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)       max((type) a, (type) 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)       min((type) a, (type) 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  * Get an aligned pointer to a value. This is meant
 113  * as a helper to pass an aligned pointer to a member in a packed structure
 114  * to a function.
 115  */
 116 #define ALIGNED_CONST_PTR(value) (((const typeof(value) []) { value }))
 117
 118 /*
 119  * lttng_strncpy returns 0 on success, or nonzero on failure.
 120  * It checks that the @src string fits into @dst_len before performing
 121  * the copy. On failure, no copy has been performed.
 122  *
 123  * dst_len includes the string's trailing NULL.
 124  */
 125 static inline
 126 int lttng_strncpy(char *dst, const char *src, size_t dst_len)
 127 {
 128         if (lttng_strnlen(src, dst_len) >= dst_len) {
 129                 /* Fail since copying would result in truncation. */
 130                 return -1;
 131         }
 132         strcpy(dst, src);
 133         return 0;
 134 }
 135
 136 #endif /* _MACROS_H */