1 /*

     2  * Copyright (c) 2012, 2017, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #include "precompiled.hpp"

    26 #include "classfile/altHashing.hpp"

    27 #include "classfile/symbolTable.hpp"

    28 #include "classfile/systemDictionary.hpp"

    29 #include "oops/markOop.hpp"

    30 #include "runtime/thread.hpp"

    31 

    32 // Get the hash code of the classes mirror if it exists, otherwise just

    33 // return a random number, which is one of the possible hash code used for

    34 // objects.  We don't want to call the synchronizer hash code to install

    35 // this value because it may safepoint.

    36 static intptr_t object_hash(Klass* k) {

    37   intptr_t hc = k->java_mirror()->mark()->hash();

    38   return hc != markOopDesc::no_hash ? hc : os::random();

    39 }

    40 

    41 // Seed value used for each alternative hash calculated.

    42 juint AltHashing::compute_seed() {

    43   jlong nanos = os::javaTimeNanos();

    44   jlong now = os::javaTimeMillis();

    45   int SEED_MATERIAL[8] = {

    46             (int) object_hash(SystemDictionary::String_klass()),

    47             (int) object_hash(SystemDictionary::System_klass()),

    48             os::random(),  // current thread isn't a java thread

    49             (int) (((julong)nanos) >> 32),

    50             (int) nanos,

    51             (int) (((julong)now) >> 32),

    52             (int) now,

    53             (int) (os::javaTimeNanos() >> 2)

    54   };

    55 

    56   return murmur3_32(SEED_MATERIAL, 8);

    57 }

    58 

    59 

    60 // Murmur3 hashing for Symbol

    61 juint AltHashing::murmur3_32(juint seed, const jbyte* data, int len) {

    62   juint h1 = seed;

    63   int count = len;

    64   int offset = 0;

    65 

    66   // body

    67   while (count >= 4) {

    68     juint k1 = (data[offset] & 0x0FF)

    69         | (data[offset + 1] & 0x0FF) << 8

    70         | (data[offset + 2] & 0x0FF) << 16

    71         | data[offset + 3] << 24;

    72 

    73     count -= 4;

    74     offset += 4;

    75 

    76     k1 *= 0xcc9e2d51;

    77     k1 = Integer_rotateLeft(k1, 15);

    78     k1 *= 0x1b873593;

    79 

    80     h1 ^= k1;

    81     h1 = Integer_rotateLeft(h1, 13);

    82     h1 = h1 * 5 + 0xe6546b64;

    83   }

    84 

    85   // tail

    86 

    87   if (count > 0) {

    88     juint k1 = 0;

    89 

    90     switch (count) {

    91       case 3:

    92         k1 ^= (data[offset + 2] & 0xff) << 16;

    93       // fall through

    94       case 2:

    95         k1 ^= (data[offset + 1] & 0xff) << 8;

    96       // fall through

    97       case 1:

    98         k1 ^= (data[offset] & 0xff);

    99       // fall through

   100       default:

   101         k1 *= 0xcc9e2d51;

   102         k1 = Integer_rotateLeft(k1, 15);

   103         k1 *= 0x1b873593;

   104         h1 ^= k1;

   105     }

   106   }

   107 

   108   // finalization

   109   h1 ^= len;

   110 

   111   // finalization mix force all bits of a hash block to avalanche

   112   h1 ^= h1 >> 16;

   113   h1 *= 0x85ebca6b;

   114   h1 ^= h1 >> 13;

   115   h1 *= 0xc2b2ae35;

   116   h1 ^= h1 >> 16;

   117 

   118   return h1;

   119 }

   120 

   121 // Murmur3 hashing for Strings

   122 juint AltHashing::murmur3_32(juint seed, const jchar* data, int len) {

   123   juint h1 = seed;

   124 

   125   int off = 0;

   126   int count = len;

   127 

   128   // body

   129   while (count >= 2) {

   130     jchar d1 = data[off++] & 0xFFFF;

   131     jchar d2 = data[off++];

   132     juint k1 = (d1 | d2 << 16);

   133 

   134     count -= 2;

   135 

   136     k1 *= 0xcc9e2d51;

   137     k1 = Integer_rotateLeft(k1, 15);

   138     k1 *= 0x1b873593;

   139 

   140     h1 ^= k1;

   141     h1 = Integer_rotateLeft(h1, 13);

   142     h1 = h1 * 5 + 0xe6546b64;

   143   }

   144 

   145   // tail

   146 

   147   if (count > 0) {

   148     juint k1 = (juint)data[off];

   149 

   150     k1 *= 0xcc9e2d51;

   151     k1 = Integer_rotateLeft(k1, 15);

   152     k1 *= 0x1b873593;

   153     h1 ^= k1;

   154   }

   155 

   156   // finalization

   157   h1 ^= len * 2; // (Character.SIZE / Byte.SIZE);

   158 

   159   // finalization mix force all bits of a hash block to avalanche

   160   h1 ^= h1 >> 16;

   161   h1 *= 0x85ebca6b;

   162   h1 ^= h1 >> 13;

   163   h1 *= 0xc2b2ae35;

   164   h1 ^= h1 >> 16;

   165 

   166   return h1;

   167 }

   168 

   169 // Hash used for the seed.

   170 juint AltHashing::murmur3_32(juint seed, const int* data, int len) {

   171   juint h1 = seed;

   172 

   173   int off = 0;

   174   int end = len;

   175 

   176   // body

   177   while (off < end) {

   178     juint k1 = (juint)data[off++];

   179 

   180     k1 *= 0xcc9e2d51;

   181     k1 = Integer_rotateLeft(k1, 15);

   182     k1 *= 0x1b873593;

   183 

   184     h1 ^= k1;

   185     h1 = Integer_rotateLeft(h1, 13);

   186     h1 = h1 * 5 + 0xe6546b64;

   187   }

   188 

   189   // tail (always empty, as body is always 32-bit chunks)

   190 

   191   // finalization

   192 

   193   h1 ^= len * 4; // (Integer.SIZE / Byte.SIZE);

   194 

   195   // finalization mix force all bits of a hash block to avalanche

   196   h1 ^= h1 >> 16;

   197   h1 *= 0x85ebca6b;

   198   h1 ^= h1 >> 13;

   199   h1 *= 0xc2b2ae35;

   200   h1 ^= h1 >> 16;

   201 

   202   return h1;

   203 }

   204 

   205 juint AltHashing::murmur3_32(const int* data, int len) {

   206   return murmur3_32(0, data, len);

   207 }