</code> if this is already an
+	 *         immutable instance.
+	 */
+	public abstract LongObjectId toObjectId();
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
new file mode 100644
index 0000000000..92a5c4250f
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
+ * 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.lfs.lib;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.text.MessageFormat;
+
+import org.eclipse.jgit.lfs.internal.LfsText;
+
+/**
+ * Misc. constants used throughout JGit LFS extension.
+ *
+ * @since 4.3
+ **/
+@SuppressWarnings("nls")
+public final class Constants {
+	/** Hash function used natively by Git LFS extension for large objects. */
+	private static final String LONG_HASH_FUNCTION = "SHA-256";
+
+	/**
+	 * A Git LFS large object hash is 256 bits, i.e. 32 bytes.
+	 * <p>
+	 * Changing this assumption is not going to be as easy as changing this
+	 * declaration.
+	 */
+	public static final int LONG_OBJECT_ID_LENGTH = 32;
+
+	/**
+	 * A Git LFS large object can be expressed as a 64 character string of
+	 * hexadecimal digits.
+	 *
+	 * @see #LONG_OBJECT_ID_LENGTH
+	 */
+	public static final int LONG_OBJECT_ID_STRING_LENGTH = LONG_OBJECT_ID_LENGTH
+			* 2;
+
+	/**
+	 * Create a new digest function for objects.
+	 *
+	 * @return a new digest object.
+	 * @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.
+	 */
+	public static MessageDigest newMessageDigest() {
+		try {
+			return MessageDigest.getInstance(LONG_HASH_FUNCTION);
+		} catch (NoSuchAlgorithmException nsae) {
+			throw new RuntimeException(MessageFormat.format(
+					LfsText.get().requiredHashFunctionNotAvailable,
+					LONG_HASH_FUNCTION), nsae);
+		}
+	}
+
+	static {
+		if (LONG_OBJECT_ID_LENGTH != newMessageDigest().getDigestLength())
+			throw new LinkageError(
+					LfsText.get().incorrectLONG_OBJECT_ID_LENGTH);
+	}
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/LongObjectId.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/LongObjectId.java
new file mode 100644
index 0000000000..c4a4e43b12
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/LongObjectId.java
@@ -0,0 +1,309 @@
+/*
+ * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
+ * 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.lfs.lib;
+
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+
+import org.eclipse.jgit.lfs.errors.InvalidLongObjectIdException;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.util.NB;
+import org.eclipse.jgit.util.RawParseUtils;
+
+/**
+ * A SHA-256 abstraction.
+ *
+ * Ported to SHA-256 from {@link ObjectId}
+ *
+ * @since 4.3
+ */
+public class LongObjectId extends AnyLongObjectId implements Serializable {
+	private static final long serialVersionUID = 1L;
+
+	private static final LongObjectId ZEROID;
+
+	private static final String ZEROID_STR;
+
+	static {
+		ZEROID = new LongObjectId(0L, 0L, 0L, 0L);
+		ZEROID_STR = ZEROID.name();
+	}
+
+	/**
+	 * Get the special all-zero LongObjectId.
+	 *
+	 * @return the all-zero LongObjectId, often used to stand-in for no object.
+	 */
+	public static final LongObjectId zeroId() {
+		return ZEROID;
+	}
+
+	/**
+	 * Test a string of characters to verify that it can be interpreted as
+	 * LongObjectId.
+	 * <p>
+	 * If true the string can be parsed with {@link #fromString(String)}.
+	 *
+	 * @param id
+	 *            the string to test.
+	 * @return true if the string can converted into an LongObjectId.
+	 */
+	public static final boolean isId(final String id) {
+		if (id.length() != Constants.LONG_OBJECT_ID_STRING_LENGTH)
+			return false;
+		try {
+			for (int i = 0; i < Constants.LONG_OBJECT_ID_STRING_LENGTH; i++) {
+				RawParseUtils.parseHexInt4((byte) id.charAt(i));
+			}
+			return true;
+		} catch (ArrayIndexOutOfBoundsException e) {
+			return false;
+		}
+	}
+
+	/**
+	 * Convert a LongObjectId into a hex string representation.
+	 *
+	 * @param i
+	 *            the id to convert. May be null.
+	 * @return the hex string conversion of this id's content.
+	 */
+	public static final String toString(final LongObjectId i) {
+		return i != null ? i.name() : ZEROID_STR;
+	}
+
+	/**
+	 * Compare two object identifier byte sequences for equality.
+	 *
+	 * @param firstBuffer
+	 *            the first buffer to compare against. Must have at least 32
+	 *            bytes from position fi through the end of the buffer.
+	 * @param fi
+	 *            first offset within firstBuffer to begin testing.
+	 * @param secondBuffer
+	 *            the second buffer to compare against. Must have at least 32
+	 *            bytes from position si through the end of the buffer.
+	 * @param si
+	 *            first offset within secondBuffer to begin testing.
+	 * @return true if the two identifiers are the same.
+	 */
+	public static boolean equals(final byte[] firstBuffer, final int fi,
+			final byte[] secondBuffer, final int si) {
+		return firstBuffer[fi] == secondBuffer[si]
+				&& firstBuffer[fi + 1] == secondBuffer[si + 1]
+				&& firstBuffer[fi + 2] == secondBuffer[si + 2]
+				&& firstBuffer[fi + 3] == secondBuffer[si + 3]
+				&& firstBuffer[fi + 4] == secondBuffer[si + 4]
+				&& firstBuffer[fi + 5] == secondBuffer[si + 5]
+				&& firstBuffer[fi + 6] == secondBuffer[si + 6]
+				&& firstBuffer[fi + 7] == secondBuffer[si + 7]
+				&& firstBuffer[fi + 8] == secondBuffer[si + 8]
+				&& firstBuffer[fi + 9] == secondBuffer[si + 9]
+				&& firstBuffer[fi + 10] == secondBuffer[si + 10]
+				&& firstBuffer[fi + 11] == secondBuffer[si + 11]
+				&& firstBuffer[fi + 12] == secondBuffer[si + 12]
+				&& firstBuffer[fi + 13] == secondBuffer[si + 13]
+				&& firstBuffer[fi + 14] == secondBuffer[si + 14]
+				&& firstBuffer[fi + 15] == secondBuffer[si + 15]
+				&& firstBuffer[fi + 16] == secondBuffer[si + 16]
+				&& firstBuffer[fi + 17] == secondBuffer[si + 17]
+				&& firstBuffer[fi + 18] == secondBuffer[si + 18]
+				&& firstBuffer[fi + 19] == secondBuffer[si + 19]
+				&& firstBuffer[fi + 20] == secondBuffer[si + 20]
+				&& firstBuffer[fi + 21] == secondBuffer[si + 21]
+				&& firstBuffer[fi + 22] == secondBuffer[si + 22]
+				&& firstBuffer[fi + 23] == secondBuffer[si + 23]
+				&& firstBuffer[fi + 24] == secondBuffer[si + 24]
+				&& firstBuffer[fi + 25] == secondBuffer[si + 25]
+				&& firstBuffer[fi + 26] == secondBuffer[si + 26]
+				&& firstBuffer[fi + 27] == secondBuffer[si + 27]
+				&& firstBuffer[fi + 28] == secondBuffer[si + 28]
+				&& firstBuffer[fi + 29] == secondBuffer[si + 29]
+				&& firstBuffer[fi + 30] == secondBuffer[si + 30]
+				&& firstBuffer[fi + 31] == secondBuffer[si + 31];
+	}
+
+	/**
+	 * Convert a LongObjectId from raw binary representation.
+	 *
+	 * @param bs
+	 *            the raw byte buffer to read from. At least 32 bytes must be
+	 *            available within this byte array.
+	 * @return the converted object id.
+	 */
+	public static final LongObjectId fromRaw(final byte[] bs) {
+		return fromRaw(bs, 0);
+	}
+
+	/**
+	 * Convert a LongObjectId from raw binary representation.
+	 *
+	 * @param bs
+	 *            the raw byte buffer to read from. At least 32 bytes after p
+	 *            must be available within this byte array.
+	 * @param p
+	 *            position to read the first byte of data from.
+	 * @return the converted object id.
+	 */
+	public static final LongObjectId fromRaw(final byte[] bs, final int p) {
+		final long a = NB.decodeInt64(bs, p);
+		final long b = NB.decodeInt64(bs, p + 8);
+		final long c = NB.decodeInt64(bs, p + 16);
+		final long d = NB.decodeInt64(bs, p + 24);
+		return new LongObjectId(a, b, c, d);
+	}
+
+	/**
+	 * Convert a LongObjectId from raw binary representation.
+	 *
+	 * @param is
+	 *            the raw long buffer to read from. At least 4 longs must be
+	 *            available within this long array.
+	 * @return the converted object id.
+	 */
+	public static final LongObjectId fromRaw(final long[] is) {
+		return fromRaw(is, 0);
+	}
+
+	/**
+	 * Convert a LongObjectId from raw binary representation.
+	 *
+	 * @param is
+	 *            the raw long buffer to read from. At least 4 longs after p
+	 *            must be available within this long array.
+	 * @param p
+	 *            position to read the first long of data from.
+	 * @return the converted object id.
+	 */
+	public static final LongObjectId fromRaw(final long[] is, final int p) {
+		return new LongObjectId(is[p], is[p + 1], is[p + 2], is[p + 3]);
+	}
+
+	/**
+	 * Convert a LongObjectId from hex characters (US-ASCII).
+	 *
+	 * @param buf
+	 *            the US-ASCII buffer to read from. At least 64 bytes after
+	 *            offset must be available within this byte array.
+	 * @param offset
+	 *            position to read the first character from.
+	 * @return the converted object id.
+	 */
+	public static final LongObjectId fromString(final byte[] buf, final int offset) {
+		return fromHexString(buf, offset);
+	}
+
+	/**
+	 * Convert a LongObjectId from hex characters.
+	 *
+	 * @param str
+	 *            the string to read from. Must be 64 characters long.
+	 * @return the converted object id.
+	 */
+	public static LongObjectId fromString(final String str) {
+		if (str.length() != Constants.LONG_OBJECT_ID_STRING_LENGTH)
+			throw new InvalidLongObjectIdException(str);
+		return fromHexString(org.eclipse.jgit.lib.Constants.encodeASCII(str),
+				0);
+	}
+
+	private static final LongObjectId fromHexString(final byte[] bs, int p) {
+		try {
+			final long a = RawParseUtils.parseHexInt64(bs, p);
+			final long b = RawParseUtils.parseHexInt64(bs, p + 16);
+			final long c = RawParseUtils.parseHexInt64(bs, p + 32);
+			final long d = RawParseUtils.parseHexInt64(bs, p + 48);
+			return new LongObjectId(a, b, c, d);
+		} catch (ArrayIndexOutOfBoundsException e1) {
+			throw new InvalidLongObjectIdException(bs, p,
+					Constants.LONG_OBJECT_ID_STRING_LENGTH);
+		}
+	}
+
+	LongObjectId(final long new_1, final long new_2, final long new_3,
+			final long new_4) {
+		w1 = new_1;
+		w2 = new_2;
+		w3 = new_3;
+		w4 = new_4;
+	}
+
+	/**
+	 * Initialize this instance by copying another existing LongObjectId.
+	 * <p>
+	 * This constructor is mostly useful for subclasses which want to extend a
+	 * LongObjectId with more properties, but initialize from an existing
+	 * LongObjectId instance acquired by other means.
+	 *
+	 * @param src
+	 *            another already parsed LongObjectId to copy the value out of.
+	 */
+	protected LongObjectId(final AnyLongObjectId src) {
+		w1 = src.w1;
+		w2 = src.w2;
+		w3 = src.w3;
+		w4 = src.w4;
+	}
+
+	@Override
+	public LongObjectId toObjectId() {
+		return this;
+	}
+
+	private void writeObject(ObjectOutputStream os) throws IOException {
+		os.writeLong(w1);
+		os.writeLong(w2);
+		os.writeLong(w3);
+		os.writeLong(w4);
+	}
+
+	private void readObject(ObjectInputStream ois) throws IOException {
+		w1 = ois.readLong();
+		w2 = ois.readLong();
+		w3 = ois.readLong();
+		w4 = ois.readLong();
+	}
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/MutableLongObjectId.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/MutableLongObjectId.java
new file mode 100644
index 0000000000..130e94ed0b
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/MutableLongObjectId.java
@@ -0,0 +1,256 @@
+/*
+ * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
+ * 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.lfs.lib;
+
+import java.text.MessageFormat;
+
+import org.eclipse.jgit.lfs.errors.InvalidLongObjectIdException;
+import org.eclipse.jgit.lfs.internal.LfsText;
+import org.eclipse.jgit.lib.MutableObjectId;
+import org.eclipse.jgit.util.NB;
+import org.eclipse.jgit.util.RawParseUtils;
+
+/**
+ * A mutable SHA-256 abstraction.
+ *
+ * Ported to SHA-256 from {@link MutableObjectId}
+ *
+ * @since 4.3
+ */
+public class MutableLongObjectId extends AnyLongObjectId {
+	/**
+	 * Empty constructor. Initialize object with default (zeros) value.
+	 */
+	public MutableLongObjectId() {
+		super();
+	}
+
+	/**
+	 * Copying constructor.
+	 *
+	 * @param src
+	 *            original entry, to copy id from
+	 */
+	MutableLongObjectId(MutableLongObjectId src) {
+		fromObjectId(src);
+	}
+
+	/**
+	 * Set any byte in the id.
+	 *
+	 * @param index
+	 *            index of the byte to set in the raw form of the ObjectId. Must
+	 *            be in range [0, {@link Constants#LONG_OBJECT_ID_LENGTH}).
+	 * @param value
+	 *            the value of the specified byte at {@code index}. Values are
+	 *            unsigned and thus are in the range [0,255] rather than the
+	 *            signed byte range of [-128, 127].
+	 * @throws ArrayIndexOutOfBoundsException
+	 *             {@code index} is less than 0, equal to
+	 *             {@link Constants#LONG_OBJECT_ID_LENGTH}, or greater than
+	 *             {@link Constants#LONG_OBJECT_ID_LENGTH}.
+	 */
+	public void setByte(int index, int value) {
+		switch (index >> 3) {
+		case 0:
+			w1 = set(w1, index & 7, value);
+			break;
+		case 1:
+			w2 = set(w2, index & 7, value);
+			break;
+		case 2:
+			w3 = set(w3, index & 7, value);
+			break;
+		case 3:
+			w4 = set(w4, index & 7, value);
+			break;
+		default:
+			throw new ArrayIndexOutOfBoundsException(index);
+		}
+	}
+
+	private static long set(long w, int index, long value) {
+		value &= 0xff;
+
+		switch (index) {
+		case 0:
+			return (w & 0x00ffffffffffffffL) | (value << 56);
+		case 1:
+			return (w & 0xff00ffffffffffffL) | (value << 48);
+		case 2:
+			return (w & 0xffff00ffffffffffL) | (value << 40);
+		case 3:
+			return (w & 0xffffff00ffffffffL) | (value << 32);
+		case 4:
+			return (w & 0xffffffff00ffffffL) | (value << 24);
+		case 5:
+			return (w & 0xffffffffff00ffffL) | (value << 16);
+		case 6:
+			return (w & 0xffffffffffff00ffL) | (value << 8);
+		case 7:
+			return (w & 0xffffffffffffff00L) | value;
+		default:
+			throw new ArrayIndexOutOfBoundsException();
+		}
+	}
+
+	/** Make this id match {@link LongObjectId#zeroId()}. */
+	public void clear() {
+		w1 = 0;
+		w2 = 0;
+		w3 = 0;
+		w4 = 0;
+	}
+
+	/**
+	 * Copy an LongObjectId into this mutable buffer.
+	 *
+	 * @param src
+	 *            the source id to copy from.
+	 */
+	public void fromObjectId(AnyLongObjectId src) {
+		this.w1 = src.w1;
+		this.w2 = src.w2;
+		this.w3 = src.w3;
+		this.w4 = src.w4;
+	}
+
+	/**
+	 * Convert an LongObjectId from raw binary representation.
+	 *
+	 * @param bs
+	 *            the raw byte buffer to read from. At least 32 bytes must be
+	 *            available within this byte array.
+	 */
+	public void fromRaw(final byte[] bs) {
+		fromRaw(bs, 0);
+	}
+
+	/**
+	 * Convert an LongObjectId from raw binary representation.
+	 *
+	 * @param bs
+	 *            the raw byte buffer to read from. At least 32 bytes after p
+	 *            must be available within this byte array.
+	 * @param p
+	 *            position to read the first byte of data from.
+	 */
+	public void fromRaw(final byte[] bs, final int p) {
+		w1 = NB.decodeInt64(bs, p);
+		w2 = NB.decodeInt64(bs, p + 8);
+		w3 = NB.decodeInt64(bs, p + 16);
+		w4 = NB.decodeInt64(bs, p + 24);
+	}
+
+	/**
+	 * Convert an LongObjectId from binary representation expressed in integers.
+	 *
+	 * @param longs
+	 *            the raw long buffer to read from. At least 4 longs must be
+	 *            available within this longs array.
+	 */
+	public void fromRaw(final long[] longs) {
+		fromRaw(longs, 0);
+	}
+
+	/**
+	 * Convert an LongObjectId from binary representation expressed in longs.
+	 *
+	 * @param longs
+	 *            the raw int buffer to read from. At least 4 longs after p must
+	 *            be available within this longs array.
+	 * @param p
+	 *            position to read the first integer of data from.
+	 *
+	 */
+	public void fromRaw(final long[] longs, final int p) {
+		w1 = longs[p];
+		w2 = longs[p + 1];
+		w3 = longs[p + 2];
+		w4 = longs[p + 3];
+	}
+
+	/**
+	 * Convert an LongObjectId from hex characters (US-ASCII).
+	 *
+	 * @param buf
+	 *            the US-ASCII buffer to read from. At least 32 bytes after
+	 *            offset must be available within this byte array.
+	 * @param offset
+	 *            position to read the first character from.
+	 */
+	public void fromString(final byte[] buf, final int offset) {
+		fromHexString(buf, offset);
+	}
+
+	/**
+	 * Convert an LongObjectId from hex characters.
+	 *
+	 * @param str
+	 *            the string to read from. Must be 64 characters long.
+	 */
+	public void fromString(final String str) {
+		if (str.length() != Constants.LONG_OBJECT_ID_STRING_LENGTH)
+			throw new IllegalArgumentException(
+					MessageFormat.format(LfsText.get().invalidLongId, str));
+		fromHexString(org.eclipse.jgit.lib.Constants.encodeASCII(str), 0);
+	}
+
+	private void fromHexString(final byte[] bs, int p) {
+		try {
+			w1 = RawParseUtils.parseHexInt64(bs, p);
+			w2 = RawParseUtils.parseHexInt64(bs, p + 16);
+			w3 = RawParseUtils.parseHexInt64(bs, p + 32);
+			w4 = RawParseUtils.parseHexInt64(bs, p + 48);
+		} catch (ArrayIndexOutOfBoundsException e1) {
+			throw new InvalidLongObjectIdException(bs, p,
+					Constants.LONG_OBJECT_ID_STRING_LENGTH);
+		}
+	}
+
+	@Override
+	public LongObjectId toObjectId() {
+		return new LongObjectId(this);
+	}
+}