/*

 * 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");

    }

  }

}