FileDescriptor.h - mozsearch

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_ipc_FileDescriptor_h

#define mozilla_ipc_FileDescriptor_h

#include "base/basictypes.h"

#include "base/process.h"

#include "mozilla/UniquePtrExtensions.h"

namespace mozilla {

namespace ipc {

// This class is used by IPDL to share file descriptors across processes. When

// sending a FileDescriptor, IPDL will transfer a duplicate of the handle into

// the remote process.

//

// To use this class add 'FileDescriptor' as an argument in the IPDL protocol

// and then pass a file descriptor from C++ to the Send method. The Recv method

// will receive a FileDescriptor& on which PlatformHandle() can be called to

// return the platform file handle.

class FileDescriptor {

 public:

  typedef base::ProcessId ProcessId;

  using UniquePlatformHandle = mozilla::UniqueFileHandle;

  using PlatformHandleType = UniquePlatformHandle::ElementType;

  // This should only ever be created by IPDL.

  struct IPDLPrivate {};

  // Represents an invalid handle.

  FileDescriptor();

  // Copy constructor will duplicate a new handle.

  FileDescriptor(const FileDescriptor& aOther);

  FileDescriptor(FileDescriptor&& aOther);

  // This constructor will duplicate a new handle.

  // The caller still have to close aHandle.

  explicit FileDescriptor(PlatformHandleType aHandle);

  explicit FileDescriptor(UniquePlatformHandle&& aHandle);

  ~FileDescriptor();

  FileDescriptor& operator=(const FileDescriptor& aOther);

  FileDescriptor& operator=(FileDescriptor&& aOther);

  // Tests mHandle against a well-known invalid platform-specific file handle

  // (e.g. -1 on POSIX, INVALID_HANDLE_VALUE on Windows).

  bool IsValid() const;

  // Returns a duplicated handle, it is caller's responsibility to close the

  // handle.

  UniquePlatformHandle ClonePlatformHandle() const;

  // Extracts the underlying handle and makes this object an invalid handle.

  // (Compare UniquePtr::release.)

  UniquePlatformHandle TakePlatformHandle();

  // Only used in nsTArray.

  bool operator==(const FileDescriptor& aOther) const;

 private:

  static UniqueFileHandle Clone(PlatformHandleType aHandle);

  UniquePlatformHandle mHandle;

};

}  // namespace ipc

}  // namespace mozilla

#endif  // mozilla_ipc_FileDescriptor_h