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