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
26 #include "precompiled.hpp"
27 #include "classfile/altHashing.hpp"
28 #include "classfile/classLoaderData.hpp"
29 #include "gc/shared/collectedHeap.hpp"
30 #include "logging/log.hpp"
31 #include "logging/logStream.hpp"
32 #include "memory/allocation.inline.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "oops/symbol.hpp"
35 #include "runtime/atomic.hpp"
36 #include "runtime/os.hpp"
37
38 uint32_t Symbol::pack_length_and_refcount(int length, int refcount) {
39 STATIC_ASSERT(max_symbol_length == ((1 << 16) - 1));
40 STATIC_ASSERT(PERM_REFCOUNT == ((1 << 16) - 1));
41 assert(length >= 0, "negative length");
42 assert(length <= max_symbol_length, "too long symbol");
43 assert(refcount >= 0, "negative refcount");
44 assert(refcount <= PERM_REFCOUNT, "invalid refcount");
45 uint32_t hi = length;
46 uint32_t lo = refcount;
47 return (hi << 16) | lo;
48 }
49
50 Symbol::Symbol(const u1* name, int length, int refcount) {
51 _length_and_refcount = pack_length_and_refcount(length, refcount);
52 _identity_hash = (short)os::random();
53 for (int i = 0; i < length; i++) {
54 byte_at_put(i, name[i]);
55 }
56 }
57
58 void* Symbol::operator new(size_t sz, int len, TRAPS) throw() {
59 int alloc_size = size(len)*wordSize;
60 address res = (address) AllocateHeap(alloc_size, mtSymbol);
61 return res;
62 }
63
64 void* Symbol::operator new(size_t sz, int len, Arena* arena, TRAPS) throw() {
65 int alloc_size = size(len)*wordSize;
66 address res = (address)arena->Amalloc_4(alloc_size);
67 return res;
68 }
69
70 void Symbol::operator delete(void *p) {
71 assert(((Symbol*)p)->refcount() == 0, "should not call this");
72 FreeHeap(p);
73 }
74
75 // ------------------------------------------------------------------
76 // Symbol::starts_with
77 //
78 // Tests if the symbol starts with the specified prefix of the given
79 // length.
80 bool Symbol::starts_with(const char* prefix, int len) const {
81 if (len > utf8_length()) return false;
82 while (len-- > 0) {
83 if (prefix[len] != char_at(len))
84 return false;
85 }
86 assert(len == -1, "we should be at the beginning");
87 return true;
88 }
89
90
91 // ------------------------------------------------------------------
92 // Symbol::index_of
93 //
94 // Finds if the given string is a substring of this symbol's utf8 bytes.
95 // Return -1 on failure. Otherwise return the first index where str occurs.
96 int Symbol::index_of_at(int i, const char* str, int len) const {
97 assert(i >= 0 && i <= utf8_length(), "oob");
98 if (len <= 0) return 0;
99 char first_char = str[0];
100 address bytes = (address) ((Symbol*)this)->base();
101 address limit = bytes + utf8_length() - len; // inclusive limit
102 address scan = bytes + i;
103 if (scan > limit)
104 return -1;
105 for (; scan <= limit; scan++) {
106 scan = (address) memchr(scan, first_char, (limit + 1 - scan));
107 if (scan == NULL)
108 return -1; // not found
109 assert(scan >= bytes+i && scan <= limit, "scan oob");
110 if (memcmp(scan, str, len) == 0)
111 return (int)(scan - bytes);
112 }
113 return -1;
114 }
115
116
117 char* Symbol::as_C_string(char* buf, int size) const {
118 if (size > 0) {
119 int len = MIN2(size - 1, utf8_length());
120 for (int i = 0; i < len; i++) {
121 buf[i] = char_at(i);
122 }
123 buf[len] = '\0';
124 }
125 return buf;
126 }
127
128 char* Symbol::as_C_string() const {
129 int len = utf8_length();
130 char* str = NEW_RESOURCE_ARRAY(char, len + 1);
131 return as_C_string(str, len + 1);
132 }
133
134 char* Symbol::as_C_string_flexible_buffer(Thread* t,
135 char* buf, int size) const {
136 char* str;
137 int len = utf8_length();
138 int buf_len = len + 1;
139 if (size < buf_len) {
140 str = NEW_RESOURCE_ARRAY(char, buf_len);
141 } else {
142 str = buf;
143 }
144 return as_C_string(str, buf_len);
145 }
146
147 void Symbol::print_utf8_on(outputStream* st) const {
148 st->print("%s", as_C_string());
149 }
150
151 void Symbol::print_symbol_on(outputStream* st) const {
152 char *s;
153 st = st ? st : tty;
154 {
155 // ResourceMark may not affect st->print(). If st is a string
156 // stream it could resize, using the same resource arena.
157 ResourceMark rm;
158 s = as_quoted_ascii();
159 s = os::strdup(s);
160 }
161 if (s == NULL) {
162 st->print("(null)");
163 } else {
164 st->print("%s", s);
165 os::free(s);
166 }
167 }
168
169 char* Symbol::as_quoted_ascii() const {
170 const char *ptr = (const char *)&_body[0];
171 int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length());
172 char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1);
173 UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1);
174 return result;
175 }
176
177 jchar* Symbol::as_unicode(int& length) const {
178 Symbol* this_ptr = (Symbol*)this;
179 length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length());
180 jchar* result = NEW_RESOURCE_ARRAY(jchar, length);
181 if (length > 0) {
182 UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length);
183 }
184 return result;
185 }
186
187 const char* Symbol::as_klass_external_name(char* buf, int size) const {
188 if (size > 0) {
189 char* str = as_C_string(buf, size);
190 int length = (int)strlen(str);
191 // Turn all '/'s into '.'s (also for array klasses)
192 for (int index = 0; index < length; index++) {
193 if (str[index] == '/') {
194 str[index] = '.';
195 }
196 }
197 return str;
198 } else {
199 return buf;
200 }
201 }
202
203 const char* Symbol::as_klass_external_name() const {
204 char* str = as_C_string();
205 int length = (int)strlen(str);
206 // Turn all '/'s into '.'s (also for array klasses)
207 for (int index = 0; index < length; index++) {
208 if (str[index] == '/') {
209 str[index] = '.';
210 }
211 }
212 return str;
213 }
214
215 // Alternate hashing for unbalanced symbol tables.
216 unsigned int Symbol::new_hash(juint seed) {
217 ResourceMark rm;
218 // Use alternate hashing algorithm on this symbol.
219 return AltHashing::murmur3_32(seed, (const jbyte*)as_C_string(), utf8_length());
220 }
221
222 // Increment refcount while checking for zero. If the Symbol's refcount becomes zero
223 // a thread could be concurrently removing the Symbol. This is used during SymbolTable
224 // lookup to avoid reviving a dead Symbol.
225 bool Symbol::try_increment_refcount() {
226 uint32_t found = _length_and_refcount;
227 while (true) {
228 uint32_t old_value = found;
229 int refc = extract_refcount(old_value);
230 if (refc == PERM_REFCOUNT) {
231 return true; // sticky max or created permanent
232 } else if (refc == 0) {
233 return false; // dead, can't revive.
234 } else {
235 found = Atomic::cmpxchg(old_value + 1, &_length_and_refcount, old_value);
236 if (found == old_value) {
237 return true; // successfully updated.
238 }
239 // refcount changed, try again.
240 }
241 }
242 }
243
244 // The increment_refcount() is called when not doing lookup. It is assumed that you
245 // have a symbol with a non-zero refcount and it can't become zero while referenced by
246 // this caller.
247 void Symbol::increment_refcount() {
248 if (!try_increment_refcount()) {
249 #ifdef ASSERT
250 print();
251 fatal("refcount has gone to zero");
252 #endif
253 }
254 #ifndef PRODUCT
255 if (refcount() != PERM_REFCOUNT) { // not a permanent symbol
256 NOT_PRODUCT(Atomic::inc(&_total_count);)
257 }
258 #endif
259 }
260
261 // Decrement refcount potentially while racing increment, so we need
262 // to check the value after attempting to decrement so that if another
263 // thread increments to PERM_REFCOUNT the value is not decremented.
264 void Symbol::decrement_refcount() {
265 uint32_t found = _length_and_refcount;
266 while (true) {
267 uint32_t old_value = found;
268 int refc = extract_refcount(old_value);
269 if (refc == PERM_REFCOUNT) {
270 return; // refcount is permanent, permanent is sticky
271 } else if (refc == 0) {
272 #ifdef ASSERT
273 print();
274 fatal("refcount underflow");
275 #endif
276 return;
277 } else {
278 found = Atomic::cmpxchg(old_value - 1, &_length_and_refcount, old_value);
279 if (found == old_value) {
280 return; // successfully updated.
281 }
282 // refcount changed, try again.
283 }
284 }
285 }
286
287 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) {
288 if (log_is_enabled(Trace, cds)) {
289 LogStream trace_stream(Log(cds)::trace());
290 trace_stream.print("Iter(Symbol): %p ", this);
291 print_value_on(&trace_stream);
292 trace_stream.cr();
293 }
294 }
295
296 void Symbol::print_on(outputStream* st) const {
297 if (this == NULL) {
298 st->print_cr("NULL");
299 } else {
300 st->print("Symbol: '");
301 print_symbol_on(st);
302 st->print("'");
303 st->print(" count %d", refcount());
304 }
305 }
306
307 // The print_value functions are present in all builds, to support the
308 // disassembler and error reporting.
309 void Symbol::print_value_on(outputStream* st) const {
310 if (this == NULL) {
311 st->print("NULL");
312 } else {
313 st->print("'");
314 for (int i = 0; i < utf8_length(); i++) {
315 st->print("%c", char_at(i));
316 }
317 st->print("'");
318 }
319 }
320
321 bool Symbol::is_valid(Symbol* s) {
322 if (!is_aligned(s, sizeof(MetaWord))) return false;
323 if ((size_t)s < os::min_page_size()) return false;
324
325 if (!os::is_readable_range(s, s + 1)) return false;
326
327 // Symbols are not allocated in Java heap.
328 if (Universe::heap()->is_in_reserved(s)) return false;
329
330 int len = s->utf8_length();
331 if (len < 0) return false;
332
333 jbyte* bytes = (jbyte*) s->bytes();
334 return os::is_readable_range(bytes, bytes + len);
335 }
336
337 // SymbolTable prints this in its statistics
338 NOT_PRODUCT(size_t Symbol::_total_count = 0;)