lib/align.h

   1 #ifndef _LTTNG_ALIGN_H
   2 #define _LTTNG_ALIGN_H
   3
   4 /*
   5  * lib/align.h
   6  *
   7  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; only
  12  * version 2.1 of the License.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #ifdef __KERNEL__
  25
  26 #include <linux/types.h>
  27 #include "bug.h"
  28
  29 #define ALIGN_FLOOR(x, a)       __ALIGN_FLOOR_MASK(x, (typeof(x)) (a) - 1)
  30 #define __ALIGN_FLOOR_MASK(x, mask)     ((x) & ~(mask))
  31 #define PTR_ALIGN_FLOOR(p, a) \
  32                         ((typeof(p)) ALIGN_FLOOR((unsigned long) (p), a))
  33
  34 /*
  35  * Align pointer on natural object alignment.
  36  */
  37 #define object_align(obj)       PTR_ALIGN(obj, __alignof__(*(obj)))
  38 #define object_align_floor(obj) PTR_ALIGN_FLOOR(obj, __alignof__(*(obj)))
  39
  40 /**
  41  * offset_align - Calculate the offset needed to align an object on its natural
  42  *                alignment towards higher addresses.
  43  * @align_drift:  object offset from an "alignment"-aligned address.
  44  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  45  *
  46  * Returns the offset that must be added to align towards higher
  47  * addresses.
  48  */
  49 #define offset_align(align_drift, alignment)                                   \
  50         ({                                                                     \
  51                 BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
  52                                    || ((alignment) & ((alignment) - 1)));      \
  53                 (((alignment) - (align_drift)) & ((alignment) - 1));           \
  54         })
  55
  56 /**
  57  * offset_align_floor - Calculate the offset needed to align an object
  58  *                      on its natural alignment towards lower addresses.
  59  * @align_drift:  object offset from an "alignment"-aligned address.
  60  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  61  *
  62  * Returns the offset that must be substracted to align towards lower addresses.
  63  */
  64 #define offset_align_floor(align_drift, alignment)                             \
  65         ({                                                                     \
  66                 BUILD_RUNTIME_BUG_ON((alignment) == 0                          \
  67                                    || ((alignment) & ((alignment) - 1)));      \
  68                 (((align_drift) - (alignment)) & ((alignment) - 1));           \
  69         })
  70
  71 #endif /* __KERNEL__ */
  72
  73 #endif