src/common/align.h

   1 /*
   2  * Copyright (C) 2010-2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   3  *
   4  * SPDX-License-Identifier: MIT
   5  *
   6  */
   7
   8 #ifndef _LTTNG_ALIGN_H
   9 #define _LTTNG_ALIGN_H
  10
  11 #include "bug.h"
  12 #include <unistd.h>
  13 #include <limits.h>
  14
  15 #ifndef PAGE_SIZE       /* Cygwin limits.h defines its own PAGE_SIZE. */
  16 #define PAGE_SIZE               sysconf(_SC_PAGE_SIZE)
  17 #endif
  18
  19
  20 /*
  21  * Align value to the next multiple of align. Returns val if it already is a
  22  * multiple of align. Align must be a power of two.
  23  */
  24 #define __lttng_align_ceil_mask(v, mask)        (((v) + (mask)) & ~(mask))
  25
  26 #define lttng_align_ceil(v, align) \
  27         __lttng_align_ceil_mask(v, (__typeof__(v)) (align) - 1)
  28
  29 /*
  30  * Align value to the previous multiple of align. Returns val if it already is a
  31  * multiple of align. Align must be a power of two.
  32  */
  33 #define __lttng_align_floor_mask(v, mask)       ((v) & ~(mask))
  34
  35 #define lttng_align_floor(v, align) \
  36         __lttng_align_floor_mask(v, (__typeof__(v)) (align) - 1)
  37
  38 /**
  39  * lttng_offset_align - Calculate the offset needed to align an object on its natural
  40  *                alignment towards higher addresses.
  41  * @align_drift:  object offset from an "alignment"-aligned address.
  42  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  43  *
  44  * Returns the offset that must be added to align towards higher
  45  * addresses.
  46  */
  47 #define lttng_offset_align(align_drift, alignment)                                     \
  48         ({                                                                     \
  49                 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0                    \
  50                                    || ((alignment) & ((alignment) - 1)));      \
  51                 (((alignment) - (align_drift)) & ((alignment) - 1));           \
  52         })
  53
  54 /**
  55  * lttng_offset_align_floor - Calculate the offset needed to align an object
  56  *                      on its natural alignment towards lower addresses.
  57  * @align_drift:  object offset from an "alignment"-aligned address.
  58  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  59  *
  60  * Returns the offset that must be substracted to align towards lower addresses.
  61  */
  62 #define lttng_offset_align_floor(align_drift, alignment)                               \
  63         ({                                                                     \
  64                 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0                    \
  65                                    || ((alignment) & ((alignment) - 1)));      \
  66                 (((align_drift) - (alignment)) & ((alignment) - 1));           \
  67         })
  68
  69 #endif /* _LTTNG_ALIGN_H */