Issue #797: fixed reuse of SHA message digests by Guava.

	Change on 2016/09/28 by tball <tball@google.com>

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=134560133

jre_emul/Classes/com/google/j2objc/security/IosSHAMessageDigest.java

@@ -18,6 +18,7 @@
 package com.google.j2objc.security;
 
 import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 import java.security.MessageDigest;
 
 /*-[
@@ -54,6 +55,21 @@ protected void engineReset() {
     buffer.reset();
   }
 
+  public Object clone() throws CloneNotSupportedException {
+      IosSHAMessageDigest obj = (IosSHAMessageDigest) super.clone();
+      // ByteArrayOutputStreams are not cloneable, so copy it.
+      obj.buffer = new ByteArrayOutputStream();
+      if (buffer.size() > 0) {
+        try {
+          obj.buffer.write(buffer.toByteArray());
+        } catch (IOException e) {
+          // Should never happen.
+          throw new AssertionError(e);
+        }
+      }
+      return obj;
+  }
+
   public static class SHA1 extends IosSHAMessageDigest {
 
     public SHA1() {

jre_emul/Tests/com/google/j2objc/security/IosSHAMessageDigestTest.java

@@ -0,0 +1,48 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.j2objc.security;
+
+import java.security.MessageDigest;
+import junit.framework.TestCase;
+
+
+/**
+ * Unit tests for {@link IosSHAMessageDigest}.
+ *
+ * @author Tom Ball
+ */
+public class IosSHAMessageDigestTest extends TestCase {
+
+  // Issue #797: cloned digests returned different hash values.
+  public void testDigestCloning() throws Exception {
+    MessageDigest digest = MessageDigest.getInstance("SHA-1");
+    String hash1 = hash("foo", (MessageDigest) digest.clone());
+    String hash2 = hash("foo", (MessageDigest) digest.clone());
+    assertEquals(hash1, hash2);
+  }
+
+  private String hash(String input, MessageDigest digest) throws Exception {
+    byte[] bytes = input.getBytes("UTF-8");
+    digest.update(bytes);
+    byte[] hash = digest.digest();
+    StringBuilder sb = new StringBuilder(2 * bytes.length);
+    for (byte b : hash) {
+      sb.append(hexDigits[(b >> 4) & 0xf]).append(hexDigits[b & 0xf]);
+    }
+    return sb.toString();
+  }
+
+  private static final char[] hexDigits = "0123456789abcdef".toCharArray();
+}

jre_emul/test_sources.mk

@@ -213,6 +213,7 @@ TEST_SOURCES := \
     com/google/j2objc/ThrowableTest.java \
     com/google/j2objc/net/NSErrorExceptionTest.java \
     com/google/j2objc/security/IosSecureRandomImplTest.java \
+    com/google/j2objc/security/IosSHAMessageDigestTest.java \
     com/google/j2objc/util/NativeTimeZoneTest.java \
     dalvik/system/JniTest.java \
     java/lang/SystemTest.java \