lib/align.h

   1 #ifndef _LTTNG_ALIGN_H
   2 #define _LTTNG_ALIGN_H
   3
   4 /*
   5  * lib/align.h
   6  *
   7  * (C) Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Dual LGPL v2.1/GPL v2 license.
  10  */
  11
  12 #ifdef __KERNEL__
  13
  14 #include <linux/types.h>
  15 #include "bug.h"
  16
  17 #define ALIGN_FLOOR(x, a)       __ALIGN_FLOOR_MASK(x, (typeof(x)) (a) - 1)
  18 #define __ALIGN_FLOOR_MASK(x, mask)     ((x) & ~(mask))
  19 #define PTR_ALIGN_FLOOR(p, a) \
  20                         ((typeof(p)) ALIGN_FLOOR((unsigned long) (p), a))
  21
  22 /*
  23  * Align pointer on natural object alignment.
  24  */
  25 #define object_align(obj)       PTR_ALIGN(obj, __alignof__(*(obj)))
  26 #define object_align_floor(obj) PTR_ALIGN_FLOOR(obj, __alignof__(*(obj)))
  27
  28 /**
  29  * offset_align - Calculate the offset needed to align an object on its natural
  30  *                alignment towards higher addresses.
  31  * @align_drift:  object offset from an "alignment"-aligned address.
  32  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  33  *
  34  * Returns the offset that must be added to align towards higher
  35  * addresses.
  36  */
  37 #define offset_align(align_drift, alignment)                                   \
  38         ({                                                                     \
  39                 BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
  40                                    || ((alignment) & ((alignment) - 1)));      \
  41                 (((alignment) - (align_drift)) & ((alignment) - 1));           \
  42         })
  43
  44 /**
  45  * offset_align_floor - Calculate the offset needed to align an object
  46  *                      on its natural alignment towards lower addresses.
  47  * @align_drift:  object offset from an "alignment"-aligned address.
  48  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  49  *
  50  * Returns the offset that must be substracted to align towards lower addresses.
  51  */
  52 #define offset_align_floor(align_drift, alignment)                             \
  53         ({                                                                     \
  54                 BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
  55                                    || ((alignment) & ((alignment) - 1)));      \
  56                 (((align_drift) - (alignment)) & ((alignment) - 1);            \
  57         })
  58
  59 #endif /* __KERNEL__ */
  60
  61 #endif