[Vala] gio: how to read N bytes into a buffer at offset M?

[Matto Marjanovic <maddog mir com>]

Hi,

The subject line explains what I am trying to do.  In plain old C,
I would simply use plain old libgio:

   GInputStream* s = ...;
   guint8 buffer[4096];
   GError* error = NULL;
   ...
   g_input_stream_read(s, buffer + M, N, NULL, &error);

How do I do this in Vala?

The 0.12 GIO bindings seemed to allow this, since read() and related methods
took a 'string' buffer parameter and a separate 'size_t' count parameter.

The 0.14 bindings, however, only all take a uint8[] parameter, and magically
derive the read size from the (full) array size.  Is there some other magic
syntax I am supposed to use to access to the functionality of the underlying
C API?

-m