mfbt/ResultExtensions.h
author Petru Lingurar <petru.lingurar@softvision.ro>
Fri, 21 Dec 2018 08:56:47 +0000
changeset 501492 65621d0fe1262af0643cec37c23b2d9ec42588ad
parent 430108 d75df8f79607ba713e4e41a78eb57e265c927856
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1513938 - Enforce a Bundle size limit and drop `privateSession` if exceeds it. r=JanH, a=jcristau The `privateSession` key would normally allow persisting the Private Browsing session across OOMs in Activity's Bundle. We need to do that to avoid storing private, sensible data on disk like we do with the normal browsing session. In some cases `privateSession` would contain a lot of data which, along with other possible concurrent transactions could overflow Binder's buffer which has a limited fixed size, currently 1Mb. To avoid this, we will drop `privateSession` from the Bundle if the resulting size is greater than a _speculative_ size of 300KBs which would mean that in the case of an OOM all Private Browsing state would be lost. Bug 1515592 is filed to investigate for a better solution. Differential Revision: https://phabricator.services.mozilla.com/D15067

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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/. */

/* Extensions to the Result type to enable simpler handling of XPCOM/NSPR results. */

#ifndef mozilla_ResultExtensions_h
#define mozilla_ResultExtensions_h

#include "mozilla/Assertions.h"
#include "nscore.h"
#include "prtypes.h"

namespace mozilla {

// Allow nsresult errors to automatically convert to nsresult values, so MOZ_TRY
// can be used in XPCOM methods with Result<T, nserror> results.
template <>
class MOZ_MUST_USE_TYPE GenericErrorResult<nsresult>
{
  nsresult mErrorValue;

  template<typename V, typename E2> friend class Result;

public:
  explicit GenericErrorResult(nsresult aErrorValue) : mErrorValue(aErrorValue)
  {
    MOZ_ASSERT(NS_FAILED(aErrorValue));
  }

  operator nsresult() { return mErrorValue; }
};

// Allow MOZ_TRY to handle `PRStatus` values.
inline Result<Ok, nsresult> ToResult(PRStatus aValue);

} // namespace mozilla

#include "mozilla/Result.h"

namespace mozilla {

inline Result<Ok, nsresult>
ToResult(nsresult aValue)
{
  if (NS_FAILED(aValue)) {
    return Err(aValue);
  }
  return Ok();
}

inline Result<Ok, nsresult>
ToResult(PRStatus aValue)
{
  if (aValue == PR_SUCCESS) {
    return Ok();
  }
  return Err(NS_ERROR_FAILURE);
}

} // namespace mozilla

#endif // mozilla_ResultExtensions_h