apps/app_stack.c

   1 /*
   2  * Asterisk -- An open source telephony toolkit.
   3  *
   4  * Copyright (c) 2004-2006 Tilghman Lesher <app_stack_v003@the-tilghman.com>.
   5  *
   6  * This code is released by the author with no restrictions on usage.
   7  *
   8  * See http://www.asterisk.org for more information about
   9  * the Asterisk project. Please do not directly contact
  10  * any of the maintainers of this project for assistance;
  11  * the project provides a web site, mailing lists and IRC
  12  * channels for your use.
  13  *
  14  * This program is free software, distributed under the terms of
  15  * the GNU General Public License Version 2. See the LICENSE file
  16  * at the top of the source tree.
  17  */
  18
  19 /*! \file
  20  *
  21  * \brief Stack applications Gosub, Return, etc.
  22  *
  23  * \author Tilghman Lesher <app_stack_v003@the-tilghman.com>
  24  *
  25  * \ingroup applications
  26  */
  27
  28 /*** MODULEINFO
  29         <use>res_agi</use>
  30  ***/
  31
  32 #include "asterisk.h"
  33
  34 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
  35
  36 #include "asterisk/pbx.h"
  37 #include "asterisk/module.h"
  38 #include "asterisk/app.h"
  39 #include "asterisk/manager.h"
  40 #include "asterisk/channel.h"
  41
  42 /* usage of AGI is optional, so indicate that to the header file */
  43 #define ASTERISK_AGI_OPTIONAL
  44 #include "asterisk/agi.h"
  45
  46 /*** DOCUMENTATION
  47         <application name="Gosub" language="en_US">
  48                 <synopsis>
  49                         Jump to label, saving return address.
  50                 </synopsis>
  51                 <syntax>
  52                         <parameter name="context" />
  53                         <parameter name="exten" />
  54                         <parameter name="priority" required="true" hasparams="optional">
  55                                 <argument name="arg1" multiple="true" required="true" />
  56                                 <argument name="argN" />
  57                         </parameter>
  58                 </syntax>
  59                 <description>
  60                         <para>Jumps to the label specified, saving the return address.</para>
  61                 </description>
  62                 <see-also>
  63                         <ref type="application">GosubIf</ref>
  64                         <ref type="application">Macro</ref>
  65                         <ref type="application">Goto</ref>
  66                         <ref type="application">Return</ref>
  67                         <ref type="application">StackPop</ref>
  68                 </see-also>
  69         </application>
  70         <application name="GosubIf" language="en_US">
  71                 <synopsis>
  72                         Conditionally jump to label, saving return address.
  73                 </synopsis>
  74                 <syntax argsep="?">
  75                         <parameter name="condition" required="true" />
  76                         <parameter name="destination" required="true" argsep=":">
  77                                 <argument name="labeliftrue" hasparams="optional">
  78                                         <argument name="arg1" required="true" multiple="true" />
  79                                         <argument name="argN" />
  80                                 </argument>
  81                                 <argument name="labeliffalse" hasparams="optional">
  82                                         <argument name="arg1" required="true" multiple="true" />
  83                                         <argument name="argN" />
  84                                 </argument>
  85                         </parameter>
  86                 </syntax>
  87                 <description>
  88                         <para>If the condition is true, then jump to labeliftrue.  If false, jumps to
  89                         labeliffalse, if specified.  In either case, a jump saves the return point
  90                         in the dialplan, to be returned to with a Return.</para>
  91                 </description>
  92                 <see-also>
  93                         <ref type="application">Gosub</ref>
  94                         <ref type="application">Return</ref>
  95                         <ref type="application">MacroIf</ref>
  96                         <ref type="function">IF</ref>
  97                         <ref type="application">GotoIf</ref>
  98                 </see-also>
  99         </application>
 100         <application name="Return" language="en_US">
 101                 <synopsis>
 102                         Return from gosub routine.
 103                 </synopsis>
 104                 <syntax>
 105                         <parameter name="value">
 106                                 <para>Return value.</para>
 107                         </parameter>
 108                 </syntax>
 109                 <description>
 110                         <para>Jumps to the last label on the stack, removing it. The return <replaceable>value</replaceable>, if
 111                         any, is saved in the channel variable <variable>GOSUB_RETVAL</variable>.</para>
 112                 </description>
 113                 <see-also>
 114                         <ref type="application">Gosub</ref>
 115                         <ref type="application">StackPop</ref>
 116                 </see-also>
 117         </application>
 118         <application name="StackPop" language="en_US">
 119                 <synopsis>
 120                         Remove one address from gosub stack.
 121                 </synopsis>
 122                 <syntax />
 123                 <description>
 124                         <para>Removes last label on the stack, discarding it.</para>
 125                 </description>
 126                 <see-also>
 127                         <ref type="application">Return</ref>
 128                         <ref type="application">Gosub</ref>
 129                 </see-also>
 130         </application>
 131         <function name="LOCAL" language="en_US">
 132                 <synopsis>
 133                         Manage variables local to the gosub stack frame.
 134                 </synopsis>
 135                 <syntax>
 136                         <parameter name="varname" required="true" />
 137                 </syntax>
 138                 <description>
 139                         <para>Read and write a variable local to the gosub stack frame, once we Return() it will be lost
 140                         (or it will go back to whatever value it had before the Gosub()).</para>
 141                 </description>
 142                 <see-also>
 143                         <ref type="application">Gosub</ref>
 144                         <ref type="application">GosubIf</ref>
 145                         <ref type="application">Return</ref>
 146                 </see-also>
 147         </function>
 148  ***/
 149
 150 static const char *app_gosub = "Gosub";
 151 static const char *app_gosubif = "GosubIf";
 152 static const char *app_return = "Return";
 153 static const char *app_pop = "StackPop";
 154
 155 static void gosub_free(void *data);
 156
 157 static struct ast_datastore_info stack_info = {
 158         .type = "GOSUB",
 159         .destroy = gosub_free,
 160 };
 161
 162 struct gosub_stack_frame {
 163         AST_LIST_ENTRY(gosub_stack_frame) entries;
 164         /* 100 arguments is all that we support anyway, but this will handle up to 255 */
 165         unsigned char arguments;
 166         struct varshead varshead;
 167         int priority;
 168         char *context;
 169         char extension[0];
 170 };
 171
 172 static int frame_set_var(struct ast_channel *chan, struct gosub_stack_frame *frame, const char *var, const char *value)
 173 {
 174         struct ast_var_t *variables;
 175         int found = 0;
 176
 177         /* Does this variable already exist? */
 178         AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
 179                 if (!strcmp(var, ast_var_name(variables))) {
 180                         found = 1;
 181                         break;
 182                 }
 183         }
 184
 185         if (!ast_strlen_zero(value)) {
 186                 if (!found) {
 187                         variables = ast_var_assign(var, "");
 188                         AST_LIST_INSERT_HEAD(&frame->varshead, variables, entries);
 189                         pbx_builtin_pushvar_helper(chan, var, value);
 190                 } else
 191                         pbx_builtin_setvar_helper(chan, var, value);
 192
 193                 manager_event(EVENT_FLAG_DIALPLAN, "VarSet",
 194                         "Channel: %s\r\n"
 195                         "Variable: LOCAL(%s)\r\n"
 196                         "Value: %s\r\n"
 197                         "Uniqueid: %s\r\n",
 198                         chan->name, var, value, chan->uniqueid);
 199         }
 200         return 0;
 201 }
 202
 203 static void gosub_release_frame(struct ast_channel *chan, struct gosub_stack_frame *frame)
 204 {
 205         struct ast_var_t *vardata;
 206
 207         /* If chan is not defined, then we're calling it as part of gosub_free,
 208          * and the channel variables will be deallocated anyway.  Otherwise, we're
 209          * just releasing a single frame, so we need to clean up the arguments for
 210          * that frame, so that we re-expose the variables from the previous frame
 211          * that were hidden by this one.
 212          */
 213         while ((vardata = AST_LIST_REMOVE_HEAD(&frame->varshead, entries))) {
 214                 if (chan)
 215                         pbx_builtin_setvar_helper(chan, ast_var_name(vardata), NULL);
 216                 ast_var_delete(vardata);
 217         }
 218
 219         ast_free(frame);
 220 }
 221
 222 static struct gosub_stack_frame *gosub_allocate_frame(const char *context, const char *extension, int priority, unsigned char arguments)
 223 {
 224         struct gosub_stack_frame *new = NULL;
 225         int len_extension = strlen(extension), len_context = strlen(context);
 226
 227         if ((new = ast_calloc(1, sizeof(*new) + 2 + len_extension + len_context))) {
 228                 AST_LIST_HEAD_INIT_NOLOCK(&new->varshead);
 229                 strcpy(new->extension, extension);
 230                 new->context = new->extension + len_extension + 1;
 231                 strcpy(new->context, context);
 232                 new->priority = priority;
 233                 new->arguments = arguments;
 234         }
 235         return new;
 236 }
 237
 238 static void gosub_free(void *data)
 239 {
 240         AST_LIST_HEAD(, gosub_stack_frame) *oldlist = data;
 241         struct gosub_stack_frame *oldframe;
 242         AST_LIST_LOCK(oldlist);
 243         while ((oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries))) {
 244                 gosub_release_frame(NULL, oldframe);
 245         }
 246         AST_LIST_UNLOCK(oldlist);
 247         AST_LIST_HEAD_DESTROY(oldlist);
 248         ast_free(oldlist);
 249 }
 250
 251 static int pop_exec(struct ast_channel *chan, void *data)
 252 {
 253         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 254         struct gosub_stack_frame *oldframe;
 255         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 256
 257         if (!stack_store) {
 258                 ast_log(LOG_WARNING, "%s called with no gosub stack allocated.\n", app_pop);
 259                 return 0;
 260         }
 261
 262         oldlist = stack_store->data;
 263         AST_LIST_LOCK(oldlist);
 264         oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
 265         AST_LIST_UNLOCK(oldlist);
 266
 267         if (oldframe) {
 268                 gosub_release_frame(chan, oldframe);
 269         } else {
 270                 ast_debug(1, "%s called with an empty gosub stack\n", app_pop);
 271         }
 272         return 0;
 273 }
 274
 275 static int return_exec(struct ast_channel *chan, void *data)
 276 {
 277         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 278         struct gosub_stack_frame *oldframe;
 279         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 280         char *retval = data;
 281
 282         if (!stack_store) {
 283                 ast_log(LOG_ERROR, "Return without Gosub: stack is unallocated\n");
 284                 return -1;
 285         }
 286
 287         oldlist = stack_store->data;
 288         AST_LIST_LOCK(oldlist);
 289         oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
 290         AST_LIST_UNLOCK(oldlist);
 291
 292         if (!oldframe) {
 293                 ast_log(LOG_ERROR, "Return without Gosub: stack is empty\n");
 294                 return -1;
 295         }
 296
 297         ast_explicit_goto(chan, oldframe->context, oldframe->extension, oldframe->priority);
 298         gosub_release_frame(chan, oldframe);
 299
 300         /* Set a return value, if any */
 301         pbx_builtin_setvar_helper(chan, "GOSUB_RETVAL", S_OR(retval, ""));
 302         return 0;
 303 }
 304
 305 static int gosub_exec(struct ast_channel *chan, void *data)
 306 {
 307         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 308         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 309         struct gosub_stack_frame *newframe;
 310         char argname[15], *tmp = ast_strdupa(data), *label, *endparen;
 311         int i;
 312         AST_DECLARE_APP_ARGS(args2,
 313                 AST_APP_ARG(argval)[100];
 314         );
 315
 316         if (ast_strlen_zero(data)) {
 317                 ast_log(LOG_ERROR, "%s requires an argument: %s([[context,]exten,]priority[(arg1[,...][,argN])])\n", app_gosub, app_gosub);
 318                 return -1;
 319         }
 320
 321         if (!stack_store) {
 322                 ast_debug(1, "Channel %s has no datastore, so we're allocating one.\n", chan->name);
 323                 stack_store = ast_datastore_alloc(&stack_info, NULL);
 324                 if (!stack_store) {
 325                         ast_log(LOG_ERROR, "Unable to allocate new datastore.  Gosub will fail.\n");
 326                         return -1;
 327                 }
 328
 329                 oldlist = ast_calloc(1, sizeof(*oldlist));
 330                 if (!oldlist) {
 331                         ast_log(LOG_ERROR, "Unable to allocate datastore list head.  Gosub will fail.\n");
 332                         ast_datastore_free(stack_store);
 333                         return -1;
 334                 }
 335
 336                 stack_store->data = oldlist;
 337                 AST_LIST_HEAD_INIT(oldlist);
 338                 ast_channel_datastore_add(chan, stack_store);
 339         }
 340
 341         /* Separate the arguments from the label */
 342         /* NOTE:  you cannot use ast_app_separate_args for this, because '(' cannot be used as a delimiter. */
 343         label = strsep(&tmp, "(");
 344         if (tmp) {
 345                 endparen = strrchr(tmp, ')');
 346                 if (endparen)
 347                         *endparen = '\0';
 348                 else
 349                         ast_log(LOG_WARNING, "Ouch.  No closing paren: '%s'?\n", (char *)data);
 350                 AST_STANDARD_APP_ARGS(args2, tmp);
 351         } else
 352                 args2.argc = 0;
 353
 354         /* Create the return address, but don't save it until we know that the Gosub destination exists */
 355         newframe = gosub_allocate_frame(chan->context, chan->exten, chan->priority + 1, args2.argc);
 356
 357         if (!newframe)
 358                 return -1;
 359
 360         if (ast_parseable_goto(chan, label)) {
 361                 ast_log(LOG_ERROR, "Gosub address is invalid: '%s'\n", (char *)data);
 362                 ast_free(newframe);
 363                 return -1;
 364         }
 365
 366         /* Now that we know for certain that we're going to a new location, set our arguments */
 367         for (i = 0; i < args2.argc; i++) {
 368                 snprintf(argname, sizeof(argname), "ARG%d", i + 1);
 369                 frame_set_var(chan, newframe, argname, args2.argval[i]);
 370                 ast_debug(1, "Setting '%s' to '%s'\n", argname, args2.argval[i]);
 371         }
 372         snprintf(argname, sizeof(argname), "%d", args2.argc);
 373         frame_set_var(chan, newframe, "ARGC", argname);
 374
 375         /* And finally, save our return address */
 376         oldlist = stack_store->data;
 377         AST_LIST_LOCK(oldlist);
 378         AST_LIST_INSERT_HEAD(oldlist, newframe, entries);
 379         AST_LIST_UNLOCK(oldlist);
 380
 381         return 0;
 382 }
 383
 384 static int gosubif_exec(struct ast_channel *chan, void *data)
 385 {
 386         char *args;
 387         int res=0;
 388         AST_DECLARE_APP_ARGS(cond,
 389                 AST_APP_ARG(ition);
 390                 AST_APP_ARG(labels);
 391         );
 392         AST_DECLARE_APP_ARGS(label,
 393                 AST_APP_ARG(iftrue);
 394                 AST_APP_ARG(iffalse);
 395         );
 396
 397         if (ast_strlen_zero(data)) {
 398                 ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
 399                 return 0;
 400         }
 401
 402         args = ast_strdupa(data);
 403         AST_NONSTANDARD_APP_ARGS(cond, args, '?');
 404         if (cond.argc != 2) {
 405                 ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
 406                 return 0;
 407         }
 408
 409         AST_NONSTANDARD_APP_ARGS(label, cond.labels, ':');
 410
 411         if (pbx_checkcondition(cond.ition)) {
 412                 if (!ast_strlen_zero(label.iftrue))
 413                         res = gosub_exec(chan, label.iftrue);
 414         } else if (!ast_strlen_zero(label.iffalse)) {
 415                 res = gosub_exec(chan, label.iffalse);
 416         }
 417
 418         return res;
 419 }
 420
 421 static int local_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
 422 {
 423         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 424         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 425         struct gosub_stack_frame *frame;
 426         struct ast_var_t *variables;
 427
 428         if (!stack_store)
 429                 return -1;
 430
 431         oldlist = stack_store->data;
 432         AST_LIST_LOCK(oldlist);
 433         frame = AST_LIST_FIRST(oldlist);
 434         AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
 435                 if (!strcmp(data, ast_var_name(variables))) {
 436                         const char *tmp;
 437                         ast_channel_lock(chan);
 438                         tmp = pbx_builtin_getvar_helper(chan, data);
 439                         ast_copy_string(buf, S_OR(tmp, ""), len);
 440                         ast_channel_unlock(chan);
 441                         break;
 442                 }
 443         }
 444         AST_LIST_UNLOCK(oldlist);
 445         return 0;
 446 }
 447
 448 static int local_write(struct ast_channel *chan, const char *cmd, char *var, const char *value)
 449 {
 450         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 451         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 452         struct gosub_stack_frame *frame;
 453
 454         if (!stack_store) {
 455                 ast_log(LOG_ERROR, "Tried to set LOCAL(%s), but we aren't within a Gosub routine\n", var);
 456                 return -1;
 457         }
 458
 459         oldlist = stack_store->data;
 460         AST_LIST_LOCK(oldlist);
 461         frame = AST_LIST_FIRST(oldlist);
 462
 463         if (frame)
 464                 frame_set_var(chan, frame, var, value);
 465
 466         AST_LIST_UNLOCK(oldlist);
 467
 468         return 0;
 469 }
 470
 471 static struct ast_custom_function local_function = {
 472         .name = "LOCAL",
 473         .write = local_write,
 474         .read = local_read,
 475 };
 476
 477 static int handle_gosub(struct ast_channel *chan, AGI *agi, int argc, char **argv)
 478 {
 479         int old_priority, priority;
 480         char old_context[AST_MAX_CONTEXT], old_extension[AST_MAX_EXTENSION];
 481         struct ast_app *theapp;
 482         char *gosub_args;
 483
 484         if (argc < 4 || argc > 5) {
 485                 return RESULT_SHOWUSAGE;
 486         }
 487
 488         ast_debug(1, "Gosub called with %d arguments: 0:%s 1:%s 2:%s 3:%s 4:%s\n", argc, argv[0], argv[1], argv[2], argv[3], argc == 5 ? argv[4] : "");
 489
 490         if (sscanf(argv[3], "%d", &priority) != 1 || priority < 1) {
 491                 /* Lookup the priority label */
 492                 if ((priority = ast_findlabel_extension(chan, argv[1], argv[2], argv[3], chan->cid.cid_num)) < 0) {
 493                         ast_log(LOG_ERROR, "Priority '%s' not found in '%s@%s'\n", argv[3], argv[2], argv[1]);
 494                         ast_agi_fdprintf(chan, agi->fd, "200 result=-1 Gosub label not found\n");
 495                         return RESULT_FAILURE;
 496                 }
 497         } else if (!ast_exists_extension(chan, argv[1], argv[2], priority, chan->cid.cid_num)) {
 498                 ast_agi_fdprintf(chan, agi->fd, "200 result=-1 Gosub label not found\n");
 499                 return RESULT_FAILURE;
 500         }
 501
 502         /* Save previous location, since we're going to change it */
 503         ast_copy_string(old_context, chan->context, sizeof(old_context));
 504         ast_copy_string(old_extension, chan->exten, sizeof(old_extension));
 505         old_priority = chan->priority;
 506
 507         if (!(theapp = pbx_findapp("Gosub"))) {
 508                 ast_log(LOG_ERROR, "Gosub() cannot be found in the list of loaded applications\n");
 509                 ast_agi_fdprintf(chan, agi->fd, "503 result=-2 Gosub is not loaded\n");
 510                 return RESULT_FAILURE;
 511         }
 512
 513         /* Apparently, if you run ast_pbx_run on a channel that already has a pbx
 514          * structure, you need to add 1 to the priority to get it to go to the
 515          * right place.  But if it doesn't have a pbx structure, then leaving off
 516          * the 1 is the right thing to do.  See how this code differs when we
 517          * call a Gosub for the CALLEE channel in Dial or Queue.
 518          */
 519         if (argc == 5) {
 520                 if (asprintf(&gosub_args, "%s,%s,%d(%s)", argv[1], argv[2], priority + 1, argv[4]) < 0) {
 521                         ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
 522                         gosub_args = NULL;
 523                 }
 524         } else {
 525                 if (asprintf(&gosub_args, "%s,%s,%d", argv[1], argv[2], priority + 1) < 0) {
 526                         ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
 527                         gosub_args = NULL;
 528                 }
 529         }
 530
 531         if (gosub_args) {
 532                 int res;
 533
 534                 ast_debug(1, "Trying gosub with arguments '%s'\n", gosub_args);
 535                 ast_copy_string(chan->context, "app_stack_gosub_virtual_context", sizeof(chan->context));
 536                 ast_copy_string(chan->exten, "s", sizeof(chan->exten));
 537                 chan->priority = 0;
 538
 539                 if ((res = pbx_exec(chan, theapp, gosub_args)) == 0) {
 540                         struct ast_pbx *pbx = chan->pbx;
 541                         /* Suppress warning about PBX already existing */
 542                         chan->pbx = NULL;
 543                         ast_agi_fdprintf(chan, agi->fd, "100 result=0 Trying...\n");
 544                         ast_pbx_run(chan);
 545                         ast_agi_fdprintf(chan, agi->fd, "200 result=0 Gosub complete\n");
 546                         if (chan->pbx) {
 547                                 ast_free(chan->pbx);
 548                         }
 549                         chan->pbx = pbx;
 550                 } else {
 551                         ast_agi_fdprintf(chan, agi->fd, "200 result=%d Gosub failed\n", res);
 552                 }
 553                 ast_free(gosub_args);
 554         } else {
 555                 ast_agi_fdprintf(chan, agi->fd, "503 result=-2 Memory allocation failure\n");
 556                 return RESULT_FAILURE;
 557         }
 558
 559         /* Restore previous location */
 560         ast_copy_string(chan->context, old_context, sizeof(chan->context));
 561         ast_copy_string(chan->exten, old_extension, sizeof(chan->exten));
 562         chan->priority = old_priority;
 563
 564         return RESULT_SUCCESS;
 565 }
 566
 567 static char usage_gosub[] =
 568 " Usage: GOSUB <context> <extension> <priority> [<optional-argument>]\n"
 569 "   Cause the channel to execute the specified dialplan subroutine, returning\n"
 570 " to the dialplan with execution of a Return()\n";
 571
 572 struct agi_command gosub_agi_command =
 573         { { "gosub", NULL }, handle_gosub, "Execute a dialplan subroutine", usage_gosub , 0 };
 574
 575 static int unload_module(void)
 576 {
 577         struct ast_context *con;
 578
 579         if (ast_agi_unregister) {
 580                 ast_agi_unregister(ast_module_info->self, &gosub_agi_command);
 581
 582                 if ((con = ast_context_find("app_stack_gosub_virtual_context"))) {
 583                         ast_context_remove_extension2(con, "s", 1, NULL, 0);
 584                         ast_context_destroy(con, "app_stack"); /* leave nothing behind */
 585                 }
 586         }
 587
 588         ast_unregister_application(app_return);
 589         ast_unregister_application(app_pop);
 590         ast_unregister_application(app_gosubif);
 591         ast_unregister_application(app_gosub);
 592         ast_custom_function_unregister(&local_function);
 593
 594         return 0;
 595 }
 596
 597 static int load_module(void)
 598 {
 599         struct ast_context *con;
 600
 601         /* usage of AGI is optional, so check to see if the ast_agi_register()
 602            function is available; if so, use it.
 603         */
 604         if (ast_agi_register) {
 605                 con = ast_context_find_or_create(NULL, NULL, "app_stack_gosub_virtual_context", "app_stack");
 606                 if (!con) {
 607                         ast_log(LOG_ERROR, "Virtual context 'app_stack_gosub_virtual_context' does not exist and unable to create\n");
 608                         return AST_MODULE_LOAD_DECLINE;
 609                 } else {
 610                         ast_add_extension2(con, 1, "s", 1, NULL, NULL, "KeepAlive", ast_strdup(""), ast_free_ptr, "app_stack");
 611                 }
 612
 613                 ast_agi_register(ast_module_info->self, &gosub_agi_command);
 614         }
 615
 616         ast_register_application_xml(app_pop, pop_exec);
 617         ast_register_application_xml(app_return, return_exec);
 618         ast_register_application_xml(app_gosubif, gosubif_exec);
 619         ast_register_application_xml(app_gosub, gosub_exec);
 620         ast_custom_function_register(&local_function);
 621
 622         return 0;
 623 }
 624
 625 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan subroutines (Gosub, Return, etc)");