core/src/flocks.c

   1 /*-----------------------------------------------------------------------------
   2 Copyright (C) Sylvain Fourmanoit <syfou@users.sourceforge.net>
   3
   4 Permission is hereby granted, free of charge, to any person obtaining a copy
   5 of this software and associated documentation files (the "Software"), to
   6 deal in the Software without restriction, including without limitation the
   7 rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
   8 sell copies of the Software, and to permit persons to whom the Software is
   9 furnished to do so, subject to the following conditions:
  10
  11 The above copyright notice and this permission notice shall be included in
  12 all copies of the Software and its documentation and acknowledgment shall be
  13 given in the documentation and software packages that this Software was
  14 used.
  15
  16 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19 THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  20 IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  22 ------------------------------------------------------------------------------*/
  23
  24 /*
  25   Abstraction for fcntl / flock file locking
  26  */
  27 #include "edesklets.h"
  28
  29 /*---------------------------------------------------------------------------*/
  30 #ifdef HAVE_FCNTL
  31 #ifdef HAVE_UNISTD_H
  32 #include <unistd.h>
  33 #endif
  34 #ifdef HAVE_FCNTL_H
  35 #include <fcntl.h>
  36 #endif
  37 #else
  38 #ifdef HAVE_FLOCK
  39 #ifdef HAVE_SYS_FILE_H
  40 #include <sys/file.h>
  41 #endif
  42 #endif
  43 #endif
  44
  45 /*---------------------------------------------------------------------------*/
  46 struct _LFILE {
  47   FILE * f;
  48   gboolean locked;
  49 };
  50
  51 /*---------------------------------------------------------------------------*/
  52 FILE * file(LFILE * lf) {return (lf)?lf->f:NULL;}
  53
  54 LFILE *
  55 fopen_locked(gchar * filename, gchar * mode,
  56              gboolean exclusive, gboolean block,
  57              GError ** error) {
  58   LFILE * lf;
  59   char * errmsg = NULL;
  60   EError errnum;
  61   gboolean errmsg_free;
  62 #ifdef HAVE_FCNTL
  63   int flags;
  64   struct flock lock;
  65 #endif
  66
  67 #define fatal(ERRNUM) \
  68   do{\
  69     errnum = ERRNUM;\
  70     errmsg = error_system();\
  71     errmsg_free = FALSE;\
  72     goto eexit;\
  73   }while(0)
  74
  75 #define bailout(ERRNUM, ...)                    \
  76   do{\
  77     errnum = ERRNUM;\
  78     errmsg = g_strdup_printf(__VA_ARGS__);\
  79     errmsg_free = TRUE;\
  80     goto eexit;\
  81   }while(0)
  82
  83   if (!(lf = g_malloc0(sizeof(LFILE))))
  84     bailout(EERROR_UNDEFINED, _("could not allocate memory"));
  85
  86   if (!(lf->f = fopen(filename, mode)))
  87     fatal(EERROR_SYSTEM);
  88
  89   if (exclusive) {
  90 #ifdef HAVE_FCNTL
  91     lock.l_type = F_WRLCK;
  92     lock.l_whence = SEEK_SET;
  93     lock.l_start = 0;
  94     lock.l_len = 0;
  95     if (fcntl(fileno(lf->f),(block)?F_SETLKW:F_SETLK, &lock)!=0) {
  96       if (!block && (errno == EACCES || errno == EAGAIN))
  97         fatal(EERROR_ALREADY_LOCKED);
  98       else
  99         fatal(EERROR_SYSTEM);
 100     }
 101     lf->locked = TRUE;
 102 #else
 103 #ifdef HAVE_FLOCK
 104     if (flock(fileno(lf->f), LOCK_EX | ((block)?0:LOCK_NB)) == -1)
 105       if (!block && errno == EWOULDBLOCK)
 106         fatal(EERROR_ALREADY_LOCKED);
 107       else
 108         fatal(EERROR_SYSTEM);
 109     lf->locked = TRUE;
 110 #else
 111     bailout(EERROR_ALREADY_LOCKED, _("No lock mechanism available"));
 112 #endif
 113 #endif
 114   }
 115   return lf;
 116
 117  eexit:
 118   if (lf) {
 119     if (lf->f) fclose(lf->f);
 120     g_free(lf);
 121   }
 122   if (error)
 123     *error = g_error_new(*EDOMAIN, errnum, "%s", errmsg);
 124   if (errmsg_free)
 125     g_free(errmsg);
 126   return NULL;
 127
 128 #undef bailout
 129 #undef fatal
 130 }
 131
 132 void
 133 fclose_locked(LFILE ** llf, GError ** error) {
 134 #ifdef HAVE_FCNTL
 135   struct flock lock;
 136 #endif
 137   if (!llf || !(*llf)) return;
 138   g_assert((*llf)->f);
 139
 140 #define fatal() \
 141 do{\
 142   if (error && *error == NULL)\
 143     *error = g_error_new(*EDOMAIN, EERROR_SYSTEM, "%s", error_system());\
 144  } while(0)
 145
 146   if ((*llf)->locked) {
 147 #ifdef HAVE_FCNTL
 148     lock.l_type = F_UNLCK;
 149     lock.l_whence = SEEK_SET;
 150     lock.l_start = 0;
 151     lock.l_len = 0;
 152     if (fcntl(fileno((*llf)->f),F_SETLK,&lock) == -1)
 153       fatal();
 154 #else
 155 #ifdef HAVE_FLOCK
 156     if (flock(fileno((*llf)->f), LOCK_UN) == -1)
 157         fatal();
 158 #endif
 159 #endif
 160   }
 161   if (fclose((*llf)->f) != 0)
 162     fatal();
 163
 164   g_free(*llf);
 165   *llf = NULL;
 166
 167 #undef fatal
 168 }