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

4 files changed, 376 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);
+	}
+}
diff --git a/org.eclipse.jgit/META-INF/MANIFEST.MF b/org.eclipse.jgit/META-INF/MANIFEST.MF
index 8b78628209..33c331b4aa 100644
--- a/org.eclipse.jgit/META-INF/MANIFEST.MF
+++ b/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)",
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/sha1/SHA1.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/sha1/SHA1.java
new file mode 100644
index 0000000000..625029d3a0
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/sha1/SHA1.java
@@ -0,0 +1,262 @@
+/*
+ * 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.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;
+	}
+}