glue/xdgmime/xdgmime.c

   1 /* -*- mode: C; c-file-style: "gnu" -*- */
   2 /* xdgmime.c: XDG Mime Spec mime resolver.  Based on version 0.11 of the spec.
   3  *
   4  * More info can be found at http://www.freedesktop.org/standards/
   5  *
   6  * Copyright (C) 2003,2004  Red Hat, Inc.
   7  * Copyright (C) 2003,2004  Jonathan Blandford <jrb@alum.mit.edu>
   8  *
   9  * Licensed under the Academic Free License version 2.0
  10  * Or under the following terms:
  11  *
  12  * This library is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public
  14  * License as published by the Free Software Foundation; either
  15  * version 2 of the License, or (at your option) any later version.
  16  *
  17  * This library is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public
  23  * License along with this library; if not, write to the
  24  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  25  * Boston, MA 02111-1307, USA.
  26  */
  27
  28 #ifdef HAVE_CONFIG_H
  29 #include <config.h>
  30 #endif
  31
  32 #include "xdgmime.h"
  33 #include "xdgmimeint.h"
  34 #include "xdgmimeglob.h"
  35 #include "xdgmimemagic.h"
  36 #include "xdgmimealias.h"
  37 #include "xdgmimeparent.h"
  38 #include "xdgmimecache.h"
  39 #include <stdio.h>
  40 #include <string.h>
  41 #include <sys/stat.h>
  42 #include <sys/types.h>
  43 #include <sys/time.h>
  44 #include <unistd.h>
  45 #include <assert.h>
  46
  47 typedef struct XdgDirTimeList XdgDirTimeList;
  48 typedef struct XdgCallbackList XdgCallbackList;
  49
  50 static int need_reread = TRUE;
  51 static time_t last_stat_time = 0;
  52
  53 static XdgGlobHash *global_hash = NULL;
  54 static XdgMimeMagic *global_magic = NULL;
  55 static XdgAliasList *alias_list = NULL;
  56 static XdgParentList *parent_list = NULL;
  57 static XdgDirTimeList *dir_time_list = NULL;
  58 static XdgCallbackList *callback_list = NULL;
  59
  60 XdgMimeCache **_caches = NULL;
  61 static int n_caches = 0;
  62
  63 const char xdg_mime_type_unknown[] = "application/octet-stream";
  64
  65
  66 enum
  67 {
  68   XDG_CHECKED_UNCHECKED,
  69   XDG_CHECKED_VALID,
  70   XDG_CHECKED_INVALID
  71 };
  72
  73 struct XdgDirTimeList
  74 {
  75   time_t mtime;
  76   char *directory_name;
  77   int checked;
  78   XdgDirTimeList *next;
  79 };
  80
  81 struct XdgCallbackList
  82 {
  83   XdgCallbackList *next;
  84   XdgCallbackList *prev;
  85   int              callback_id;
  86   XdgMimeCallback  callback;
  87   void            *data;
  88   XdgMimeDestroy   destroy;
  89 };
  90
  91 /* Function called by xdg_run_command_on_dirs.  If it returns TRUE, further
  92  * directories aren't looked at */
  93 typedef int (*XdgDirectoryFunc) (const char *directory,
  94                                  void       *user_data);
  95
  96 static XdgDirTimeList *
  97 xdg_dir_time_list_new (void)
  98 {
  99   XdgDirTimeList *retval;
 100
 101   retval = calloc (1, sizeof (XdgDirTimeList));
 102   retval->checked = XDG_CHECKED_UNCHECKED;
 103
 104   return retval;
 105 }
 106
 107 static void
 108 xdg_dir_time_list_free (XdgDirTimeList *list)
 109 {
 110   XdgDirTimeList *next;
 111
 112   while (list)
 113     {
 114       next = list->next;
 115       free (list->directory_name);
 116       free (list);
 117       list = next;
 118     }
 119 }
 120
 121 static int
 122 xdg_mime_init_from_directory (const char *directory)
 123 {
 124   char *file_name;
 125   struct stat st;
 126   XdgDirTimeList *list;
 127
 128   assert (directory != NULL);
 129
 130   file_name = malloc (strlen (directory) + strlen ("/mime/mime.cache") + 1);
 131   strcpy (file_name, directory); strcat (file_name, "/mime/mime.cache");
 132   if (stat (file_name, &st) == 0)
 133     {
 134       XdgMimeCache *cache = _xdg_mime_cache_new_from_file (file_name);
 135
 136       if (cache != NULL)
 137         {
 138           list = xdg_dir_time_list_new ();
 139           list->directory_name = file_name;
 140           list->mtime = st.st_mtime;
 141           list->next = dir_time_list;
 142           dir_time_list = list;
 143
 144           _caches = realloc (_caches, sizeof (XdgMimeCache *) * (n_caches + 2));
 145           _caches[n_caches] = cache;
 146           _caches[n_caches + 1] = NULL;
 147           n_caches++;
 148
 149           return FALSE;
 150         }
 151     }
 152   free (file_name);
 153
 154   file_name = malloc (strlen (directory) + strlen ("/mime/globs") + 1);
 155   strcpy (file_name, directory); strcat (file_name, "/mime/globs");
 156   if (stat (file_name, &st) == 0)
 157     {
 158       _xdg_mime_glob_read_from_file (global_hash, file_name);
 159
 160       list = xdg_dir_time_list_new ();
 161       list->directory_name = file_name;
 162       list->mtime = st.st_mtime;
 163       list->next = dir_time_list;
 164       dir_time_list = list;
 165     }
 166   else
 167     {
 168       free (file_name);
 169     }
 170
 171   file_name = malloc (strlen (directory) + strlen ("/mime/magic") + 1);
 172   strcpy (file_name, directory); strcat (file_name, "/mime/magic");
 173   if (stat (file_name, &st) == 0)
 174     {
 175       _xdg_mime_magic_read_from_file (global_magic, file_name);
 176
 177       list = xdg_dir_time_list_new ();
 178       list->directory_name = file_name;
 179       list->mtime = st.st_mtime;
 180       list->next = dir_time_list;
 181       dir_time_list = list;
 182     }
 183   else
 184     {
 185       free (file_name);
 186     }
 187
 188   file_name = malloc (strlen (directory) + strlen ("/mime/aliases") + 1);
 189   strcpy (file_name, directory); strcat (file_name, "/mime/aliases");
 190   _xdg_mime_alias_read_from_file (alias_list, file_name);
 191   free (file_name);
 192
 193   file_name = malloc (strlen (directory) + strlen ("/mime/subclasses") + 1);
 194   strcpy (file_name, directory); strcat (file_name, "/mime/subclasses");
 195   _xdg_mime_parent_read_from_file (parent_list, file_name);
 196   free (file_name);
 197
 198   return FALSE; /* Keep processing */
 199 }
 200
 201 /* Runs a command on all the directories in the search path */
 202 static void
 203 xdg_run_command_on_dirs (XdgDirectoryFunc  func,
 204                          void             *user_data)
 205 {
 206   const char *xdg_data_home;
 207   const char *xdg_data_dirs;
 208   const char *ptr;
 209
 210   xdg_data_home = getenv ("XDG_DATA_HOME");
 211   if (xdg_data_home)
 212     {
 213       if ((func) (xdg_data_home, user_data))
 214         return;
 215     }
 216   else
 217     {
 218       const char *home;
 219
 220       home = getenv ("HOME");
 221       if (home != NULL)
 222         {
 223           char *guessed_xdg_home;
 224           int stop_processing;
 225
 226           guessed_xdg_home = malloc (strlen (home) + strlen ("/.local/share/") + 1);
 227           strcpy (guessed_xdg_home, home);
 228           strcat (guessed_xdg_home, "/.local/share/");
 229           stop_processing = (func) (guessed_xdg_home, user_data);
 230           free (guessed_xdg_home);
 231
 232           if (stop_processing)
 233             return;
 234         }
 235     }
 236
 237   xdg_data_dirs = getenv ("XDG_DATA_DIRS");
 238   if (xdg_data_dirs == NULL)
 239     xdg_data_dirs = "/usr/local/share/:/usr/share/";
 240
 241   ptr = xdg_data_dirs;
 242
 243   while (*ptr != '\000')
 244     {
 245       const char *end_ptr;
 246       char *dir;
 247       int len;
 248       int stop_processing;
 249
 250       end_ptr = ptr;
 251       while (*end_ptr != ':' && *end_ptr != '\000')
 252         end_ptr ++;
 253
 254       if (end_ptr == ptr)
 255         {
 256           ptr++;
 257           continue;
 258         }
 259
 260       if (*end_ptr == ':')
 261         len = end_ptr - ptr;
 262       else
 263         len = end_ptr - ptr + 1;
 264       dir = malloc (len + 1);
 265       strncpy (dir, ptr, len);
 266       dir[len] = '\0';
 267       stop_processing = (func) (dir, user_data);
 268       free (dir);
 269
 270       if (stop_processing)
 271         return;
 272
 273       ptr = end_ptr;
 274     }
 275 }
 276
 277 /* Checks file_path to make sure it has the same mtime as last time it was
 278  * checked.  If it has a different mtime, or if the file doesn't exist, it
 279  * returns FALSE.
 280  *
 281  * FIXME: This doesn't protect against permission changes.
 282  */
 283 static int
 284 xdg_check_file (const char *file_path,
 285                 int        *exists)
 286 {
 287   struct stat st;
 288
 289   /* If the file exists */
 290   if (stat (file_path, &st) == 0)
 291     {
 292       XdgDirTimeList *list;
 293
 294       if (exists)
 295         *exists = TRUE;
 296
 297       for (list = dir_time_list; list; list = list->next)
 298         {
 299           if (! strcmp (list->directory_name, file_path) &&
 300               st.st_mtime == list->mtime)
 301             {
 302               if (list->checked == XDG_CHECKED_UNCHECKED)
 303                 list->checked = XDG_CHECKED_VALID;
 304               else if (list->checked == XDG_CHECKED_VALID)
 305                 list->checked = XDG_CHECKED_INVALID;
 306
 307               return (list->checked != XDG_CHECKED_VALID);
 308             }
 309         }
 310       return TRUE;
 311     }
 312
 313   if (exists)
 314     *exists = FALSE;
 315
 316   return FALSE;
 317 }
 318
 319 static int
 320 xdg_check_dir (const char *directory,
 321                int        *invalid_dir_list)
 322 {
 323   int invalid, exists;
 324   char *file_name;
 325
 326   assert (directory != NULL);
 327
 328   /* Check the mime.cache file */
 329   file_name = malloc (strlen (directory) + strlen ("/mime/mime.cache") + 1);
 330   strcpy (file_name, directory); strcat (file_name, "/mime/mime.cache");
 331   invalid = xdg_check_file (file_name, &exists);
 332   free (file_name);
 333   if (invalid)
 334     {
 335       *invalid_dir_list = TRUE;
 336       return TRUE;
 337     }
 338   else if (exists)
 339     {
 340       return FALSE;
 341     }
 342
 343   /* Check the globs file */
 344   file_name = malloc (strlen (directory) + strlen ("/mime/globs") + 1);
 345   strcpy (file_name, directory); strcat (file_name, "/mime/globs");
 346   invalid = xdg_check_file (file_name, NULL);
 347   free (file_name);
 348   if (invalid)
 349     {
 350       *invalid_dir_list = TRUE;
 351       return TRUE;
 352     }
 353
 354   /* Check the magic file */
 355   file_name = malloc (strlen (directory) + strlen ("/mime/magic") + 1);
 356   strcpy (file_name, directory); strcat (file_name, "/mime/magic");
 357   invalid = xdg_check_file (file_name, NULL);
 358   free (file_name);
 359   if (invalid)
 360     {
 361       *invalid_dir_list = TRUE;
 362       return TRUE;
 363     }
 364
 365   return FALSE; /* Keep processing */
 366 }
 367
 368 /* Walks through all the mime files stat()ing them to see if they've changed.
 369  * Returns TRUE if they have. */
 370 static int
 371 xdg_check_dirs (void)
 372 {
 373   XdgDirTimeList *list;
 374   int invalid_dir_list = FALSE;
 375
 376   for (list = dir_time_list; list; list = list->next)
 377     list->checked = XDG_CHECKED_UNCHECKED;
 378
 379   xdg_run_command_on_dirs ((XdgDirectoryFunc) xdg_check_dir,
 380                            &invalid_dir_list);
 381
 382   if (invalid_dir_list)
 383     return TRUE;
 384
 385   for (list = dir_time_list; list; list = list->next)
 386     {
 387       if (list->checked != XDG_CHECKED_VALID)
 388         return TRUE;
 389     }
 390
 391   return FALSE;
 392 }
 393
 394 /* We want to avoid stat()ing on every single mime call, so we only look for
 395  * newer files every 5 seconds.  This will return TRUE if we need to reread the
 396  * mime data from disk.
 397  */
 398 static int
 399 xdg_check_time_and_dirs (void)
 400 {
 401   struct timeval tv;
 402   time_t current_time;
 403   int retval = FALSE;
 404
 405   gettimeofday (&tv, NULL);
 406   current_time = tv.tv_sec;
 407
 408   if (current_time >= last_stat_time + 5)
 409     {
 410       retval = xdg_check_dirs ();
 411       last_stat_time = current_time;
 412     }
 413
 414   return retval;
 415 }
 416
 417 /* Called in every public function.  It reloads the hash function if need be.
 418  */
 419 static void
 420 xdg_mime_init (void)
 421 {
 422   if (xdg_check_time_and_dirs ())
 423     {
 424       xdg_mime_shutdown ();
 425     }
 426
 427   if (need_reread)
 428     {
 429       global_hash = _xdg_glob_hash_new ();
 430       global_magic = _xdg_mime_magic_new ();
 431       alias_list = _xdg_mime_alias_list_new ();
 432       parent_list = _xdg_mime_parent_list_new ();
 433
 434       xdg_run_command_on_dirs ((XdgDirectoryFunc) xdg_mime_init_from_directory,
 435                                NULL);
 436
 437       need_reread = FALSE;
 438     }
 439 }
 440
 441 const char *
 442 xdg_mime_get_mime_type_for_data (const void *data,
 443                                  size_t      len)
 444 {
 445   const char *mime_type;
 446
 447   xdg_mime_init ();
 448
 449   if (_caches)
 450     return _xdg_mime_cache_get_mime_type_for_data (data, len);
 451
 452   mime_type = _xdg_mime_magic_lookup_data (global_magic, data, len, NULL, 0);
 453
 454   if (mime_type)
 455     return mime_type;
 456
 457   return XDG_MIME_TYPE_UNKNOWN;
 458 }
 459
 460 const char *
 461 xdg_mime_get_mime_type_for_file (const char  *file_name,
 462                                  struct stat *statbuf)
 463 {
 464   const char *mime_type;
 465   /* currently, only a few globs occur twice, and none
 466    * more often, so 5 seems plenty.
 467    */
 468   const char *mime_types[5];
 469   FILE *file;
 470   unsigned char *data;
 471   int max_extent;
 472   int bytes_read;
 473   struct stat buf;
 474   const char *base_name;
 475   int n;
 476
 477   if (file_name == NULL)
 478     return NULL;
 479   if (! _xdg_utf8_validate (file_name))
 480     return NULL;
 481
 482   xdg_mime_init ();
 483
 484   if (_caches)
 485     return _xdg_mime_cache_get_mime_type_for_file (file_name, statbuf);
 486
 487   base_name = _xdg_get_base_name (file_name);
 488   n = _xdg_glob_hash_lookup_file_name (global_hash, base_name, mime_types, 5);
 489
 490   if (n == 1)
 491     return mime_types[0];
 492
 493   if (!statbuf)
 494     {
 495       if (stat (file_name, &buf) != 0)
 496         return XDG_MIME_TYPE_UNKNOWN;
 497
 498       statbuf = &buf;
 499     }
 500
 501   if (!S_ISREG (statbuf->st_mode))
 502     return XDG_MIME_TYPE_UNKNOWN;
 503
 504   /* FIXME: Need to make sure that max_extent isn't totally broken.  This could
 505    * be large and need getting from a stream instead of just reading it all
 506    * in. */
 507   max_extent = _xdg_mime_magic_get_buffer_extents (global_magic);
 508   data = malloc (max_extent);
 509   if (data == NULL)
 510     return XDG_MIME_TYPE_UNKNOWN;
 511
 512   file = fopen (file_name, "r");
 513   if (file == NULL)
 514     {
 515       free (data);
 516       return XDG_MIME_TYPE_UNKNOWN;
 517     }
 518
 519   bytes_read = fread (data, 1, max_extent, file);
 520   if (ferror (file))
 521     {
 522       free (data);
 523       fclose (file);
 524       return XDG_MIME_TYPE_UNKNOWN;
 525     }
 526
 527   mime_type = _xdg_mime_magic_lookup_data (global_magic, data, bytes_read,
 528                                            mime_types, n);
 529
 530   free (data);
 531   fclose (file);
 532
 533   if (mime_type)
 534     return mime_type;
 535
 536   return XDG_MIME_TYPE_UNKNOWN;
 537 }
 538
 539 const char *
 540 xdg_mime_get_mime_type_from_file_name (const char *file_name)
 541 {
 542   const char *mime_type;
 543
 544   xdg_mime_init ();
 545
 546   if (_caches)
 547     return _xdg_mime_cache_get_mime_type_from_file_name (file_name);
 548
 549   if (_xdg_glob_hash_lookup_file_name (global_hash, file_name, &mime_type, 1))
 550     return mime_type;
 551   else
 552     return XDG_MIME_TYPE_UNKNOWN;
 553 }
 554
 555 int
 556 xdg_mime_is_valid_mime_type (const char *mime_type)
 557 {
 558   /* FIXME: We should make this a better test
 559    */
 560   return _xdg_utf8_validate (mime_type);
 561 }
 562
 563 void
 564 xdg_mime_shutdown (void)
 565 {
 566   XdgCallbackList *list;
 567
 568   /* FIXME: Need to make this (and the whole library) thread safe */
 569   if (dir_time_list)
 570     {
 571       xdg_dir_time_list_free (dir_time_list);
 572       dir_time_list = NULL;
 573     }
 574
 575   if (global_hash)
 576     {
 577       _xdg_glob_hash_free (global_hash);
 578       global_hash = NULL;
 579     }
 580   if (global_magic)
 581     {
 582       _xdg_mime_magic_free (global_magic);
 583       global_magic = NULL;
 584     }
 585
 586   if (alias_list)
 587     {
 588       _xdg_mime_alias_list_free (alias_list);
 589       alias_list = NULL;
 590     }
 591
 592   if (parent_list)
 593     {
 594       _xdg_mime_parent_list_free (parent_list);
 595       parent_list = NULL;
 596     }
 597
 598   if (_caches)
 599     {
 600       int i;
 601
 602       for (i = 0; i < n_caches; i++)
 603         _xdg_mime_cache_unref (_caches[i]);
 604       free (_caches);
 605       _caches = NULL;
 606       n_caches = 0;
 607     }
 608
 609   for (list = callback_list; list; list = list->next)
 610     (list->callback) (list->data);
 611
 612   need_reread = TRUE;
 613 }
 614
 615 int
 616 xdg_mime_get_max_buffer_extents (void)
 617 {
 618   xdg_mime_init ();
 619
 620   if (_caches)
 621     return _xdg_mime_cache_get_max_buffer_extents ();
 622
 623   return _xdg_mime_magic_get_buffer_extents (global_magic);
 624 }
 625
 626 const char *
 627 _xdg_mime_unalias_mime_type (const char *mime_type)
 628 {
 629   const char *lookup;
 630
 631   if (_caches)
 632     return _xdg_mime_cache_unalias_mime_type (mime_type);
 633
 634   if ((lookup = _xdg_mime_alias_list_lookup (alias_list, mime_type)) != NULL)
 635     return lookup;
 636
 637   return mime_type;
 638 }
 639
 640 const char *
 641 xdg_mime_unalias_mime_type (const char *mime_type)
 642 {
 643   xdg_mime_init ();
 644
 645   return _xdg_mime_unalias_mime_type (mime_type);
 646 }
 647
 648 int
 649 _xdg_mime_mime_type_equal (const char *mime_a,
 650                            const char *mime_b)
 651 {
 652   const char *unalias_a, *unalias_b;
 653
 654   unalias_a = _xdg_mime_unalias_mime_type (mime_a);
 655   unalias_b = _xdg_mime_unalias_mime_type (mime_b);
 656
 657   if (strcmp (unalias_a, unalias_b) == 0)
 658     return 1;
 659
 660   return 0;
 661 }
 662
 663 int
 664 xdg_mime_mime_type_equal (const char *mime_a,
 665                           const char *mime_b)
 666 {
 667   xdg_mime_init ();
 668
 669   return _xdg_mime_mime_type_equal (mime_a, mime_b);
 670 }
 671
 672 int
 673 xdg_mime_media_type_equal (const char *mime_a,
 674                            const char *mime_b)
 675 {
 676   char *sep;
 677
 678   xdg_mime_init ();
 679
 680   sep = strchr (mime_a, '/');
 681
 682   if (sep && strncmp (mime_a, mime_b, sep - mime_a + 1) == 0)
 683     return 1;
 684
 685   return 0;
 686 }
 687
 688 #if 1
 689 static int
 690 xdg_mime_is_super_type (const char *mime)
 691 {
 692   int length;
 693   const char *type;
 694
 695   length = strlen (mime);
 696   type = &(mime[length - 2]);
 697
 698   if (strcmp (type, "/*") == 0)
 699     return 1;
 700
 701   return 0;
 702 }
 703 #endif
 704
 705 int
 706 _xdg_mime_mime_type_subclass (const char *mime,
 707                               const char *base)
 708 {
 709   const char *umime, *ubase;
 710   const char **parents;
 711
 712   if (_caches)
 713     return _xdg_mime_cache_mime_type_subclass (mime, base);
 714
 715   umime = _xdg_mime_unalias_mime_type (mime);
 716   ubase = _xdg_mime_unalias_mime_type (base);
 717
 718   if (strcmp (umime, ubase) == 0)
 719     return 1;
 720
 721 #if 1
 722   /* Handle supertypes */
 723   if (xdg_mime_is_super_type (ubase) &&
 724       xdg_mime_media_type_equal (umime, ubase))
 725     return 1;
 726 #endif
 727
 728   /*  Handle special cases text/plain and application/octet-stream */
 729   if (strcmp (ubase, "text/plain") == 0 &&
 730       strncmp (umime, "text/", 5) == 0)
 731     return 1;
 732
 733   if (strcmp (ubase, "application/octet-stream") == 0)
 734     return 1;
 735
 736   parents = _xdg_mime_parent_list_lookup (parent_list, umime);
 737   for (; parents && *parents; parents++)
 738     {
 739       if (_xdg_mime_mime_type_subclass (*parents, ubase))
 740         return 1;
 741     }
 742
 743   return 0;
 744 }
 745
 746 int
 747 xdg_mime_mime_type_subclass (const char *mime,
 748                              const char *base)
 749 {
 750   xdg_mime_init ();
 751
 752   return _xdg_mime_mime_type_subclass (mime, base);
 753 }
 754
 755 char **
 756 xdg_mime_list_mime_parents (const char *mime)
 757 {
 758   const char **parents;
 759   char **result;
 760   int i, n;
 761
 762   if (_caches)
 763     return _xdg_mime_cache_list_mime_parents (mime);
 764
 765   parents = xdg_mime_get_mime_parents (mime);
 766
 767   if (!parents)
 768     return NULL;
 769
 770   for (i = 0; parents[i]; i++) ;
 771
 772   n = (i + 1) * sizeof (char *);
 773   result = (char **) malloc (n);
 774   memcpy (result, parents, n);
 775
 776   return result;
 777 }
 778
 779 const char **
 780 xdg_mime_get_mime_parents (const char *mime)
 781 {
 782   const char *umime;
 783
 784   xdg_mime_init ();
 785
 786   umime = _xdg_mime_unalias_mime_type (mime);
 787
 788   return _xdg_mime_parent_list_lookup (parent_list, umime);
 789 }
 790
 791 void
 792 xdg_mime_dump (void)
 793 {
 794   printf ("*** ALIASES ***\n\n");
 795   _xdg_mime_alias_list_dump (alias_list);
 796   printf ("\n*** PARENTS ***\n\n");
 797   _xdg_mime_parent_list_dump (parent_list);
 798 }
 799
 800
 801 /* Registers a function to be called every time the mime database reloads its files
 802  */
 803 int
 804 xdg_mime_register_reload_callback (XdgMimeCallback  callback,
 805                                    void            *data,
 806                                    XdgMimeDestroy   destroy)
 807 {
 808   XdgCallbackList *list_el;
 809   static int callback_id = 1;
 810
 811   /* Make a new list element */
 812   list_el = calloc (1, sizeof (XdgCallbackList));
 813   list_el->callback_id = callback_id;
 814   list_el->callback = callback;
 815   list_el->data = data;
 816   list_el->destroy = destroy;
 817   list_el->next = callback_list;
 818   if (list_el->next)
 819     list_el->next->prev = list_el;
 820
 821   callback_list = list_el;
 822   callback_id ++;
 823
 824   return callback_id - 1;
 825 }
 826
 827 void
 828 xdg_mime_remove_callback (int callback_id)
 829 {
 830   XdgCallbackList *list;
 831
 832   for (list = callback_list; list; list = list->next)
 833     {
 834       if (list->callback_id == callback_id)
 835         {
 836           if (list->next)
 837             list->next = list->prev;
 838
 839           if (list->prev)
 840             list->prev->next = list->next;
 841           else
 842             callback_list = list->next;
 843
 844           /* invoke the destroy handler */
 845           (list->destroy) (list->data);
 846           free (list);
 847           return;
 848         }
 849     }
 850 }