Method acquire_buffer

sql/threadpool_winsockets.cc:96–104

Returns a buffer, or NULL if no free buffers. LIFO policy is implemented, so we do not touch too many pages (no std::stack though) */

  pages (no std::stack though)
*/
char *AIO_buffer_cache::acquire_buffer()
{
  std::unique_lock<std::mutex> lk(m_mtx);
  if (m_cache.empty())
    return nullptr;
  auto p= m_cache.back();
  m_cache.pop_back();
  return p;
}

void AIO_buffer_cache::release_buffer(char *v)
{