Getting an array of bytes out of Windows::Storage::Streams::IBuffer

Question

I have an object that implements the interface Windows::Storage::Streams::IBuffer, and I want to get an array of bytes out of it, however while looking at the d

Answer 1

Use the extension method like a static method:

IBuffer *buffer;
array<unsigned char>^ result= System::Runtime::InteropServices::WindowsRuntime::WindowsRuntimeBufferExtensions::ToArray(buffer);

Answer 2

This is a C++/CX version:

std::vector<unsigned char> getData( ::Windows::Storage::Streams::IBuffer^ buf )
{
    auto reader = ::Windows::Storage::Streams::DataReader::FromBuffer(buf);

    std::vector<unsigned char> data(reader->UnconsumedBufferLength);

    if ( !data.empty() )
        reader->ReadBytes(
            ::Platform::ArrayReference<unsigned char>(
                &data[0], data.size()));

    return data;
}

For more information see Array and WriteOnlyArray (C++/CX).

Answer 3

Also check this method:

IBuffer -> Platform::Array
CryptographicBuffer.CopyToByteArray

Platform::Array -> IBuffer
CryptographicBuffer.CreateFromByteArray

As a side note, if you want to create Platform::Array from simple C++ array you could use Platform::ArrayReference, for example:

char* c = "sdsd";
Platform::ArrayReference<unsigned char> arraywrapper((unsigned char*) c, sizeof(c));

Answer 4

You can use IBufferByteAccess, through exotic COM casts:

byte* GetPointerToPixelData(IBuffer^ buffer)
{
   // Cast to Object^, then to its underlying IInspectable interface.

   Object^ obj = buffer;
   ComPtr<IInspectable> insp(reinterpret_cast<IInspectable*>(obj));

   // Query the IBufferByteAccess interface.
   ComPtr<IBufferByteAccess> bufferByteAccess;
   ThrowIfFailed(insp.As(&bufferByteAccess));

   // Retrieve the buffer data.

   byte* pixels = nullptr;
   ThrowIfFailed(bufferByteAccess->Buffer(&pixels));

   return pixels;

}

Code sample copied from http://cm-bloggers.blogspot.fi/2012/09/accessing-image-pixel-data-in-ccx.html

Answer 5

This should work with WinRT extensions:

// Windows::Storage::Streams::DataReader
// buffer is assumed to be of type Windows::Storage::Streams::IBuffer
// BYTE = unsigned char

DataReader^ reader = DataReader::FromBuffer(buffer);

BYTE *extracted = new BYTE[buffer->Length];

// NOTE: This will read directly into the allocated "extracted" buffer
reader->ReadBytes(Platform::ArrayReference<BYTE>(extracted, buffer->Length));

// ... do something with extracted...

delete [] extracted; // don't forget to free the space

Answer 6

Since this question is tagged c++, here's a solution using C++/WinRT. It essentially does the same as this answer under the hood, but is way more accessible. The (undocumented) data() helper on the IBuffer projection does all the heavy lifting:

uint8_t* GetPointerToPixelData(::winrt::Windows::Storage::Streams::IBuffer const& buffer)
{
    return buffer.data();
}

There is unfortunately no official documentation (yet), and I only stumbled across this in the sample code for the WritableBitmap.PixelBuffer property (make sure to select "C++/WinRT" from the language dropdown at the top right).

An identical solution (querying for the IBufferByteAccess interface) is also available from that documentation entry when selecting "C++/CX" from the language dropdown.