Hello Alon & Joel,
I think that c++/js promise is more like syntax sugar, I mean you are
still writing async programs, but the syntax allows you to write in a sync
way, which could be more comfortable. I doubt if
`emscripten_sync_wget2_data` is a simple solution as long as you want a
real sync function in C++, and I'm really interested if you make it works
without an overhaul of other parts of your program.
I also learned a little bit about generators before, I'm not sure if it
will work deep inside the calling chain: For example, if A calls B and B
calls C, where C is a generator, I doubt if it is possible for A to control
(pause/resume) B & C, without letting B be aware of it. If this is not
possible, it might be necessary to rewrite all the functions to handle
generator pause/resume events, so essentially we are still writing async
C++.
No matter what library/syntax you are using, async C++ can always be
translated with emscripten out-of-the-box, but it might be better to use
the JS engine instead of a separate event loop implemented in C++ -- maybe
this is what you meant in `emscripten_sync_wget2_data`?
On the other hand, if you want a real sync C++ which is then magically
transformed into async JS, AFAIK one possible solution is to mark async
function in JS, then transform it using streamline.js or similar tools,
this is what I have done with vim.js. But it's too hacky, and might not
work well with the optimization phases in emscripten (reloop, ASM.js etc),
so it might not be worth it for a large project.
Hopefully we will have an elegant and effective solution after the
summer.
regards,
- Lu
On Sunday, March 16, 2014 4:43:40 PM UTC+8, Joel Croteau wrote:
>
> I would like to have a function that makes an async call, and returns
> control to the browser during the call, then resumes once the async call is
> complete. However, I would like this to appear to the calling code to be a
> synchronous call. So for instance, I could do something like this:
>
> struct FileInfo
> {
> void* buffer;
> unsigned size;
> };
>
> FileInfo loadUrl(const char* url)
> {
> FileInfo info;
> emscripten_async_wget2_data(url, "GET", "", &info, false, onload,
> onerror, onprogress);
> emscripten_pause(); // Blocks until emscripten_resume() is called
> return info;
> }
>
> void onerror(void* ptr, int code, const char* desc)
> {
> // Handle not found, etc.
> }
>
> void onprogress(void* ptr, int loaded, int total)
> {
> // Update progress bar
> }
>
> void onload(void* ptr, void* buffer, unsigned size)
> {
> static_cast<FileInfo*>(ptr)->buffer = buffer;
> static_cast<FileInfo*>(ptr)->size = size;
>
> emscripten_resume(); // Now loadUrl resumes and returns FileInfo.
> }
>
> Is there any way to do this?
>
--
You received this message because you are subscribed to the Google Groups
"emscripten-discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
