1 /*
2 * Copyright (c) 1997, 2025, 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_CLASSFILE_STRINGTABLE_HPP
26 #define SHARE_CLASSFILE_STRINGTABLE_HPP
27
28 #include "memory/allStatic.hpp"
29 #include "memory/padded.hpp"
30 #include "oops/oop.hpp"
31 #include "oops/oopHandle.hpp"
32 #include "oops/weakHandle.hpp"
33 #include "utilities/tableStatistics.hpp"
34
35 class CompactHashtableWriter;
36 class JavaThread;
37 class SerializeClosure;
38
39 class StringTableConfig;
40
41 class StringTable : AllStatic {
42 friend class StringTableConfig;
43
44 static volatile bool _has_work;
45
46 // Set if one bucket is out of balance due to hash algorithm deficiency
47 static volatile bool _needs_rehashing;
48
49 static OopStorage* _oop_storage;
50
51 static void grow(JavaThread* jt);
52 static void clean_dead_entries(JavaThread* jt);
53
54 static double get_load_factor();
55 static double get_dead_factor(size_t num_dead);
56
57 public:
58 typedef struct StringWrapperInternal StringWrapper;
59
60 // Unnamed int needed to fit CompactHashtable's equals type signature
61 static bool wrapped_string_equals(oop java_string, const StringWrapper& wrapped_str, int = 0);
62
63 private:
64 static const char* get_symbol_utf8(const StringWrapper& symbol_str);
65 static unsigned int hash_wrapped_string(const StringWrapper& wrapped_str);
66 static const jchar* to_unicode(const StringWrapper& wrapped_str, int &len, TRAPS);
67 static Handle handle_from_wrapped_string(const StringWrapper& wrapped_str, TRAPS);
68
69 // GC support
70
71 // Callback for GC to notify of changes that might require cleaning or resize.
72 static void gc_notification(size_t num_dead);
73 static void trigger_concurrent_work();
74
75 static void item_added();
76 static void item_removed();
77
78 static oop intern(const StringWrapper& name, TRAPS);
79 static oop do_intern(const StringWrapper& name, uintx hash, TRAPS);
80 static oop do_lookup(const StringWrapper& name, uintx hash);
81
82 static void print_table_statistics(outputStream* st);
83
84 public:
85 static size_t table_size();
86 static TableStatistics get_table_statistics();
87
88 static void create_table();
89
90 static void do_concurrent_work(JavaThread* jt);
91 static bool has_work();
92
93 // Probing
94 static oop lookup(Symbol* symbol);
95 static oop lookup(const jchar* chars, int length);
96
97 // Interning
98 static oop intern(Symbol* symbol, TRAPS);
99 static oop intern(oop string, TRAPS);
100 static oop intern(const char* utf8_string, TRAPS);
101
102 // Rehash the string table if it gets out of balance
103 private:
104 static bool should_grow();
105 static bool maybe_rehash_table();
106 public:
107 static void rehash_table();
108 static bool needs_rehashing() { return _needs_rehashing; }
109 static inline void update_needs_rehash(bool rehash);
110
111 // Sharing
112 #if INCLUDE_CDS_JAVA_HEAP
113 static inline oop read_string_from_compact_hashtable(address base_address, u4 index);
114
115 private:
116 static bool _is_two_dimensional_shared_strings_array;
117 static OopHandle _shared_strings_array;
118 static int _shared_strings_array_root_index;
119
120 // All the shared strings are referenced through _shared_strings_array to keep them alive.
121 // Each shared string is stored as a 32-bit index in ::_shared_table. The index
122 // is interpreted in two ways:
123 //
124 // [1] _is_two_dimensional_shared_strings_array = false: _shared_strings_array is an Object[].
125 // Each shared string is stored as _shared_strings_array[index]
126 //
127 // [2] _is_two_dimensional_shared_strings_array = true: _shared_strings_array is an Object[][]
128 // This happens when there are too many elements in the shared table. We store them
129 // using two levels of objArrays, such that none of the arrays are too big for
130 // ArchiveHeapWriter::is_too_large_to_archive(). In this case, the index is splited into two
131 // parts. Each shared string is stored as _shared_strings_array[primary_index][secondary_index]:
132 //
133 // [bits 31 .. 14][ bits 13 .. 0 ]
134 // primary_index secondary_index
135 const static int _secondary_array_index_bits = 14;
136 const static int _secondary_array_max_length = 1 << _secondary_array_index_bits;
137 const static int _secondary_array_index_mask = _secondary_array_max_length - 1;
138
139 // make sure _secondary_array_index_bits is not too big
140 static void verify_secondary_array_index_bits() PRODUCT_RETURN;
141 #endif // INCLUDE_CDS_JAVA_HEAP
142
143 private:
144 static oop lookup_shared(const StringWrapper& name, unsigned int hash) NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
145 public:
146 static oop lookup_shared(const jchar* name, int len) NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
147 static size_t shared_entry_count() NOT_CDS_JAVA_HEAP_RETURN_(0);
148 static void allocate_shared_strings_array(TRAPS) NOT_CDS_JAVA_HEAP_RETURN;
149 static oop init_shared_strings_array() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
150 static void write_shared_table() NOT_CDS_JAVA_HEAP_RETURN;
151 static void set_shared_strings_array_index(int root_index) NOT_CDS_JAVA_HEAP_RETURN;
152 static void serialize_shared_table_header(SerializeClosure* soc) NOT_CDS_JAVA_HEAP_RETURN;
153
154 // Jcmd
155 static void dump(outputStream* st, bool verbose=false);
156 // Debugging
157 static size_t verify_and_compare_entries();
158 static void verify();
159 };
160
161 #endif // SHARE_CLASSFILE_STRINGTABLE_HPP