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.
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23 */
24
25 #ifndef SHARE_VM_CLASSFILE_STRINGTABLE_HPP
26 #define SHARE_VM_CLASSFILE_STRINGTABLE_HPP
27
28 #include "utilities/hashtable.hpp"
29
30 template <class T, class N> class CompactHashtable;
31 class CompactStringTableWriter;
32 class FileMapInfo;
33 class SerializeClosure;
34
35 class StringTable : public RehashableHashtable<oop, mtSymbol> {
36 friend class VMStructs;
37 friend class Symbol;
38
39 private:
40 // The string table
41 static StringTable* _the_table;
42
43 // Shared string table
44 static CompactHashtable<oop, char> _shared_table;
45 static bool _shared_string_mapped;
46
47 // Set if one bucket is out of balance due to hash algorithm deficiency
48 static bool _needs_rehashing;
49
50 // Claimed high water mark for parallel chunked scanning
51 static volatile int _parallel_claimed_idx;
52
53 static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);
54 oop basic_add(int index, Handle string_or_null, jchar* name, int len,
55 unsigned int hashValue, TRAPS);
56
57 oop lookup_in_main_table(int index, jchar* chars, int length, unsigned int hashValue);
58 static oop lookup_shared(jchar* name, int len, unsigned int hash);
59
60 // Apply the give oop closure to the entries to the buckets
61 // in the range [start_idx, end_idx).
62 static void buckets_oops_do(OopClosure* f, int start_idx, int end_idx);
63
64 typedef StringTable::BucketUnlinkContext BucketUnlinkContext;
65 // Unlink or apply the give oop closure to the entries to the buckets
66 // in the range [start_idx, end_idx). Unlinked bucket entries are collected in the given
67 // context to be freed later.
68 // This allows multiple threads to work on the table at once.
69 static void buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, BucketUnlinkContext* context);
70
71 // Hashing algorithm, used as the hash value used by the
72 // StringTable for bucket selection and comparison (stored in the
73 // HashtableEntry structures). This is used in the String.intern() method.
74 static unsigned int hash_string(const jchar* s, int len);
75 static unsigned int hash_string(oop string);
76 static unsigned int alt_hash_string(const jchar* s, int len);
77
78 // Accessors for the string roots in the hashtable entries.
79 // Use string_object_no_keepalive() only when the value is not returned
80 // outside of a scope where a thread transition is possible.
81 static oop string_object(HashtableEntry<oop, mtSymbol>* entry);
82 static oop string_object_no_keepalive(HashtableEntry<oop, mtSymbol>* entry);
83 static void set_string_object(HashtableEntry<oop, mtSymbol>* entry, oop string);
84
85 StringTable() : RehashableHashtable<oop, mtSymbol>((int)StringTableSize,
86 sizeof (HashtableEntry<oop, mtSymbol>)) {}
87
88 StringTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
89 : RehashableHashtable<oop, mtSymbol>((int)StringTableSize, sizeof (HashtableEntry<oop, mtSymbol>), t,
90 number_of_entries) {}
91 public:
92 // The string table
93 static StringTable* the_table() { return _the_table; }
94
95 // Size of one bucket in the string table. Used when checking for rollover.
96 static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
97
98 static void create_table() {
99 assert(_the_table == NULL, "One string table allowed.");
100 _the_table = new StringTable();
101 }
102
103 // GC support
104 // Delete pointers to otherwise-unreachable objects.
105 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f) {
106 int processed = 0;
107 int removed = 0;
108 unlink_or_oops_do(cl, f, &processed, &removed);
109 }
110 static void unlink(BoolObjectClosure* cl) {
111 int processed = 0;
112 int removed = 0;
113 unlink_or_oops_do(cl, NULL, &processed, &removed);
114 }
115 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
116 static void unlink(BoolObjectClosure* cl, int* processed, int* removed) {
117 unlink_or_oops_do(cl, NULL, processed, removed);
118 }
119 // Serially invoke "f->do_oop" on the locations of all oops in the table.
120 static void oops_do(OopClosure* f);
121
122 // Possibly parallel versions of the above
123 static void possibly_parallel_unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
124 static void possibly_parallel_unlink(BoolObjectClosure* cl, int* processed, int* removed) {
125 possibly_parallel_unlink_or_oops_do(cl, NULL, processed, removed);
126 }
127 static void possibly_parallel_oops_do(OopClosure* f);
128
129 // Internal test.
130 static void test_alt_hash() PRODUCT_RETURN;
131
132 // Probing
133 static oop lookup(Symbol* symbol);
134 static oop lookup(jchar* chars, int length);
135
136 // Interning
137 static oop intern(Symbol* symbol, TRAPS);
138 static oop intern(oop string, TRAPS);
139 static oop intern(const char *utf8_string, TRAPS);
140
141 // Debugging
142 static void verify();
143 static void dump(outputStream* st, bool verbose=false);
144
145 enum VerifyMesgModes {
146 _verify_quietly = 0,
147 _verify_with_mesgs = 1
148 };
149
150 enum VerifyRetTypes {
151 _verify_pass = 0,
152 _verify_fail_continue = 1,
153 _verify_fail_done = 2
154 };
155
156 static VerifyRetTypes compare_entries(int bkt1, int e_cnt1,
157 HashtableEntry<oop, mtSymbol>* e_ptr1,
158 int bkt2, int e_cnt2,
159 HashtableEntry<oop, mtSymbol>* e_ptr2);
160 static VerifyRetTypes verify_entry(int bkt, int e_cnt,
161 HashtableEntry<oop, mtSymbol>* e_ptr,
162 VerifyMesgModes mesg_mode);
163 static int verify_and_compare_entries();
164
165 // Sharing
166 static void set_shared_string_mapped() { _shared_string_mapped = true; }
167 static bool shared_string_mapped() { return _shared_string_mapped; }
168 static void shared_oops_do(OopClosure* f) NOT_CDS_JAVA_HEAP_RETURN;
169 static bool copy_shared_string(GrowableArray<MemRegion> *string_space,
170 CompactStringTableWriter* ch_table) NOT_CDS_JAVA_HEAP_RETURN_(false);
171 static oop create_archived_string(oop s, Thread* THREAD) NOT_CDS_JAVA_HEAP_RETURN_(NULL);
172 static void write_to_archive(GrowableArray<MemRegion> *string_space) NOT_CDS_JAVA_HEAP_RETURN;
173 static void serialize(SerializeClosure* soc) NOT_CDS_JAVA_HEAP_RETURN;
174
175 // Rehash the symbol table if it gets out of balance
176 static void rehash_table();
177 static bool needs_rehashing() { return _needs_rehashing; }
178
179 // Parallel chunked scanning
180 static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
181 static int parallel_claimed_index() { return _parallel_claimed_idx; }
182 };
183 #endif // SHARE_VM_CLASSFILE_STRINGTABLE_HPP