Merge changes from topic 'SHAttered'

* changes:
  Switch to pure Java SHA1 for ObjectId
  Pure Java SHA-1

org.eclipse.jgit.test/META-INF/MANIFEST.MF

@@ -49,6 +49,7 @@ Import-Package: com.googlecode.javaewah;version="[1.1.6,2.0.0)",
  org.eclipse.jgit.treewalk.filter;version="[4.7.0,4.8.0)",
  org.eclipse.jgit.util;version="[4.7.0,4.8.0)",
  org.eclipse.jgit.util.io;version="[4.7.0,4.8.0)",
+ org.eclipse.jgit.util.sha1;version="[4.7.0,4.8.0)",
  org.junit;version="[4.4.0,5.0.0)",
  org.junit.experimental.theories;version="[4.4.0,5.0.0)",
  org.junit.rules;version="[4.11.0,5.0.0)",

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/sha1/SHA1Test.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2017, Google Inc.
+ * 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.util.sha1;
+
+import static org.junit.Assert.assertEquals;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Test;
+
+public class SHA1Test {
+	private static final String TEST1 = "abc";
+
+	private static final String TEST2a = "abcdbcdecdefdefgefghfghighijhi";
+	private static final String TEST2b = "jkijkljklmklmnlmnomnopnopq";
+	private static final String TEST2 = TEST2a + TEST2b;
+
+	@Test
+	public void test0() throws NoSuchAlgorithmException {
+		ObjectId exp = ObjectId
+				.fromString("da39a3ee5e6b4b0d3255bfef95601890afd80709");
+
+		MessageDigest m = MessageDigest.getInstance("SHA-1");
+		m.update(new byte[] {});
+		ObjectId m1 = ObjectId.fromRaw(m.digest());
+
+		SHA1 s = SHA1.newInstance();
+		s.update(new byte[] {});
+		ObjectId s1 = ObjectId.fromRaw(s.digest());
+
+		assertEquals(m1, s1);
+		assertEquals(exp, s1);
+	}
+
+	@Test
+	public void test1() throws NoSuchAlgorithmException {
+		ObjectId exp = ObjectId
+				.fromString("a9993e364706816aba3e25717850c26c9cd0d89d");
+
+		MessageDigest m = MessageDigest.getInstance("SHA-1");
+		m.update(TEST1.getBytes(StandardCharsets.UTF_8));
+		ObjectId m1 = ObjectId.fromRaw(m.digest());
+
+		SHA1 s = SHA1.newInstance();
+		s.update(TEST1.getBytes(StandardCharsets.UTF_8));
+		ObjectId s1 = ObjectId.fromRaw(s.digest());
+
+		assertEquals(m1, s1);
+		assertEquals(exp, s1);
+	}
+
+	@Test
+	public void test2() throws NoSuchAlgorithmException {
+		ObjectId exp = ObjectId
+				.fromString("84983e441c3bd26ebaae4aa1f95129e5e54670f1");
+
+		MessageDigest m = MessageDigest.getInstance("SHA-1");
+		m.update(TEST2.getBytes(StandardCharsets.UTF_8));
+		ObjectId m1 = ObjectId.fromRaw(m.digest());
+
+		SHA1 s = SHA1.newInstance();
+		s.update(TEST2.getBytes(StandardCharsets.UTF_8));
+		ObjectId s1 = ObjectId.fromRaw(s.digest());
+
+		assertEquals(m1, s1);
+		assertEquals(exp, s1);
+	}
+}

org.eclipse.jgit/META-INF/MANIFEST.MF

@@ -138,6 +138,7 @@ Export-Package: org.eclipse.jgit.annotations;version="4.7.0",
    org.eclipse.jgit.storage.file,
    org.ietf.jgss",
  org.eclipse.jgit.util.io;version="4.7.0",
+ org.eclipse.jgit.util.sha1;version="4.7.0",
  org.eclipse.jgit.util.time;version="4.7.0"
 Bundle-RequiredExecutionEnvironment: JavaSE-1.8
 Import-Package: com.googlecode.javaewah;version="[1.1.6,2.0.0)",

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsInserter.java

@@ -90,6 +90,7 @@
 import org.eclipse.jgit.util.NB;
 import org.eclipse.jgit.util.TemporaryBuffer;
 import org.eclipse.jgit.util.io.CountingOutputStream;
+import org.eclipse.jgit.util.sha1.SHA1;
 
 /** Inserts objects into the DFS. */
 public class DfsInserter extends ObjectInserter {
@@ -168,7 +169,7 @@ public ObjectId insert(int type, long len, InputStream in)
 		}
 
 		long offset = beginObject(type, len);
-		MessageDigest md = digest();
+		SHA1 md = SHA1.newInstance();
 		md.update(Constants.encodedTypeString(type));
 		md.update((byte) ' ');
 		md.update(Constants.encodeASCII(len));
@@ -183,7 +184,7 @@ public ObjectId insert(int type, long len, InputStream in)
 			len -= n;
 		}
 		packOut.compress.finish();
-		return endObject(ObjectId.fromRaw(md.digest()), offset);
+		return endObject(md.toObjectId(), offset);
 	}
 
 	private byte[] insertBuffer(long len) {

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectoryInserter.java

@@ -49,12 +49,11 @@
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
+import java.io.FilterOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.channels.Channels;
-import java.security.DigestOutputStream;
-import java.security.MessageDigest;
 import java.text.MessageFormat;
 import java.util.zip.Deflater;
 import java.util.zip.DeflaterOutputStream;
@@ -69,6 +68,7 @@
 import org.eclipse.jgit.transport.PackParser;
 import org.eclipse.jgit.util.FileUtils;
 import org.eclipse.jgit.util.IO;
+import org.eclipse.jgit.util.sha1.SHA1;
 
 /** Creates loose objects in a {@link ObjectDirectory}. */
 class ObjectDirectoryInserter extends ObjectInserter {
@@ -140,9 +140,9 @@ ObjectId insert(int type, long len, InputStream is, boolean createDuplicate)
 			return insert(type, buf, 0, actLen, createDuplicate);
 
 		} else {
-			MessageDigest md = digest();
+			SHA1 md = SHA1.newInstance();
 			File tmp = toTemp(md, type, len, is);
-			ObjectId id = ObjectId.fromRaw(md.digest());
+			ObjectId id = md.toObjectId();
 			return insertOneObject(tmp, id, createDuplicate);
 		}
 	}
@@ -193,7 +193,7 @@ public void close() {
 	}
 
 	@SuppressWarnings("resource" /* java 7 */)
-	private File toTemp(final MessageDigest md, final int type, long len,
+	private File toTemp(final SHA1 md, final int type, long len,
 			final InputStream is) throws IOException, FileNotFoundException,
 			Error {
 		boolean delete = true;
@@ -205,7 +205,7 @@ private File toTemp(final MessageDigest md, final int type, long len,
 				if (config.getFSyncObjectFiles())
 					out = Channels.newOutputStream(fOut.getChannel());
 				DeflaterOutputStream cOut = compress(out);
-				DigestOutputStream dOut = new DigestOutputStream(cOut, md);
+				SHA1OutputStream dOut = new SHA1OutputStream(cOut, md);
 				writeHeader(dOut, type, len);
 
 				final byte[] buf = buffer();
@@ -285,4 +285,25 @@ private static EOFException shortInput(long missing) {
 		return new EOFException(MessageFormat.format(
 				JGitText.get().inputDidntMatchLength, Long.valueOf(missing)));
 	}
+
+	private static class SHA1OutputStream extends FilterOutputStream {
+		private final SHA1 md;
+
+		SHA1OutputStream(OutputStream out, SHA1 md) {
+			super(out);
+			this.md = md;
+		}
+
+		@Override
+		public void write(int b) throws IOException {
+			md.update((byte) b);
+			out.write(b);
+		}
+
+		@Override
+		public void write(byte[] in, int p, int n) throws IOException {
+			md.update(in, p, n);
+			out.write(in, p, n);
+		}
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/lib/MutableObjectId.java

@@ -208,6 +208,24 @@ public void fromRaw(final int[] ints, final int p) {
 		w5 = ints[p + 4];
 	}
 
+	/**
+	 * Convert an ObjectId from binary representation expressed in integers.
+	 *
+	 * @param a
+	 * @param b
+	 * @param c
+	 * @param d
+	 * @param e
+	 * @since 4.7
+	 */
+	public void set(int a, int b, int c, int d, int e) {
+		w1 = a;
+		w2 = b;
+		w3 = c;
+		w4 = d;
+		w5 = e;
+	}
+
 	/**
 	 * Convert an ObjectId from hex characters (US-ASCII).
 	 *

org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectId.java

@@ -248,8 +248,17 @@ private static final ObjectId fromHexString(final byte[] bs, int p) {
 		}
 	}
 
-	ObjectId(final int new_1, final int new_2, final int new_3,
+	/**
-			final int new_4, final int new_5) {
+	 * Construct an ObjectId from 160 bits provided in 5 words.
+	 *
+	 * @param new_1
+	 * @param new_2
+	 * @param new_3
+	 * @param new_4
+	 * @param new_5
+	 * @since 4.7
+	 */
+	public ObjectId(int new_1, int new_2, int new_3, int new_4, int new_5) {
 		w1 = new_1;
 		w2 = new_2;
 		w3 = new_3;

org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java

@@ -50,10 +50,10 @@
 import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
-import java.security.MessageDigest;
 
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.transport.PackParser;
+import org.eclipse.jgit.util.sha1.SHA1;
 
 /**
  * Inserts objects into an existing {@code ObjectDatabase}.
@@ -177,15 +177,11 @@ public void close() {
 		}
 	}
 
-	/** Digest to compute the name of an object. */
-	private final MessageDigest digest;
-
 	/** Temporary working buffer for streaming data through. */
 	private byte[] tempBuffer;
 
 	/** Create a new inserter for a database. */
 	protected ObjectInserter() {
-		digest = Constants.newMessageDigest();
 	}
 
 	/**
@@ -220,9 +216,8 @@ protected byte[] buffer() {
 	}
 
 	/** @return digest to help compute an ObjectId */
-	protected MessageDigest digest() {
+	protected SHA1 digest() {
-		digest.reset();
+		return SHA1.newInstance();
-		return digest;
 	}
 
 	/**
@@ -252,13 +247,13 @@ public ObjectId idFor(int type, byte[] data) {
 	 * @return the name of the object.
 	 */
 	public ObjectId idFor(int type, byte[] data, int off, int len) {
-		MessageDigest md = digest();
+		SHA1 md = SHA1.newInstance();
 		md.update(Constants.encodedTypeString(type));
 		md.update((byte) ' ');
 		md.update(Constants.encodeASCII(len));
 		md.update((byte) 0);
 		md.update(data, off, len);
-		return ObjectId.fromRaw(md.digest());
+		return md.toObjectId();
 	}
 
 	/**
@@ -277,7 +272,7 @@ public ObjectId idFor(int type, byte[] data, int off, int len) {
 	 */
 	public ObjectId idFor(int objectType, long length, InputStream in)
 			throws IOException {
-		MessageDigest md = digest();
+		SHA1 md = SHA1.newInstance();
 		md.update(Constants.encodedTypeString(objectType));
 		md.update((byte) ' ');
 		md.update(Constants.encodeASCII(length));
@@ -290,7 +285,7 @@ public ObjectId idFor(int objectType, long length, InputStream in)
 			md.update(buf, 0, n);
 			length -= n;
 		}
-		return ObjectId.fromRaw(md.digest());
+		return md.toObjectId();
 	}
 
 	/**

org.eclipse.jgit/src/org/eclipse/jgit/transport/PackParser.java

@@ -83,6 +83,7 @@
 import org.eclipse.jgit.util.BlockList;
 import org.eclipse.jgit.util.IO;
 import org.eclipse.jgit.util.NB;
+import org.eclipse.jgit.util.sha1.SHA1;
 
 /**
  * Parses a pack stream and imports it for an {@link ObjectInserter}.
@@ -116,8 +117,6 @@ public static enum Source {
 
 	private byte[] hdrBuf;
 
-	private final MessageDigest objectDigest;
-
 	private final MutableObjectId tempObjectId;
 
 	private InputStream in;
@@ -206,7 +205,6 @@ protected PackParser(final ObjectDatabase odb, final InputStream src) {
 		buf = new byte[BUFFER_SIZE];
 		tempBuffer = new byte[BUFFER_SIZE];
 		hdrBuf = new byte[64];
-		objectDigest = Constants.newMessageDigest();
 		tempObjectId = new MutableObjectId();
 		packDigest = Constants.newMessageDigest();
 		checkObjectCollisions = true;
@@ -667,12 +665,13 @@ private void resolveDeltas(DeltaVisit visit, final int type,
 						JGitText.get().corruptionDetectedReReadingAt,
 						Long.valueOf(visit.delta.position)));
 
+			SHA1 objectDigest = SHA1.newInstance();
 			objectDigest.update(Constants.encodedTypeString(type));
 			objectDigest.update((byte) ' ');
 			objectDigest.update(Constants.encodeASCII(visit.data.length));
 			objectDigest.update((byte) 0);
 			objectDigest.update(visit.data);
-			tempObjectId.fromRaw(objectDigest.digest(), 0);
+			objectDigest.digest(tempObjectId);
 
 			verifySafeObject(tempObjectId, type, visit.data);
 
@@ -1024,6 +1023,7 @@ private void indexOneObject() throws IOException {
 
 	private void whole(final long pos, final int type, final long sz)
 			throws IOException {
+		SHA1 objectDigest = SHA1.newInstance();
 		objectDigest.update(Constants.encodedTypeString(type));
 		objectDigest.update((byte) ' ');
 		objectDigest.update(Constants.encodeASCII(sz));
@@ -1043,7 +1043,7 @@ private void whole(final long pos, final int type, final long sz)
 				cnt += r;
 			}
 			inf.close();
-			tempObjectId.fromRaw(objectDigest.digest(), 0);
+			objectDigest.digest(tempObjectId);
 			checkContentLater = isCheckObjectCollisions()
 					&& readCurs.has(tempObjectId);
 			data = null;
@@ -1051,7 +1051,7 @@ private void whole(final long pos, final int type, final long sz)
 		} else {
 			data = inflateAndReturn(Source.INPUT, sz);
 			objectDigest.update(data);
-			tempObjectId.fromRaw(objectDigest.digest(), 0);
+			objectDigest.digest(tempObjectId);
 			verifySafeObject(tempObjectId, type, data);
 		}
 

org.eclipse.jgit/src/org/eclipse/jgit/treewalk/WorkingTreeIterator.java

@@ -56,7 +56,6 @@
 import java.nio.CharBuffer;
 import java.nio.charset.CharacterCodingException;
 import java.nio.charset.CharsetEncoder;
-import java.security.MessageDigest;
 import java.text.MessageFormat;
 import java.util.Arrays;
 import java.util.Collections;
@@ -99,6 +98,7 @@
 import org.eclipse.jgit.util.TemporaryBuffer.LocalFile;
 import org.eclipse.jgit.util.io.AutoLFInputStream;
 import org.eclipse.jgit.util.io.EolStreamTypeUtil;
+import org.eclipse.jgit.util.sha1.SHA1;
 
 /**
  * Walks a working directory tree as part of a {@link TreeWalk}.
@@ -364,7 +364,7 @@ private byte[] idBufferBlob(final Entry e) {
 			if (is == null)
 				return zeroid;
 			try {
-				state.initializeDigestAndReadBuffer();
+				state.initializeReadBuffer();
 
 				final long len = e.getLength();
 				InputStream filteredIs = possiblyFilteredInputStream(e, is, len,
@@ -1099,10 +1099,9 @@ private static long computeLength(InputStream in) throws IOException {
 	}
 
 	private byte[] computeHash(InputStream in, long length) throws IOException {
-		final MessageDigest contentDigest = state.contentDigest;
+		SHA1 contentDigest = SHA1.newInstance();
 		final byte[] contentReadBuffer = state.contentReadBuffer;
 
-		contentDigest.reset();
 		contentDigest.update(hblob);
 		contentDigest.update((byte) ' ');
 
@@ -1330,9 +1329,6 @@ private static final class IteratorState {
 		/** File name character encoder. */
 		final CharsetEncoder nameEncoder;
 
-		/** Digest computer for {@link #contentId} computations. */
-		MessageDigest contentDigest;
-
 		/** Buffer used to perform {@link #contentId} computations. */
 		byte[] contentReadBuffer;
 
@@ -1347,9 +1343,8 @@ private static final class IteratorState {
 			this.nameEncoder = Constants.CHARSET.newEncoder();
 		}
 
-		void initializeDigestAndReadBuffer() {
+		void initializeReadBuffer() {
-			if (contentDigest == null) {
+			if (contentReadBuffer == null) {
-				contentDigest = Constants.newMessageDigest();
 				contentReadBuffer = new byte[BUFFER_SIZE];
 			}
 		}

org.eclipse.jgit/src/org/eclipse/jgit/util/sha1/SHA1.java

@@ -0,0 +1,289 @@
+/*
+ * Copyright (C) 2017, Google Inc.
+ * 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.util.sha1;
+
+import java.util.Arrays;
+
+import org.eclipse.jgit.lib.MutableObjectId;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.util.NB;
+
+/**
+ * Pure Java implementation of SHA-1 from FIPS 180-1 / RFC 3174.
+ *
+ * <p>
+ * See <a href="https://tools.ietf.org/html/rfc3174">RFC 3174</a>.
+ *
+ * @since 4.7
+ */
+public class SHA1 {
+	/** @return a new context to compute a SHA-1 hash of data. */
+	public static SHA1 newInstance() {
+		return new SHA1();
+	}
+
+	// Magic initialization constants defined by FIPS180.
+	private int h0 = 0x67452301;
+	private int h1 = 0xEFCDAB89;
+	private int h2 = 0x98BADCFE;
+	private int h3 = 0x10325476;
+	private int h4 = 0xC3D2E1F0;
+	private final int[] w = new int[80];
+
+	/** Buffer to accumulate partial blocks to 64 byte alignment. */
+	private final byte[] buffer = new byte[64];
+
+	/** Total number of bytes in the message. */
+	private long length;
+
+	private SHA1() {
+	}
+
+	/**
+	 * Update the digest computation by adding a byte.
+	 *
+	 * @param b
+	 */
+	public void update(byte b) {
+		int bufferLen = (int) (length & 63);
+		length++;
+		buffer[bufferLen] = b;
+		if (bufferLen == 63) {
+			compress(buffer, 0);
+		}
+	}
+
+	/**
+	 * Update the digest computation by adding bytes to the message.
+	 *
+	 * @param in
+	 *            input array of bytes.
+	 */
+	public void update(byte[] in) {
+		update(in, 0, in.length);
+	}
+
+	/**
+	 * Update the digest computation by adding bytes to the message.
+	 *
+	 * @param in
+	 *            input array of bytes.
+	 * @param p
+	 *            offset to start at from {@code in}.
+	 * @param len
+	 *            number of bytes to hash.
+	 */
+	public void update(byte[] in, int p, int len) {
+		// SHA-1 compress can only process whole 64 byte blocks.
+		// Hold partial updates in buffer, whose length is the low bits.
+		int bufferLen = (int) (length & 63);
+		length += len;
+
+		if (bufferLen > 0) {
+			int n = Math.min(64 - bufferLen, len);
+			System.arraycopy(in, p, buffer, bufferLen, n);
+			p += n;
+			len -= n;
+			if (bufferLen + n < 64) {
+				return;
+			}
+			compress(buffer, 0);
+		}
+		while (len >= 64) {
+			compress(in, p);
+			p += 64;
+			len -= 64;
+		}
+		if (len > 0) {
+			System.arraycopy(in, p, buffer, 0, len);
+		}
+	}
+
+	private void compress(byte[] block, int p) {
+		// Method 1 from RFC 3174 section 6.1.
+		// Method 2 (circular queue of 16 words) is slower.
+		int a = h0, b = h1, c = h2, d = h3, e = h4;
+
+		// Round 1: 0 <= t <= 15 comes from the input block.
+		for (int t = 0; t < 16; t++) {
+			int temp = NB.decodeInt32(block, p + (t << 2));
+			w[t] = temp;
+			temp += ((a << 5) | (a >>> 27)) // S^5(A)
+					+ (((c ^ d) & b) ^ d) // f: 0 <= t <= 19
+					+ e + 0x5A827999;
+			e = d;
+			d = c;
+			c = (b << 30) | (b >>> 2); // S^30(B)
+			b = a;
+			a = temp;
+		}
+
+		// RFC 3174 6.1.b, extend state vector to 80 words.
+		for (int t = 16; t < 80; t++) {
+			int x = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16];
+			w[t] = (x << 1) | (x >>> 31); // S^1(...)
+		}
+
+		// Round 1: tail
+		for (int t = 16; t < 20; t++) {
+			int temp = ((a << 5) | (a >>> 27)) // S^5(A)
+					+ (((c ^ d) & b) ^ d) // f: 0 <= t <= 19
+					+ e + w[t] + 0x5A827999;
+			e = d;
+			d = c;
+			c = (b << 30) | (b >>> 2); // S^30(B)
+			b = a;
+			a = temp;
+		}
+
+		// Round 2
+		for (int t = 20; t < 40; t++) {
+			int temp = ((a << 5) | (a >>> 27)) // S^5(A)
+					+ (b ^ c ^ d) // f: 20 <= t <= 39
+					+ e + w[t] + 0x6ED9EBA1;
+			e = d;
+			d = c;
+			c = (b << 30) | (b >>> 2); // S^30(B)
+			b = a;
+			a = temp;
+		}
+
+		// Round 3
+		for (int t = 40; t < 60; t++) {
+			int temp = ((a << 5) | (a >>> 27)) // S^5(A)
+					+ ((b & c) | (d & (b | c))) // f: 40 <= t <= 59
+					+ e + w[t] + 0x8F1BBCDC;
+			e = d;
+			d = c;
+			c = (b << 30) | (b >>> 2); // S^30(B)
+			b = a;
+			a = temp;
+		}
+
+		// Round 4
+		for (int t = 60; t < 80; t++) {
+			int temp = ((a << 5) | (a >>> 27)) // S^5(A)
+					+ (b ^ c ^ d) // f: 60 <= t <= 79
+					+ e + w[t] + 0xCA62C1D6;
+			e = d;
+			d = c;
+			c = (b << 30) | (b >>> 2); // S^30(B)
+			b = a;
+			a = temp;
+		}
+
+		h0 += a;
+		h1 += b;
+		h2 += c;
+		h3 += d;
+		h4 += e;
+	}
+
+	private void finish() {
+		int bufferLen = (int) (length & 63);
+		if (bufferLen > 55) {
+			// Last block is too small; pad, compress, pad another block.
+			buffer[bufferLen++] = (byte) 0x80;
+			Arrays.fill(buffer, bufferLen, 64, (byte) 0);
+			compress(buffer, 0);
+			Arrays.fill(buffer, 0, 56, (byte) 0);
+		} else {
+			// Last block can hold padding and length.
+			buffer[bufferLen++] = (byte) 0x80;
+			Arrays.fill(buffer, bufferLen, 56, (byte) 0);
+		}
+
+		// SHA-1 appends the length of the message in bits after the
+		// padding block (above). Here length is in bytes. Multiply by
+		// 8 by shifting by 3 as part of storing the 64 bit byte length
+		// into the two words expected in the trailer.
+		NB.encodeInt32(buffer, 56, (int) (length >>> (32 - 3)));
+		NB.encodeInt32(buffer, 60, (int) (length << 3));
+		compress(buffer, 0);
+	}
+
+	/**
+	 * Finish the digest and return the resulting hash.
+	 * <p>
+	 * Once {@code digest()} is called, this instance should be discarded.
+	 *
+	 * @return the bytes for the resulting hash.
+	 */
+	public byte[] digest() {
+		finish();
+
+		byte[] b = new byte[20];
+		NB.encodeInt32(b, 0, h0);
+		NB.encodeInt32(b, 4, h1);
+		NB.encodeInt32(b, 8, h2);
+		NB.encodeInt32(b, 12, h3);
+		NB.encodeInt32(b, 16, h4);
+		return b;
+	}
+
+	/**
+	 * Finish the digest and return the resulting hash.
+	 * <p>
+	 * Once {@code digest()} is called, this instance should be discarded.
+	 *
+	 * @return the ObjectId for the resulting hash.
+	 */
+	public ObjectId toObjectId() {
+		finish();
+		return new ObjectId(h0, h1, h2, h3, h4);
+	}
+
+	/**
+	 * Finish the digest and return the resulting hash.
+	 * <p>
+	 * Once {@code digest()} is called, this instance should be discarded.
+	 *
+	 * @param id
+	 *            destination to copy the digest to.
+	 */
+	public void digest(MutableObjectId id) {
+		finish();
+		id.set(h0, h1, h2, h3, h4);
+	}
+}