gecko-dev/mfbt/ResultExtensions.h

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/* -*- 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