I managed to resolve this by replacing the global.WebAssembly object with a
Proxy which intercepts the "compile" and "instantiate" methods. When one of
those methods is called I start a background thread which is polling the
main looper at regular intervals, pumps the message loop and executes any
pending microtasks. When the method completes, the background thread is
destroyed.
On Sunday, January 19, 2020 at 12:40:23 AM UTC+2, ibon wrote:
>
> Hi Darin,
>
> I do embed v8 on android on a regular basis.
> Unlike you, I run v8 bound to gl thread, and as a rule of thumb for
> performance reasons always on a different than the main thread.
> I need to, at least, run `v8::platform::PumpMessageLoop(&platform,
> isolate_);` to have promises executed.
> In my case, this is executed consistently once every gl thread tick, 60
> times a sec.
>
> Your webassembly example, throws this btw: "TypeError:
> WebAssembly.instantiate(): Imports argument must be present and must be an
> object"
>
> Hope that helps.
>
>
> El viernes, 17 de enero de 2020, 16:29:12 (UTC+1), Darin Dimitrov escribió:
>>
>> Thanks Clemens. I would be very happy if someone more familiar could
>> provide some insight.
>>
>> Any pointers in the Google Chrome source code for Android would also be
>> helpful. I suppose they have already faced this problem and implemented it
>> properly.
>>
>>
>> On Thursday, January 16, 2020 at 3:41:22 PM UTC+2, Clemens Backes wrote:
>>>
>>> On Thu, Jan 16, 2020 at 2:23 PM Darin Dimitrov <darin....@gmail.com>
>>> wrote:
>>>
>>>> Thanks Clemens.
>>>>
>>>> This works fine but it blocks the main thread. What would be the best
>>>> approach to handle this in an Android app? Would writing a custom platform
>>>> help in this case?
>>>>
>>>
>>> I don't know about Android development, and I am not a platform expert,
>>> so maybe others can chime in.
>>> I guess that your own platform implementation would help because you
>>> would get notified of new tasks that get scheduled.
>>>
>>> On Wednesday, January 15, 2020 at 5:12:39 PM UTC+2, Clemens Hammacher
>>>> wrote:
>>>>>
>>>>> Hi Darin,
>>>>>
>>>>> WebAssembly.instantiate works asynchronously, so you have to keep
>>>>> your program running for a while to wait for the asynchronous result, and
>>>>> keep pumping the message loop and running microtasks to actually execute
>>>>> the compilation tasks and promise resolution tasks that get added from
>>>>> the
>>>>> background.
>>>>>
>>>>
>>>>>
>>>>> This is probably not the most elegant solution, but it works:
>>>>> [...]
>>>>> script->Run(context).ToLocal(&result);
>>>>> // Keep running for 10 seconds, pumping the message loop and running
>>>>> // microtasks.
>>>>> auto start = std::chrono::system_clock::now();
>>>>> do {
>>>>> v8::platform::PumpMessageLoop(platform.get(), isolate);
>>>>> isolate->RunMicrotasks();
>>>>> } while (std::chrono::duration_cast<std::chrono::seconds>(
>>>>> std::chrono::system_clock::now() - start)
>>>>> .count() < 10);
>>>>>
>>>>> Hope that helps,
>>>>> Clemens
>>>>>
>>>>>
>>>>> On Wed, Jan 15, 2020 at 9:15 AM Darin Dimitrov <darin....@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> I have embedded V8 (7.8.279.19) inside my Android application and
>>>>>> tried executing a script that compiles a WebAssembly module.
>>>>>>
>>>>>> Unfortunately the promise returned by the "WebAssembly.compile"
>>>>>> method is never completed (neither the "then" or the "catch" methods are
>>>>>> invoked). The same happens with the "WebAssembly.instantiate" method:
>>>>>>
>>>>>> std::unique_ptr<v8::Platform> platform = v8::platform::
>>>>>> NewDefaultPlatform();
>>>>>> v8::V8::InitializePlatform(platform.get());
>>>>>> v8::V8::Initialize();
>>>>>>
>>>>>> v8::Isolate::CreateParams create_params;
>>>>>> create_params.array_buffer_allocator = v8::ArrayBuffer::Allocator::
>>>>>> NewDefaultAllocator();
>>>>>> v8::Isolate* isolate = v8::Isolate::New(create_params);
>>>>>> v8::Isolate::Scope isolate_scope(isolate);
>>>>>> v8::HandleScope scope(isolate);
>>>>>> auto global_template = v8::ObjectTemplate::New(isolate);
>>>>>> global_template->Set(v8::String::NewFromUtf8(isolate, "log", v8::
>>>>>> NewStringType::kNormal).ToLocalChecked(), v8::FunctionTemplate::New(
>>>>>> isolate, [](const v8::FunctionCallbackInfo<v8::Value>& info) {
>>>>>> v8::Isolate* isolate = info.GetIsolate();
>>>>>> v8::String::Utf8Value utf(isolate, info[0].As<v8::String>());
>>>>>> __android_log_print(ANDROID_LOG_DEBUG, "V8Native", "%s",*utf);
>>>>>> }));
>>>>>>
>>>>>> v8::Local<v8::Context> context = v8::Context::New(isolate, nullptr,
>>>>>> global_template);
>>>>>> v8::Context::Scope context_scope(context);
>>>>>> const char* csource = R"(
>>>>>> let bytes = new Uint8Array([
>>>>>> 0,97,115,109,1,0,0,0,1,8,2,96,1,127,0,96,0,0,2,8,1,2,106,
>>>>>> 115,1,95,0,0,3,2,1,1,8,1,1,10,9,1,7,0,65,185,10,16,0,11
>>>>>> ]);
>>>>>> log('before the call');
>>>>>> WebAssembly
>>>>>> .instantiate(bytes)
>>>>>> .then(obj => log('success'))
>>>>>> .catch(err => log('log'));
>>>>>> )";
>>>>>> v8::Local<v8::String> source = v8::String::NewFromUtf8(isolate,
>>>>>> csource, v8::NewStringType::kNormal).ToLocalChecked();
>>>>>> v8::Local<v8::Script> script = v8::Script::Compile(context, source).
>>>>>> ToLocalChecked();
>>>>>> v8::Local<v8::Value> result;
>>>>>> script->Run(context).ToLocal(&result);
>>>>>>
>>>>>>
>>>>>>
>>>>>> Do you have any idea what I might be missing here? The same javascript
>>>>>> code works fine in the desktop browser.
>>>>>>
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>>>>>> .
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>> Clemens Backes
>>>>>
>>>>> Software Engineer
>>>>>
>>>>> clem...@google.com
>>>>>
>>>>>
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>>>> .
>>>>
>>>
>>> --
>>>
>>> Clemens Backes
>>>
>>> Software Engineer
>>>
>>> clem...@google.com
>>>
>>>
>>> Google Germany GmbH
>>>
>>> Erika-Mann-Straße 33
>>>
>>> 80636 München
>>>
>>> Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
>>>
>>> Registergericht und -nummer: Hamburg, HRB 86891
>>>
>>> Sitz der Gesellschaft: Hamburg
>>>
>>> Diese E-Mail ist vertraulich. Falls sie diese fälschlicherweise erhalten
>>> haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter,
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>>> dass die E-Mail an die falsche Person gesendet wurde.
>>>
>>>
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>>> and attachments, and please let me know that it has gone to the wrong
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>>>
>>>
>>>
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