rev 48017 : [mq]: Access_strings
1 /*
2 * Copyright (c) 1997, 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 #ifndef SHARE_VM_CLASSFILE_STRINGTABLE_HPP
26 #define SHARE_VM_CLASSFILE_STRINGTABLE_HPP
27
28 #include "memory/allocation.inline.hpp"
29 #include "utilities/hashtable.hpp"
30
31 template <class T, class N> class CompactHashtable;
32 class CompactStringTableWriter;
33 class FileMapInfo;
34 class SerializeClosure;
35
36 class StringTable : public RehashableHashtable<oop, mtSymbol> {
37 friend class VMStructs;
38 friend class Symbol;
39
40 private:
41 // The string table
42 static StringTable* _the_table;
43
44 // Shared string table
45 static CompactHashtable<oop, char> _shared_table;
46 static bool _shared_string_mapped;
47
48 // Set if one bucket is out of balance due to hash algorithm deficiency
49 static bool _needs_rehashing;
50
51 // Claimed high water mark for parallel chunked scanning
52 static volatile int _parallel_claimed_idx;
53
54 static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);
55 oop basic_add(int index, Handle string_or_null, jchar* name, int len,
56 unsigned int hashValue, TRAPS);
57
58 oop lookup_in_main_table(int index, jchar* chars, int length, unsigned int hashValue);
59 static oop lookup_shared(jchar* name, int len, unsigned int hash);
60
61 // Apply the give oop closure to the entries to the buckets
62 // in the range [start_idx, end_idx).
63 static void buckets_oops_do(OopClosure* f, int start_idx, int end_idx);
64
65 typedef StringTable::BucketUnlinkContext BucketUnlinkContext;
66 // Unlink or apply the give oop closure to the entries to the buckets
67 // in the range [start_idx, end_idx). Unlinked bucket entries are collected in the given
68 // context to be freed later.
69 // This allows multiple threads to work on the table at once.
70 static void buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, BucketUnlinkContext* context);
71
72 // Hashing algorithm, used as the hash value used by the
73 // StringTable for bucket selection and comparison (stored in the
74 // HashtableEntry structures). This is used in the String.intern() method.
75 static unsigned int hash_string(const jchar* s, int len);
76 static unsigned int hash_string(oop string);
77 static unsigned int alt_hash_string(const jchar* s, int len);
78
79 StringTable() : RehashableHashtable<oop, mtSymbol>((int)StringTableSize,
80 sizeof (HashtableEntry<oop, mtSymbol>)) {}
81
82 StringTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
83 : RehashableHashtable<oop, mtSymbol>((int)StringTableSize, sizeof (HashtableEntry<oop, mtSymbol>), t,
84 number_of_entries) {}
85 public:
86 // The string table
87 static StringTable* the_table() { return _the_table; }
88
89 // Size of one bucket in the string table. Used when checking for rollover.
90 static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
91
92 static void create_table() {
93 assert(_the_table == NULL, "One string table allowed.");
94 _the_table = new StringTable();
95 }
96
97 // GC support
98 // Delete pointers to otherwise-unreachable objects.
99 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f) {
100 int processed = 0;
101 int removed = 0;
102 unlink_or_oops_do(cl, f, &processed, &removed);
103 }
104 static void unlink(BoolObjectClosure* cl) {
105 int processed = 0;
106 int removed = 0;
107 unlink_or_oops_do(cl, NULL, &processed, &removed);
108 }
109 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
110 static void unlink(BoolObjectClosure* cl, int* processed, int* removed) {
111 unlink_or_oops_do(cl, NULL, processed, removed);
112 }
113 // Serially invoke "f->do_oop" on the locations of all oops in the table.
114 static void oops_do(OopClosure* f);
115
116 // Possibly parallel versions of the above
117 static void possibly_parallel_unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
118 static void possibly_parallel_unlink(BoolObjectClosure* cl, int* processed, int* removed) {
119 possibly_parallel_unlink_or_oops_do(cl, NULL, processed, removed);
120 }
121 static void possibly_parallel_oops_do(OopClosure* f);
122
123 // Internal test.
124 static void test_alt_hash() PRODUCT_RETURN;
125
126 // Probing
127 static oop lookup(Symbol* symbol);
128 static oop lookup(jchar* chars, int length);
129
130 // Interning
131 static oop intern(Symbol* symbol, TRAPS);
132 static oop intern(oop string, TRAPS);
133 static oop intern(const char *utf8_string, TRAPS);
134
135 // Debugging
136 static void verify();
137 static void dump(outputStream* st, bool verbose=false);
138
139 enum VerifyMesgModes {
140 _verify_quietly = 0,
141 _verify_with_mesgs = 1
142 };
143
144 enum VerifyRetTypes {
145 _verify_pass = 0,
146 _verify_fail_continue = 1,
147 _verify_fail_done = 2
148 };
149
150 static VerifyRetTypes compare_entries(int bkt1, int e_cnt1,
151 HashtableEntry<oop, mtSymbol>* e_ptr1,
152 int bkt2, int e_cnt2,
153 HashtableEntry<oop, mtSymbol>* e_ptr2);
154 static VerifyRetTypes verify_entry(int bkt, int e_cnt,
155 HashtableEntry<oop, mtSymbol>* e_ptr,
156 VerifyMesgModes mesg_mode);
157 static int verify_and_compare_entries();
158
159 // Sharing
160 static void set_shared_string_mapped() { _shared_string_mapped = true; }
161 static bool shared_string_mapped() { return _shared_string_mapped; }
162 static void shared_oops_do(OopClosure* f) NOT_CDS_JAVA_HEAP_RETURN;
163 static bool copy_shared_string(GrowableArray<MemRegion> *string_space,
164 CompactStringTableWriter* ch_table) NOT_CDS_JAVA_HEAP_RETURN_(false);
165 static oop create_archived_string(oop s, Thread* THREAD) NOT_CDS_JAVA_HEAP_RETURN_(NULL);
166 static void write_to_archive(GrowableArray<MemRegion> *string_space) NOT_CDS_JAVA_HEAP_RETURN;
167 static void serialize(SerializeClosure* soc) NOT_CDS_JAVA_HEAP_RETURN;
168
169 // Rehash the symbol table if it gets out of balance
170 static void rehash_table();
171 static bool needs_rehashing() { return _needs_rehashing; }
172
173 // Parallel chunked scanning
174 static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
175 static int parallel_claimed_index() { return _parallel_claimed_idx; }
176 };
177 #endif // SHARE_VM_CLASSFILE_STRINGTABLE_HPP
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