text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #pragma once
  
  #include <AK/OwnPtr.h>
  #include <AK/WeakPtr.h>
  #include <Kernel/VM/MemoryManager.h>
  #include <Kernel/VM/PurgeableVMObject.h>
  
  namespace Kernel {
  
  class SharedBuffer {
  private:
      struct Reference {
          Reference(pid_t pid)
              : pid(pid)
          {
          }
  
          pid_t pid;
          unsigned count { 0 };
          WeakPtr<Region> region;
      };
  
  public:
      SharedBuffer(int id, int size)
          : m_shbuf_id(id)
          , m_vmobject(PurgeableVMObject::create_with_size(size))
      {
  #ifdef SHARED_BUFFER_DEBUG
          dbg() << "Created shared buffer " << m_shbuf_id << " of size " << size;
  #endif
      }
  
      ~SharedBuffer()
      {
  #ifdef SHARED_BUFFER_DEBUG
          dbg() << "Destroyed shared buffer " << m_shbuf_id << " of size " << size();
  #endif
      }
  
      void sanity_check(const char* what);
      bool is_shared_with(pid_t peer_pid) const;
      void* ref_for_process_and_get_address(Process& process);
      void share_with(pid_t peer_pid);
      void share_globally() { m_global = true; }
      void deref_for_process(Process& process);
      void disown(pid_t pid);
      size_t size() const { return m_vmobject->size(); }
      void destroy_if_unused();
      void seal();
      PurgeableVMObject& vmobject() { return m_vmobject; }
      const PurgeableVMObject& vmobject() const { return m_vmobject; }
      int id() const { return m_shbuf_id; }
  
  private:
      int m_shbuf_id { -1 };
      bool m_writable { true };
      bool m_global { false };
      NonnullRefPtr<PurgeableVMObject> m_vmobject;
      Vector<Reference, 2> m_refs;
      unsigned m_total_refs { 0 };
  };
  
  Lockable<HashMap<int, NonnullOwnPtr<SharedBuffer>>>& shared_buffers();
  
  }
  