hotspot/src/share/vm/classfile/symbolTable.cpp - platform/libcore - Git at Google

 /*
  * Copyright 1997-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  *
  */

 # include "incls/_precompiled.incl"
 # include "incls/_symbolTable.cpp.incl"

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

 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);
 }

 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);
     }
   }
 }

 // Needed for preloading classes in signatures when compiling.

 symbolOop SymbolTable::probe(const char* name, int len) {
   unsigned int hashValue = hash_symbol(name, len);
   int index = the_table()->hash_to_index(hashValue);
   return the_table()->lookup(index, name, len, hashValue);
 }


 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 occured 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 occured 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");
     }
   }
 }
	/*
	* Copyright 1997-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
	* CA 95054 USA or visit www.sun.com if you need additional information or
	* have any questions.
	*
	*/

	# include "incls/_precompiled.incl"
	# include "incls/_symbolTable.cpp.incl"

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

	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);
	}

	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);
	}
	}
	}

	// Needed for preloading classes in signatures when compiling.

	symbolOop SymbolTable::probe(const char* name, int len) {
	unsigned int hashValue = hash_symbol(name, len);
	int index = the_table()->hash_to_index(hashValue);
	return the_table()->lookup(index, name, len, hashValue);
	}


	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 occured 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 occured 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 = 31h + (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");
	}
	}
	}