/*

 * Copyright (c) 2003, 2012, 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/altHashing.hpp"

#include "classfile/javaClasses.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/filemap.hpp"

#include "memory/resourceArea.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/safepoint.hpp"

#include "utilities/dtrace.hpp"

#include "utilities/hashtable.hpp"

#include "utilities/hashtable.inline.hpp"

#include "utilities/numberSeq.hpp"

// This is a generic hashtable, designed to be used for the symbol

// and string tables.

//

// It is implemented as an open hash table with a fixed number of buckets.

//

// %note:

//  - HashtableEntrys are allocated in blocks to reduce the space overhead.

template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {

  BasicHashtableEntry<F>* entry;

  if (_free_list) {

    entry = _free_list;

    _free_list = _free_list->next();

  } else {

    if (_first_free_entry + _entry_size >= _end_block) {

      int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));

      int len = _entry_size * block_size;

      len = 1 << log2_intptr(len); // round down to power of 2

      assert(len >= _entry_size, "");

      _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);

      _end_block = _first_free_entry + len;

    }

    entry = (BasicHashtableEntry<F>*)_first_free_entry;

    _first_free_entry += _entry_size;

  }

  assert(_entry_size % HeapWordSize == 0, "");

  entry->set_hash(hashValue);

  return entry;

}

template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {

  HashtableEntry<T, F>* entry;

  entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);

  entry->set_literal(obj);

  return entry;

}

// Check to see if the hashtable is unbalanced.  The caller set a flag to

// rehash at the next safepoint.  If this bucket is 60 times greater than the

// expected average bucket length, it's an unbalanced hashtable.

// This is somewhat an arbitrary heuristic but if one bucket gets to

// rehash_count which is currently 100, there's probably something wrong.

template <MEMFLAGS F> bool BasicHashtable<F>::check_rehash_table(int count) {

  assert(table_size() != 0, "underflow");

  if (count > (((double)number_of_entries()/(double)table_size())*rehash_multiple)) {

    // Set a flag for the next safepoint, which should be at some guaranteed

    // safepoint interval.

    return true;

  }

  return false;

}

template <class T, MEMFLAGS F> jint Hashtable<T, F>::_seed = 0;

// Create a new table and using alternate hash code, populate the new table

// with the existing elements.   This can be used to change the hash code

// and could in the future change the size of the table.

template <class T, MEMFLAGS F> void Hashtable<T, F>::move_to(Hashtable<T, F>* new_table) {

  // Initialize the global seed for hashing.

  _seed = AltHashing::compute_seed();

  assert(seed() != 0, "shouldn't be zero");

  int saved_entry_count = this->number_of_entries();

  // Iterate through the table and create a new entry for the new table

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

    for (HashtableEntry<T, F>* p = bucket(i); p != NULL; ) {

      HashtableEntry<T, F>* next = p->next();

      T string = p->literal();

      // Use alternate hashing algorithm on the symbol in the first table

      unsigned int hashValue = string->new_hash(seed());

      // Get a new index relative to the new table (can also change size)

      int index = new_table->hash_to_index(hashValue);

      p->set_hash(hashValue);

      // Keep the shared bit in the Hashtable entry to indicate that this entry

      // can't be deleted.   The shared bit is the LSB in the _next field so

      // walking the hashtable past these entries requires

      // BasicHashtableEntry::make_ptr() call.

      bool keep_shared = p->is_shared();

      this->unlink_entry(p);

      new_table->add_entry(index, p);

      if (keep_shared) {

        p->set_shared();

      }

      p = next;

    }

  }

  // give the new table the free list as well

  new_table->copy_freelist(this);

  assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");

  // Destroy memory used by the buckets in the hashtable.  The memory

  // for the elements has been used in a new table and is not

  // destroyed.  The memory reuse will benefit resizing the SystemDictionary

  // to avoid a memory allocation spike at safepoint.

  BasicHashtable<F>::free_buckets();

}

template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {

  if (NULL != _buckets) {

    // Don't delete the buckets in the shared space.  They aren't

    // allocated by os::malloc

    if (!UseSharedSpaces ||

        !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {

       FREE_C_HEAP_ARRAY(HashtableBucket, _buckets, F);

    }

    _buckets = NULL;

  }

}

// Reverse the order of elements in the hash buckets.

template <MEMFLAGS F> void BasicHashtable<F>::reverse() {

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

    BasicHashtableEntry<F>* new_list = NULL;

    BasicHashtableEntry<F>* p = bucket(i);

    while (p != NULL) {

      BasicHashtableEntry<F>* next = p->next();

      p->set_next(new_list);

      new_list = p;

      p = next;

    }

    *bucket_addr(i) = new_list;

  }

}

// Copy the table to the shared space.

template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char** top, char* end) {

  // Dump the hash table entries.

  intptr_t *plen = (intptr_t*)(*top);

  *top += sizeof(*plen);

  int i;

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

    for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();

                              *p != NULL;

                               p = (*p)->next_addr()) {

      if (*top + entry_size() > end) {

        report_out_of_shared_space(SharedMiscData);

      }

      *p = (BasicHashtableEntry<F>*)memcpy(*top, *p, entry_size());

      *top += entry_size();

    }

  }

  *plen = (char*)(*top) - (char*)plen - sizeof(*plen);

  // Set the shared bit.

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

    for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {

      p->set_shared();

    }

  }

}

// Reverse the order of elements in the hash buckets.

template <class T, MEMFLAGS F> void Hashtable<T, F>::reverse(void* boundary) {

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

    HashtableEntry<T, F>* high_list = NULL;

    HashtableEntry<T, F>* low_list = NULL;

    HashtableEntry<T, F>* last_low_entry = NULL;

    HashtableEntry<T, F>* p = bucket(i);

    while (p != NULL) {

      HashtableEntry<T, F>* next = p->next();

      if ((void*)p->literal() >= boundary) {

        p->set_next(high_list);

        high_list = p;

      } else {

        p->set_next(low_list);

        low_list = p;

        if (last_low_entry == NULL) {

          last_low_entry = p;

        }

      }

      p = next;

    }

    if (low_list != NULL) {

      *bucket_addr(i) = low_list;

      last_low_entry->set_next(high_list);

    } else {

      *bucket_addr(i) = high_list;

    }

  }

}

template <class T, MEMFLAGS F> int Hashtable<T, F>::literal_size(Symbol *symbol) {

  return symbol->size() * HeapWordSize;

}

template <class T, MEMFLAGS F> int Hashtable<T, F>::literal_size(oop oop) {

  // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,

  // and the String.value array is shared by several Strings. However, starting from JDK8,

  // the String.value array is not shared anymore.

  assert(oop != NULL && oop->klass() == SystemDictionary::String_klass(), "only strings are supported");

  return (oop->size() + java_lang_String::value(oop)->size()) * HeapWordSize;

}

// Dump footprint and bucket length statistics

//

// Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to

// add a new function Hashtable<T, F>::literal_size(MyNewType lit)

template <class T, MEMFLAGS F> void Hashtable<T, F>::dump_table(outputStream* st, const char *table_name) {

  NumberSeq summary;

  int literal_bytes = 0;

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

    int count = 0;

    for (HashtableEntry<T, F>* e = bucket(i);

       e != NULL; e = e->next()) {

      count++;

      literal_bytes += literal_size(e->literal());

    }

    summary.add((double)count);

  }

  double num_buckets = summary.num();

  double num_entries = summary.sum();

  int bucket_bytes = (int)num_buckets * sizeof(bucket(0));

  int entry_bytes  = (int)num_entries * sizeof(HashtableEntry<T, F>);

  int total_bytes = literal_bytes +  bucket_bytes + entry_bytes;

  double bucket_avg  = (num_buckets <= 0) ? 0 : (bucket_bytes  / num_buckets);

  double entry_avg   = (num_entries <= 0) ? 0 : (entry_bytes   / num_entries);

  double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);

  st->print_cr("%s statistics:", table_name);

  st->print_cr("Number of buckets       : %9d = %9d bytes, avg %7.3f", (int)num_buckets, bucket_bytes,  bucket_avg);

  st->print_cr("Number of entries       : %9d = %9d bytes, avg %7.3f", (int)num_entries, entry_bytes,   entry_avg);

  st->print_cr("Number of literals      : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);

  st->print_cr("Total footprint         : %9s = %9d bytes", "", total_bytes);

  st->print_cr("Average bucket size     : %9.3f", summary.avg());

  st->print_cr("Variance of bucket size : %9.3f", summary.variance());

  st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());

  st->print_cr("Maximum bucket size     : %9d", (int)summary.maximum());

}

// Dump the hash table buckets.

template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char** top, char* end) {

  intptr_t len = _table_size * sizeof(HashtableBucket<F>);

  *(intptr_t*)(*top) = len;

  *top += sizeof(intptr_t);

  *(intptr_t*)(*top) = _number_of_entries;

  *top += sizeof(intptr_t);

  if (*top + len > end) {

    report_out_of_shared_space(SharedMiscData);

  }

  _buckets = (HashtableBucket<F>*)memcpy(*top, _buckets, len);

  *top += len;

}

#ifndef PRODUCT

template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {

  ResourceMark rm;

  for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {

    HashtableEntry<T, F>* entry = bucket(i);

    while(entry != NULL) {

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

      entry->literal()->print();

      tty->cr();

      entry = entry->next();

    }

  }

}

template <MEMFLAGS F> void BasicHashtable<F>::verify() {

  int count = 0;

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

    for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {

      ++count;

    }

  }

  assert(count == number_of_entries(), "number of hashtable entries incorrect");

}

#endif // PRODUCT

#ifdef ASSERT

template <MEMFLAGS F> void BasicHashtable<F>::verify_lookup_length(double load) {

  if ((double)_lookup_length / (double)_lookup_count > load * 2.0) {

    warning("Performance bug: SystemDictionary lookup_count=%d "

            "lookup_length=%d average=%lf load=%f",

            _lookup_count, _lookup_length,

            (double) _lookup_length / _lookup_count, load);

  }

}

#endif

// Explicitly instantiate these types

template class Hashtable<ConstantPool*, mtClass>;

template class Hashtable<Symbol*, mtSymbol>;

template class Hashtable<Klass*, mtClass>;

template class Hashtable<oop, mtClass>;

#ifdef SOLARIS

template class Hashtable<oop, mtSymbol>;

#endif

template class Hashtable<oopDesc*, mtSymbol>;

template class Hashtable<Symbol*, mtClass>;

template class HashtableEntry<Symbol*, mtSymbol>;

template class HashtableEntry<Symbol*, mtClass>;

template class HashtableEntry<oop, mtSymbol>;

template class BasicHashtableEntry<mtSymbol>;

template class BasicHashtableEntry<mtCode>;

template class BasicHashtable<mtClass>;

template class BasicHashtable<mtSymbol>;

template class BasicHashtable<mtCode>;

template class BasicHashtable<mtInternal>;