Thanks for the tips
I agree regarding upgrading from 3.28, unfortunately for the time being I'm
stuck with it as a consequence of various trade offs (I'm using JXcore
which is built on 3.28 and I can't migrate away because of time constraints)
I'm trying the externalize + weak persistent handle method, here's my code
now
//weak callback, frees the raw data and handle
void ArrayBufferWeakCallback(const v8::WeakCallbackData<v8::ArrayBuffer, v8
::Persistent<v8::ArrayBuffer>>& info){
Print::Debug("ArrayBufferWeakCallback fired");
void* rawData = info.GetValue()->GetIndexedPropertiesExternalArrayData();
info.GetValue().Clear();
info.GetParameter()->Reset();
free(rawData);
free(info.GetParameter());
}
//...
v8::Local<v8::ArrayBufferView> bufferView = dataArg.As<v8::ArrayBufferView
>();
size_t byteLength = bufferView->ByteLength();
size_t byteOffset = bufferView->ByteOffset();
bufferView->Buffer()->Externalize();
//create weak persistent handle with callback to above code
v8::Persistent<v8::ArrayBuffer>* persistent = new v8::Persistent<v8::
ArrayBuffer>();
persistent->Reset(isolate, buffer);
persistent->SetWeak<v8::Persistent<v8::ArrayBuffer>>(persistent,
ArrayBufferWeakCallback);
const void* rawData = bufferView->GetIndexedPropertiesExternalArrayData();
const unsigned char* bytePtr = static_cast<const unsigned char*>(rawData);
glBufferData(target, byteLength, bytePtr + byteOffset, usage);
REPORT_GL_ERRORS();
The callback seems to fire as expected and there's no segfaults so I think
this might be the solution! Could you have a quick read to see I'm not
setting myself up for failure by rolling this approach out across my code?
Many thanks,
George
On Monday, February 22, 2016 at 7:59:15 AM UTC, Jochen Eisinger wrote:
>
> Please note that 3.28 is a really old version of V8 which is full of known
> issues and no longer maintained.
>
> In general, you'll wait to externalize the buffer and keep a weak
> persistent handle to the buffer - once the weak callback was triggered, you
> know that you can free the backing store (if you no longer need it
> otherwise).
>
> More current versions of V8 also have a method
> ArrayBufferView::CopyContents that allows you to access the backing store
> without externalizing the underlying buffer.
>
> On Sun, Feb 21, 2016 at 11:27 PM George Corney <[email protected]
> <javascript:>> wrote:
>
>> Hello,
>>
>> I'm working with typed arrays in v8 3.28, I've got a native function that
>> takes a Float32Array from javascript and passes the float* data off to a gl
>> call (glBufferData).
>>
>> I discovered that using just
>> const void* rawData = bufferView->GetIndexedPropertiesExternalArrayData
>> ();
>> works, but not reliably, the data gets passes to glBufferData correctly
>> most of the time, but not always!
>>
>> I've found creating a persistent handle before getting the data pointer,
>> and then reseting handle after the glBufferData solves the problem, but is
>> it the right approach? Am I leaking memory / risking sending incorrect data
>> to glBufferData? Here's the snippet
>>
>> v8::Local<v8::ArrayBufferView> bufferView =
>> dataArg.As<v8::ArrayBufferView>();
>> size_t byteLength = bufferView->ByteLength();
>> size_t byteOffset = bufferView->ByteOffset();
>>
>> v8::Persistent<v8::ArrayBuffer> persistent;
>> persistent.Reset(__contextORisolate, bufferView->Buffer());
>>
>> const void* rawData = bufferView->GetIndexedPropertiesExternalArrayData();
>> const unsigned char* bytePtr = static_cast<const unsigned char*>(rawData);
>>
>> glBufferData(target, byteLength, bytePtr + byteOffset, usage);
>> REPORT_GL_ERRORS();
>>
>> persistent.Reset();
>>
>>
>> -------
>>
>> If this the wrong approach, I think the next thing is to use
>> bufferView->Buffer()->Externalize();
>> before getting the data pointer. In this case I'm then responsible for
>> freeing the data - If this is necessary, could you explain how to do this?
>> Can it be done without altering the ArrayBufferAllocator?
>>
>>
>> Many thanks!
>> George Corney
>>
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