text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #pragma once
  
  #include <AK/HashMap.h>
  #include <AK/Types.h>
  #include <Kernel/FileSystem/FileSystem.h>
  #include <Kernel/FileSystem/Inode.h>
  #include <Kernel/Forward.h>
  #include <Kernel/KBufferBuilder.h>
  #include <Kernel/Locking/Mutex.h>
  #include <Kernel/ProcessExposed.h>
  #include <Kernel/UnixTypes.h>
  
  namespace Kernel {
  
  class ProcFS final : public FileSystem {
      friend class ProcFSInode;
      friend class ProcFSDirectoryInode;
      friend class ProcFSProcessDirectoryInode;
      friend class ProcFSGlobalInode;
      friend class ProcFSAssociatedProcessInode;
      friend class ProcFSProcessSubDirectoryInode;
  
  public:
      virtual ~ProcFS() override;
      static ErrorOr<NonnullRefPtr<ProcFS>> try_create();
  
      virtual ErrorOr<void> initialize() override;
      virtual StringView class_name() const override { return "ProcFS"sv; }
  
      virtual Inode& root_inode() override;
  
  private:
      ProcFS();
  
      RefPtr<ProcFSDirectoryInode> m_root_inode;
  };
  
  class ProcFSInode : public Inode {
      friend class ProcFS;
  
  public:
      virtual ~ProcFSInode() override;
  
  protected:
      ProcFSInode(const ProcFS&, InodeIndex);
  
      ProcFS& procfs() { return static_cast<ProcFS&>(Inode::fs()); }
      ProcFS const& procfs() const { return static_cast<ProcFS const&>(Inode::fs()); }
  
      // ^Inode
      virtual ErrorOr<void> attach(OpenFileDescription& description) = 0;
      virtual void did_seek(OpenFileDescription&, off_t) = 0;
      virtual ErrorOr<void> flush_metadata() override final;
      virtual ErrorOr<NonnullRefPtr<Inode>> create_child(StringView name, mode_t, dev_t, UserID, GroupID) override final;
      virtual ErrorOr<void> add_child(Inode&, const StringView& name, mode_t) override final;
      virtual ErrorOr<void> remove_child(const StringView& name) override final;
      virtual ErrorOr<void> chmod(mode_t) override final;
      virtual ErrorOr<void> chown(UserID, GroupID) override final;
  };
  
  class ProcFSGlobalInode : public ProcFSInode {
      friend class ProcFS;
  
  public:
      static ErrorOr<NonnullRefPtr<ProcFSGlobalInode>> try_create(const ProcFS&, const ProcFSExposedComponent&);
      virtual ~ProcFSGlobalInode() override {};
      StringView name() const;
  
  protected:
      ProcFSGlobalInode(const ProcFS&, const ProcFSExposedComponent&);
  
      // ^Inode
      virtual ErrorOr<void> attach(OpenFileDescription& description) override final;
      virtual ErrorOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, OpenFileDescription*) const override final;
      virtual ErrorOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, OpenFileDescription*) override final;
      virtual void did_seek(OpenFileDescription&, off_t) override final;
      virtual InodeMetadata metadata() const override;
      virtual ErrorOr<void> traverse_as_directory(Function<bool(FileSystem::DirectoryEntryView const&)>) const override;
      virtual ErrorOr<NonnullRefPtr<Inode>> lookup(StringView) override;
      virtual ErrorOr<void> truncate(u64) override final;
      virtual ErrorOr<void> set_mtime(time_t) override final;
  
      NonnullRefPtr<ProcFSExposedComponent> m_associated_component;
  };
  
  class ProcFSLinkInode : public ProcFSGlobalInode {
      friend class ProcFS;
  
  public:
      static ErrorOr<NonnullRefPtr<ProcFSLinkInode>> try_create(const ProcFS&, const ProcFSExposedComponent&);
  
  protected:
      ProcFSLinkInode(const ProcFS&, const ProcFSExposedComponent&);
      virtual InodeMetadata metadata() const override;
  };
  
  class ProcFSDirectoryInode final : public ProcFSGlobalInode {
      friend class ProcFS;
  
  public:
      static ErrorOr<NonnullRefPtr<ProcFSDirectoryInode>> try_create(const ProcFS&, const ProcFSExposedComponent&);
      virtual ~ProcFSDirectoryInode() override;
  
  protected:
      ProcFSDirectoryInode(const ProcFS&, const ProcFSExposedComponent&);
      // ^Inode
      virtual InodeMetadata metadata() const override;
      virtual ErrorOr<void> traverse_as_directory(Function<bool(FileSystem::DirectoryEntryView const&)>) const override;
      virtual ErrorOr<NonnullRefPtr<Inode>> lookup(StringView name) override;
  };
  
  class ProcFSProcessAssociatedInode : public ProcFSInode {
      friend class ProcFS;
  
  protected:
      ProcFSProcessAssociatedInode(const ProcFS&, ProcessID, InodeIndex);
      ProcessID associated_pid() const { return m_pid; }
  
      // ^Inode
      virtual ErrorOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, OpenFileDescription*) override final;
  
  private:
      const ProcessID m_pid;
  };
  
  class ProcFSProcessDirectoryInode final : public ProcFSProcessAssociatedInode {
      friend class ProcFS;
  
  public:
      static ErrorOr<NonnullRefPtr<ProcFSProcessDirectoryInode>> try_create(const ProcFS&, ProcessID);
  
  private:
      ProcFSProcessDirectoryInode(const ProcFS&, ProcessID);
      // ^Inode
      virtual ErrorOr<void> attach(OpenFileDescription& description) override;
      virtual void did_seek(OpenFileDescription&, off_t) override { }
      virtual InodeMetadata metadata() const override;
      virtual ErrorOr<void> traverse_as_directory(Function<bool(FileSystem::DirectoryEntryView const&)>) const override;
      virtual ErrorOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, OpenFileDescription*) const override final;
      virtual ErrorOr<NonnullRefPtr<Inode>> lookup(StringView name) override;
  };
  
  class ProcFSProcessSubDirectoryInode final : public ProcFSProcessAssociatedInode {
      friend class ProcFS;
  
  public:
      static ErrorOr<NonnullRefPtr<ProcFSProcessSubDirectoryInode>> try_create(const ProcFS&, SegmentedProcFSIndex::ProcessSubDirectory, ProcessID);
  
  private:
      ProcFSProcessSubDirectoryInode(const ProcFS&, SegmentedProcFSIndex::ProcessSubDirectory, ProcessID);
      // ^Inode
      virtual ErrorOr<void> attach(OpenFileDescription& description) override;
      virtual void did_seek(OpenFileDescription&, off_t) override;
      virtual InodeMetadata metadata() const override;
      virtual ErrorOr<void> traverse_as_directory(Function<bool(FileSystem::DirectoryEntryView const&)>) const override;
      virtual ErrorOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, OpenFileDescription*) const override final;
      virtual ErrorOr<NonnullRefPtr<Inode>> lookup(StringView name) override;
  
      const SegmentedProcFSIndex::ProcessSubDirectory m_sub_directory_type;
  };
  
  class ProcFSProcessPropertyInode final : public ProcFSProcessAssociatedInode {
      friend class ProcFS;
  
  public:
      static ErrorOr<NonnullRefPtr<ProcFSProcessPropertyInode>> try_create_for_file_description_link(const ProcFS&, unsigned, ProcessID);
      static ErrorOr<NonnullRefPtr<ProcFSProcessPropertyInode>> try_create_for_thread_stack(const ProcFS&, ThreadID, ProcessID);
      static ErrorOr<NonnullRefPtr<ProcFSProcessPropertyInode>> try_create_for_pid_property(const ProcFS&, SegmentedProcFSIndex::MainProcessProperty, ProcessID);
  
  private:
      ProcFSProcessPropertyInode(const ProcFS&, SegmentedProcFSIndex::MainProcessProperty, ProcessID);
      ProcFSProcessPropertyInode(const ProcFS&, ThreadID, ProcessID);
      ProcFSProcessPropertyInode(const ProcFS&, unsigned, ProcessID);
      // ^Inode
      virtual ErrorOr<void> attach(OpenFileDescription& description) override;
      virtual void did_seek(OpenFileDescription&, off_t) override;
      virtual InodeMetadata metadata() const override;
      virtual ErrorOr<void> traverse_as_directory(Function<bool(FileSystem::DirectoryEntryView const&)>) const override;
      virtual ErrorOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, OpenFileDescription*) const override final;
      virtual ErrorOr<NonnullRefPtr<Inode>> lookup(StringView name) override final;
  
      ErrorOr<void> refresh_data(OpenFileDescription& description);
      ErrorOr<void> try_to_acquire_data(Process& process, KBufferBuilder& builder) const;
  
      const SegmentedProcFSIndex::ProcessSubDirectory m_parent_sub_directory_type;
      union {
          SegmentedProcFSIndex::MainProcessProperty property_type;
          unsigned property_index;
      } m_possible_data;
      mutable Mutex m_refresh_lock;
  };
  }
  