On Tue, Sep 5, 2017 at 10:08 PM, Jean-Philippe André <j...@videolan.org> wrote:
> Hi,
>
> 2017-09-05 21:57 GMT+09:00 Gustavo Sverzut Barbieri <barbi...@gmail.com>:
>
>> With eolian one could declare a future using C++ template-like syntax:
>>
>> future<int>
>>
>> That is, a future that provides (resolves to) an integer. With
>> Eina_Value, this will be an Eina_Value->type == EINA_VALUE_TYPE_INT.
>>
>> In some cases, when multiple values are needed, it would be written as:
>>
>> future<int, string>
>>
>> That is, a future that provides both an integer and a string. In the
>> old representation one would only get a "void *value", and would need
>> to do its casts and hope for the best. With Eina_Value, this will be
>> an Eina_Value->type == EINA_VALUE_TYPE_STRUCT, with internal pointer
>> being an Eina_Value_Struct, that contains an Eina_Value_Struct_Desc
>> with the members, memory layout is like:
>>
>> value = (Eina_Value) {
>> .type = EINA_VALUE_TYPE_STRUCT,
>> .value.ptr = &(Eina_Value_Struct){
>> .desc = EINA_VALUE_STRUCT_DESC_MYSTRUCT,
>> .memory = &mystruct,
>> },
>> };
>>
>> Easily accessible with:
>>
>> eina_value_struct_get(value, "member_name", &ret);
>>
>> Or directly (check/get could be made single-line with a helper function):
>>
>> // safety first!
>> if (eina_value_struct_desc_get(&value) == EINA_VALUE_STRUCT_DESC_
>> MYSTRUCT)
>> {
>> Eina_Value_Struct st;
>> eina_value_get(&value, &st);
>> My_Struct *mst = st.memory;
>>
>> mst->member_name; // from here on, no more checks are required
>> }
>>
>> My proposal is to extend eolian syntax to allow named parameters and
>> it would generate the structure, typedef and EINA_VALUE_STRUCT_DESC,
>> all exposed in .eo.h file. Example:
>>
>> future<age: int, name: string>
>>
>> Generates: my_class.eo.h
>>
>> typedef struct _My_Class_Future_Result_Age_Name {
>> int age;
>> char *name;
>> } My_Class_Result_Age_Name;
>>
>> EOAPI const Eina_Value_Struct_Desc
>> *EINA_VALUE_STRUCT_DESC_MY_CLASS_FUTURE_RESULT_AGE_NAME;
>>
>> Generates: my_class.eo.c
>>
>> static /* not const! */ Eina_Value_Struct_Member
>> _EINA_VALUE_STRUCT_MEMBERS_MY_CLASS_FUTURE_RESULT_AGE_NAME[] = {
>> {"age", NULL /* type placeholder */,
>> offsetof(My_Class_Result_Age_Name, age)},
>> {"name", NULL /* type placeholder */,
>> offsetof(My_Class_Result_Age_Name, name)},
>> };
>>
>> static const Eina_Value_Struct_Desc
>> _EINA_VALUE_STRUCT_DESC_MY_CLASS_FUTURE_RESULT_AGE_NAME = {
>> EINA_VALUE_STRUCT_DESC_VERSION,
>> NULL, /* ops */
>> _EINA_VALUE_STRUCT_DESC_MEMBERS_MY_CLASS_FUTURE_RESULT_AGE_NAME,
>> EINA_C_ARRAY_LENGTH(_EINA_VALUE_STRUCT_MEMBERS_MY_CLASS_
>> FUTURE_RESULT_AGE_NAME),
>> sizeof(My_Class_Result_Age_Name),
>> };
>>
>> EOAPI const Eina_Value_Struct_Desc
>> *EINA_VALUE_STRUCT_DESC_MY_CLASS_FUTURE_RESULT_AGE_NAME;
>>
>> // inside class constructor using it:
>> _class_constructor(...) {
>> if (_EINA_VALUE_STRUCT_MEMBERS_MY_CLASS_FUTURE_RESULT_AGE_
>> NAME[0].type
>> == NULL)
>> {
>> _EINA_VALUE_STRUCT_MEMBERS_MY_CLASS_FUTURE_RESULT_AGE_NAME[
>> 0].type
>> = EINA_VALUE_TYPE_INT;
>> _EINA_VALUE_STRUCT_MEMBERS_MY_CLASS_FUTURE_RESULT_AGE_NAME[
>> 1].type
>> = EINA_VALUE_TYPE_STRING;
>> }
>> }
>>
>> The constructor thing is because EINA_VALUE_TYPE_INT and
>> EINA_VALUE_TYPE_STRING are declared in other libraries, thus cannot be
>> resolved at compile-time.
>>
>> Another option is to ignore that from Eolian signature, not allowing
>> structs there -- one could use future<generic_value>. But as you can
>> see, to make proper use of structures one need to type a lot, which
>> could be easily automated by Eolian.
>>
>>
> Can't we just declare the struct in EO and use it inside the future<> ?
> Like:
>
> struct Future_Struct_Value {
> age: int;
> sex: bool;
> }
>
> class Abc {
> methods {
> future_do {
> return: future<Future_Struct_Value>;
> }
> }
> }
Could... everything else would be the same, except the name would be
explicitly defined. works for me.
--
Gustavo Sverzut Barbieri
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