Pure Java SHA-1

This implementation is derived straight from the description written
in RFC 3174.  On Mac OS X with Java 1.8.0_91 it offers similar
throughput as MessageDigest SHA-1:

  system   239.75 MiB/s
  system   244.71 MiB/s
  system   245.00 MiB/s
  system   244.92 MiB/s

  sha1     234.08 MiB/s
  sha1     244.50 MiB/s
  sha1     242.99 MiB/s
  sha1     241.73 MiB/s

This is the fastest implementation I could come up with.  Common SHA-1
implementation tricks such as unrolling loops creates a method too
large for the JIT to effectively optimize, resulting in lower overall
hashing throughput. Using a preprocessor to perform the register
renaming of A-E also didn't help, as again the method was too large
for the JIT to effectively optimize.

Fortunately the fastest version is a naive, straight-forward
implementation very close to the description in RFC 3174.

Change-Id: I228b05c4a294ca2ad51386cf0e47978c68e1aa42

2 files changed, 113 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/META-INF/MANIFEST.MF b/org.eclipse.jgit.test/META-INF/MANIFEST.MF
index a8a70df69a..fca6eec3fa 100644
--- a/org.eclipse.jgit.test/META-INF/MANIFEST.MF
+++ b/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)",
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/sha1/SHA1Test.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/sha1/SHA1Test.java
new file mode 100644
index 0000000000..c53080455c
--- /dev/null
+++ b/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);
+	}
+}