gecko-dev/ipc/glue/FileDescriptorUtils.cpp

/* -*- 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/. */

#include "FileDescriptorUtils.h"

#include "nsIEventTarget.h"

#include "nsCOMPtr.h"
#include "nsDebug.h"
#include "nsNetCID.h"
#include "nsServiceManagerUtils.h"
#include "nsThreadUtils.h"
#include "prio.h"
#include "private/pprio.h"

#include <errno.h>
#ifdef XP_WIN
#  include <io.h>
#else
#  include <unistd.h>
#endif

using mozilla::ipc::CloseFileRunnable;

#ifdef DEBUG

CloseFileRunnable::CloseFileRunnable(const FileDescriptor& aFileDescriptor)
    : mFileDescriptor(aFileDescriptor) {
  MOZ_ASSERT(aFileDescriptor.IsValid());
}

#endif  // DEBUG

CloseFileRunnable::~CloseFileRunnable() {
  if (mFileDescriptor.IsValid()) {
    // It's probably safer to take the main thread IO hit here rather than leak
    // the file descriptor.
    CloseFile();
  }
}

NS_IMPL_ISUPPORTS(CloseFileRunnable, nsIRunnable)

void CloseFileRunnable::Dispatch() {
  nsCOMPtr<nsIEventTarget> eventTarget =
      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
  NS_ENSURE_TRUE_VOID(eventTarget);

  nsresult rv = eventTarget->Dispatch(this, NS_DISPATCH_NORMAL);
  NS_ENSURE_SUCCESS_VOID(rv);
}

void CloseFileRunnable::CloseFile() {
  // It's possible for this to happen on the main thread if the dispatch to the
  // stream service fails so we can't assert the thread on which we're running.
  mFileDescriptor = FileDescriptor();
}

NS_IMETHODIMP
CloseFileRunnable::Run() {
  MOZ_ASSERT(!NS_IsMainThread());

  CloseFile();
  return NS_OK;
}

namespace mozilla {
namespace ipc {

FILE* FileDescriptorToFILE(const FileDescriptor& aDesc, const char* aOpenMode) {
  if (!aDesc.IsValid()) {
    errno = EBADF;
    return nullptr;
  }
  auto handle = aDesc.ClonePlatformHandle();
#ifdef XP_WIN
  int fd = _open_osfhandle(static_cast<intptr_t>(handle.get()), 0);
  if (fd == -1) {
    return nullptr;
  }
  Unused << handle.release();
#else
  int fd = handle.release();
#endif
  FILE* file = fdopen(fd, aOpenMode);
  if (!file) {
    int saved_errno = errno;
    close(fd);
    errno = saved_errno;
  }
  return file;
}

FileDescriptor FILEToFileDescriptor(FILE* aStream) {
  if (!aStream) {
    errno = EBADF;
    return FileDescriptor();
  }
#ifdef XP_WIN
  int fd = _fileno(aStream);
  if (fd == -1) {
    return FileDescriptor();
  }
  return FileDescriptor(reinterpret_cast<HANDLE>(_get_osfhandle(fd)));
#else
  return FileDescriptor(fileno(aStream));
#endif
}

}  // namespace ipc
}  // namespace mozilla