How to handle the class IBuffer in my interface

Question

Hi: all

I want to write a Ansync ReadData API like the  ReadAsync API of IInputStream,

Windows::Foundation::IAsyncOperationWithProgress<Windows::Storage::Streams::IBuffer^, unsigned int>^ ReadAsync(Windows::Storage::Streams::IBuffer^ buffer, unsigned int count, Windows::Storage::Streams::InputStreamOptions options)

 I want to send the byte data to the caller of this Ansync Read API, But I do not know how to use the parameter "IBuffer^buffer",

Below is my codes of the API :

IAsyncOperationWithProgress<IBuffer^, unsigned int>^ INetworkIORandomAccessStream::ReadAsync(IBuffer^ buffer, unsigned int count, InputStreamOptions options)
{

	return create_async([this](progress_reporter<unsigned int> progress) {
		//How to send the byte data in this case
		//return (IBuffer^)buffer; 
    });

}

Please give me some help . Thanks

Answer 1

Hi Pitt.Chen,

To access the data in the buffer query the IBuffer for its IBufferByteAccess interface.

--Rob

Answer 2

Hello,

We can not return two value in IAsyncOperationWithProgress. You can use int* to get the int return value, and the unsigned int should be uint32 in C++/CX. Please follow these codes:

// In .h file
using namespace Windows::Storage::Streams;
		Windows::Foundation::IAsyncActionWithProgress
<IBuffer^>^ ReadAsync(IBuffer^ buffer, unsigned int count, InputStreamOptions options,int* outcount);



// In .cpp file
using namespace Windows::Foundation;
using namespace Windows::Foundation::Collections;
using namespace Concurrency;

IAsyncActionWithProgress<IBuffer^>^ WinRTComponent::ReadAsync(
IBuffer^ buffer, unsigned int count, InputStreamOptions options, int* outcount)
{
	return create_async([this](progress_reporter<IBuffer^> progress) {
		//How to send the byte data in this case
		//return (IBuffer^)buffer; 
		});
}

Best regards,
Jesse

---

Jesse Jiang [MSFT]
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