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.
  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 Symbol::Symbol(const u1* name, int length, int refcount) {
  38   _refcount = refcount;
  39   _length = length;
  40   _identity_hash = (short)os::random();
  41   for (int i = 0; i < _length; i++) {
  42     byte_at_put(i, name[i]);
  43   }
  44 }
  45 
  46 void* Symbol::operator new(size_t sz, int len, TRAPS) throw() {
  47   int alloc_size = size(len)*wordSize;
  48   address res = (address) AllocateHeap(alloc_size, mtSymbol);
  49   return res;
  50 }
  51 
  52 void* Symbol::operator new(size_t sz, int len, Arena* arena, TRAPS) throw() {
  53   int alloc_size = size(len)*wordSize;
  54   address res = (address)arena->Amalloc_4(alloc_size);
  55   return res;
  56 }
  57 
  58 void Symbol::operator delete(void *p) {
  59   assert(((Symbol*)p)->refcount() == 0, "should not call this");
  60   FreeHeap(p);
  61 }
  62 
  63 // ------------------------------------------------------------------
  64 // Symbol::starts_with
  65 //
  66 // Tests if the symbol starts with the specified prefix of the given
  67 // length.
  68 bool Symbol::starts_with(const char* prefix, int len) const {
  69   if (len > utf8_length()) return false;
  70   while (len-- > 0) {
  71     if (prefix[len] != (char) byte_at(len))
  72       return false;
  73   }
  74   assert(len == -1, "we should be at the beginning");
  75   return true;
  76 }
  77 
  78 
  79 // ------------------------------------------------------------------
  80 // Symbol::index_of
  81 //
  82 // Finds if the given string is a substring of this symbol's utf8 bytes.
  83 // Return -1 on failure.  Otherwise return the first index where str occurs.
  84 int Symbol::index_of_at(int i, const char* str, int len) const {
  85   assert(i >= 0 && i <= utf8_length(), "oob");
  86   if (len <= 0)  return 0;
  87   char first_char = str[0];
  88   address bytes = (address) ((Symbol*)this)->base();
  89   address limit = bytes + utf8_length() - len;  // inclusive limit
  90   address scan = bytes + i;
  91   if (scan > limit)
  92     return -1;
  93   for (; scan <= limit; scan++) {
  94     scan = (address) memchr(scan, first_char, (limit + 1 - scan));
  95     if (scan == NULL)
  96       return -1;  // not found
  97     assert(scan >= bytes+i && scan <= limit, "scan oob");
  98     if (memcmp(scan, str, len) == 0)
  99       return (int)(scan - bytes);
 100   }
 101   return -1;
 102 }
 103 
 104 
 105 char* Symbol::as_C_string(char* buf, int size) const {
 106   if (size > 0) {
 107     int len = MIN2(size - 1, utf8_length());
 108     for (int i = 0; i < len; i++) {
 109       buf[i] = byte_at(i);
 110     }
 111     buf[len] = '\0';
 112   }
 113   return buf;
 114 }
 115 
 116 char* Symbol::as_C_string() const {
 117   int len = utf8_length();
 118   char* str = NEW_RESOURCE_ARRAY(char, len + 1);
 119   return as_C_string(str, len + 1);
 120 }
 121 
 122 char* Symbol::as_C_string_flexible_buffer(Thread* t,
 123                                                  char* buf, int size) const {
 124   char* str;
 125   int len = utf8_length();
 126   int buf_len = len + 1;
 127   if (size < buf_len) {
 128     str = NEW_RESOURCE_ARRAY(char, buf_len);
 129   } else {
 130     str = buf;
 131   }
 132   return as_C_string(str, buf_len);
 133 }
 134 
 135 void Symbol::print_utf8_on(outputStream* st) const {
 136   st->print("%s", as_C_string());
 137 }
 138 
 139 void Symbol::print_symbol_on(outputStream* st) const {
 140   char *s;
 141   st = st ? st : tty;
 142   {
 143     // ResourceMark may not affect st->print(). If st is a string
 144     // stream it could resize, using the same resource arena.
 145     ResourceMark rm;
 146     s = as_quoted_ascii();
 147     s = os::strdup(s);
 148   }
 149   if (s == NULL) {
 150     st->print("(null)");
 151   } else {
 152     st->print("%s", s);
 153     os::free(s);
 154   }
 155 }
 156 
 157 char* Symbol::as_quoted_ascii() const {
 158   const char *ptr = (const char *)&_body[0];
 159   int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length());
 160   char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1);
 161   UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1);
 162   return result;
 163 }
 164 
 165 jchar* Symbol::as_unicode(int& length) const {
 166   Symbol* this_ptr = (Symbol*)this;
 167   length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length());
 168   jchar* result = NEW_RESOURCE_ARRAY(jchar, length);
 169   if (length > 0) {
 170     UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length);
 171   }
 172   return result;
 173 }
 174 
 175 const char* Symbol::as_klass_external_name(char* buf, int size) const {
 176   if (size > 0) {
 177     char* str    = as_C_string(buf, size);
 178     int   length = (int)strlen(str);
 179     // Turn all '/'s into '.'s (also for array klasses)
 180     for (int index = 0; index < length; index++) {
 181       if (str[index] == '/') {
 182         str[index] = '.';
 183       }
 184     }
 185     return str;
 186   } else {
 187     return buf;
 188   }
 189 }
 190 
 191 const char* Symbol::as_klass_external_name() const {
 192   char* str    = as_C_string();
 193   int   length = (int)strlen(str);
 194   // Turn all '/'s into '.'s (also for array klasses)
 195   for (int index = 0; index < length; index++) {
 196     if (str[index] == '/') {
 197       str[index] = '.';
 198     }
 199   }
 200   return str;
 201 }
 202 
 203 // Alternate hashing for unbalanced symbol tables.
 204 unsigned int Symbol::new_hash(juint seed) {
 205   ResourceMark rm;
 206   // Use alternate hashing algorithm on this symbol.
 207   return AltHashing::murmur3_32(seed, (const jbyte*)as_C_string(), utf8_length());
 208 }
 209 
 210 void Symbol::increment_refcount() {
 211   // Only increment the refcount if non-negative.  If negative either
 212   // overflow has occurred or it is a permanent symbol in a read only
 213   // shared archive.
 214   if (_refcount >= 0) { // not a permanent symbol
 215     Atomic::inc(&_refcount);
 216     NOT_PRODUCT(Atomic::inc(&_total_count);)
 217   }
 218 }
 219 
 220 void Symbol::decrement_refcount() {
 221   if (_refcount >= 0) { // not a permanent symbol
 222     jshort new_value = Atomic::add(-1, &_refcount);
 223 #ifdef ASSERT
 224     if (new_value == -1) { // we have transitioned from 0 -> -1
 225       print();
 226       assert(false, "reference count underflow for symbol");
 227     }
 228 #endif
 229     (void)new_value;
 230   }
 231 }
 232 
 233 void Symbol::metaspace_pointers_do(MetaspaceClosure* it) {
 234   if (log_is_enabled(Trace, cds)) {
 235     LogStream trace_stream(Log(cds)::trace());
 236     trace_stream.print("Iter(Symbol): %p ", this);
 237     print_value_on(&trace_stream);
 238     trace_stream.cr();
 239   }
 240 }
 241 
 242 void Symbol::print_on(outputStream* st) const {
 243   if (this == NULL) {
 244     st->print_cr("NULL");
 245   } else {
 246     st->print("Symbol: '");
 247     print_symbol_on(st);
 248     st->print("'");
 249     st->print(" count %d", refcount());
 250   }
 251 }
 252 
 253 // The print_value functions are present in all builds, to support the
 254 // disassembler and error reporting.
 255 void Symbol::print_value_on(outputStream* st) const {
 256   if (this == NULL) {
 257     st->print("NULL");
 258   } else {
 259     st->print("'");
 260     for (int i = 0; i < utf8_length(); i++) {
 261       st->print("%c", byte_at(i));
 262     }
 263     st->print("'");
 264   }
 265 }
 266 
 267 // SymbolTable prints this in its statistics
 268 NOT_PRODUCT(int Symbol::_total_count = 0;)