include/lttng/align.h

   1 #ifndef _UST_ALIGN_H
   2 #define _UST_ALIGN_H
   3
   4 /*
   5  * lttng/align.h
   6  *
   7  * (C) Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
  10  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
  11  *
  12  * Permission is hereby granted to use or copy this program
  13  * for any purpose,  provided the above notices are retained on all copies.
  14  * Permission to modify the code and to distribute modified code is granted,
  15  * provided the above notices are retained, and a notice that the code was
  16  * modified is included with the above copyright notice.
  17  */
  18
  19 #include <lttng/bug.h>
  20
  21 /*
  22  * Align pointer on natural object alignment.
  23  */
  24 #define object_align(obj)       PTR_ALIGN(obj, __alignof__(*(obj)))
  25 #define object_align_floor(obj) PTR_ALIGN_FLOOR(obj, __alignof__(*(obj)))
  26
  27 /**
  28  * offset_align - Calculate the offset needed to align an object on its natural
  29  *                alignment towards higher addresses.
  30  * @align_drift:  object offset from an "alignment"-aligned address.
  31  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  32  *
  33  * Returns the offset that must be added to align towards higher
  34  * addresses.
  35  */
  36 #define offset_align(align_drift, alignment)                                   \
  37         ({                                                                     \
  38                 BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
  39                                    || ((alignment) & ((alignment) - 1)));      \
  40                 (((alignment) - (align_drift)) & ((alignment) - 1));           \
  41         })
  42
  43 /**
  44  * offset_align_floor - Calculate the offset needed to align an object
  45  *                      on its natural alignment towards lower addresses.
  46  * @align_drift:  object offset from an "alignment"-aligned address.
  47  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  48  *
  49  * Returns the offset that must be substracted to align towards lower addresses.
  50  */
  51 #define offset_align_floor(align_drift, alignment)                             \
  52         ({                                                                     \
  53                 BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
  54                                    || ((alignment) & ((alignment) - 1)));      \
  55                 (((align_drift) - (alignment)) & ((alignment) - 1);            \
  56         })
  57
  58 #endif /* _UST_ALIGN_H */