- obj->Pointer = pipe_buffer_map_range(pipe->screen, st_obj->buffer, offset, length, flags);
+ /*
+ * We go out of way here to hide the degenerate yet valid case of zero
+ * length range from the pipe driver.
+ */
+ if (!length) {
+ obj->Pointer = &st_bufferobj_zero_length_range;
+ }
+ else {
+ obj->Pointer = pipe_buffer_map_range(pipe->screen, st_obj->buffer, offset, length, flags);
+ if (obj->Pointer) {
+ obj->Pointer = (ubyte *) obj->Pointer + offset;
+ }
+ }
+