src/misc/modules.c

   1 /*****************************************************************************
   2  * modules.c : Built-in and plugin modules management functions
   3  *****************************************************************************
   4  * Copyright (C) 2001 VideoLAN
   5  * $Id: modules.c,v 1.27 2001/04/28 03:36:25 sam Exp $
   6  *
   7  * Authors: Samuel Hocevar <sam@zoy.org>
   8  *          Ethan C. Baldridge <BaldridgeE@cadmus.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  23  *****************************************************************************/
  24 #include "defs.h"
  25
  26 #include "config.h"
  27
  28 /* Some faulty libcs have a broken struct dirent when _FILE_OFFSET_BITS
  29  * is set to 64. Don't try to be cleverer. */
  30 #ifdef _FILE_OFFSET_BITS
  31 #undef _FILE_OFFSET_BITS
  32 #endif
  33
  34 #include <stdlib.h>                                      /* free(), strtol() */
  35 #include <stdio.h>                                              /* sprintf() */
  36 #include <string.h>                                              /* strdup() */
  37 #include <dirent.h>
  38
  39 #if defined(HAVE_DLFCN_H)                                /* Linux, BSD, Hurd */
  40 #   include <dlfcn.h>                        /* dlopen(), dlsym(), dlclose() */
  41 #   define HAVE_DYNAMIC_PLUGINS
  42 #elif defined(HAVE_IMAGE_H)                                          /* BeOS */
  43 #   include <image.h>
  44 #   define HAVE_DYNAMIC_PLUGINS
  45 #else
  46 #   undef HAVE_DYNAMIC_PLUGINS
  47 #endif
  48
  49 #ifdef SYS_BEOS
  50 #   include "beos_specific.h"
  51 #endif
  52
  53 #ifdef SYS_DARWIN1_3
  54 #   include "darwin_specific.h"
  55 #endif
  56
  57 #include "common.h"
  58 #include "threads.h"
  59
  60 #include "intf_msg.h"
  61 #include "modules.h"
  62 #ifdef HAVE_DYNAMIC_PLUGINS
  63 #include "modules_core.h"
  64 #endif
  65 #include "modules_builtin.h"
  66
  67 /* Local prototypes */
  68 #ifdef HAVE_DYNAMIC_PLUGINS
  69 static int AllocatePluginModule ( module_bank_t *, char * );
  70 #endif
  71 static int AllocateBuiltinModule( module_bank_t *,
  72                                   int ( * ) ( module_t * ),
  73                                   int ( * ) ( module_t * ),
  74                                   int ( * ) ( module_t * ) );
  75 static int DeleteModule ( module_bank_t * p_bank, module_t * );
  76 static int LockModule   ( module_t * );
  77 static int UnlockModule ( module_t * );
  78 #ifdef HAVE_DYNAMIC_PLUGINS
  79 static int HideModule   ( module_t * );
  80 static int CallSymbol   ( module_t *, char * );
  81 #endif
  82
  83 /*****************************************************************************
  84  * module_CreateBank: create the module bank.
  85  *****************************************************************************
  86  * This function creates a module bank structure.
  87  *****************************************************************************/
  88 module_bank_t * module_CreateBank( void )
  89 {
  90     module_bank_t * p_bank;
  91
  92     p_bank = malloc( sizeof( module_bank_t ) );
  93
  94     return( p_bank );
  95 }
  96
  97 /*****************************************************************************
  98  * module_InitBank: create the module bank.
  99  *****************************************************************************
 100  * This function creates a module bank structure and fills it with the
 101  * built-in modules, as well as all the plugin modules it can find.
 102  *****************************************************************************/
 103 void module_InitBank( module_bank_t * p_bank )
 104 {
 105 #ifdef HAVE_DYNAMIC_PLUGINS
 106     static char * path[] = { ".", "lib", PLUGIN_PATH, NULL, NULL };
 107
 108     char **         ppsz_path = path;
 109     char *          psz_fullpath;
 110     char *          psz_file;
 111 #if defined( SYS_BEOS ) || defined( SYS_DARWIN1_3 )
 112     char *          psz_vlcpath = system_GetProgramPath();
 113     int             i_vlclen = strlen( psz_vlcpath );
 114     boolean_t       b_notinroot;
 115 #endif
 116     DIR *           dir;
 117     struct dirent * file;
 118 #endif /* HAVE_DYNAMIC_PLUGINS */
 119
 120     p_bank->first = NULL;
 121     vlc_mutex_init( &p_bank->lock );
 122
 123     intf_WarnMsg( 1, "module: module bank initialized" );
 124
 125     intf_WarnMsg( 2, "module: checking built-in modules" );
 126
 127     ALLOCATE_ALL_BUILTINS();
 128
 129 #ifdef HAVE_DYNAMIC_PLUGINS
 130     intf_WarnMsg( 2, "module: checking plugin modules" );
 131
 132     for( ; *ppsz_path != NULL ; ppsz_path++ )
 133     {
 134         /* Store strlen(*ppsz_path) for later use. */
 135         int i_dirlen = strlen( *ppsz_path );
 136
 137 #if defined( SYS_BEOS ) || defined( SYS_DARWIN1_3 )
 138         b_notinroot = 0;
 139         /* Under BeOS, we need to add beos_GetProgramPath() to access
 140          * files under the current directory */
 141         if( ( i_dirlen > 1 ) && strncmp( *ppsz_path, "/", 1 ) )
 142         {
 143             i_dirlen += i_vlclen + 2;
 144             b_notinroot = 1;
 145
 146             psz_fullpath = malloc( i_dirlen );
 147             if( psz_fullpath == NULL )
 148             {
 149                 continue;
 150             }
 151             sprintf( psz_fullpath, "%s/%s", psz_vlcpath, *ppsz_path );
 152         }
 153         else
 154 #endif
 155         {
 156             psz_fullpath = *ppsz_path;
 157         }
 158
 159         intf_WarnMsgImm( 3, "module: browsing `%s'", psz_fullpath );
 160
 161         if( (dir = opendir( psz_fullpath )) )
 162         {
 163             /* Parse the directory and try to load all files it contains. */
 164             while( (file = readdir( dir )) )
 165             {
 166                 int i_filelen = strlen( file->d_name );
 167
 168                 /* We only load files ending with ".so" */
 169                 if( i_filelen > 3
 170                         && !strncmp( file->d_name + i_filelen - 3, ".so", 3 ) )
 171                 {
 172                     psz_file = malloc( i_dirlen + i_filelen + 2 );
 173                     if( psz_file == NULL )
 174                     {
 175                         continue;
 176                     }
 177                     sprintf( psz_file, "%s/%s", psz_fullpath, file->d_name );
 178
 179                     /* We created a nice filename -- now we just try to load
 180                      * it as a plugin module. */
 181                     AllocatePluginModule( p_bank, psz_file );
 182
 183                     /* We don't care if the allocation succeeded */
 184                     free( psz_file );
 185                 }
 186             }
 187
 188             /* Close the directory if successfully opened */
 189             closedir( dir );
 190         }
 191
 192 #if defined( SYS_BEOS ) || defined( SYS_DARWIN1_3 )
 193         if( b_notinroot )
 194         {
 195             free( psz_fullpath );
 196         }
 197 #endif
 198     }
 199 #endif /* HAVE_DYNAMIC_PLUGINS */
 200
 201     return;
 202 }
 203
 204 /*****************************************************************************
 205  * module_DestroyBank: destroy the module bank.
 206  *****************************************************************************
 207  * This function unloads all unused plugin modules and removes the module
 208  * bank in case of success.
 209  *****************************************************************************/
 210 void module_DestroyBank( module_bank_t * p_bank )
 211 {
 212     module_t * p_next;
 213
 214     while( p_bank->first != NULL )
 215     {
 216         if( DeleteModule( p_bank, p_bank->first ) )
 217         {
 218             /* Module deletion failed */
 219             intf_ErrMsg( "module error: `%s' can't be removed. trying harder.",
 220                          p_bank->first->psz_name );
 221
 222             /* We just free the module by hand. Niahahahahaha. */
 223             p_next = p_bank->first->next;
 224             free(p_bank->first);
 225             p_bank->first = p_next;
 226         }
 227     }
 228
 229     /* Destroy the lock */
 230     vlc_mutex_destroy( &p_bank->lock );
 231
 232     /* We can free the module bank */
 233     free( p_bank );
 234
 235     return;
 236 }
 237
 238 /*****************************************************************************
 239  * module_ResetBank: reset the module bank.
 240  *****************************************************************************
 241  * This function resets the module bank by unloading all unused plugin
 242  * modules.
 243  *****************************************************************************/
 244 void module_ResetBank( module_bank_t * p_bank )
 245 {
 246     intf_ErrMsg( "FIXME: module_ResetBank unimplemented" );
 247     return;
 248 }
 249
 250 /*****************************************************************************
 251  * module_ManageBank: manage the module bank.
 252  *****************************************************************************
 253  * This function parses the module bank and hides modules that have been
 254  * unused for a while.
 255  *****************************************************************************/
 256 void module_ManageBank( module_bank_t * p_bank )
 257 {
 258 #ifdef HAVE_DYNAMIC_PLUGINS
 259     module_t * p_module;
 260
 261     /* We take the global lock */
 262     vlc_mutex_lock( &p_bank->lock );
 263
 264     /* Parse the module list to see if any modules need to be unloaded */
 265     for( p_module = p_bank->first ;
 266          p_module != NULL ;
 267          p_module = p_module->next )
 268     {
 269         /* If the module is unused and if it is a plugin module... */
 270         if( p_module->i_usage == 0 && !p_module->b_builtin )
 271         {
 272             if( p_module->i_unused_delay < MODULE_HIDE_DELAY )
 273             {
 274                 p_module->i_unused_delay++;
 275             }
 276             else
 277             {
 278                 intf_WarnMsg( 3, "module: hiding unused plugin module `%s'",
 279                               p_module->psz_name );
 280                 HideModule( p_module );
 281
 282                 /* Break here, so that we only hide one module at a time */
 283                 break;
 284             }
 285         }
 286     }
 287
 288     /* We release the global lock */
 289     vlc_mutex_unlock( &p_bank->lock );
 290 #endif /* HAVE_DYNAMIC_PLUGINS */
 291
 292     return;
 293 }
 294
 295 /*****************************************************************************
 296  * module_Need: return the best module function, given a capability list.
 297  *****************************************************************************
 298  * This function returns the module that best fits the asked capabilities.
 299  *****************************************************************************/
 300 module_t * module_Need( module_bank_t *p_bank,
 301                         int i_capabilities, void *p_data )
 302 {
 303     module_t * p_module;
 304     module_t * p_bestmodule = NULL;
 305     int i_score, i_totalscore, i_bestscore = 0;
 306     int i_index;
 307
 308     /* We take the global lock */
 309     vlc_mutex_lock( &p_bank->lock );
 310
 311     /* Parse the module list for capabilities and probe each of them */
 312     for( p_module = p_bank->first ;
 313          p_module != NULL ;
 314          p_module = p_module->next )
 315     {
 316         /* Test that this module can do everything we need */
 317         if( ( p_module->i_capabilities & i_capabilities ) == i_capabilities )
 318         {
 319             i_totalscore = 0;
 320
 321             LockModule( p_module );
 322
 323             /* Parse all the requested capabilities and test them */
 324             for( i_index = 0 ; (1 << i_index) <= i_capabilities ; i_index++ )
 325             {
 326                 if( ( (1 << i_index) & i_capabilities ) )
 327                 {
 328                     i_score = ( (function_list_t *)p_module->p_functions)
 329                                                   [i_index].pf_probe( p_data );
 330
 331                     if( i_score )
 332                     {
 333                         i_totalscore += i_score;
 334                     }
 335                     else
 336                     {
 337                         break;
 338                     }
 339                 }
 340             }
 341
 342             /* If the high score was broken, we have a new champion */
 343             if( i_totalscore > i_bestscore )
 344             {
 345                 /* Keep the current module locked, but release the previous */
 346                 if( p_bestmodule != NULL )
 347                 {
 348                     UnlockModule( p_bestmodule );
 349                 }
 350
 351                 /* This is the new best module */
 352                 i_bestscore = i_totalscore;
 353                 p_bestmodule = p_module;
 354             }
 355             else
 356             {
 357                 /* This module wasn't interesting, unlock it and forget it */
 358                 UnlockModule( p_module );
 359             }
 360         }
 361     }
 362
 363     /* We can release the global lock, module refcount was incremented */
 364     vlc_mutex_unlock( &p_bank->lock );
 365
 366     if( p_bestmodule != NULL )
 367     {
 368         intf_WarnMsg( 3, "module: locking module `%s'",
 369                       p_bestmodule->psz_name );
 370     }
 371
 372     /* Don't forget that the module is still locked if bestmodule != NULL */
 373     return( p_bestmodule );
 374 }
 375
 376 /*****************************************************************************
 377  * module_Unneed: decrease the usage count of a module.
 378  *****************************************************************************
 379  * This function must be called by the thread that called module_Need, to
 380  * decrease the reference count and allow for hiding of modules.
 381  *****************************************************************************/
 382 void module_Unneed( module_bank_t * p_bank, module_t * p_module )
 383 {
 384     /* We take the global lock */
 385     vlc_mutex_lock( &p_bank->lock );
 386
 387     /* Just unlock the module - we can't do anything if it fails,
 388      * so there is no need to check the return value. */
 389     UnlockModule( p_module );
 390
 391     intf_WarnMsg( 3, "module: unlocking module `%s'", p_module->psz_name );
 392
 393     /* We release the global lock */
 394     vlc_mutex_unlock( &p_bank->lock );
 395
 396     return;
 397 }
 398
 399 /*****************************************************************************
 400  * Following functions are local.
 401  *****************************************************************************/
 402
 403 #ifdef HAVE_DYNAMIC_PLUGINS
 404 /*****************************************************************************
 405  * AllocatePluginModule: load a module into memory and initialize it.
 406  *****************************************************************************
 407  * This function loads a dynamically loadable module and allocates a structure
 408  * for its information data. The module can then be handled by module_Need,
 409  * module_Unneed and HideModule. It can be removed by DeleteModule.
 410  *****************************************************************************/
 411 static int AllocatePluginModule( module_bank_t * p_bank, char * psz_filename )
 412 {
 413     module_t * p_module, * p_othermodule;
 414     module_handle_t handle;
 415
 416     /* Try to dynamically load the module. */
 417     if( module_load( psz_filename, &handle ) )
 418     {
 419         /* The plugin module couldn't be opened */
 420         intf_WarnMsgImm( 3, "module warning: cannot open %s (%s)",
 421                          psz_filename, module_error() );
 422         return( -1 );
 423     }
 424
 425     /* Now that we have successfully loaded the module, we can
 426      * allocate a structure for it */
 427     p_module = malloc( sizeof( module_t ) );
 428     if( p_module == NULL )
 429     {
 430         intf_ErrMsg( "module error: can't allocate p_module" );
 431         module_unload( handle );
 432         return( -1 );
 433     }
 434
 435     /* We need to fill these since they may be needed by CallSymbol() */
 436     p_module->is.plugin.psz_filename = psz_filename;
 437     p_module->is.plugin.handle = handle;
 438
 439     /* Initialize the module : fill p_module->psz_name, etc. */
 440     if( CallSymbol( p_module, "InitModule" ) != 0 )
 441     {
 442         /* We couldn't call InitModule() */
 443         free( p_module );
 444         module_unload( handle );
 445         return( -1 );
 446     }
 447
 448     /* Check that version numbers match */
 449     if( strcmp( VERSION, p_module->psz_version ) )
 450     {
 451         free( p_module );
 452         module_unload( handle );
 453         return( -1 );
 454     }
 455
 456     /* Check that we don't already have a module with this name */
 457     for( p_othermodule = p_bank->first ;
 458          p_othermodule != NULL ;
 459          p_othermodule = p_othermodule->next )
 460     {
 461         if( !strcmp( p_othermodule->psz_name, p_module->psz_name ) )
 462         {
 463             free( p_module );
 464             module_unload( handle );
 465             return( -1 );
 466         }
 467     }
 468
 469     /* Activate the module : fill the capability structure, etc. */
 470     if( CallSymbol( p_module, "ActivateModule" ) != 0 )
 471     {
 472         /* We couldn't call ActivateModule() */
 473         free( p_module );
 474         module_unload( handle );
 475         return( -1 );
 476     }
 477
 478     /* We strdup() these entries so that they are still valid when the
 479      * module is unloaded. */
 480     p_module->is.plugin.psz_filename =
 481             strdup( p_module->is.plugin.psz_filename );
 482     p_module->psz_name = strdup( p_module->psz_name );
 483     p_module->psz_longname = strdup( p_module->psz_longname );
 484     p_module->psz_version = strdup( p_module->psz_version );
 485     if( p_module->is.plugin.psz_filename == NULL
 486             || p_module->psz_name == NULL
 487             || p_module->psz_longname == NULL
 488             || p_module->psz_version == NULL )
 489     {
 490         intf_ErrMsg( "module error: can't duplicate strings" );
 491         free( p_module->is.plugin.psz_filename );
 492         free( p_module->psz_name );
 493         free( p_module->psz_longname );
 494         free( p_module->psz_version );
 495         free( p_module );
 496         module_unload( handle );
 497         return( -1 );
 498     }
 499
 500     /* Everything worked fine ! The module is ready to be added to the list. */
 501     p_module->i_usage = 0;
 502     p_module->i_unused_delay = 0;
 503
 504     p_module->b_builtin = 0;
 505
 506     /* Link module into the linked list */
 507     if( p_bank->first != NULL )
 508     {
 509         p_bank->first->prev = p_module;
 510     }
 511     p_module->next = p_bank->first;
 512     p_module->prev = NULL;
 513     p_bank->first = p_module;
 514
 515     /* Immediate message so that a slow module doesn't make the user wait */
 516     intf_WarnMsgImm( 2, "module: plugin module `%s', %s",
 517                      p_module->psz_name, p_module->psz_longname );
 518
 519     return( 0 );
 520 }
 521 #endif /* HAVE_DYNAMIC_PLUGINS */
 522
 523 /*****************************************************************************
 524  * AllocateBuiltinModule: initialize a built-in module.
 525  *****************************************************************************
 526  * This function registers a built-in module and allocates a structure
 527  * for its information data. The module can then be handled by module_Need,
 528  * module_Unneed and HideModule. It can be removed by DeleteModule.
 529  *****************************************************************************/
 530 static int AllocateBuiltinModule( module_bank_t * p_bank,
 531                                   int ( *pf_init ) ( module_t * ),
 532                                   int ( *pf_activate ) ( module_t * ),
 533                                   int ( *pf_deactivate ) ( module_t * ) )
 534 {
 535     module_t * p_module, * p_othermodule;
 536
 537     /* Now that we have successfully loaded the module, we can
 538      * allocate a structure for it */
 539     p_module = malloc( sizeof( module_t ) );
 540     if( p_module == NULL )
 541     {
 542         intf_ErrMsg( "module error: can't allocate p_module" );
 543         return( -1 );
 544     }
 545
 546     /* Initialize the module : fill p_module->psz_name, etc. */
 547     if( pf_init( p_module ) != 0 )
 548     {
 549         /* With a well-written module we shouldn't have to print an
 550          * additional error message here, but just make sure. */
 551         intf_ErrMsg( "module error: failed calling init in builtin module" );
 552         free( p_module );
 553         return( -1 );
 554     }
 555
 556     /* Check that version numbers match */
 557     if( strcmp( VERSION, p_module->psz_version ) )
 558     {
 559         free( p_module );
 560         return( -1 );
 561     }
 562
 563     /* Check that we don't already have a module with this name */
 564     for( p_othermodule = p_bank->first ;
 565          p_othermodule != NULL ;
 566          p_othermodule = p_othermodule->next )
 567     {
 568         if( !strcmp( p_othermodule->psz_name, p_module->psz_name ) )
 569         {
 570             free( p_module );
 571             return( -1 );
 572         }
 573     }
 574
 575     if( pf_activate( p_module ) != 0 )
 576     {
 577         /* With a well-written module we shouldn't have to print an
 578          * additional error message here, but just make sure. */
 579         intf_ErrMsg( "module error: failed calling activate "
 580                      "in builtin module" );
 581         free( p_module );
 582         return( -1 );
 583     }
 584
 585     /* We strdup() these entries so that they are still valid when the
 586      * module is unloaded. */
 587     p_module->psz_name = strdup( p_module->psz_name );
 588     p_module->psz_longname = strdup( p_module->psz_longname );
 589     p_module->psz_version = strdup( p_module->psz_version );
 590     if( p_module->psz_name == NULL
 591             || p_module->psz_longname == NULL
 592             || p_module->psz_version == NULL )
 593     {
 594         intf_ErrMsg( "module error: can't duplicate strings" );
 595         free( p_module->psz_name );
 596         free( p_module->psz_longname );
 597         free( p_module->psz_version );
 598         free( p_module );
 599         return( -1 );
 600     }
 601
 602     /* Everything worked fine ! The module is ready to be added to the list. */
 603     p_module->i_usage = 0;
 604     p_module->i_unused_delay = 0;
 605
 606     p_module->b_builtin = 1;
 607     p_module->is.builtin.pf_deactivate = pf_deactivate;
 608
 609     /* Link module into the linked list */
 610     if( p_bank->first != NULL )
 611     {
 612         p_bank->first->prev = p_module;
 613     }
 614     p_module->next = p_bank->first;
 615     p_module->prev = NULL;
 616     p_bank->first = p_module;
 617
 618     /* Immediate message so that a slow module doesn't make the user wait */
 619     intf_WarnMsgImm( 2, "module: builtin module `%s', %s",
 620                      p_module->psz_name, p_module->psz_longname );
 621
 622     return( 0 );
 623 }
 624
 625 /*****************************************************************************
 626  * DeleteModule: delete a module and its structure.
 627  *****************************************************************************
 628  * This function can only be called if i_usage <= 0.
 629  *****************************************************************************/
 630 static int DeleteModule( module_bank_t * p_bank, module_t * p_module )
 631 {
 632     /* If the module is not in use but is still in memory, we first have
 633      * to hide it and remove it from memory before we can free the
 634      * data structure. */
 635     if( p_module->b_builtin )
 636     {
 637         if( p_module->i_usage != 0 )
 638         {
 639             intf_ErrMsg( "module error: trying to free builtin module `%s' with"
 640                          " usage %i", p_module->psz_name, p_module->i_usage );
 641             return( -1 );
 642         }
 643         else
 644         {
 645             /* We deactivate the module now. */
 646             p_module->is.builtin.pf_deactivate( p_module );
 647         }
 648     }
 649 #ifdef HAVE_DYNAMIC_PLUGINS
 650     else
 651     {
 652         if( p_module->i_usage >= 1 )
 653         {
 654             intf_ErrMsg( "module error: trying to free module `%s' which is"
 655                          " still in use", p_module->psz_name );
 656             return( -1 );
 657         }
 658
 659         /* Two possibilities here: i_usage == -1 and the module is already
 660          * unloaded, we can continue, or i_usage == 0, and we have to hide
 661          * the module before going on. */
 662         if( p_module->i_usage == 0 )
 663         {
 664             if( HideModule( p_module ) != 0 )
 665             {
 666                 return( -1 );
 667             }
 668         }
 669     }
 670 #endif
 671
 672     /* Unlink the module from the linked list. */
 673     if( p_module == p_bank->first )
 674     {
 675         p_bank->first = p_module->next;
 676     }
 677
 678     if( p_module->prev != NULL )
 679     {
 680         p_module->prev->next = p_module->next;
 681     }
 682
 683     if( p_module->next != NULL )
 684     {
 685         p_module->next->prev = p_module->prev;
 686     }
 687
 688     /* We free the structures that we strdup()ed in Allocate*Module(). */
 689 #ifdef HAVE_DYNAMIC_PLUGINS
 690     if( !p_module->b_builtin )
 691     {
 692         free( p_module->is.plugin.psz_filename );
 693     }
 694 #endif
 695     free( p_module->psz_name );
 696     free( p_module->psz_longname );
 697     free( p_module->psz_version );
 698
 699     free( p_module );
 700
 701     return( 0 );
 702 }
 703
 704 /*****************************************************************************
 705  * LockModule: increase the usage count of a module and load it if needed.
 706  *****************************************************************************
 707  * This function has to be called before a thread starts using a module. If
 708  * the module is already loaded, we just increase its usage count. If it isn't
 709  * loaded, we have to dynamically open it and initialize it.
 710  * If you successfully call LockModule() at any moment, be careful to call
 711  * UnlockModule() when you don't need it anymore.
 712  *****************************************************************************/
 713 static int LockModule( module_t * p_module )
 714 {
 715     if( p_module->i_usage >= 0 )
 716     {
 717         /* This module is already loaded and activated, we can return */
 718         p_module->i_usage++;
 719         return( 0 );
 720     }
 721
 722     if( p_module->b_builtin )
 723     {
 724         /* A built-in module should always have a refcount >= 0 ! */
 725         intf_ErrMsg( "module error: built-in module `%s' has refcount %i",
 726                      p_module->psz_name, p_module->i_usage );
 727         return( -1 );
 728     }
 729
 730 #ifdef HAVE_DYNAMIC_PLUGINS
 731     if( p_module->i_usage != -1 )
 732     {
 733         /* This shouldn't happen. Ever. We have serious problems here. */
 734         intf_ErrMsg( "module error: plugin module `%s' has refcount %i",
 735                      p_module->psz_name, p_module->i_usage );
 736         return( -1 );
 737     }
 738
 739     /* i_usage == -1, which means that the module isn't in memory */
 740     if( module_load( p_module->is.plugin.psz_filename,
 741                      &p_module->is.plugin.handle ) )
 742     {
 743         /* The plugin module couldn't be opened */
 744         intf_ErrMsg( "module error: cannot open %s (%s)",
 745                      p_module->is.plugin.psz_filename, module_error() );
 746         return( -1 );
 747     }
 748
 749     /* FIXME: what to do if the guy modified the plugin while it was
 750      * unloaded ? It makes XMMS crash nastily, perhaps we should try
 751      * to be a bit more clever here. */
 752
 753     /* Activate the module : fill the capability structure, etc. */
 754     if( CallSymbol( p_module, "ActivateModule" ) != 0 )
 755     {
 756         /* We couldn't call ActivateModule() -- looks nasty, but
 757          * we can't do much about it. Just try to unload module. */
 758         module_unload( p_module->is.plugin.handle );
 759         p_module->i_usage = -1;
 760         return( -1 );
 761     }
 762
 763     /* Everything worked fine ! The module is ready to be used */
 764     p_module->i_usage = 1;
 765 #endif /* HAVE_DYNAMIC_PLUGINS */
 766
 767     return( 0 );
 768 }
 769
 770 /*****************************************************************************
 771  * UnlockModule: decrease the usage count of a module.
 772  *****************************************************************************
 773  * We decrease the usage count of a module so that we know when a module
 774  * becomes unused and can be hidden.
 775  *****************************************************************************/
 776 static int UnlockModule( module_t * p_module )
 777 {
 778     if( p_module->i_usage <= 0 )
 779     {
 780         /* This shouldn't happen. Ever. We have serious problems here. */
 781         intf_ErrMsg( "module error: trying to call module_Unneed() on `%s'"
 782                      " which isn't even in use", p_module->psz_name );
 783         return( -1 );
 784     }
 785
 786     /* This module is still in use, we can return */
 787     p_module->i_usage--;
 788     p_module->i_unused_delay = 0;
 789
 790     return( 0 );
 791 }
 792
 793 #ifdef HAVE_DYNAMIC_PLUGINS
 794 /*****************************************************************************
 795  * HideModule: remove a module from memory but keep its structure.
 796  *****************************************************************************
 797  * This function can only be called if i_usage == 0. It will make a call
 798  * to the module's inner DeactivateModule() symbol, and then unload it
 799  * from memory. A call to module_Need() will automagically load it again.
 800  *****************************************************************************/
 801 static int HideModule( module_t * p_module )
 802 {
 803     if( p_module->b_builtin )
 804     {
 805         /* A built-in module should never be hidden. */
 806         intf_ErrMsg( "module error: trying to hide built-in module `%s'",
 807                      p_module->psz_name );
 808         return( -1 );
 809     }
 810
 811     if( p_module->i_usage >= 1 )
 812     {
 813         intf_ErrMsg( "module error: trying to hide module `%s' which is still"
 814                      " in use", p_module->psz_name );
 815         return( -1 );
 816     }
 817
 818     if( p_module->i_usage <= -1 )
 819     {
 820         intf_ErrMsg( "module error: trying to hide module `%s' which is already"
 821                      " hidden", p_module->psz_name );
 822         return( -1 );
 823     }
 824
 825     /* Deactivate the module : free the capability structure, etc. */
 826     if( CallSymbol( p_module, "DeactivateModule" ) != 0 )
 827     {
 828         /* We couldn't call DeactivateModule() -- looks nasty, but
 829          * we can't do much about it. Just try to unload module anyway. */
 830         module_unload( p_module->is.plugin.handle );
 831         p_module->i_usage = -1;
 832         return( -1 );
 833     }
 834
 835     /* Everything worked fine, we can safely unload the module. */
 836     module_unload( p_module->is.plugin.handle );
 837     p_module->i_usage = -1;
 838
 839     return( 0 );
 840 }
 841
 842 /*****************************************************************************
 843  * CallSymbol: calls a module symbol.
 844  *****************************************************************************
 845  * This function calls a symbol given its name and a module structure. The
 846  * symbol MUST refer to a function returning int and taking a module_t* as
 847  * an argument.
 848  *****************************************************************************/
 849 static int CallSymbol( module_t * p_module, char * psz_name )
 850 {
 851     typedef int ( symbol_t ) ( module_t * p_module );
 852     symbol_t * p_symbol;
 853
 854     /* Try to resolve the symbol */
 855     p_symbol = module_getsymbol( p_module->is.plugin.handle, psz_name );
 856
 857     if( !p_symbol )
 858     {
 859         /* We couldn't load the symbol */
 860         intf_WarnMsg( 3, "module warning: "
 861                          "cannot find symbol %s in module %s (%s)",
 862                          psz_name, p_module->is.plugin.psz_filename,
 863                          module_error() );
 864         return( -1 );
 865     }
 866
 867     /* We can now try to call the symbol */
 868     if( p_symbol( p_module ) != 0 )
 869     {
 870         /* With a well-written module we shouldn't have to print an
 871          * additional error message here, but just make sure. */
 872         intf_ErrMsg( "module error: failed calling symbol %s in module %s",
 873                      psz_name, p_module->is.plugin.psz_filename );
 874         return( -1 );
 875     }
 876
 877     /* Everything worked fine, we can return */
 878     return( 0 );
 879 }
 880 #endif /* HAVE_DYNAMIC_PLUGINS */
 881