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 #include "asterisk/agi.h"
  42
  43 /*** DOCUMENTATION
  44         <application name="Gosub" language="en_US">
  45                 <synopsis>
  46                         Jump to label, saving return address.
  47                 </synopsis>
  48                 <syntax>
  49                         <parameter name="context" />
  50                         <parameter name="exten" />
  51                         <parameter name="priority" required="true" hasparams="optional">
  52                                 <argument name="arg1" multiple="true" required="true" />
  53                                 <argument name="argN" />
  54                         </parameter>
  55                 </syntax>
  56                 <description>
  57                         <para>Jumps to the label specified, saving the return address.</para>
  58                 </description>
  59                 <see-also>
  60                         <ref type="application">GosubIf</ref>
  61                         <ref type="application">Macro</ref>
  62                         <ref type="application">Goto</ref>
  63                         <ref type="application">Return</ref>
  64                         <ref type="application">StackPop</ref>
  65                 </see-also>
  66         </application>
  67         <application name="GosubIf" language="en_US">
  68                 <synopsis>
  69                         Conditionally jump to label, saving return address.
  70                 </synopsis>
  71                 <syntax argsep="?">
  72                         <parameter name="condition" required="true" />
  73                         <parameter name="destination" required="true" argsep=":">
  74                                 <argument name="labeliftrue" hasparams="optional">
  75                                         <argument name="arg1" required="true" multiple="true" />
  76                                         <argument name="argN" />
  77                                 </argument>
  78                                 <argument name="labeliffalse" hasparams="optional">
  79                                         <argument name="arg1" required="true" multiple="true" />
  80                                         <argument name="argN" />
  81                                 </argument>
  82                         </parameter>
  83                 </syntax>
  84                 <description>
  85                         <para>If the condition is true, then jump to labeliftrue.  If false, jumps to
  86                         labeliffalse, if specified.  In either case, a jump saves the return point
  87                         in the dialplan, to be returned to with a Return.</para>
  88                 </description>
  89                 <see-also>
  90                         <ref type="application">Gosub</ref>
  91                         <ref type="application">Return</ref>
  92                         <ref type="application">MacroIf</ref>
  93                         <ref type="function">IF</ref>
  94                         <ref type="application">GotoIf</ref>
  95                 </see-also>
  96         </application>
  97         <application name="Return" language="en_US">
  98                 <synopsis>
  99                         Return from gosub routine.
 100                 </synopsis>
 101                 <syntax>
 102                         <parameter name="value">
 103                                 <para>Return value.</para>
 104                         </parameter>
 105                 </syntax>
 106                 <description>
 107                         <para>Jumps to the last label on the stack, removing it. The return <replaceable>value</replaceable>, if
 108                         any, is saved in the channel variable <variable>GOSUB_RETVAL</variable>.</para>
 109                 </description>
 110                 <see-also>
 111                         <ref type="application">Gosub</ref>
 112                         <ref type="application">StackPop</ref>
 113                 </see-also>
 114         </application>
 115         <application name="StackPop" language="en_US">
 116                 <synopsis>
 117                         Remove one address from gosub stack.
 118                 </synopsis>
 119                 <syntax />
 120                 <description>
 121                         <para>Removes last label on the stack, discarding it.</para>
 122                 </description>
 123                 <see-also>
 124                         <ref type="application">Return</ref>
 125                         <ref type="application">Gosub</ref>
 126                 </see-also>
 127         </application>
 128         <function name="LOCAL" language="en_US">
 129                 <synopsis>
 130                         Manage variables local to the gosub stack frame.
 131                 </synopsis>
 132                 <syntax>
 133                         <parameter name="varname" required="true" />
 134                 </syntax>
 135                 <description>
 136                         <para>Read and write a variable local to the gosub stack frame, once we Return() it will be lost
 137                         (or it will go back to whatever value it had before the Gosub()).</para>
 138                 </description>
 139                 <see-also>
 140                         <ref type="application">Gosub</ref>
 141                         <ref type="application">GosubIf</ref>
 142                         <ref type="application">Return</ref>
 143                 </see-also>
 144         </function>
 145         <function name="LOCAL_PEEK" language="en_US">
 146                 <synopsis>
 147                         Retrieve variables hidden by the local gosub stack frame.
 148                 </synopsis>
 149                 <syntax>
 150                         <parameter name="n" required="true" />
 151                         <parameter name="varname" required="true" />
 152                 </syntax>
 153                 <description>
 154                         <para>Read a variable <replaceable>varname</replaceable> hidden by
 155                         <replaceable>n</replaceable> levels of gosub stack frames.  Note that ${LOCAL_PEEK(0,foo)}
 156                         is the same as ${foo}, since the value of <replaceable>n</replaceable> peeks under 0 levels of
 157                         stack frames; in other words, 0 is the current level.  If <replaceable>n</replaceable> exceeds
 158                         the available number of stack frames, then an empty string is returned.</para>
 159                 </description>
 160                 <see-also>
 161                         <ref type="application">Gosub</ref>
 162                         <ref type="application">GosubIf</ref>
 163                         <ref type="application">Return</ref>
 164                 </see-also>
 165         </function>
 166  ***/
 167
 168 static const char *app_gosub = "Gosub";
 169 static const char *app_gosubif = "GosubIf";
 170 static const char *app_return = "Return";
 171 static const char *app_pop = "StackPop";
 172
 173 static void gosub_free(void *data);
 174
 175 static struct ast_datastore_info stack_info = {
 176         .type = "GOSUB",
 177         .destroy = gosub_free,
 178 };
 179
 180 struct gosub_stack_frame {
 181         AST_LIST_ENTRY(gosub_stack_frame) entries;
 182         /* 100 arguments is all that we support anyway, but this will handle up to 255 */
 183         unsigned char arguments;
 184         struct varshead varshead;
 185         int priority;
 186         char *context;
 187         char extension[0];
 188 };
 189
 190 static int frame_set_var(struct ast_channel *chan, struct gosub_stack_frame *frame, const char *var, const char *value)
 191 {
 192         struct ast_var_t *variables;
 193         int found = 0;
 194
 195         /* Does this variable already exist? */
 196         AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
 197                 if (!strcmp(var, ast_var_name(variables))) {
 198                         found = 1;
 199                         break;
 200                 }
 201         }
 202
 203         if (!ast_strlen_zero(value)) {
 204                 if (!found) {
 205                         variables = ast_var_assign(var, "");
 206                         AST_LIST_INSERT_HEAD(&frame->varshead, variables, entries);
 207                         pbx_builtin_pushvar_helper(chan, var, value);
 208                 } else
 209                         pbx_builtin_setvar_helper(chan, var, value);
 210
 211                 manager_event(EVENT_FLAG_DIALPLAN, "VarSet",
 212                         "Channel: %s\r\n"
 213                         "Variable: LOCAL(%s)\r\n"
 214                         "Value: %s\r\n"
 215                         "Uniqueid: %s\r\n",
 216                         chan->name, var, value, chan->uniqueid);
 217         }
 218         return 0;
 219 }
 220
 221 static void gosub_release_frame(struct ast_channel *chan, struct gosub_stack_frame *frame)
 222 {
 223         struct ast_var_t *vardata;
 224
 225         /* If chan is not defined, then we're calling it as part of gosub_free,
 226          * and the channel variables will be deallocated anyway.  Otherwise, we're
 227          * just releasing a single frame, so we need to clean up the arguments for
 228          * that frame, so that we re-expose the variables from the previous frame
 229          * that were hidden by this one.
 230          */
 231         while ((vardata = AST_LIST_REMOVE_HEAD(&frame->varshead, entries))) {
 232                 if (chan)
 233                         pbx_builtin_setvar_helper(chan, ast_var_name(vardata), NULL);
 234                 ast_var_delete(vardata);
 235         }
 236
 237         ast_free(frame);
 238 }
 239
 240 static struct gosub_stack_frame *gosub_allocate_frame(const char *context, const char *extension, int priority, unsigned char arguments)
 241 {
 242         struct gosub_stack_frame *new = NULL;
 243         int len_extension = strlen(extension), len_context = strlen(context);
 244
 245         if ((new = ast_calloc(1, sizeof(*new) + 2 + len_extension + len_context))) {
 246                 AST_LIST_HEAD_INIT_NOLOCK(&new->varshead);
 247                 strcpy(new->extension, extension);
 248                 new->context = new->extension + len_extension + 1;
 249                 strcpy(new->context, context);
 250                 new->priority = priority;
 251                 new->arguments = arguments;
 252         }
 253         return new;
 254 }
 255
 256 static void gosub_free(void *data)
 257 {
 258         AST_LIST_HEAD(, gosub_stack_frame) *oldlist = data;
 259         struct gosub_stack_frame *oldframe;
 260         AST_LIST_LOCK(oldlist);
 261         while ((oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries))) {
 262                 gosub_release_frame(NULL, oldframe);
 263         }
 264         AST_LIST_UNLOCK(oldlist);
 265         AST_LIST_HEAD_DESTROY(oldlist);
 266         ast_free(oldlist);
 267 }
 268
 269 static int pop_exec(struct ast_channel *chan, void *data)
 270 {
 271         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 272         struct gosub_stack_frame *oldframe;
 273         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 274
 275         if (!stack_store) {
 276                 ast_log(LOG_WARNING, "%s called with no gosub stack allocated.\n", app_pop);
 277                 return 0;
 278         }
 279
 280         oldlist = stack_store->data;
 281         AST_LIST_LOCK(oldlist);
 282         oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
 283         AST_LIST_UNLOCK(oldlist);
 284
 285         if (oldframe) {
 286                 gosub_release_frame(chan, oldframe);
 287         } else {
 288                 ast_debug(1, "%s called with an empty gosub stack\n", app_pop);
 289         }
 290         return 0;
 291 }
 292
 293 static int return_exec(struct ast_channel *chan, void *data)
 294 {
 295         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 296         struct gosub_stack_frame *oldframe;
 297         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 298         char *retval = data;
 299
 300         if (!stack_store) {
 301                 ast_log(LOG_ERROR, "Return without Gosub: stack is unallocated\n");
 302                 return -1;
 303         }
 304
 305         oldlist = stack_store->data;
 306         AST_LIST_LOCK(oldlist);
 307         oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
 308         AST_LIST_UNLOCK(oldlist);
 309
 310         if (!oldframe) {
 311                 ast_log(LOG_ERROR, "Return without Gosub: stack is empty\n");
 312                 return -1;
 313         }
 314
 315         ast_explicit_goto(chan, oldframe->context, oldframe->extension, oldframe->priority);
 316         gosub_release_frame(chan, oldframe);
 317
 318         /* Set a return value, if any */
 319         pbx_builtin_setvar_helper(chan, "GOSUB_RETVAL", S_OR(retval, ""));
 320         return 0;
 321 }
 322
 323 static int gosub_exec(struct ast_channel *chan, void *data)
 324 {
 325         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 326         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 327         struct gosub_stack_frame *newframe;
 328         char argname[15], *tmp = ast_strdupa(data), *label, *endparen;
 329         int i;
 330         AST_DECLARE_APP_ARGS(args2,
 331                 AST_APP_ARG(argval)[100];
 332         );
 333
 334         if (ast_strlen_zero(data)) {
 335                 ast_log(LOG_ERROR, "%s requires an argument: %s([[context,]exten,]priority[(arg1[,...][,argN])])\n", app_gosub, app_gosub);
 336                 return -1;
 337         }
 338
 339         if (!stack_store) {
 340                 ast_debug(1, "Channel %s has no datastore, so we're allocating one.\n", chan->name);
 341                 stack_store = ast_datastore_alloc(&stack_info, NULL);
 342                 if (!stack_store) {
 343                         ast_log(LOG_ERROR, "Unable to allocate new datastore.  Gosub will fail.\n");
 344                         return -1;
 345                 }
 346
 347                 oldlist = ast_calloc(1, sizeof(*oldlist));
 348                 if (!oldlist) {
 349                         ast_log(LOG_ERROR, "Unable to allocate datastore list head.  Gosub will fail.\n");
 350                         ast_datastore_free(stack_store);
 351                         return -1;
 352                 }
 353
 354                 stack_store->data = oldlist;
 355                 AST_LIST_HEAD_INIT(oldlist);
 356                 ast_channel_datastore_add(chan, stack_store);
 357         }
 358
 359         /* Separate the arguments from the label */
 360         /* NOTE:  you cannot use ast_app_separate_args for this, because '(' cannot be used as a delimiter. */
 361         label = strsep(&tmp, "(");
 362         if (tmp) {
 363                 endparen = strrchr(tmp, ')');
 364                 if (endparen)
 365                         *endparen = '\0';
 366                 else
 367                         ast_log(LOG_WARNING, "Ouch.  No closing paren: '%s'?\n", (char *)data);
 368                 AST_STANDARD_APP_ARGS(args2, tmp);
 369         } else
 370                 args2.argc = 0;
 371
 372         /* Create the return address, but don't save it until we know that the Gosub destination exists */
 373         newframe = gosub_allocate_frame(chan->context, chan->exten, chan->priority + 1, args2.argc);
 374
 375         if (!newframe)
 376                 return -1;
 377
 378         if (ast_parseable_goto(chan, label)) {
 379                 ast_log(LOG_ERROR, "Gosub address is invalid: '%s'\n", (char *)data);
 380                 ast_free(newframe);
 381                 return -1;
 382         }
 383
 384         /* Now that we know for certain that we're going to a new location, set our arguments */
 385         for (i = 0; i < args2.argc; i++) {
 386                 snprintf(argname, sizeof(argname), "ARG%d", i + 1);
 387                 frame_set_var(chan, newframe, argname, args2.argval[i]);
 388                 ast_debug(1, "Setting '%s' to '%s'\n", argname, args2.argval[i]);
 389         }
 390         snprintf(argname, sizeof(argname), "%d", args2.argc);
 391         frame_set_var(chan, newframe, "ARGC", argname);
 392
 393         /* And finally, save our return address */
 394         oldlist = stack_store->data;
 395         AST_LIST_LOCK(oldlist);
 396         AST_LIST_INSERT_HEAD(oldlist, newframe, entries);
 397         AST_LIST_UNLOCK(oldlist);
 398
 399         return 0;
 400 }
 401
 402 static int gosubif_exec(struct ast_channel *chan, void *data)
 403 {
 404         char *args;
 405         int res=0;
 406         AST_DECLARE_APP_ARGS(cond,
 407                 AST_APP_ARG(ition);
 408                 AST_APP_ARG(labels);
 409         );
 410         AST_DECLARE_APP_ARGS(label,
 411                 AST_APP_ARG(iftrue);
 412                 AST_APP_ARG(iffalse);
 413         );
 414
 415         if (ast_strlen_zero(data)) {
 416                 ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
 417                 return 0;
 418         }
 419
 420         args = ast_strdupa(data);
 421         AST_NONSTANDARD_APP_ARGS(cond, args, '?');
 422         if (cond.argc != 2) {
 423                 ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
 424                 return 0;
 425         }
 426
 427         AST_NONSTANDARD_APP_ARGS(label, cond.labels, ':');
 428
 429         if (pbx_checkcondition(cond.ition)) {
 430                 if (!ast_strlen_zero(label.iftrue))
 431                         res = gosub_exec(chan, label.iftrue);
 432         } else if (!ast_strlen_zero(label.iffalse)) {
 433                 res = gosub_exec(chan, label.iffalse);
 434         }
 435
 436         return res;
 437 }
 438
 439 static int local_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
 440 {
 441         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 442         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 443         struct gosub_stack_frame *frame;
 444         struct ast_var_t *variables;
 445
 446         if (!stack_store)
 447                 return -1;
 448
 449         oldlist = stack_store->data;
 450         AST_LIST_LOCK(oldlist);
 451         frame = AST_LIST_FIRST(oldlist);
 452         AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
 453                 if (!strcmp(data, ast_var_name(variables))) {
 454                         const char *tmp;
 455                         ast_channel_lock(chan);
 456                         tmp = pbx_builtin_getvar_helper(chan, data);
 457                         ast_copy_string(buf, S_OR(tmp, ""), len);
 458                         ast_channel_unlock(chan);
 459                         break;
 460                 }
 461         }
 462         AST_LIST_UNLOCK(oldlist);
 463         return 0;
 464 }
 465
 466 static int local_write(struct ast_channel *chan, const char *cmd, char *var, const char *value)
 467 {
 468         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
 469         AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
 470         struct gosub_stack_frame *frame;
 471
 472         if (!stack_store) {
 473                 ast_log(LOG_ERROR, "Tried to set LOCAL(%s), but we aren't within a Gosub routine\n", var);
 474                 return -1;
 475         }
 476
 477         oldlist = stack_store->data;
 478         AST_LIST_LOCK(oldlist);
 479         frame = AST_LIST_FIRST(oldlist);
 480
 481         if (frame)
 482                 frame_set_var(chan, frame, var, value);
 483
 484         AST_LIST_UNLOCK(oldlist);
 485
 486         return 0;
 487 }
 488
 489 static struct ast_custom_function local_function = {
 490         .name = "LOCAL",
 491         .write = local_write,
 492         .read = local_read,
 493 };
 494
 495 static int peek_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
 496 {
 497         int found = 0, n;
 498         struct ast_var_t *variables;
 499         AST_DECLARE_APP_ARGS(args,
 500                 AST_APP_ARG(n);
 501                 AST_APP_ARG(name);
 502         );
 503
 504         if (!chan) {
 505                 ast_log(LOG_ERROR, "LOCAL_PEEK must be called on an active channel\n");
 506                 return -1;
 507         }
 508
 509         AST_STANDARD_APP_ARGS(args, data);
 510         n = atoi(args.n);
 511         *buf = '\0';
 512
 513         ast_channel_lock(chan);
 514         AST_LIST_TRAVERSE(&chan->varshead, variables, entries) {
 515                 if (!strcmp(args.name, ast_var_name(variables)) && ++found > n) {
 516                         ast_copy_string(buf, ast_var_value(variables), len);
 517                         break;
 518                 }
 519         }
 520         ast_channel_unlock(chan);
 521         return 0;
 522 }
 523
 524 static struct ast_custom_function peek_function = {
 525         .name = "LOCAL_PEEK",
 526         .synopsis = "Peeks at variables within the variable stack",
 527         .syntax = "LOCAL_PEEK(<n>|<varname>)",
 528         .read = peek_read,
 529 };
 530
 531 static int handle_gosub(struct ast_channel *chan, AGI *agi, int argc, char **argv)
 532 {
 533         int old_priority, priority;
 534         char old_context[AST_MAX_CONTEXT], old_extension[AST_MAX_EXTENSION];
 535         struct ast_app *theapp;
 536         char *gosub_args;
 537
 538         if (argc < 4 || argc > 5) {
 539                 return RESULT_SHOWUSAGE;
 540         }
 541
 542         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] : "");
 543
 544         if (sscanf(argv[3], "%d", &priority) != 1 || priority < 1) {
 545                 /* Lookup the priority label */
 546                 if ((priority = ast_findlabel_extension(chan, argv[1], argv[2], argv[3], chan->cid.cid_num)) < 0) {
 547                         ast_log(LOG_ERROR, "Priority '%s' not found in '%s@%s'\n", argv[3], argv[2], argv[1]);
 548                         ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
 549                         return RESULT_FAILURE;
 550                 }
 551         } else if (!ast_exists_extension(chan, argv[1], argv[2], priority, chan->cid.cid_num)) {
 552                 ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
 553                 return RESULT_FAILURE;
 554         }
 555
 556         /* Save previous location, since we're going to change it */
 557         ast_copy_string(old_context, chan->context, sizeof(old_context));
 558         ast_copy_string(old_extension, chan->exten, sizeof(old_extension));
 559         old_priority = chan->priority;
 560
 561         if (!(theapp = pbx_findapp("Gosub"))) {
 562                 ast_log(LOG_ERROR, "Gosub() cannot be found in the list of loaded applications\n");
 563                 ast_agi_send(agi->fd, chan, "503 result=-2 Gosub is not loaded\n");
 564                 return RESULT_FAILURE;
 565         }
 566
 567         /* Apparently, if you run ast_pbx_run on a channel that already has a pbx
 568          * structure, you need to add 1 to the priority to get it to go to the
 569          * right place.  But if it doesn't have a pbx structure, then leaving off
 570          * the 1 is the right thing to do.  See how this code differs when we
 571          * call a Gosub for the CALLEE channel in Dial or Queue.
 572          */
 573         if (argc == 5) {
 574                 if (asprintf(&gosub_args, "%s,%s,%d(%s)", argv[1], argv[2], priority + 1, argv[4]) < 0) {
 575                         ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
 576                         gosub_args = NULL;
 577                 }
 578         } else {
 579                 if (asprintf(&gosub_args, "%s,%s,%d", argv[1], argv[2], priority + 1) < 0) {
 580                         ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
 581                         gosub_args = NULL;
 582                 }
 583         }
 584
 585         if (gosub_args) {
 586                 int res;
 587
 588                 ast_debug(1, "Trying gosub with arguments '%s'\n", gosub_args);
 589                 ast_copy_string(chan->context, "app_stack_gosub_virtual_context", sizeof(chan->context));
 590                 ast_copy_string(chan->exten, "s", sizeof(chan->exten));
 591                 chan->priority = 0;
 592
 593                 if ((res = pbx_exec(chan, theapp, gosub_args)) == 0) {
 594                         struct ast_pbx *pbx = chan->pbx;
 595                         /* Suppress warning about PBX already existing */
 596                         chan->pbx = NULL;
 597                         ast_agi_send(agi->fd, chan, "100 result=0 Trying...\n");
 598                         ast_pbx_run(chan);
 599                         ast_agi_send(agi->fd, chan, "200 result=0 Gosub complete\n");
 600                         if (chan->pbx) {
 601                                 ast_free(chan->pbx);
 602                         }
 603                         chan->pbx = pbx;
 604                 } else {
 605                         ast_agi_send(agi->fd, chan, "200 result=%d Gosub failed\n", res);
 606                 }
 607                 ast_free(gosub_args);
 608         } else {
 609                 ast_agi_send(agi->fd, chan, "503 result=-2 Memory allocation failure\n");
 610                 return RESULT_FAILURE;
 611         }
 612
 613         /* Restore previous location */
 614         ast_copy_string(chan->context, old_context, sizeof(chan->context));
 615         ast_copy_string(chan->exten, old_extension, sizeof(chan->exten));
 616         chan->priority = old_priority;
 617
 618         return RESULT_SUCCESS;
 619 }
 620
 621 static char usage_gosub[] =
 622 " Usage: GOSUB <context> <extension> <priority> [<optional-argument>]\n"
 623 "   Cause the channel to execute the specified dialplan subroutine, returning\n"
 624 " to the dialplan with execution of a Return()\n";
 625
 626 struct agi_command gosub_agi_command =
 627         { { "gosub", NULL }, handle_gosub, "Execute a dialplan subroutine", usage_gosub , 0 };
 628
 629 static int unload_module(void)
 630 {
 631         struct ast_context *con;
 632
 633         if (ast_agi_unregister(ast_module_info->self, &gosub_agi_command) == 1) {
 634                 if ((con = ast_context_find("app_stack_gosub_virtual_context"))) {
 635                         ast_context_remove_extension2(con, "s", 1, NULL, 0);
 636                         ast_context_destroy(con, "app_stack"); /* leave nothing behind */
 637                 }
 638         }
 639
 640         ast_unregister_application(app_return);
 641         ast_unregister_application(app_pop);
 642         ast_unregister_application(app_gosubif);
 643         ast_unregister_application(app_gosub);
 644         ast_custom_function_unregister(&local_function);
 645         ast_custom_function_unregister(&peek_function);
 646
 647         return 0;
 648 }
 649
 650 static int load_module(void)
 651 {
 652         struct ast_context *con;
 653
 654         if (ast_agi_register(ast_module_info->self, &gosub_agi_command) == 1) {
 655                 if (!(con = ast_context_find_or_create(NULL, NULL, "app_stack_gosub_virtual_context", "app_stack"))) {
 656                         ast_log(LOG_ERROR, "Virtual context 'app_stack_gosub_virtual_context' does not exist and unable to create\n");
 657                         return AST_MODULE_LOAD_DECLINE;
 658                 } else {
 659                         ast_add_extension2(con, 1, "s", 1, NULL, NULL, "KeepAlive", ast_strdup(""), ast_free_ptr, "app_stack");
 660                 }
 661         }
 662
 663         ast_register_application_xml(app_pop, pop_exec);
 664         ast_register_application_xml(app_return, return_exec);
 665         ast_register_application_xml(app_gosubif, gosubif_exec);
 666         ast_register_application_xml(app_gosub, gosub_exec);
 667         ast_custom_function_register(&local_function);
 668         ast_custom_function_register(&peek_function);
 669
 670         return 0;
 671 }
 672
 673 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan subroutines (Gosub, Return, etc)");