align.h: Implement ALIGN_FLOOR macro
[lttng-tools.git] / 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 __ALIGN_FLOOR_MASK(v, mask) ((v) & ~(mask))
39
40 #ifndef ALIGN_FLOOR
41 #define ALIGN_FLOOR(v, align) __ALIGN_FLOOR_MASK(v, (__typeof__(v)) (align) - 1)
42 #endif
43
44 #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
45
46 /**
47 * offset_align - Calculate the offset needed to align an object on its natural
48 * alignment towards higher addresses.
49 * @align_drift: object offset from an "alignment"-aligned address.
50 * @alignment: natural object alignment. Must be non-zero, power of 2.
51 *
52 * Returns the offset that must be added to align towards higher
53 * addresses.
54 */
55 #define offset_align(align_drift, alignment) \
56 ({ \
57 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0 \
58 || ((alignment) & ((alignment) - 1))); \
59 (((alignment) - (align_drift)) & ((alignment) - 1)); \
60 })
61
62 /**
63 * offset_align_floor - Calculate the offset needed to align an object
64 * on its natural alignment towards lower addresses.
65 * @align_drift: object offset from an "alignment"-aligned address.
66 * @alignment: natural object alignment. Must be non-zero, power of 2.
67 *
68 * Returns the offset that must be substracted to align towards lower addresses.
69 */
70 #define offset_align_floor(align_drift, alignment) \
71 ({ \
72 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0 \
73 || ((alignment) & ((alignment) - 1))); \
74 (((align_drift) - (alignment)) & ((alignment) - 1)); \
75 })
76
77 #endif /* _LTTNG_ALIGN_H */
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