/*

 * 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 "gc/z/zList.inline.hpp"

#include "gc/z/zMemory.inline.hpp"

#include "memory/allocation.inline.hpp"

uintptr_t ZMemoryManager::alloc_from_front(size_t size) {

  ZListIterator<ZMemory> iter(&_freelist);

  for (ZMemory* area; iter.next(&area);) {

    if (area->size() >= size) {

      if (area->size() == size) {

        // Exact match, remove area

        const uintptr_t start = area->start();

        _freelist.remove(area);

        delete area;

        return start;

      } else {

        // Larger than requested, shrink area

        const uintptr_t start = area->start();

        area->shrink_from_front(size);

        return start;

      }

    }

  }

  // Out of memory

  return UINTPTR_MAX;

}

uintptr_t ZMemoryManager::alloc_from_back(size_t size) {

  ZListReverseIterator<ZMemory> iter(&_freelist);

  for (ZMemory* area; iter.next(&area);) {

    if (area->size() >= size) {

      if (area->size() == size) {

        // Exact match, remove area

        const uintptr_t start = area->start();

        _freelist.remove(area);

        delete area;

        return start;

      } else {

        // Larger than requested, shrink area

        area->shrink_from_back(size);

        return area->end();

      }

    }

  }

  // Out of memory

  return UINTPTR_MAX;

}

void ZMemoryManager::free(uintptr_t start, size_t size) {

  assert(start != UINTPTR_MAX, "Invalid address");

  const uintptr_t end = start + size;

  ZListIterator<ZMemory> iter(&_freelist);

  for (ZMemory* area; iter.next(&area);) {

    if (start < area->start()) {

      ZMemory* const prev = _freelist.prev(area);

      if (prev != NULL && start == prev->end()) {

        if (end == area->start()) {

          // Merge with prev and current area

          prev->grow_from_back(size + area->size());

          _freelist.remove(area);

          delete area;

        } else {

          // Merge with prev area

          prev->grow_from_back(size);

        }

      } else if (end == area->start()) {

        // Merge with current area

        area->grow_from_front(size);

      } else {

        // Insert new area before current area

        assert(end < area->start(), "Areas must not overlap");

        ZMemory* new_area = new ZMemory(start, size);

        _freelist.insert_before(area, new_area);

      }

      // Done

      return;

    }

  }

  // Insert last

  ZMemory* const last = _freelist.last();

  if (last != NULL && start == last->end()) {

    // Merge with last area

    last->grow_from_back(size);

  } else {

    // Insert new area last

    ZMemory* new_area = new ZMemory(start, size);

    _freelist.insert_last(new_area);

  }

}