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Support Error parameter in signal handlers

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This commit is contained in:
Stanislav Angelovic
2021-07-22 15:48:50 +02:00
committed by Stanislav Angelovič
parent d77bb6b869
commit c422de641a
3 changed files with 41 additions and 4 deletions
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31
include/sdbus-c++/ConvenienceApiClasses.inl
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@ -640,11 +640,34 @@ namespace sdbus {
// as a storage for the argument values deserialized from the signal message.
tuple_of_function_input_arg_types_t<_Function> signalArgs;
// Deserialize input arguments from the signal message into the tuple
signal >> signalArgs;
// The signal handler can take pure signal parameters only, or an additional `const Error*` as its first
// parameter. In the former case, if the deserialization fails (e.g. due to signature mismatch),
// the failure is ignored (and signal simply dropped). In the latter case, the deserialization failure
// will be communicated as a non-zero Error pointer to the client's signal handler.
if constexpr (has_error_param_v<_Function>)
{
// Deserialize input arguments from the signal message into the tuple
try
{
signal >> signalArgs;
}
catch (const sdbus::Error& e)
{
// Invoke callback with error argument and input arguments from the tuple.
sdbus::apply(callback, &e, signalArgs);
}
// Invoke callback with input arguments from the tuple.
sdbus::apply(callback, signalArgs);
// Invoke callback with no error and input arguments from the tuple.
sdbus::apply(callback, nullptr, signalArgs);
}
else
{
// Deserialize input arguments from the signal message into the tuple
signal >> signalArgs;
// Invoke callback with input arguments from the tuple.
sdbus::apply(callback, signalArgs);
}
});
}

5
include/sdbus-c++/TypeTraits.h
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@ -378,12 +378,14 @@ namespace sdbus {
: public function_traits_base<_ReturnType, _Args...>
{
static constexpr bool is_async = false;
static constexpr bool has_error_param = false;
};
template <typename... _Args>
struct function_traits<void(const Error*, _Args...)>
: public function_traits_base<void, _Args...>
{
static constexpr bool has_error_param = true;
};
template <typename... _Args, typename... _Results>
@ -443,6 +445,9 @@ namespace sdbus {
template <class _Function>
constexpr auto is_async_method_v = function_traits<_Function>::is_async;
template <class _Function>
constexpr auto has_error_param_v = function_traits<_Function>::has_error_param;
template <typename _FunctionType>
using function_arguments_t = typename function_traits<_FunctionType>::arguments_type;