libusbgx: Add offsetof() and container_of() macros

Add some macros which are widely used in linux
kernel and may be useful also in this library.

Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Reviewed-by: Pawel Szewczyk <p.szewczyk@samsung.com>

diff --git a/include/usbg/usbg_internal.h b/include/usbg/usbg_internal.h
index dbbd0dd..793319c 100644 (file)
--- a/include/usbg/usbg_internal.h
+++ b/include/usbg/usbg_internal.h
@@ -28,6 +28,16 @@
  * @file include/usbg/usbg_internal.h
  */
 
+#ifndef offsetof
+#define offsetof(type, member)  __builtin_offsetof (type, member)
+#endif /* offsetof */
+
+#ifndef container_of
+#define container_of(ptr, type, field) ({                               \
+                        const typeof(((type *)0)->field) *member = (ptr); \
+                        (type *)( (char *)member - offsetof(type, field) ); \
+                })
+#endif /* container_of */
 
 struct usbg_state
 {