mirror of
https://github.com/matrix-construct/construct
synced 2024-11-09 03:21:15 +01:00
68 lines
2.3 KiB
C++
68 lines
2.3 KiB
C++
// Matrix Construct
|
|
//
|
|
// Copyright (C) Matrix Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice is present in all copies. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_CTX_FAULT_H
|
|
|
|
namespace ircd::ctx
|
|
{
|
|
IRCD_EXCEPTION(error, aborted)
|
|
IRCD_EXCEPTION(aborted, unhandled_fault)
|
|
|
|
template<class... args> struct fault;
|
|
}
|
|
|
|
// Faults add the notion of recoverable exceptions. C++ exceptions are not, as
|
|
// they destruct the stack and then clobber everything with the catch branch.
|
|
// A fault is an error handling device alternative to throwing an exception;
|
|
// Hitting a fault may stop the context until the fault is serviced to continue
|
|
// or a real exception is thrown to abort the context.
|
|
//
|
|
// A compelling example is std::bad_alloc, or an out of memory condition. A
|
|
// fault allows other contexts to free up their resources after which the
|
|
// faulty context can continue without having to unwind the work it's already
|
|
// made progress on to try again.
|
|
//
|
|
// Faults begin with the cost of a function call to a handler at the point of
|
|
// the fault. The handler's template specifies the argument list so the fault
|
|
// can safely observe or modify your data. The call to fault has no return
|
|
// value. If it returns the fault has been successfully serviced.
|
|
//
|
|
// Fault handlers must return true to default the faulty context. Handlers are
|
|
// also responsible for detecting if they are executing with an active
|
|
// exception which makes returning false considered a DOUBLE FAULT. This may
|
|
// lead to program termination because it's basically throwing an exception from
|
|
// a destructor (and can be useful proper behavior).
|
|
//
|
|
template<class... args>
|
|
struct ircd::ctx::fault
|
|
{
|
|
using handler = std::function<bool (args&&...)>;
|
|
|
|
handler h;
|
|
|
|
virtual bool handle(args&&... a)
|
|
{
|
|
if(unlikely(!h))
|
|
throw unhandled_fault{};
|
|
|
|
return h(std::forward<args>(a)...);
|
|
}
|
|
|
|
void operator()(args&&... a)
|
|
{
|
|
if(!handle(std::forward<args>(a)...))
|
|
throw aborted{};
|
|
}
|
|
|
|
fault(handler h)
|
|
:h{std::move(h)}
|
|
{}
|
|
};
|