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 /*

  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/javaClasses.hpp"

 #include "classfile/symbolTable.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "gc_interface/collectedHeap.inline.hpp"

 #include "memory/filemap.hpp"

 #include "memory/gcLocker.inline.hpp"

 #include "oops/oop.inline.hpp"

 #include "oops/oop.inline2.hpp"

 #include "oops/symbolKlass.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "utilities/hashtable.inline.hpp"

 // --------------------------------------------------------------------------

 SymbolTable* SymbolTable::_the_table = NULL;

 // Lookup a symbol in a bucket.

 symbolOop SymbolTable::lookup(int index, const char* name,

                               int len, unsigned int hash) {

   for (HashtableEntry* e = bucket(index); e != NULL; e = e->next()) {

     if (e->hash() == hash) {

       symbolOop sym = symbolOop(e->literal());

       if (sym->equals(name, len)) {

         return sym;

       }

     }

   }

   return NULL;

 }

 // We take care not to be blocking while holding the

 // SymbolTable_lock. Otherwise, the system might deadlock, since the

 // symboltable is used during compilation (VM_thread) The lock free

 // synchronization is simplified by the fact that we do not delete

 // entries in the symbol table during normal execution (only during

 // safepoints).

 symbolOop SymbolTable::lookup(const char* name, int len, TRAPS) {

   unsigned int hashValue = hash_symbol(name, len);

   int index = the_table()->hash_to_index(hashValue);

   symbolOop s = the_table()->lookup(index, name, len, hashValue);

   // Found

   if (s != NULL) return s;

   // Otherwise, add to symbol to table

   return the_table()->basic_add(index, (u1*)name, len, hashValue, CHECK_NULL);

 }

 symbolOop SymbolTable::lookup(symbolHandle sym, int begin, int end, TRAPS) {

   char* buffer;

   int index, len;

   unsigned int hashValue;

   char* name;

   {

     debug_only(No_Safepoint_Verifier nsv;)

     name = (char*)sym->base() + begin;

     len = end - begin;

     hashValue = hash_symbol(name, len);

     index = the_table()->hash_to_index(hashValue);

     symbolOop s = the_table()->lookup(index, name, len, hashValue);

     // Found

     if (s != NULL) return s;

   }

   // Otherwise, add to symbol to table. Copy to a C string first.

   char stack_buf[128];

   ResourceMark rm(THREAD);

   if (len <= 128) {

     buffer = stack_buf;

   } else {

     buffer = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, len);

   }

   for (int i=0; i<len; i++) {

     buffer[i] = name[i];

   }

   // Make sure there is no safepoint in the code above since name can't move.

   // We can't include the code in No_Safepoint_Verifier because of the

   // ResourceMark.

   return the_table()->basic_add(index, (u1*)buffer, len, hashValue, CHECK_NULL);

 }

 symbolOop SymbolTable::lookup_only(const char* name, int len,

                                    unsigned int& hash) {

   hash = hash_symbol(name, len);

   int index = the_table()->hash_to_index(hash);

   return the_table()->lookup(index, name, len, hash);

 }

 // Suggestion: Push unicode-based lookup all the way into the hashing

 // and probing logic, so there is no need for convert_to_utf8 until

 // an actual new symbolOop is created.

 symbolOop SymbolTable::lookup_unicode(const jchar* name, int utf16_length, TRAPS) {

   int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);

   char stack_buf[128];

   if (utf8_length < (int) sizeof(stack_buf)) {

     char* chars = stack_buf;

     UNICODE::convert_to_utf8(name, utf16_length, chars);

     return lookup(chars, utf8_length, THREAD);

   } else {

     ResourceMark rm(THREAD);

     char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);;

     UNICODE::convert_to_utf8(name, utf16_length, chars);

     return lookup(chars, utf8_length, THREAD);

   }

 }

 symbolOop SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,

                                            unsigned int& hash) {

   int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);

   char stack_buf[128];

   if (utf8_length < (int) sizeof(stack_buf)) {

     char* chars = stack_buf;

     UNICODE::convert_to_utf8(name, utf16_length, chars);

     return lookup_only(chars, utf8_length, hash);

   } else {

     ResourceMark rm;

     char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);;

     UNICODE::convert_to_utf8(name, utf16_length, chars);

     return lookup_only(chars, utf8_length, hash);

   }

 }

 void SymbolTable::add(constantPoolHandle cp, int names_count,

                       const char** names, int* lengths, int* cp_indices,

                       unsigned int* hashValues, TRAPS) {

   SymbolTable* table = the_table();

   bool added = table->basic_add(cp, names_count, names, lengths,

                                 cp_indices, hashValues, CHECK);

   if (!added) {

     // do it the hard way

     for (int i=0; i<names_count; i++) {

       int index = table->hash_to_index(hashValues[i]);

       symbolOop sym = table->basic_add(index, (u1*)names[i], lengths[i],

                                        hashValues[i], CHECK);

       cp->symbol_at_put(cp_indices[i], sym);

     }

   }

 }

 symbolOop SymbolTable::basic_add(int index, u1 *name, int len,

                                  unsigned int hashValue, TRAPS) {

   assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),

          "proposed name of symbol must be stable");

   // We assume that lookup() has been called already, that it failed,

   // and symbol was not found.  We create the symbol here.

   symbolKlass* sk  = (symbolKlass*) Universe::symbolKlassObj()->klass_part();

   symbolOop s_oop = sk->allocate_symbol(name, len, CHECK_NULL);

   symbolHandle sym (THREAD, s_oop);

   // Allocation must be done before grapping the SymbolTable_lock lock

   MutexLocker ml(SymbolTable_lock, THREAD);

   assert(sym->equals((char*)name, len), "symbol must be properly initialized");

   // Since look-up was done lock-free, we need to check if another

   // thread beat us in the race to insert the symbol.

   symbolOop test = lookup(index, (char*)name, len, hashValue);

   if (test != NULL) {

     // A race occurred and another thread introduced the symbol, this one

     // will be dropped and collected.

     return test;

   }

   HashtableEntry* entry = new_entry(hashValue, sym());

   add_entry(index, entry);

   return sym();

 }

 bool SymbolTable::basic_add(constantPoolHandle cp, int names_count,

                             const char** names, int* lengths,

                             int* cp_indices, unsigned int* hashValues,

                             TRAPS) {

   symbolKlass* sk  = (symbolKlass*) Universe::symbolKlassObj()->klass_part();

   symbolOop sym_oops[symbol_alloc_batch_size];

   bool allocated = sk->allocate_symbols(names_count, names, lengths,

                                         sym_oops, CHECK_false);

   if (!allocated) {

     return false;

   }

   symbolHandle syms[symbol_alloc_batch_size];

   int i;

   for (i=0; i<names_count; i++) {

     syms[i] = symbolHandle(THREAD, sym_oops[i]);

   }

   // Allocation must be done before grabbing the SymbolTable_lock lock

   MutexLocker ml(SymbolTable_lock, THREAD);

   for (i=0; i<names_count; i++) {

     assert(syms[i]->equals(names[i], lengths[i]), "symbol must be properly initialized");

     // Since look-up was done lock-free, we need to check if another

     // thread beat us in the race to insert the symbol.

     int index = hash_to_index(hashValues[i]);

     symbolOop test = lookup(index, names[i], lengths[i], hashValues[i]);

     if (test != NULL) {

       // A race occurred and another thread introduced the symbol, this one

       // will be dropped and collected. Use test instead.

       cp->symbol_at_put(cp_indices[i], test);

     } else {

       symbolOop sym = syms[i]();

       HashtableEntry* entry = new_entry(hashValues[i], sym);

       add_entry(index, entry);

       cp->symbol_at_put(cp_indices[i], sym);

     }

   }

   return true;

 }

 void SymbolTable::verify() {

   for (int i = 0; i < the_table()->table_size(); ++i) {

     HashtableEntry* p = the_table()->bucket(i);

     for ( ; p != NULL; p = p->next()) {

       symbolOop s = symbolOop(p->literal());

       guarantee(s != NULL, "symbol is NULL");

       s->verify();

       guarantee(s->is_perm(), "symbol not in permspace");

       unsigned int h = hash_symbol((char*)s->bytes(), s->utf8_length());

       guarantee(p->hash() == h, "broken hash in symbol table entry");

       guarantee(the_table()->hash_to_index(h) == i,

                 "wrong index in symbol table");

     }

   }

 }

 //---------------------------------------------------------------------------

 // Non-product code

 #ifndef PRODUCT

 void SymbolTable::print_histogram() {

   MutexLocker ml(SymbolTable_lock);

   const int results_length = 100;

   int results[results_length];

   int i,j;

   // initialize results to zero

   for (j = 0; j < results_length; j++) {

     results[j] = 0;

   }

   int total = 0;

   int max_symbols = 0;

   int out_of_range = 0;

   for (i = 0; i < the_table()->table_size(); i++) {

     HashtableEntry* p = the_table()->bucket(i);

     for ( ; p != NULL; p = p->next()) {

       int counter = symbolOop(p->literal())->utf8_length();

       total += counter;

       if (counter < results_length) {

         results[counter]++;

       } else {

         out_of_range++;

       }

       max_symbols = MAX2(max_symbols, counter);

     }

   }

   tty->print_cr("Symbol Table:");

   tty->print_cr("%8s %5d", "Total  ", total);

   tty->print_cr("%8s %5d", "Maximum", max_symbols);

   tty->print_cr("%8s %3.2f", "Average",

           ((float) total / (float) the_table()->table_size()));

   tty->print_cr("%s", "Histogram:");

   tty->print_cr(" %s %29s", "Length", "Number chains that length");

   for (i = 0; i < results_length; i++) {

     if (results[i] > 0) {

       tty->print_cr("%6d %10d", i, results[i]);

     }

   }

   int line_length = 70;

   tty->print_cr("%s %30s", " Length", "Number chains that length");

   for (i = 0; i < results_length; i++) {

     if (results[i] > 0) {

       tty->print("%4d", i);

       for (j = 0; (j < results[i]) && (j < line_length);  j++) {

         tty->print("%1s", "*");

       }

       if (j == line_length) {

         tty->print("%1s", "+");

       }

       tty->cr();

     }

   }

   tty->print_cr(" %s %d: %d\n", "Number chains longer than",

                     results_length, out_of_range);

 }

 #endif // PRODUCT

 // --------------------------------------------------------------------------

 #ifdef ASSERT

 class StableMemoryChecker : public StackObj {

   enum { _bufsize = wordSize*4 };

   address _region;

   jint    _size;

   u1      _save_buf[_bufsize];

   int sample(u1* save_buf) {

     if (_size <= _bufsize) {

       memcpy(save_buf, _region, _size);

       return _size;

     } else {

       // copy head and tail

       memcpy(&save_buf[0],          _region,                      _bufsize/2);

       memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);

       return (_bufsize/2)*2;

     }

   }

  public:

   StableMemoryChecker(const void* region, jint size) {

     _region = (address) region;

     _size   = size;

     sample(_save_buf);

   }

   bool verify() {

     u1 check_buf[sizeof(_save_buf)];

     int check_size = sample(check_buf);

     return (0 == memcmp(_save_buf, check_buf, check_size));

   }

   void set_region(const void* region) { _region = (address) region; }

 };

 #endif

 // --------------------------------------------------------------------------

 // Compute the hash value for a java.lang.String object which would

 // contain the characters passed in. This hash value is used for at

 // least two purposes.

 //

 // (a) As the hash value used by the StringTable for bucket selection

 //     and comparison (stored in the HashtableEntry structures).  This

 //     is used in the String.intern() method.

 //

 // (b) As the hash value used by the String object itself, in

 //     String.hashCode().  This value is normally calculate in Java code

 //     in the String.hashCode method(), but is precomputed for String

 //     objects in the shared archive file.

 //

 //     For this reason, THIS ALGORITHM MUST MATCH String.hashCode().

 int StringTable::hash_string(jchar* s, int len) {

   unsigned h = 0;

   while (len-- > 0) {

     h = 31*h + (unsigned) *s;

     s++;

   }

   return h;

 }

 StringTable* StringTable::_the_table = NULL;

 oop StringTable::lookup(int index, jchar* name,

                         int len, unsigned int hash) {

   for (HashtableEntry* l = bucket(index); l != NULL; l = l->next()) {

     if (l->hash() == hash) {

       if (java_lang_String::equals(l->literal(), name, len)) {

         return l->literal();

       }

     }

   }

   return NULL;

 }

 oop StringTable::basic_add(int index, Handle string_or_null, jchar* name,

                            int len, unsigned int hashValue, TRAPS) {

   debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));

   assert(!Universe::heap()->is_in_reserved(name) || GC_locker::is_active(),

          "proposed name of symbol must be stable");

   Handle string;

   // try to reuse the string if possible

   if (!string_or_null.is_null() && string_or_null()->is_perm()) {

     string = string_or_null;

   } else {

     string = java_lang_String::create_tenured_from_unicode(name, len, CHECK_NULL);

   }

   // Allocation must be done before grapping the SymbolTable_lock lock

   MutexLocker ml(StringTable_lock, THREAD);

   assert(java_lang_String::equals(string(), name, len),

          "string must be properly initialized");

   // Since look-up was done lock-free, we need to check if another

   // thread beat us in the race to insert the symbol.

   oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)

   if (test != NULL) {

     // Entry already added

     return test;

   }

   HashtableEntry* entry = new_entry(hashValue, string());

   add_entry(index, entry);

   return string();

 }

 oop StringTable::lookup(symbolOop symbol) {

   ResourceMark rm;

   int length;

   jchar* chars = symbol->as_unicode(length);

   unsigned int hashValue = hash_string(chars, length);

   int index = the_table()->hash_to_index(hashValue);

   return the_table()->lookup(index, chars, length, hashValue);

 }

 oop StringTable::intern(Handle string_or_null, jchar* name,

                         int len, TRAPS) {

   unsigned int hashValue = hash_string(name, len);

   int index = the_table()->hash_to_index(hashValue);

   oop string = the_table()->lookup(index, name, len, hashValue);

   // Found

   if (string != NULL) return string;

   // Otherwise, add to symbol to table

   return the_table()->basic_add(index, string_or_null, name, len,

                                 hashValue, CHECK_NULL);

 }

 oop StringTable::intern(symbolOop symbol, TRAPS) {

   if (symbol == NULL) return NULL;

   ResourceMark rm(THREAD);

   int length;

   jchar* chars = symbol->as_unicode(length);

   Handle string;

   oop result = intern(string, chars, length, CHECK_NULL);

   return result;

 }

 oop StringTable::intern(oop string, TRAPS)

 {

   if (string == NULL) return NULL;

   ResourceMark rm(THREAD);

   int length;

   Handle h_string (THREAD, string);

   jchar* chars = java_lang_String::as_unicode_string(string, length);

   oop result = intern(h_string, chars, length, CHECK_NULL);

   return result;

 }

 oop StringTable::intern(const char* utf8_string, TRAPS) {

   if (utf8_string == NULL) return NULL;

   ResourceMark rm(THREAD);

   int length = UTF8::unicode_length(utf8_string);

   jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);

   UTF8::convert_to_unicode(utf8_string, chars, length);

   Handle string;

   oop result = intern(string, chars, length, CHECK_NULL);

   return result;

 }

 void StringTable::verify() {

   for (int i = 0; i < the_table()->table_size(); ++i) {

     HashtableEntry* p = the_table()->bucket(i);

     for ( ; p != NULL; p = p->next()) {

       oop s = p->literal();

       guarantee(s != NULL, "interned string is NULL");

       guarantee(s->is_perm(), "interned string not in permspace");

       int length;

       jchar* chars = java_lang_String::as_unicode_string(s, length);

       unsigned int h = hash_string(chars, length);

       guarantee(p->hash() == h, "broken hash in string table entry");

       guarantee(the_table()->hash_to_index(h) == i,

                 "wrong index in string table");

     }

   }

 }