So now what I understood is, `Emterpreter.handle` should occupy the whole
function, or other parts might be execute twice?
For example:
function f() {
do_something();
EmterpreterAsync.handle(..);
do_something_else();
}
Then both do_something/do_something_else might be called twice (unexpected).
Further, if C code calls a 'nested' EmterpreterAsync.handle, like this
func_in_C -> func1_in_js -> ... -> funcN_in_js -> EmterpreterAsync.handle,
so everything in the chain will be called twice, as EmterpreterAsync only
interprets the C code. Am I right?
On Monday, April 13, 2015 at 7:06:00 AM UTC+8, Alon Zakai wrote:
>
> Yes, and resume occurs in fact before you reach the end of that method, on
> the *second* time it is called, when it is restarted. So if you save the
> return value somewhere, you can just return it there. But, this is
> confusing.
>
> So we should have a proper API for this. I implemented one in
>
>
> https://github.com/kripken/emscripten/commit/d80417c665dd45e1893cb85aa8523efe57c7d58c
>
> , see the testcase there. The resume() function has a post argument, which
> runs right after the stack was recreated and we are about to finish the
> async operation. That means it is right before the async-causing function
> exits, so it is a proper time to return a value. I made it so return values
> from that post will be returned. Note that you need to return
> EmterpreterAsync.handle() for that to work, as in the testcase in that
> commit.
>
> - Alon
>
>
> On Fri, Apr 10, 2015 at 8:37 PM, 王璐 <[email protected] <javascript:>>
> wrote:
>
>> Did you mean something like this?
>>
>> EmterpreterAsync.handle(...);
>> return something;
>>
>>
>> But the return value might not be available until the callback, e.g. to
>> get a key input, so I need to set the return value in `resume`.
>>
>>
>>
>> regards,
>> - Lu
>>
>> On Saturday, April 11, 2015 at 5:07:37 AM UTC+8, Alon Zakai wrote:
>>>
>>> I think if you add a return in g - outside of the handle() call - it
>>> will just be returned. It will however be returned both the first time when
>>> called (and starting to unwind the stack) and the second time when
>>> restarted (after reconstructing the stack). You could tell which of those
>>> you are in using EmterpreterAsync.state. Might be nicer to add an API for
>>> that.
>>>
>>> - Alon
>>>
>>>
>>> On Fri, Apr 10, 2015 at 3:47 AM, Lu Wang <[email protected]> wrote:
>>>
>>>> Hi all,
>>>>
>>>> Is there a way to return something from an async function with
>>>> emterpreter? For example:
>>>>
>>>> ///main.c
>>>> void f() {
>>>> printf("%d\n", g());
>>>> }
>>>>
>>>> ///main.js
>>>> function g() {
>>>> EmterpreterAsync.handle(function(resume) {
>>>> setTimeout(function() {
>>>> resume(return_value); // ???
>>>> }, 1000);
>>>> });
>>>> }
>>>>
>>>>
>>>> I saw that `resume` already takes a few parameters, so maybe we
>>>> cannot simply do so. Currently the closet way is to write the return value
>>>> into some memory address, but it would be better if the return value can
>>>> be
>>>> passed directly to the C code.
>>>>
>>>>
>>>> regards,
>>>> - Lu
>>>>
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>>>
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