AllocateFirstNodeOnPage

AllocateFirstNodeOnPage.cpp

SMDataQueueBase::Node* SMDataQueueBase::AllocateFirstNodeOnPage(size_t size)
{
  if(m_FreePages.empty())
  {
    // garbage collect
    m_UsedPages.erase(std::remove_if(m_UsedPages.begin(), m_UsedPages.end(), [this](unsigned pageId) -> bool
    { 
      const bool isFree = m_Pages[pageId]->NodesOwned == 0;
      if (isFree)
      {
        m_FreePages.push_back(pageId);
      }
      return isFree;
    }), m_UsedPages.end() );
  }

  unsigned freePage = MAX_SHARED_PAGES;
  for(auto it = m_FreePages.begin(); it != m_FreePages.end(); ++it)
  { 
    if(m_Pages[*it]->GetDataSize() >= size)
    {
      freePage = *it;
      break;
    }
  }

  if(freePage != MAX_SHARED_PAGES)
  {
    m_UsedPages.push_back(freePage);
    m_FreePages.erase(m_FreePages.begin() + freePage);
  }
  else
  {
    AllocatePage(std::max(size*2, DEFAULT_PAGE_SIZE));
    freePage = m_SharedData->m_AllocatedPagesCount - 1;
    m_UsedPages.push_back(freePage);
  }
  
  Node* node = new (m_Pages[freePage]->GetData()) Node(size, freePage, 0);
  m_Pages[freePage]->AddNode();

  return node;
}