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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_LaunchError_h
#define mozilla_ipc_LaunchError_h
#include "mozilla/StaticString.h"
#include "nsError.h" // for nsresult
#if defined(XP_WIN)
# include <windows.h>
# include <winerror.h>
#endif
namespace mozilla::ipc {
class LaunchError {
public:
// The context of an error code (at the very least, the function that emitted
// it and where it was called) is fundamentally necessary to interpret its
// value. Since we should have that, we're not too fussed about integral
// coercions, so long as we don't lose any bits.
//
// Under POSIX, the usual OS-error type is `int`. Under Windows, the usual
// error type is `HRESULT`, which (despite having bitfield semantics) is
// ultimately a typedef for a flavor of (signed) `long`. For simplicity, and
// in the absence of other constraints, our "error type" container is simply
// the join of these two.
using ErrorType = long;
// Constructor.
//
// The default of `0` is intended for failure cases where we don't have an
// error code -- usually because the function we've called to determine
// failure has only a boolean return, but also for when we've detected some
// internal failure and there's no appropriate `nsresult` for it.
explicit LaunchError(StaticString aFunction, ErrorType aError = 0)
: mFunction(aFunction), mError(aError) {}
#ifdef WIN32
// The error code returned by ::GetLastError() is (usually) not an HRESULT.
// This convenience-function maps its return values to the segment of
// HRESULT's namespace reserved for that.
//
// This is not formally necessary -- the error location should suffice to
// disambiguate -- but it's nice to have it converted when reading through
// error-values: `0x80070005` is marginally more human-meaningful than `5`.
static LaunchError FromWin32Error(StaticString aFunction, DWORD aError) {
return LaunchError(aFunction, HRESULT_FROM_WIN32(aError));
}
#endif
// By design, `nsresult` does not implicitly coerce to an integer.
LaunchError(StaticString aFunction, nsresult aError)
: mFunction(aFunction), mError((ErrorType)aError) {}
StaticString FunctionName() const { return mFunction; }
ErrorType ErrorCode() const { return mError; }
private:
StaticString mFunction;
ErrorType mError;
};
} // namespace mozilla::ipc
#endif // ifndef mozilla_ipc_LaunchError_h
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