performance improvements for large files

Former-commit-id: 6a49a7066cb01c613b5c6f07c8497601a88e7f8d

dependency-check-utils/src/main/java/org/owasp/dependencycheck/utils/Checksum.java

@@ -1,9 +1,28 @@
+/*
+ * This file is part of dependency-check-core.
+ *
+ * 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.
+ *
+ * Copyright (c) 2014 Jeremy Long. All Rights Reserved.
+ */
 package org.owasp.dependencycheck.utils;
 
+import java.io.BufferedInputStream;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.security.DigestInputStream;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.logging.Level;
@@ -12,11 +31,7 @@ import java.util.logging.Logger;
 /**
  * Includes methods to generate the MD5 and SHA1 checksum.
  *
- * This code was copied from Real's How To. It has been slightly modified.
+ * @author Jeremy Long <jeremy.long@owasp.org>
- *
- * Written and compiled by Réal Gagnon ©1998-2012
- *
- * @author Real's How To: http://www.rgagnon.com/javadetails/java-0416.html
  *
  */
 public final class Checksum {
@@ -25,6 +40,7 @@ public final class Checksum {
      * The logger.
      */
     private static final Logger LOGGER = Logger.getLogger(Checksum.class.getName());
+
     /**
      * Private constructor for a utility class.
      */
@@ -32,30 +48,25 @@ public final class Checksum {
     }
 
     /**
-     * <p>Creates the cryptographic checksum of a given file using the specified
+     * <p>
-     * algorithm.</p> <p>This algorithm was copied and heavily modified from
+     * Creates the cryptographic checksum of a given file using the specified algorithm.</p>
-     * Real's How To: http://www.rgagnon.com/javadetails/java-0416.html</p>
      *
      * @param algorithm the algorithm to use to calculate the checksum
      * @param file the file to calculate the checksum for
      * @return the checksum
      * @throws IOException when the file does not exist
-     * @throws NoSuchAlgorithmException when an algorithm is specified that does
+     * @throws NoSuchAlgorithmException when an algorithm is specified that does not exist
-     * not exist
      */
     public static byte[] getChecksum(String algorithm, File file) throws NoSuchAlgorithmException, IOException {
+        MessageDigest digest = MessageDigest.getInstance(algorithm);
         InputStream fis = null;
-        byte[] buffer = new byte[1024];
-        MessageDigest complete = MessageDigest.getInstance(algorithm);
-        int numRead;
         try {
             fis = new FileInputStream(file);
-            do {
+            BufferedInputStream bis = new BufferedInputStream(fis);
-                numRead = fis.read(buffer);
+            DigestInputStream dis = new DigestInputStream(bis, digest);
-                if (numRead > 0) {
+            //yes, we are reading in a buffer for performance reasons - 1 byte at a time is SLOW
-                    complete.update(buffer, 0, numRead);
+            byte[] buffer = new byte[8192];
-                }
+            while (dis.read(buffer) != -1);
-            } while (numRead != -1);
         } finally {
             if (fis != null) {
                 try {
@@ -65,7 +76,7 @@ public final class Checksum {
                 }
             }
         }
-        return complete.digest();
+        return digest.digest();
     }
 
     /**
@@ -93,12 +104,17 @@ public final class Checksum {
         byte[] b = getChecksum("SHA1", file);
         return getHex(b);
     }
+    /**
+     * Hex code characters used in getHex.
+     */
     private static final String HEXES = "0123456789ABCDEF";
 
     /**
-     * <p>Converts a byte array into a hex string.</p>
+     * <p>
+     * Converts a byte array into a hex string.</p>
      *
-     * <p>This method was copied from <a
+     * <p>
+     * This method was copied from <a
      * href="http://www.rgagnon.com/javadetails/java-0596.html">http://www.rgagnon.com/javadetails/java-0596.html</a></p>
      *
      * @param raw a byte array