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 /*

  * Copyright (c) 2001, 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.

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  */

 #ifndef SHARE_VM_MEMORY_FREELIST_HPP

 #define SHARE_VM_MEMORY_FREELIST_HPP

 #include "gc_implementation/shared/allocationStats.hpp"

 class CompactibleFreeListSpace;

 // A class for maintaining a free list of Chunk's.  The FreeList

 // maintains a the structure of the list (head, tail, etc.) plus

 // statistics for allocations from the list.  The links between items

 // are not part of FreeList.  The statistics are

 // used to make decisions about coalescing Chunk's when they

 // are swept during collection.

 //

 // See the corresponding .cpp file for a description of the specifics

 // for that implementation.

 class Mutex;

 template <class Chunk_t>

 class FreeList VALUE_OBJ_CLASS_SPEC {

   friend class CompactibleFreeListSpace;

   friend class VMStructs;

  private:

   Chunk_t*      _head;          // Head of list of free chunks

   Chunk_t*      _tail;          // Tail of list of free chunks

   size_t        _size;          // Size in Heap words of each chunk

   ssize_t       _count;         // Number of entries in list

  protected:

 #ifdef ASSERT

   Mutex*        _protecting_lock;

 #endif

   // Asserts false if the protecting lock (if any) is not held.

   void assert_proper_lock_protection_work() const PRODUCT_RETURN;

   void assert_proper_lock_protection() const {

 #ifdef ASSERT

     if (_protecting_lock != NULL)

       assert_proper_lock_protection_work();

 #endif

   }

   void increment_count()    {

     _count++;

   }

   void decrement_count() {

     _count--;

     assert(_count >= 0, "Count should not be negative");

   }

  public:

   // Constructor

   // Construct a list without any entries.

   FreeList();

   // Do initialization

   void initialize();

   // Reset the head, tail, and count of a free list.

   void reset();

   // Declare the current free list to be protected by the given lock.

 #ifdef ASSERT

   Mutex* protecting_lock() const { return _protecting_lock; }

   void set_protecting_lock(Mutex* v) {

     _protecting_lock = v;

   }

 #endif

   // Accessors.

   Chunk_t* head() const {

     assert_proper_lock_protection();

     return _head;

   }

   void set_head(Chunk_t* v) {

     assert_proper_lock_protection();

     _head = v;

     assert(!_head || _head->size() == _size, "bad chunk size");

   }

   // Set the head of the list and set the prev field of non-null

   // values to NULL.

   void link_head(Chunk_t* v);

   Chunk_t* tail() const {

     assert_proper_lock_protection();

     return _tail;

   }

   void set_tail(Chunk_t* v) {

     assert_proper_lock_protection();

     _tail = v;

     assert(!_tail || _tail->size() == _size, "bad chunk size");

   }

   // Set the tail of the list and set the next field of non-null

   // values to NULL.

   void link_tail(Chunk_t* v) {

     assert_proper_lock_protection();

     set_tail(v);

     if (v != NULL) {

       v->clear_next();

     }

   }

   // No locking checks in read-accessors: lock-free reads (only) are benign.

   // Readers are expected to have the lock if they are doing work that

   // requires atomicity guarantees in sections of code.

   size_t size() const {

     return _size;

   }

   void set_size(size_t v) {

     assert_proper_lock_protection();

     _size = v;

   }

   ssize_t count() const { return _count; }

   void set_count(ssize_t v) { _count = v;}

   size_t get_better_size() { return size(); }

   size_t returned_bytes() const { ShouldNotReachHere(); return 0; }

   void set_returned_bytes(size_t v) {}

   void increment_returned_bytes_by(size_t v) {}

   // Unlink head of list and return it.  Returns NULL if

   // the list is empty.

   Chunk_t* get_chunk_at_head();

   // Remove the first "n" or "count", whichever is smaller, chunks from the

   // list, setting "fl", which is required to be empty, to point to them.

   void getFirstNChunksFromList(size_t n, FreeList<Chunk_t>* fl);

   // Unlink this chunk from it's free list

   void remove_chunk(Chunk_t* fc);

   // Add this chunk to this free list.

   void return_chunk_at_head(Chunk_t* fc);

   void return_chunk_at_tail(Chunk_t* fc);

   // Similar to returnChunk* but also records some diagnostic

   // information.

   void return_chunk_at_head(Chunk_t* fc, bool record_return);

   void return_chunk_at_tail(Chunk_t* fc, bool record_return);

   // Prepend "fl" (whose size is required to be the same as that of "this")

   // to the front of "this" list.

   void prepend(FreeList<Chunk_t>* fl);

   // Verify that the chunk is in the list.

   // found.  Return NULL if "fc" is not found.

   bool verify_chunk_in_free_list(Chunk_t* fc) const;

   // Printing support

   static void print_labels_on(outputStream* st, const char* c);

   void print_on(outputStream* st, const char* c = NULL) const;

 };

 #endif // SHARE_VM_MEMORY_FREELIST_HPP