161 lines
4.1 KiB
C++
161 lines
4.1 KiB
C++
/*
|
|
RESULT.hpp - intermediary token representing the result of an operation
|
|
|
|
Copyright (C) Lumiera.org
|
|
2010, Hermann Vosseler <Ichthyostega@web.de>
|
|
|
|
This program is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU General Public License as
|
|
published by the Free Software Foundation; either version 2 of
|
|
the License, or (at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program; if not, write to the Free Software
|
|
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
|
|
*/
|
|
|
|
|
|
/** @file result.hpp
|
|
** Intermediary value object to represent the result of an operation.
|
|
** This operation might have produced a value result or failed with an exception.
|
|
** Typically, the Result token is used _inline_ -- immediately either invoking
|
|
** one of the member function or employing the built-in result type conversion.
|
|
** It will be copyable iff the result value is copyable. There is an implicit
|
|
** valid or failure state, which can be tested. Any attempt to get the value
|
|
** of an invalid result token will cause an exception to be thrown.
|
|
**
|
|
** @see vault::ThreadJoinable usage example
|
|
*/
|
|
|
|
|
|
|
|
#ifndef LIB_RESULT_H
|
|
#define LIB_RESULT_H
|
|
|
|
#include "lib/error.hpp"
|
|
#include "lib/wrapper.hpp"
|
|
#include "lib/util.hpp"
|
|
|
|
#include <utility>
|
|
#include <string>
|
|
|
|
|
|
|
|
namespace lib {
|
|
|
|
using util::isnil;
|
|
using std::string;
|
|
namespace error = lumiera::error;
|
|
|
|
|
|
|
|
/**
|
|
* Optional Result value or status of some operation.
|
|
* It can be created for passing a result produced by the operation, or the
|
|
* failure to do so. The value can be retrieved by implicit or explicit conversion.
|
|
* @throw error::State on any attempt to access the value in case of failure
|
|
* @warning this class has a lot of implicit conversions;
|
|
* care should be taken when defining functions
|
|
* to take Result instances as parameter....
|
|
*/
|
|
template<typename RES>
|
|
class Result
|
|
{
|
|
string failureLog_;
|
|
wrapper::ItemWrapper<RES> value_;
|
|
|
|
public:
|
|
/** mark an invalid/failed result */
|
|
Result (string const& failureReason ="no result")
|
|
: failureLog_{failureReason}
|
|
{ }
|
|
|
|
/** failed result, with reason given.*/
|
|
Result (lumiera::Error const& reason)
|
|
: failureLog_{reason.what()}
|
|
{ }
|
|
|
|
/** standard case: valid result */
|
|
Result (RES&& value)
|
|
: failureLog_{}
|
|
, value_{std::forward<RES> (value)}
|
|
{ }
|
|
|
|
|
|
|
|
bool
|
|
isValid() const
|
|
{
|
|
return value_.isValid();
|
|
}
|
|
|
|
void
|
|
maybeThrow() const
|
|
{
|
|
if (not isValid())
|
|
throw error::State (failureLog_, lumiera_error_peek());
|
|
}
|
|
|
|
operator RES() const
|
|
{
|
|
maybeThrow();
|
|
return *value_;
|
|
}
|
|
|
|
template<typename TY>
|
|
TY
|
|
get() const
|
|
{
|
|
maybeThrow();
|
|
return static_cast<TY> (*value_);
|
|
}
|
|
};
|
|
|
|
|
|
/**
|
|
* Specialisation for signalling success or failure,
|
|
* without returning any value result.
|
|
*/
|
|
template<>
|
|
class Result<void>
|
|
{
|
|
string failureLog_;
|
|
|
|
public:
|
|
/** mark either failure (default) or success */
|
|
Result (bool success =false)
|
|
: failureLog_{success? "": "operation failed"}
|
|
{ }
|
|
|
|
/** failed result, with reason given.*/
|
|
Result (lumiera::Error const& reason)
|
|
: failureLog_{reason.what()}
|
|
{ }
|
|
|
|
|
|
|
|
bool
|
|
isValid() const
|
|
{
|
|
return isnil (failureLog_);
|
|
}
|
|
|
|
void
|
|
maybeThrow() const
|
|
{
|
|
if (not isValid())
|
|
throw error::State (failureLog_, lumiera_error_peek());
|
|
}
|
|
};
|
|
|
|
|
|
|
|
|
|
} // namespace lib
|
|
#endif
|