src/share/classes/java/util/zip/CRC32.java

*** 1,7 ****
  /*
!  * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
--- 1,7 ----
  /*
!  * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
*** 23,32 ****
--- 23,33 ----
   * questions.
   */
  
  package java.util.zip;
  
+ import java.lang.reflect.Field;
  import java.nio.ByteBuffer;
  import sun.nio.ch.DirectBuffer;
  
  /**
   * A class that can be used to compute the CRC-32 of a data stream.
*** 53,63 ****
       * eight bits of the argument b).
       *
       * @param b the byte to update the checksum with
       */
      public void update(int b) {
!         crc = update(crc, b);
      }
  
      /**
       * Updates the CRC-32 checksum with the specified array of bytes.
       */
--- 54,67 ----
       * eight bits of the argument b).
       *
       * @param b the byte to update the checksum with
       */
      public void update(int b) {
!         int c = ~ crc;
!         b = timesXtoThe32[(b ^ c) & 0xFF];
!         b = b ^ (c >>> 8);
!         crc = ~b;
      }
  
      /**
       * Updates the CRC-32 checksum with the specified array of bytes.
       */
*** 66,77 ****
--- 70,86 ----
              throw new NullPointerException();
          }
          if (off < 0 || len < 0 || off > b.length - len) {
              throw new ArrayIndexOutOfBoundsException();
          }
+ 
+         if (len < javaCRCIfSmallerThan) {
+             crc = updateBytesSimple(crc, b, off, len);
+         } else {
              crc = updateBytes(crc, b, off, len);
          }
+     }
  
      /**
       * Updates the CRC-32 checksum with the specified array of bytes.
       *
       * @param b the array of bytes to update the checksum with
*** 129,134 ****
--- 138,183 ----
      private native static int update(int crc, int b);
      private native static int updateBytes(int crc, byte[] b, int off, int len);
  
      private native static int updateByteBuffer(int adler, long addr,
                                                 int off, int len);
+ 
+     /**
+      *  Simple byte-at-a-time CRC for avoiding the overhead of native call.
+      *  Breakeven ranges between 60 and 100 bytes.
+      */
+     private static int updateBytesSimple(int crc, byte[] b, int off, int len) {
+         int[] a = timesXtoThe32;
+         if (a.length < 256)
+             throw new ArrayIndexOutOfBoundsException();
+         int c = ~crc;
+         for (int i = 0; i < len; i++ ) {
+             int x0 = b[i + off];
+             x0 = a[(x0 ^ c) & 0xFF];
+             c = x0 ^ (c >>> 8);
+         }
+         return ~c;
+     }
+ 
+     /**
+      * Returns true if CLMUL is both requested and supported.
+      */
+     private native static boolean init(int[] timesXtoThe32, boolean try_use_clmul);
+ 
+     /**
+      * timesXtoThe32[a] = rep(poly(a)*x**32)
+      */
+     static int[] timesXtoThe32;
+ 
+     /**
+      * Estimated CRC size below which the JNI overhead is too large.
+      * May be modified depending on platform properties.
+      */
+     static int javaCRCIfSmallerThan = 80;
+ 
+     static {
+       timesXtoThe32 = new int[256];
+       boolean try_use_clmul =
+            "true".equals(sun.misc.VM.getSavedProperty("sun.zip.clmulSupported"));
+       init(timesXtoThe32, try_use_clmul);
+     }
  }