On Thu, Jan 16, 2020 at 2:23 PM Darin Dimitrov <darin.dimit...@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
cleme...@google.com
Google Germany GmbH
Erika-Mann-Straße 33
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