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 }