writing NON unity data into a rendertexture

OK I'm new to unity but have been writing OpenGL in C++ for years, I've searched the forums but I can't seem to find any answers.
So we are attempting to move legacy OpenGL graphics to a native windows only unity application.
I have created a simple Quad with a rendertexture, now I want to update the texture with externally sourced data, generated by a legacy application that writes a 512x512x4 array of pixel data into a shared memory area.
I have successfully mapped this data to an IntPtr in C# using the windows CreateFileMapping and MapViewOfFile API's, and I know the pixel data is being seen correctly in C#.

The script has the RenderTexture object visible but I cannot see how to update the underlying texture in Unity/C#.

In the Old legacy system I would have used:
glBindTexture(GL_TEXTURE_2D, textureId);

glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, 512, 512, 0, GL_RGBA, GL_UNSIGNED_BYTE, memPtr );

where memPtr is the address of the start of the pixel data, and textureId is the Gl ID returned from GlGenTextures();

Anyone any idea as to where I should look, or if someone know how to do this, some examples please.

 

Thank You,
after some fiddling I have managed to get it to work with the LoadRawTexture example