1 /*
2 * Copyright (c) 1997, 2013, 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 #ifndef SHARE_VM_CLASSFILE_STRINGTABLE_HPP
26 #define SHARE_VM_CLASSFILE_STRINGTABLE_HPP
27
28 #include "memory/allocation.inline.hpp"
29 #include "oops/symbol.hpp"
30 #include "utilities/hashtable.hpp"
31
32 class StringTable : public Hashtable<oop, mtSymbol> {
33 friend class VMStructs;
34
35 private:
36 // The string table
37 static StringTable* _the_table;
38
39 // Set if one bucket is out of balance due to hash algorithm deficiency
40 static bool _needs_rehashing;
41
42 // Claimed high water mark for parallel chunked scanning
43 static volatile int _parallel_claimed_idx;
44
45 static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);
46 oop basic_add(int index, Handle string_or_null, jchar* name, int len,
47 unsigned int hashValue, TRAPS);
48
49 oop lookup(int index, jchar* chars, int length, unsigned int hashValue);
50
51 // Apply the give oop closure to the entries to the buckets
52 // in the range [start_idx, end_idx).
53 static void buckets_oops_do(OopClosure* f, int start_idx, int end_idx);
54 // Unlink or apply the give oop closure to the entries to the buckets
55 // in the range [start_idx, end_idx).
56 static void buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed);
57
58 StringTable() : Hashtable<oop, mtSymbol>((int)StringTableSize,
59 sizeof (HashtableEntry<oop, mtSymbol>)) {}
60
61 StringTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
62 : Hashtable<oop, mtSymbol>((int)StringTableSize, sizeof (HashtableEntry<oop, mtSymbol>), t,
63 number_of_entries) {}
64 public:
65 // The string table
66 static StringTable* the_table() { return _the_table; }
67
68 // Size of one bucket in the string table. Used when checking for rollover.
69 static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
70
71 static void create_table() {
72 assert(_the_table == NULL, "One string table allowed.");
73 _the_table = new StringTable();
74 }
75
76 // GC support
77 // Delete pointers to otherwise-unreachable objects.
78 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f) {
79 int processed = 0;
80 int removed = 0;
81 unlink_or_oops_do(cl, f, &processed, &removed);
82 }
83 static void unlink(BoolObjectClosure* cl) {
84 int processed = 0;
85 int removed = 0;
86 unlink_or_oops_do(cl, NULL, &processed, &removed);
87 }
88 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
89 static void unlink(BoolObjectClosure* cl, int* processed, int* removed) {
90 unlink_or_oops_do(cl, NULL, processed, removed);
91 }
92 // Serially invoke "f->do_oop" on the locations of all oops in the table.
93 static void oops_do(OopClosure* f);
94
95 // Possibly parallel versions of the above
96 static void possibly_parallel_unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
97 static void possibly_parallel_unlink(BoolObjectClosure* cl, int* processed, int* removed) {
98 possibly_parallel_unlink_or_oops_do(cl, NULL, processed, removed);
99 }
100 static void possibly_parallel_oops_do(OopClosure* f);
101
102 // Hashing algorithm, used as the hash value used by the
103 // StringTable for bucket selection and comparison (stored in the
104 // HashtableEntry structures). This is used in the String.intern() method.
105 static unsigned int hash_string(const jchar* s, int len);
106
107 // Internal test.
108 static void test_alt_hash() PRODUCT_RETURN;
109
110 // Probing
111 static oop lookup(Symbol* symbol);
112 static oop lookup(jchar* chars, int length);
113
114 // Interning
115 static oop intern(Symbol* symbol, TRAPS);
116 static oop intern(oop string, TRAPS);
117 static oop intern(const char *utf8_string, TRAPS);
118
119 // Debugging
120 static void verify();
121 static void dump(outputStream* st);
122
123 enum VerifyMesgModes {
124 _verify_quietly = 0,
125 _verify_with_mesgs = 1
126 };
127
128 enum VerifyRetTypes {
129 _verify_pass = 0,
130 _verify_fail_continue = 1,
131 _verify_fail_done = 2
132 };
133
134 static VerifyRetTypes compare_entries(int bkt1, int e_cnt1,
135 HashtableEntry<oop, mtSymbol>* e_ptr1,
136 int bkt2, int e_cnt2,
137 HashtableEntry<oop, mtSymbol>* e_ptr2);
138 static VerifyRetTypes verify_entry(int bkt, int e_cnt,
139 HashtableEntry<oop, mtSymbol>* e_ptr,
140 VerifyMesgModes mesg_mode);
141 static int verify_and_compare_entries();
142
143 // Sharing
144 static void copy_buckets(char** top, char*end) {
145 the_table()->Hashtable<oop, mtSymbol>::copy_buckets(top, end);
146 }
147 static void copy_table(char** top, char*end) {
148 the_table()->Hashtable<oop, mtSymbol>::copy_table(top, end);
149 }
150 static void reverse() {
151 the_table()->Hashtable<oop, mtSymbol>::reverse();
152 }
153
154 // Rehash the symbol table if it gets out of balance
155 static void rehash_table();
156 static bool needs_rehashing() { return _needs_rehashing; }
157
158 // Parallel chunked scanning
159 static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
160 static int parallel_claimed_index() { return _parallel_claimed_idx; }
161 };
162 #endif // SHARE_VM_CLASSFILE_STRINGTABLE_HPP