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 #ifndef PAGE_MASK       /* macOS defines its own PAGE_MASK. */
  29 #define PAGE_MASK               (~(PAGE_SIZE - 1))
  30 #endif
  31
  32 #define __ALIGN_MASK(v, mask)   (((v) + (mask)) & ~(mask))
  33
  34 #ifndef ALIGN           /* macOS defines its own ALIGN. */
  35 #define ALIGN(v, align)         __ALIGN_MASK(v, (__typeof__(v)) (align) - 1)
  36 #endif
  37
  38 #define PAGE_ALIGN(addr)        ALIGN(addr, PAGE_SIZE)
  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                 LTTNG_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                 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0                    \
  67                                    || ((alignment) & ((alignment) - 1)));      \
  68                 (((align_drift) - (alignment)) & ((alignment) - 1));           \
  69         })
  70
  71 #endif /* _LTTNG_ALIGN_H */