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.
   */
  
  #include <AK/Memory.h>
  #include <Kernel/FileSystem/Inode.h>
  #include <Kernel/FileSystem/InodeWatcher.h>
  
  namespace Kernel {
  
  NonnullRefPtr<InodeWatcher> InodeWatcher::create(Inode& inode)
  {
      return adopt(*new InodeWatcher(inode));
  }
  
  InodeWatcher::InodeWatcher(Inode& inode)
      : m_inode(inode)
  {
      inode.register_watcher({}, *this);
  }
  
  InodeWatcher::~InodeWatcher()
  {
      if (auto inode = m_inode.strong_ref())
          inode->unregister_watcher({}, *this);
  }
  
  bool InodeWatcher::can_read(const FileDescription&, size_t) const
  {
      return !m_queue.is_empty() || !m_inode;
  }
  
  bool InodeWatcher::can_write(const FileDescription&, size_t) const
  {
      return true;
  }
  
  KResultOr<size_t> InodeWatcher::read(FileDescription&, size_t, UserOrKernelBuffer& buffer, size_t buffer_size)
  {
      LOCKER(m_lock);
      ASSERT(!m_queue.is_empty() || !m_inode);
  
      if (!m_inode)
          return 0;
  
      auto event = m_queue.dequeue();
  
      if (buffer_size < sizeof(Event))
          return buffer_size;
  
      size_t bytes_to_write = min(buffer_size, sizeof(event));
  
      ssize_t nwritten = buffer.write_buffered<sizeof(event)>(bytes_to_write, [&](u8* data, size_t data_bytes) {
          memcpy(data, &event, bytes_to_write);
          return (ssize_t)data_bytes;
      });
      if (nwritten < 0)
          return KResult(nwritten);
      evaluate_block_conditions();
      return bytes_to_write;
  }
  
  KResultOr<size_t> InodeWatcher::write(FileDescription&, size_t, const UserOrKernelBuffer&, size_t)
  {
      return KResult(-EIO);
  }
  
  String InodeWatcher::absolute_path(const FileDescription&) const
  {
      if (auto inode = m_inode.strong_ref())
          return String::format("InodeWatcher:%s", inode->identifier().to_string().characters());
      return "InodeWatcher:(gone)";
  }
  
  void InodeWatcher::notify_inode_event(Badge<Inode>, Event::Type event_type)
  {
      LOCKER(m_lock);
      m_queue.enqueue({ event_type });
      evaluate_block_conditions();
  }
  
  void InodeWatcher::notify_child_added(Badge<Inode>, const InodeIdentifier& child_id)
  {
      LOCKER(m_lock);
      m_queue.enqueue({ Event::Type::ChildAdded, child_id.index() });
      evaluate_block_conditions();
  }
  
  void InodeWatcher::notify_child_removed(Badge<Inode>, const InodeIdentifier& child_id)
  {
      LOCKER(m_lock);
      m_queue.enqueue({ Event::Type::ChildRemoved, child_id.index() });
      evaluate_block_conditions();
  }
  
  }
  