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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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
31template <class T, class N> class CompactHashtable;
32class CompactStringTableWriter;
33class FileMapInfo;
34class SerializeClosure;
35
36class StringTable : public RehashableHashtable<oop, mtSymbol> {
37  friend class VMStructs;
38  friend class Symbol;
39
40private:
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) {}
85public:
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
178