1 /*
   2  * Copyright (c) 2012, 2014, 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 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             (int) 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 }
 208 
 209 #ifndef PRODUCT
 210 // Overloaded versions for internal test.
 211 juint AltHashing::murmur3_32(const jbyte* data, int len) {
 212   return murmur3_32(0, data, len);
 213 }
 214 
 215 juint AltHashing::murmur3_32(const jchar* data, int len) {
 216   return murmur3_32(0, data, len);
 217 }
 218 
 219 // Internal test for alternate hashing.  Translated from JDK version
 220 // test/sun/misc/Hashing.java
 221 static const jbyte ONE_BYTE[] = { (jbyte) 0x80};
 222 static const jbyte TWO_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81};
 223 static const jchar ONE_CHAR[] = { (jchar) 0x8180};
 224 static const jbyte THREE_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82};
 225 static const jbyte FOUR_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82, (jbyte) 0x83};
 226 static const jchar TWO_CHAR[] = { (jchar) 0x8180, (jchar) 0x8382};
 227 static const jint ONE_INT[] = { 0x83828180};
 228 static const jbyte SIX_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82, (jbyte) 0x83, (jbyte) 0x84, (jbyte) 0x85};
 229 static const jchar THREE_CHAR[] = { (jchar) 0x8180, (jchar) 0x8382, (jchar) 0x8584};
 230 static const jbyte EIGHT_BYTE[] = {
 231   (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82,
 232   (jbyte) 0x83, (jbyte) 0x84, (jbyte) 0x85,
 233   (jbyte) 0x86, (jbyte) 0x87};
 234 static const jchar FOUR_CHAR[] = {
 235   (jchar) 0x8180, (jchar) 0x8382,
 236   (jchar) 0x8584, (jchar) 0x8786};
 237 
 238 static const jint TWO_INT[] = { 0x83828180, 0x87868584};
 239 
 240 static const juint MURMUR3_32_X86_CHECK_VALUE = 0xB0F57EE3;
 241 
 242 void AltHashing::testMurmur3_32_ByteArray() {
 243   // printf("testMurmur3_32_ByteArray\n");
 244 
 245   jbyte vector[256];
 246   jbyte hashes[4 * 256];
 247 
 248   for (int i = 0; i < 256; i++) {
 249     vector[i] = (jbyte) i;
 250   }
 251 
 252   // Hash subranges {}, {0}, {0,1}, {0,1,2}, ..., {0,...,255}
 253   for (int i = 0; i < 256; i++) {
 254     juint hash = murmur3_32(256 - i, vector, i);
 255     hashes[i * 4] = (jbyte) hash;
 256     hashes[i * 4 + 1] = (jbyte)(hash >> 8);
 257     hashes[i * 4 + 2] = (jbyte)(hash >> 16);
 258     hashes[i * 4 + 3] = (jbyte)(hash >> 24);
 259   }
 260 
 261   // hash to get const result.
 262   juint final_hash = murmur3_32(hashes, 4*256);
 263 
 264   assert (MURMUR3_32_X86_CHECK_VALUE == final_hash,

 265           "Calculated hash result not as expected. Expected %08X got %08X\n",
 266           MURMUR3_32_X86_CHECK_VALUE,
 267           final_hash);
 268 }
 269 
 270 void AltHashing::testEquivalentHashes() {
 271   juint jbytes, jchars, ints;
 272 
 273   // printf("testEquivalentHashes\n");
 274 
 275   jbytes = murmur3_32(TWO_BYTE, 2);
 276   jchars = murmur3_32(ONE_CHAR, 1);
 277   assert (jbytes == jchars,
 278           "Hashes did not match. b:%08x != c:%08x\n", jbytes, jchars);
 279 
 280   jbytes = murmur3_32(FOUR_BYTE, 4);
 281   jchars = murmur3_32(TWO_CHAR, 2);
 282   ints = murmur3_32(ONE_INT, 1);
 283   assert ((jbytes == jchars) && (jbytes == ints),
 284           "Hashes did not match. b:%08x != c:%08x != i:%08x\n", jbytes, jchars, ints);
 285 
 286   jbytes = murmur3_32(SIX_BYTE, 6);
 287   jchars = murmur3_32(THREE_CHAR, 3);
 288   assert (jbytes == jchars,
 289          "Hashes did not match. b:%08x != c:%08x\n", jbytes, jchars);
 290 
 291   jbytes = murmur3_32(EIGHT_BYTE, 8);
 292   jchars = murmur3_32(FOUR_CHAR, 4);
 293   ints = murmur3_32(TWO_INT, 2);
 294   assert ((jbytes == jchars) && (jbytes == ints),
 295           "Hashes did not match. b:%08x != c:%08x != i:%08x\n", jbytes, jchars, ints);
 296 }
 297 
 298 // Returns true if the alternate hashcode is correct
 299 void AltHashing::test_alt_hash() {
 300   testMurmur3_32_ByteArray();
 301   testEquivalentHashes();
 302 }
 303 #endif // PRODUCT
--- EOF ---