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 <string.h>
  24 #include <common/compat/string.h>
  25
  26 /*
  27  * Takes a pointer x and transform it so we can use it to access members
  28  * without a function call. Here an example:
  29  *
  30  *    #define GET_SIZE(x) LTTNG_REF(x)->size
  31  *
  32  *    struct { int size; } s;
  33  *
  34  *    printf("size : %d\n", GET_SIZE(&s));
  35  *
  36  * For this example we can't use something like this for compatibility purpose
  37  * since this will fail:
  38  *
  39  *    #define GET_SIZE(x) x->size;
  40  *
  41  * This is mostly use for the compatibility layer of lttng-tools. See
  42  * poll/epoll for a good example. Since x can be on the stack or allocated
  43  * memory using malloc(), we must use generic accessors for compat in order to
  44  * *not* use a function to access members and not the variable name.
  45  */
  46 #define LTTNG_REF(x) ((typeof(*x) *)(x))
  47
  48 /*
  49  * Memory allocation zeroed
  50  */
  51 static inline
  52 void *zmalloc(size_t len)
  53 {
  54         return calloc(1, len);
  55 }
  56
  57 #ifndef ARRAY_SIZE
  58 #define ARRAY_SIZE(array)   (sizeof(array) / (sizeof((array)[0])))
  59 #endif
  60
  61 #ifndef max
  62 #define max(a, b) ((a) > (b) ? (a) : (b))
  63 #endif
  64
  65 #ifndef max_t
  66 #define max_t(type, a, b)       ((type) max(a, b))
  67 #endif
  68
  69 #ifndef min
  70 #define min(a, b) ((a) < (b) ? (a) : (b))
  71 #endif
  72
  73 #ifndef LTTNG_PACKED
  74 #define LTTNG_PACKED __attribute__((__packed__))
  75 #endif
  76
  77 #ifndef LTTNG_HIDDEN
  78 #define LTTNG_HIDDEN __attribute__((visibility("hidden")))
  79 #endif
  80
  81 /*
  82  * lttng_strncpy returns 0 on success, or nonzero on failure.
  83  * It checks that the @src string fits into @dst_len before performing
  84  * the copy. On failure, no copy has been performed.
  85  *
  86  * dst_len includes the string's trailing NULL.
  87  */
  88 static inline
  89 int lttng_strncpy(char *dst, const char *src, size_t dst_len)
  90 {
  91         if (lttng_strnlen(src, dst_len) == dst_len) {
  92                 /* Fail since copying would result in truncation. */
  93                 return -1;
  94         }
  95         strncpy(dst, src, dst_len);
  96         /*
  97          * Be extra careful and put final \0 at the end after strncpy(),
  98          * even though we checked the length before. This makes Coverity
  99          * happy.
 100          */
 101         dst[dst_len - 1] = '\0';
 102         return 0;
 103 }
 104
 105 #endif /* _MACROS_H */