src/common/align.h

   1 #ifndef _LTTNG_ALIGN_H
   2 #define _LTTNG_ALIGN_H
   3
   4 /*
   5  * align.h
   6  *
   7  * (C) Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a copy
  10  * of this software and associated documentation files (the "Software"), to deal
  11  * in the Software without restriction, including without limitation the rights
  12  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13  * copies of the Software, and to permit persons to whom the Software is
  14  * furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included in
  17  * all copies or substantial portions of the Software.
  18  */
  19
  20 #include "bug.h"
  21 #include <unistd.h>
  22 #include <limits.h>
  23
  24 #ifndef PAGE_SIZE       /* Cygwin limits.h defines its own PAGE_SIZE */
  25 #define PAGE_SIZE               sysconf(_SC_PAGE_SIZE)
  26 #endif
  27
  28 #define PAGE_MASK               (~(PAGE_SIZE - 1))
  29 #define __ALIGN_MASK(v, mask)   (((v) + (mask)) & ~(mask))
  30 #define ALIGN(v, align)         __ALIGN_MASK(v, (__typeof__(v)) (align) - 1)
  31 #define PAGE_ALIGN(addr)        ALIGN(addr, PAGE_SIZE)
  32
  33 /**
  34  * offset_align - Calculate the offset needed to align an object on its natural
  35  *                alignment towards higher addresses.
  36  * @align_drift:  object offset from an "alignment"-aligned address.
  37  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  38  *
  39  * Returns the offset that must be added to align towards higher
  40  * addresses.
  41  */
  42 #define offset_align(align_drift, alignment)                                   \
  43         ({                                                                     \
  44                 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0                    \
  45                                    || ((alignment) & ((alignment) - 1)));      \
  46                 (((alignment) - (align_drift)) & ((alignment) - 1));           \
  47         })
  48
  49 /**
  50  * offset_align_floor - Calculate the offset needed to align an object
  51  *                      on its natural alignment towards lower addresses.
  52  * @align_drift:  object offset from an "alignment"-aligned address.
  53  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  54  *
  55  * Returns the offset that must be substracted to align towards lower addresses.
  56  */
  57 #define offset_align_floor(align_drift, alignment)                             \
  58         ({                                                                     \
  59                 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0                    \
  60                                    || ((alignment) & ((alignment) - 1)));      \
  61                 (((align_drift) - (alignment)) & ((alignment) - 1));           \
  62         })
  63
  64 #endif /* _LTTNG_ALIGN_H */