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?
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
> <javascript:>> 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 <javascript:>
>
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