Add initial prototype.

3-mid/opengl/private/gid/gid-buffering.ads

@@ -0,0 +1,28 @@
+private package GID.Buffering is
+
+  -- Attach a buffer to a stream.
+  procedure Attach_Stream(
+    b   :    out Input_buffer;
+    stm : in     Stream_Access
+  );
+
+  function Is_stream_attached(b: Input_buffer) return Boolean;
+
+  -- From the first call to Get_Byte, subsequent bytes must be read
+  -- through Get_Byte as well since the stream is partly read in advance
+  procedure Get_Byte(b: in out Input_buffer; byte: out U8);
+  pragma Inline(Get_Byte);
+
+private
+
+  subtype Size_test_a is Byte_Array(1..19);
+  subtype Size_test_b is Ada.Streams.Stream_Element_Array(1..19);
+
+  -- is_mapping_possible: Compile-time test for checking if
+  -- a Byte_Array is equivalemnt to a Ada.Streams.Stream_Element_Array.
+  --
+  is_mapping_possible: constant Boolean:=
+    Size_test_a'Size = Size_test_b'Size and
+    Size_test_a'Alignment = Size_test_b'Alignment;
+
+end GID.Buffering;