1 /*
2 * Copyright (c) 1997, 2018, 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_COMPACTHASHTABLE_HPP
26 #define SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP
27
28 #include "oops/array.hpp"
29 #include "oops/symbol.hpp"
30 #include "utilities/hashtable.hpp"
31
32
33 template <
34 typename K,
35 typename V,
36 V (*DECODE)(address base_address, u4 offset),
37 bool (*EQUALS)(V value, K key, int len)
38 >
39 class CompactHashtable;
40 class NumberSeq;
41 class SimpleCompactHashtable;
42 class SerializeClosure;
43
44 // Stats for symbol tables in the CDS archive
45 class CompactHashtableStats {
46 public:
47 int hashentry_count;
48 int hashentry_bytes;
49 int bucket_count;
50 int bucket_bytes;
51 };
52
53 #if INCLUDE_CDS
54 /////////////////////////////////////////////////////////////////////////
55 //
56 // The compact hash table writer. Used at dump time for writing out
57 // the compact table to the shared archive.
58 //
59 // At dump time, the CompactHashtableWriter obtains all entries from the
60 // symbol/string table and adds them to a new temporary hash table. The hash
61 // table size (number of buckets) is calculated using
62 // '(num_entries + bucket_size - 1) / bucket_size'. The default bucket
63 // size is 4 and can be changed by -XX:SharedSymbolTableBucketSize option.
64 // 4 is chosen because it produces smaller sized bucket on average for
65 // faster lookup. It also has relatively small number of empty buckets and
66 // good distribution of the entries.
67 //
68 // We use a simple hash function (hash % num_bucket) for the table.
69 // The new table is compacted when written out. Please see comments
70 // above the CompactHashtable class for the table layout detail. The bucket
71 // offsets are written to the archive as part of the compact table. The
72 // bucket offset is encoded in the low 30-bit (0-29) and the bucket type
73 // (regular or compact) are encoded in bit[31, 30]. For buckets with more
74 // than one entry, both hash and entry offset are written to the
75 // table. For buckets with only one entry, only the entry offset is written
76 // to the table and the buckets are tagged as compact in their type bits.
77 // Buckets without entry are skipped from the table. Their offsets are
78 // still written out for faster lookup.
79 //
80 class CompactHashtableWriter: public StackObj {
81 public:
82 class Entry {
83 unsigned int _hash;
84 u4 _value;
85
86 public:
87 Entry() {}
88 Entry(unsigned int hash, u4 val) : _hash(hash), _value(val) {}
89
90 u4 value() {
91 return _value;
92 }
93 unsigned int hash() {
94 return _hash;
95 }
96
97 bool operator==(const CompactHashtableWriter::Entry& other) {
98 return (_value == other._value && _hash == other._hash);
99 }
100 }; // class CompactHashtableWriter::Entry
101
102 private:
103 int _num_entries;
104 int _num_buckets;
105 int _num_empty_buckets;
106 int _num_value_only_buckets;
107 int _num_other_buckets;
108 GrowableArray<Entry>** _buckets;
109 CompactHashtableStats* _stats;
110 Array<u4>* _compact_buckets;
111 Array<u4>* _compact_entries;
112
113 public:
114 // This is called at dump-time only
115 CompactHashtableWriter(int num_buckets, CompactHashtableStats* stats);
116 ~CompactHashtableWriter();
117
118 void add(unsigned int hash, u4 value);
119
120 private:
121 void allocate_table();
122 void dump_table(NumberSeq* summary);
123
124 public:
125 void dump(SimpleCompactHashtable *cht, const char* table_name);
126 };
127 #endif // INCLUDE_CDS
128
129 #define REGULAR_BUCKET_TYPE 0
130 #define VALUE_ONLY_BUCKET_TYPE 1
131 #define TABLEEND_BUCKET_TYPE 3
132 #define BUCKET_OFFSET_MASK 0x3FFFFFFF
133 #define BUCKET_OFFSET(info) ((info) & BUCKET_OFFSET_MASK)
134 #define BUCKET_TYPE_SHIFT 30
135 #define BUCKET_TYPE(info) (((info) & ~BUCKET_OFFSET_MASK) >> BUCKET_TYPE_SHIFT)
136 #define BUCKET_INFO(offset, type) (((type) << BUCKET_TYPE_SHIFT) | ((offset) & BUCKET_OFFSET_MASK))
137
138 /////////////////////////////////////////////////////////////////////////////
139 //
140 // CompactHashtable is used to store the CDS archive's symbol/string tables.
141 //
142 // Because these tables are read-only (no entries can be added/deleted) at run-time
143 // and tend to have large number of entries, we try to minimize the footprint
144 // cost per entry.
145 //
146 // The CompactHashtable is split into two arrays
147 //
148 // u4 buckets[num_buckets+1]; // bit[31,30]: type; bit[29-0]: offset
149 // u4 entries[<variable size>]
150 //
151 // The size of buckets[] is 'num_buckets + 1'. Each entry of
152 // buckets[] is a 32-bit encoding of the bucket type and bucket offset,
153 // with the type in the left-most 2-bit and offset in the remaining 30-bit.
154 // The last entry is a special type. It contains the end of the last
155 // bucket.
156 //
157 // There are two types of buckets, regular buckets and value_only buckets. The
158 // value_only buckets have '01' in their highest 2-bit, and regular buckets have
159 // '00' in their highest 2-bit.
160 //
161 // For normal buckets, each entry is 8 bytes in the entries[]:
162 // u4 hash; /* symbol/string hash */
163 // union {
164 // u4 offset; /* Symbol* sym = (Symbol*)(base_address + offset) */
165 // narrowOop str; /* String narrowOop encoding */
166 // }
167 //
168 //
169 // For value_only buckets, each entry has only the 4-byte 'offset' in the entries[].
170 //
171 // Example -- note that the second bucket is a VALUE_ONLY_BUCKET_TYPE so the hash code
172 // is skipped.
173 // buckets[0, 4, 5, ....]
174 // | | |
175 // | | +---+
176 // | | |
177 // | +----+ |
178 // v v v
179 // entries[H,O,H,O,O,H,O,H,O.....]
180 //
181 // See CompactHashtable::lookup() for how the table is searched at runtime.
182 // See CompactHashtableWriter::dump() for how the table is written at CDS
183 // dump time.
184 //
185 class SimpleCompactHashtable {
186 protected:
187 address _base_address;
188 u4 _bucket_count;
189 u4 _entry_count;
190 u4* _buckets;
191 u4* _entries;
192
193 public:
194 SimpleCompactHashtable() {
195 _entry_count = 0;
196 _bucket_count = 0;
197 _buckets = 0;
198 _entries = 0;
199 }
200
201 void reset() {
202 _bucket_count = 0;
203 _entry_count = 0;
204 _buckets = 0;
205 _entries = 0;
206 }
207
208 void init(address base_address, u4 entry_count, u4 bucket_count, u4* buckets, u4* entries) {
209 _base_address = base_address;
210 _bucket_count = bucket_count;
211 _entry_count = entry_count;
212 _buckets = buckets;
213 _entries = entries;
214 }
215
216 // For reading from/writing to the CDS archive
217 void serialize(SerializeClosure* soc) NOT_CDS_RETURN;
218
219 inline bool empty() {
220 return (_entry_count == 0);
221 }
222 };
223
224 template <
225 typename K,
226 typename V,
227 V (*DECODE)(address base_address, u4 offset),
228 bool (*EQUALS)(V value, K key, int len)
229 >
230 class CompactHashtable : public SimpleCompactHashtable {
231 friend class VMStructs;
232
233 V decode(u4 offset) const {
234 return DECODE(_base_address, offset);
235 }
236
237 public:
238 CompactHashtable() : SimpleCompactHashtable() {}
239
240 // Lookup a value V from the compact table using key K
241 inline V lookup(K key, unsigned int hash, int len) const {
242 if (_entry_count > 0) {
243 int index = hash % _bucket_count;
244 u4 bucket_info = _buckets[index];
245 u4 bucket_offset = BUCKET_OFFSET(bucket_info);
246 int bucket_type = BUCKET_TYPE(bucket_info);
247 u4* entry = _entries + bucket_offset;
248
249 if (bucket_type == VALUE_ONLY_BUCKET_TYPE) {
250 V value = decode(entry[0]);
251 if (EQUALS(value, key, len)) {
252 return value;
253 }
254 } else {
255 // This is a regular bucket, which has more than one
256 // entries. Each entry is a pair of entry (hash, offset).
257 // Seek until the end of the bucket.
258 u4* entry_max = _entries + BUCKET_OFFSET(_buckets[index + 1]);
259 while (entry < entry_max) {
260 unsigned int h = (unsigned int)(entry[0]);
261 if (h == hash) {
262 V value = decode(entry[1]);
263 if (EQUALS(value, key, len)) {
264 return value;
265 }
266 }
267 entry += 2;
268 }
269 }
270 }
271 return NULL;
272 }
273
274 template <class ITER>
275 inline void iterate(ITER* iter) const {
276 for (u4 i = 0; i < _bucket_count; i++) {
277 u4 bucket_info = _buckets[i];
278 u4 bucket_offset = BUCKET_OFFSET(bucket_info);
279 int bucket_type = BUCKET_TYPE(bucket_info);
280 u4* entry = _entries + bucket_offset;
281
282 if (bucket_type == VALUE_ONLY_BUCKET_TYPE) {
283 iter->do_value(decode(entry[0]));
284 } else {
285 u4*entry_max = _entries + BUCKET_OFFSET(_buckets[i + 1]);
286 while (entry < entry_max) {
287 iter->do_value(decode(entry[1]));
288 entry += 2;
289 }
290 }
291 }
292 }
293 };
294
295 ////////////////////////////////////////////////////////////////////////
296 //
297 // Read/Write the contents of a hashtable textual dump (created by
298 // SymbolTable::dump and StringTable::dump).
299 // Because the dump file may be big (hundred of MB in extreme cases),
300 // we use mmap for fast access when reading it.
301 //
302 class HashtableTextDump {
303 int _fd;
304 const char* _base;
305 const char* _p;
306 const char* _end;
307 const char* _filename;
308 size_t _size;
309 int _prefix_type;
310 int _line_no;
311 public:
312 HashtableTextDump(const char* filename);
313 ~HashtableTextDump();
314
315 enum {
316 SymbolPrefix = 1 << 0,
317 StringPrefix = 1 << 1,
318 Unknown = 1 << 2
319 };
320
321 void quit(const char* err, const char* msg);
322
323 inline int remain() {
324 return (int)(_end - _p);
325 }
326
327 void corrupted(const char *p, const char *msg);
328
329 inline void corrupted_if(bool cond, const char *msg) {
330 if (cond) {
331 corrupted(_p, msg);
332 }
333 }
334
335 bool skip_newline();
336 int skip(char must_be_char);
337 void skip_past(char c);
338 void check_version(const char* ver);
339
340 inline void get_num(char delim, int *num) {
341 const char* p = _p;
342 const char* end = _end;
343 u8 n = 0;
344
345 while (p < end) {
346 char c = *p++;
347 if ('0' <= c && c <= '9') {
348 n = n * 10 + (c - '0');
349 if (n > (u8)INT_MAX) {
350 corrupted(_p, "Num overflow");
351 }
352 } else if (c == delim) {
353 _p = p;
354 *num = (int)n;
355 return;
356 } else {
357 // Not [0-9], not 'delim'
358 corrupted(_p, "Unrecognized format");;
359 }
360 }
361
362 corrupted(_end, "Incorrect format");
363 ShouldNotReachHere();
364 }
365
366 void scan_prefix_type();
367 int scan_prefix(int* utf8_length);
368 int scan_string_prefix();
369 int scan_symbol_prefix();
370
371 jchar unescape(const char* from, const char* end, int count);
372 void get_utf8(char* utf8_buffer, int utf8_length);
373 static void put_utf8(outputStream* st, const char* utf8_string, int utf8_length);
374 };
375
376 #endif // SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP