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