c42cddd5050ca163a612e9f1744f9b7aaf03da5b
[lttng-tools.git] / src / common / macros.h
1 /*
2 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
3 * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License, version 2 only,
7 * as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 *
14 * You should have received a copy of the GNU General Public License along
15 * with this program; if not, write to the Free Software Foundation, Inc.,
16 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
17 */
18
19 #ifndef _MACROS_H
20 #define _MACROS_H
21
22 #include <stdlib.h>
23 #include <stddef.h>
24 #include <string.h>
25 #include <common/compat/string.h>
26
27 /*
28 * Takes a pointer x and transform it so we can use it to access members
29 * without a function call. Here an example:
30 *
31 * #define GET_SIZE(x) LTTNG_REF(x)->size
32 *
33 * struct { int size; } s;
34 *
35 * printf("size : %d\n", GET_SIZE(&s));
36 *
37 * For this example we can't use something like this for compatibility purpose
38 * since this will fail:
39 *
40 * #define GET_SIZE(x) x->size;
41 *
42 * This is mostly use for the compatibility layer of lttng-tools. See
43 * poll/epoll for a good example. Since x can be on the stack or allocated
44 * memory using malloc(), we must use generic accessors for compat in order to
45 * *not* use a function to access members and not the variable name.
46 */
47 #define LTTNG_REF(x) ((typeof(*x) *)(x))
48
49 /*
50 * Memory allocation zeroed
51 */
52 static inline
53 void *zmalloc(size_t len)
54 {
55 return calloc(1, len);
56 }
57
58 #ifndef ARRAY_SIZE
59 #define ARRAY_SIZE(array) (sizeof(array) / (sizeof((array)[0])))
60 #endif
61
62 #ifndef container_of
63 #define container_of(ptr, type, member) \
64 ({ \
65 const typeof(((type *)NULL)->member) * __ptr = (ptr); \
66 (type *)((char *)__ptr - offsetof(type, member)); \
67 })
68 #endif
69
70 #ifndef max
71 #define max(a, b) ((a) > (b) ? (a) : (b))
72 #endif
73
74 #ifndef max_t
75 #define max_t(type, a, b) ((type) max(a, b))
76 #endif
77
78 #ifndef min
79 #define min(a, b) ((a) < (b) ? (a) : (b))
80 #endif
81
82 #ifndef min_t
83 #define min_t(type, a, b) ((type) min(a, b))
84 #endif
85
86 #ifndef LTTNG_PACKED
87 #define LTTNG_PACKED __attribute__((__packed__))
88 #endif
89
90 /*
91 * Align value to the next multiple of align. Returns val if it already is a
92 * multiple of align. Align must be a power of two.
93 */
94 #define ALIGN_TO(value, align) ((value + (align - 1)) & ~(align - 1))
95
96 /*
97 * LTTNG_HIDDEN: set the hidden attribute for internal functions
98 * On Windows, symbols are local unless explicitly exported,
99 * see https://gcc.gnu.org/wiki/Visibility
100 */
101 #if defined(_WIN32) || defined(__CYGWIN__)
102 #define LTTNG_HIDDEN
103 #else
104 #define LTTNG_HIDDEN __attribute__((visibility("hidden")))
105 #endif
106
107 #define member_sizeof(type, field) sizeof(((type *) 0)->field)
108
109 #define ASSERT_LOCKED(lock) assert(pthread_mutex_trylock(&lock))
110
111 /*
112 * lttng_strncpy returns 0 on success, or nonzero on failure.
113 * It checks that the @src string fits into @dst_len before performing
114 * the copy. On failure, no copy has been performed.
115 *
116 * dst_len includes the string's trailing NULL.
117 */
118 static inline
119 int lttng_strncpy(char *dst, const char *src, size_t dst_len)
120 {
121 if (lttng_strnlen(src, dst_len) >= dst_len) {
122 /* Fail since copying would result in truncation. */
123 return -1;
124 }
125 strcpy(dst, src);
126 return 0;
127 }
128
129 #endif /* _MACROS_H */
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