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 #include <unistd.h>
  21
  22 #define PAGE_SIZE               sysconf(_SC_PAGE_SIZE)
  23 #define PAGE_MASK               (~(PAGE_SIZE - 1))
  24 #define __ALIGN_MASK(v, mask)   (((v) + (mask)) & ~(mask))
  25 #define ALIGN(v, align)         __ALIGN_MASK(v, (typeof(v)) (align) - 1)
  26 #define PAGE_ALIGN(addr)        ALIGN(addr, PAGE_SIZE)
  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 /* _UST_ALIGN_H */