/*

 * Copyright (c) 2003, 2017, 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

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 */

#ifndef SHARE_VM_UTILITIES_HASHTABLE_HPP

#define SHARE_VM_UTILITIES_HASHTABLE_HPP

#include "classfile/classLoaderData.hpp"

#include "memory/allocation.hpp"

#include "oops/oop.hpp"

#include "oops/symbol.hpp"

#include "runtime/handles.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:

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

template <MEMFLAGS F> class BasicHashtableEntry : public CHeapObj<F> {

  friend class VMStructs;

private:

  unsigned int         _hash;           // 32-bit hash for item

  // Link to next element in the linked list for this bucket.  EXCEPT

  // bit 0 set indicates that this entry is shared and must not be

  // unlinked from the table. Bit 0 is set during the dumping of the

  // archive. Since shared entries are immutable, _next fields in the

  // shared entries will not change.  New entries will always be

  // unshared and since pointers are align, bit 0 will always remain 0

  // with no extra effort.

  BasicHashtableEntry<F>* _next;

  // Windows IA64 compiler requires subclasses to be able to access these

protected:

  // Entry objects should not be created, they should be taken from the

  // free list with BasicHashtable.new_entry().

  BasicHashtableEntry() { ShouldNotReachHere(); }

  // Entry objects should not be destroyed.  They should be placed on

  // the free list instead with BasicHashtable.free_entry().

  ~BasicHashtableEntry() { ShouldNotReachHere(); }

public:

  unsigned int hash() const             { return _hash; }

  void set_hash(unsigned int hash)      { _hash = hash; }

  unsigned int* hash_addr()             { return &_hash; }

  static BasicHashtableEntry<F>* make_ptr(BasicHashtableEntry<F>* p) {

    return (BasicHashtableEntry*)((intptr_t)p & -2);

  }

  BasicHashtableEntry<F>* next() const {

    return make_ptr(_next);

  }

  void set_next(BasicHashtableEntry<F>* next) {

    _next = next;

  }

  BasicHashtableEntry<F>** next_addr() {

    return &_next;

  }

  bool is_shared() const {

    return ((intptr_t)_next & 1) != 0;

  }

  void set_shared() {

    _next = (BasicHashtableEntry<F>*)((intptr_t)_next | 1);

  }

};

template <class T, MEMFLAGS F> class HashtableEntry : public BasicHashtableEntry<F> {

  friend class VMStructs;

private:

  T               _literal;          // ref to item in table.

public:

  // Literal

  T literal() const                   { return _literal; }

  T* literal_addr()                   { return &_literal; }

  void set_literal(T s)               { _literal = s; }

  HashtableEntry* next() const {

    return (HashtableEntry*)BasicHashtableEntry<F>::next();

  }

  HashtableEntry** next_addr() {

    return (HashtableEntry**)BasicHashtableEntry<F>::next_addr();

  }

};

template <MEMFLAGS F> class HashtableBucket : public CHeapObj<F> {

  friend class VMStructs;

private:

  // Instance variable

  BasicHashtableEntry<F>*       _entry;

public:

  // Accessing

  void clear()                        { _entry = NULL; }

  // The following methods use order access methods to avoid race

  // conditions in multiprocessor systems.

  BasicHashtableEntry<F>* get_entry() const;

  void set_entry(BasicHashtableEntry<F>* l);

  // The following method is not MT-safe and must be done under lock.

  BasicHashtableEntry<F>** entry_addr()  { return &_entry; }

};

template <MEMFLAGS F> class BasicHashtable : public CHeapObj<F> {

  friend class VMStructs;

public:

  BasicHashtable(int table_size, int entry_size);

  BasicHashtable(int table_size, int entry_size,

                 HashtableBucket<F>* buckets, int number_of_entries);

  // Sharing support.

  size_t count_bytes_for_buckets();

  size_t count_bytes_for_table();

  void copy_buckets(char* top, char* end);

  void copy_table(char* top, char* end);

  // Bucket handling

  int hash_to_index(unsigned int full_hash) const {

    int h = full_hash % _table_size;

    assert(h >= 0 && h < _table_size, "Illegal hash value");

    return h;

  }

private:

  // Instance variables

  int               _table_size;

  HashtableBucket<F>*     _buckets;

  BasicHashtableEntry<F>* volatile _free_list;

  char*             _first_free_entry;

  char*             _end_block;

  int               _entry_size;

  volatile int      _number_of_entries;

protected:

  void initialize(int table_size, int entry_size, int number_of_entries);

  // Accessor

  int entry_size() const { return _entry_size; }

  // The following method is MT-safe and may be used with caution.

  BasicHashtableEntry<F>* bucket(int i) const;

  // The following method is not MT-safe and must be done under lock.

  BasicHashtableEntry<F>** bucket_addr(int i) { return _buckets[i].entry_addr(); }

  // Attempt to get an entry from the free list

  BasicHashtableEntry<F>* new_entry_free_list();

  // Table entry management

  BasicHashtableEntry<F>* new_entry(unsigned int hashValue);

  // Used when moving the entry to another table

  // Clean up links, but do not add to free_list

  void unlink_entry(BasicHashtableEntry<F>* entry) {

    entry->set_next(NULL);

    --_number_of_entries;

  }

  // Move over freelist and free block for allocation

  void copy_freelist(BasicHashtable* src) {

    _free_list = src->_free_list;

    src->_free_list = NULL;

    _first_free_entry = src->_first_free_entry;

    src->_first_free_entry = NULL;

    _end_block = src->_end_block;

    src->_end_block = NULL;

  }

  // Free the buckets in this hashtable

  void free_buckets();

  // Helper data structure containing context for the bucket entry unlink process,

  // storing the unlinked buckets in a linked list.

  // Also avoids the need to pass around these four members as parameters everywhere.

  struct BucketUnlinkContext {

    int _num_processed;

    int _num_removed;

    // Head and tail pointers for the linked list of removed entries.

    BasicHashtableEntry<F>* _removed_head;

    BasicHashtableEntry<F>* _removed_tail;

    BucketUnlinkContext() : _num_processed(0), _num_removed(0), _removed_head(NULL), _removed_tail(NULL) {

    }

    void free_entry(BasicHashtableEntry<F>* entry);

  };

  // Add of bucket entries linked together in the given context to the global free list. This method

  // is mt-safe wrt. to other calls of this method.

  void bulk_free_entries(BucketUnlinkContext* context);

public:

  int table_size() const { return _table_size; }

  void set_entry(int index, BasicHashtableEntry<F>* entry);

  void add_entry(int index, BasicHashtableEntry<F>* entry);

  void free_entry(BasicHashtableEntry<F>* entry);

  int number_of_entries() const { return _number_of_entries; }

  template <class T> void verify_table(const char* table_name) PRODUCT_RETURN;

};

template <class T, MEMFLAGS F> class Hashtable : public BasicHashtable<F> {

  friend class VMStructs;

public:

  Hashtable(int table_size, int entry_size)

    : BasicHashtable<F>(table_size, entry_size) { }

  Hashtable(int table_size, int entry_size,

                   HashtableBucket<F>* buckets, int number_of_entries)

    : BasicHashtable<F>(table_size, entry_size, buckets, number_of_entries) { }

  // Debugging

  void print()               PRODUCT_RETURN;

  unsigned int compute_hash(const Symbol* name) const {

    return (unsigned int) name->identity_hash();

  }

  int index_for(const Symbol* name) const {

    return this->hash_to_index(compute_hash(name));

  }

  void print_table_statistics(outputStream* st, const char *table_name);

 protected:

  // Table entry management

  HashtableEntry<T, F>* new_entry(unsigned int hashValue, T obj);

  // Don't create and use freelist of HashtableEntry.

  HashtableEntry<T, F>* allocate_new_entry(unsigned int hashValue, T obj);

  // The following method is MT-safe and may be used with caution.

  HashtableEntry<T, F>* bucket(int i) const {

    return (HashtableEntry<T, F>*)BasicHashtable<F>::bucket(i);

  }

  // The following method is not MT-safe and must be done under lock.

  HashtableEntry<T, F>** bucket_addr(int i) {

    return (HashtableEntry<T, F>**)BasicHashtable<F>::bucket_addr(i);

  }

};

template <class T, MEMFLAGS F> class RehashableHashtable : public Hashtable<T, F> {

 friend class VMStructs;

 protected:

  enum {

    rehash_count = 100,

    rehash_multiple = 60

  };

  // Check that the table is unbalanced

  bool check_rehash_table(int count);

 public:

  RehashableHashtable(int table_size, int entry_size)

    : Hashtable<T, F>(table_size, entry_size) { }

  RehashableHashtable(int table_size, int entry_size,

                   HashtableBucket<F>* buckets, int number_of_entries)

    : Hashtable<T, F>(table_size, entry_size, buckets, number_of_entries) { }

  // Function to move these elements into the new table.

  void move_to(RehashableHashtable<T, F>* new_table);

  static bool use_alternate_hashcode();

  static juint seed();

 private:

  static juint _seed;

};

template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::_seed = 0;

template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::seed() { return _seed; };

template <class T, MEMFLAGS F> bool  RehashableHashtable<T, F>::use_alternate_hashcode() { return _seed != 0; };

#endif // SHARE_VM_UTILITIES_HASHTABLE_HPP