+struct gl_client_array;
+struct gl_context;
+
+/**
+ * Returns a pointer to the vertex attribute data in a client array,
+ * or the offset into the vertex buffer for an array that resides in
+ * a vertex buffer.
+ */
+static inline const GLubyte *
+_mesa_vertex_attrib_address(const struct gl_vertex_attrib_array *array,
+ const struct gl_vertex_buffer_binding *binding)
+{
+ if (_mesa_is_bufferobj(binding->BufferObj))
+ return (const GLubyte *) (binding->Offset + array->RelativeOffset);
+ else
+ return array->Ptr;
+}
+
+/**
+ * Sets the fields in a gl_client_array to values derived from a
+ * gl_vertex_attrib_array and a gl_vertex_buffer_binding.
+ */
+static inline void
+_mesa_update_client_array(struct gl_context *ctx,
+ struct gl_client_array *dst,
+ const struct gl_vertex_attrib_array *src,
+ const struct gl_vertex_buffer_binding *binding)
+{
+ dst->Size = src->Size;
+ dst->Type = src->Type;
+ dst->Format = src->Format;
+ dst->Stride = src->Stride;
+ dst->StrideB = binding->Stride;
+ dst->Ptr = _mesa_vertex_attrib_address(src, binding);
+ dst->Enabled = src->Enabled;
+ dst->Normalized = src->Normalized;
+ dst->Integer = src->Integer;
+ dst->InstanceDivisor = binding->InstanceDivisor;
+ dst->_ElementSize = src->_ElementSize;
+ _mesa_reference_buffer_object(ctx, &dst->BufferObj, binding->BufferObj);
+}
+
+static inline bool
+_mesa_attr_zero_aliases_vertex(struct gl_context *ctx)
+{
+ const bool is_forward_compatible_context =
+ ctx->Const.ContextFlags & GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT;
+
+ /* In OpenGL 3.1 attribute 0 becomes non-magic, just like in OpenGL ES
+ * 2.0. Note that we cannot just check for API_OPENGL_COMPAT here because
+ * that will erroneously allow this usage in a 3.0 forward-compatible
+ * context too.
+ */
+ return (ctx->API == API_OPENGLES
+ || (ctx->API == API_OPENGL_COMPAT
+ && !is_forward_compatible_context));
+}