app_stack.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (c) 2004-2006 Tilghman Lesher <app_stack_v003@the-tilghman.com>.
 *
 * This code is released by the author with no restrictions on usage.
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Stack applications Gosub, Return, etc.
 *
 * \author Tilghman Lesher <app_stack_v003@the-tilghman.com>
 * 
 * \ingroup applications
 */

/*** MODULEINFO
   <use>res_agi</use>
 ***/

#include "asterisk.h"
 
ASTERISK_FILE_VERSION(__FILE__, "$Revision: 236303 $")

#include "asterisk/pbx.h"
#include "asterisk/module.h"
#include "asterisk/app.h"
#include "asterisk/manager.h"
#include "asterisk/channel.h"
#include "asterisk/agi.h"

/*** DOCUMENTATION
   <application name="Gosub" language="en_US">
      <synopsis>
         Jump to label, saving return address.
      </synopsis>
      <syntax>
         <parameter name="context" />
         <parameter name="exten" />
         <parameter name="priority" required="true" hasparams="optional">
            <argument name="arg1" multiple="true" required="true" />
            <argument name="argN" />
         </parameter>
      </syntax>
      <description>
         <para>Jumps to the label specified, saving the return address.</para>
      </description>
      <see-also>
         <ref type="application">GosubIf</ref>
         <ref type="application">Macro</ref>
         <ref type="application">Goto</ref>
         <ref type="application">Return</ref>
         <ref type="application">StackPop</ref>
      </see-also>
   </application>
   <application name="GosubIf" language="en_US">
      <synopsis>
         Conditionally jump to label, saving return address.
      </synopsis>
      <syntax argsep="?">
         <parameter name="condition" required="true" />
         <parameter name="destination" required="true" argsep=":">
            <argument name="labeliftrue" hasparams="optional">
               <argument name="arg1" required="true" multiple="true" />
               <argument name="argN" />
            </argument>
            <argument name="labeliffalse" hasparams="optional">
               <argument name="arg1" required="true" multiple="true" />
               <argument name="argN" />
            </argument>
         </parameter>
      </syntax>
      <description>
         <para>If the condition is true, then jump to labeliftrue.  If false, jumps to
         labeliffalse, if specified.  In either case, a jump saves the return point
         in the dialplan, to be returned to with a Return.</para>
      </description>
      <see-also>
         <ref type="application">Gosub</ref>
         <ref type="application">Return</ref>
         <ref type="application">MacroIf</ref>
         <ref type="function">IF</ref>
         <ref type="application">GotoIf</ref>
      </see-also>
   </application>
   <application name="Return" language="en_US">
      <synopsis>
         Return from gosub routine.
      </synopsis>
      <syntax>
         <parameter name="value">
            <para>Return value.</para>
         </parameter>
      </syntax>
      <description>
         <para>Jumps to the last label on the stack, removing it. The return <replaceable>value</replaceable>, if
         any, is saved in the channel variable <variable>GOSUB_RETVAL</variable>.</para>
      </description>
      <see-also>
         <ref type="application">Gosub</ref>
         <ref type="application">StackPop</ref>
      </see-also>
   </application>
   <application name="StackPop" language="en_US">
      <synopsis>
         Remove one address from gosub stack.
      </synopsis>
      <syntax />
      <description>
         <para>Removes last label on the stack, discarding it.</para>
      </description>
      <see-also>
         <ref type="application">Return</ref>
         <ref type="application">Gosub</ref>
      </see-also>
   </application>
   <function name="LOCAL" language="en_US">
      <synopsis>
         Manage variables local to the gosub stack frame.
      </synopsis>
      <syntax>
         <parameter name="varname" required="true" />
      </syntax>
      <description>
         <para>Read and write a variable local to the gosub stack frame, once we Return() it will be lost
         (or it will go back to whatever value it had before the Gosub()).</para>
      </description>
      <see-also>
         <ref type="application">Gosub</ref>
         <ref type="application">GosubIf</ref>
         <ref type="application">Return</ref>
      </see-also>
   </function>
   <function name="LOCAL_PEEK" language="en_US">
      <synopsis>
         Retrieve variables hidden by the local gosub stack frame.
      </synopsis>
      <syntax>
         <parameter name="n" required="true" />
         <parameter name="varname" required="true" />
      </syntax>
      <description>
         <para>Read a variable <replaceable>varname</replaceable> hidden by
         <replaceable>n</replaceable> levels of gosub stack frames.  Note that ${LOCAL_PEEK(0,foo)}
         is the same as <variable>foo</variable>, since the value of <replaceable>n</replaceable>
         peeks under 0 levels of stack frames; in other words, 0 is the current level.  If
         <replaceable>n</replaceable> exceeds the available number of stack frames, then an empty
         string is returned.</para>
      </description>
      <see-also>
         <ref type="application">Gosub</ref>
         <ref type="application">GosubIf</ref>
         <ref type="application">Return</ref>
      </see-also>
   </function>
 ***/

static const char *app_gosub = "Gosub";
static const char *app_gosubif = "GosubIf";
static const char *app_return = "Return";
static const char *app_pop = "StackPop";

static void gosub_free(void *data);

static struct ast_datastore_info stack_info = {
   .type = "GOSUB",
   .destroy = gosub_free,
};

struct gosub_stack_frame {
   AST_LIST_ENTRY(gosub_stack_frame) entries;
   /* 100 arguments is all that we support anyway, but this will handle up to 255 */
   unsigned char arguments;
   struct varshead varshead;
   int priority;
   unsigned int is_agi:1;
   char *context;
   char extension[0];
};

static int frame_set_var(struct ast_channel *chan, struct gosub_stack_frame *frame, const char *var, const char *value)
{
   struct ast_var_t *variables;
   int found = 0;

   /* Does this variable already exist? */
   AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
      if (!strcmp(var, ast_var_name(variables))) {
         found = 1;
         break;
      }
   }

   if (!found) {
      variables = ast_var_assign(var, "");
      AST_LIST_INSERT_HEAD(&frame->varshead, variables, entries);
      pbx_builtin_pushvar_helper(chan, var, value);
   } else {
      pbx_builtin_setvar_helper(chan, var, value);
   }

   manager_event(EVENT_FLAG_DIALPLAN, "VarSet",
      "Channel: %s\r\n"
      "Variable: LOCAL(%s)\r\n"
      "Value: %s\r\n"
      "Uniqueid: %s\r\n",
      chan->name, var, value, chan->uniqueid);
   return 0;
}

static void gosub_release_frame(struct ast_channel *chan, struct gosub_stack_frame *frame)
{
   struct ast_var_t *vardata;

   /* If chan is not defined, then we're calling it as part of gosub_free,
    * and the channel variables will be deallocated anyway.  Otherwise, we're
    * just releasing a single frame, so we need to clean up the arguments for
    * that frame, so that we re-expose the variables from the previous frame
    * that were hidden by this one.
    */
   while ((vardata = AST_LIST_REMOVE_HEAD(&frame->varshead, entries))) {
      if (chan)
         pbx_builtin_setvar_helper(chan, ast_var_name(vardata), NULL);  
      ast_var_delete(vardata);
   }

   ast_free(frame);
}

static struct gosub_stack_frame *gosub_allocate_frame(const char *context, const char *extension, int priority, unsigned char arguments)
{
   struct gosub_stack_frame *new = NULL;
   int len_extension = strlen(extension), len_context = strlen(context);

   if ((new = ast_calloc(1, sizeof(*new) + 2 + len_extension + len_context))) {
      AST_LIST_HEAD_INIT_NOLOCK(&new->varshead);
      strcpy(new->extension, extension);
      new->context = new->extension + len_extension + 1;
      strcpy(new->context, context);
      new->priority = priority;
      new->arguments = arguments;
   }
   return new;
}

static void gosub_free(void *data)
{
   AST_LIST_HEAD(, gosub_stack_frame) *oldlist = data;
   struct gosub_stack_frame *oldframe;
   AST_LIST_LOCK(oldlist);
   while ((oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries))) {
      gosub_release_frame(NULL, oldframe);
   }
   AST_LIST_UNLOCK(oldlist);
   AST_LIST_HEAD_DESTROY(oldlist);
   ast_free(oldlist);
}

static int pop_exec(struct ast_channel *chan, void *data)
{
   struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
   struct gosub_stack_frame *oldframe;
   AST_LIST_HEAD(, gosub_stack_frame) *oldlist;

   if (!stack_store) {
      ast_log(LOG_WARNING, "%s called with no gosub stack allocated.\n", app_pop);
      return 0;
   }

   oldlist = stack_store->data;
   AST_LIST_LOCK(oldlist);
   oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
   AST_LIST_UNLOCK(oldlist);

   if (oldframe) {
      gosub_release_frame(chan, oldframe);
   } else {
      ast_debug(1, "%s called with an empty gosub stack\n", app_pop);
   }
   return 0;
}

static int return_exec(struct ast_channel *chan, void *data)
{
   struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
   struct gosub_stack_frame *oldframe;
   AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
   char *retval = data;
   int res = 0;

   if (!stack_store) {
      ast_log(LOG_ERROR, "Return without Gosub: stack is unallocated\n");
      return -1;
   }

   oldlist = stack_store->data;
   AST_LIST_LOCK(oldlist);
   oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
   AST_LIST_UNLOCK(oldlist);

   if (!oldframe) {
      ast_log(LOG_ERROR, "Return without Gosub: stack is empty\n");
      return -1;
   } else if (oldframe->is_agi) {
      /* Exit from AGI */
      res = -1;
   }

   ast_explicit_goto(chan, oldframe->context, oldframe->extension, oldframe->priority);
   gosub_release_frame(chan, oldframe);

   /* Set a return value, if any */
   pbx_builtin_setvar_helper(chan, "GOSUB_RETVAL", S_OR(retval, ""));
   return res;
}

static int gosub_exec(struct ast_channel *chan, void *data)
{
   struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
   AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
   struct gosub_stack_frame *newframe;
   char argname[15], *tmp = ast_strdupa(data), *label, *endparen;
   int i;
   AST_DECLARE_APP_ARGS(args2,
      AST_APP_ARG(argval)[100];
   );

   if (ast_strlen_zero(data)) {
      ast_log(LOG_ERROR, "%s requires an argument: %s([[context,]exten,]priority[(arg1[,...][,argN])])\n", app_gosub, app_gosub);
      return -1;
   }

   if (!stack_store) {
      ast_debug(1, "Channel %s has no datastore, so we're allocating one.\n", chan->name);
      stack_store = ast_datastore_alloc(&stack_info, NULL);
      if (!stack_store) {
         ast_log(LOG_ERROR, "Unable to allocate new datastore.  Gosub will fail.\n");
         return -1;
      }

      oldlist = ast_calloc(1, sizeof(*oldlist));
      if (!oldlist) {
         ast_log(LOG_ERROR, "Unable to allocate datastore list head.  Gosub will fail.\n");
         ast_datastore_free(stack_store);
         return -1;
      }

      stack_store->data = oldlist;
      AST_LIST_HEAD_INIT(oldlist);
      ast_channel_datastore_add(chan, stack_store);
   }

   /* Separate the arguments from the label */
   /* NOTE:  you cannot use ast_app_separate_args for this, because '(' cannot be used as a delimiter. */
   label = strsep(&tmp, "(");
   if (tmp) {
      endparen = strrchr(tmp, ')');
      if (endparen)
         *endparen = '\0';
      else
         ast_log(LOG_WARNING, "Ouch.  No closing paren: '%s'?\n", (char *)data);
      AST_STANDARD_RAW_ARGS(args2, tmp);
   } else
      args2.argc = 0;

   /* Create the return address, but don't save it until we know that the Gosub destination exists */
   newframe = gosub_allocate_frame(chan->context, chan->exten, chan->priority + 1, args2.argc);

   if (!newframe) {
      return -1;
   }

   if (ast_parseable_goto(chan, label)) {
      ast_log(LOG_ERROR, "Gosub address is invalid: '%s'\n", (char *)data);
      ast_free(newframe);
      return -1;
   }

   if (!ast_exists_extension(chan, chan->context, chan->exten, ast_test_flag(chan, AST_FLAG_IN_AUTOLOOP) ? chan->priority + 1 : chan->priority, chan->cid.cid_num)) {
      ast_log(LOG_ERROR, "Attempt to reach a non-existent destination for gosub: (Context:%s, Extension:%s, Priority:%d)\n",
            chan->context, chan->exten, chan->priority);
      ast_copy_string(chan->context, newframe->context, sizeof(chan->context));
      ast_copy_string(chan->exten, newframe->extension, sizeof(chan->exten));
      chan->priority = newframe->priority;
      ast_free(newframe);
      return -1;
   }

   /* Now that we know for certain that we're going to a new location, set our arguments */
   for (i = 0; i < args2.argc; i++) {
      snprintf(argname, sizeof(argname), "ARG%d", i + 1);
      frame_set_var(chan, newframe, argname, args2.argval[i]);
      ast_debug(1, "Setting '%s' to '%s'\n", argname, args2.argval[i]);
   }
   snprintf(argname, sizeof(argname), "%d", args2.argc);
   frame_set_var(chan, newframe, "ARGC", argname);

   /* And finally, save our return address */
   oldlist = stack_store->data;
   AST_LIST_LOCK(oldlist);
   AST_LIST_INSERT_HEAD(oldlist, newframe, entries);
   AST_LIST_UNLOCK(oldlist);

   return 0;
}

static int gosubif_exec(struct ast_channel *chan, void *data)
{
   char *args;
   int res=0;
   AST_DECLARE_APP_ARGS(cond,
      AST_APP_ARG(ition);
      AST_APP_ARG(labels);
   );
   AST_DECLARE_APP_ARGS(label,
      AST_APP_ARG(iftrue);
      AST_APP_ARG(iffalse);
   );

   if (ast_strlen_zero(data)) {
      ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
      return 0;
   }

   args = ast_strdupa(data);
   AST_NONSTANDARD_RAW_ARGS(cond, args, '?');
   if (cond.argc != 2) {
      ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
      return 0;
   }

   AST_NONSTANDARD_RAW_ARGS(label, cond.labels, ':');

   if (pbx_checkcondition(cond.ition)) {
      if (!ast_strlen_zero(label.iftrue))
         res = gosub_exec(chan, label.iftrue);
   } else if (!ast_strlen_zero(label.iffalse)) {
      res = gosub_exec(chan, label.iffalse);
   }

   return res;
}

static int local_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
{
   struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
   AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
   struct gosub_stack_frame *frame;
   struct ast_var_t *variables;

   if (!stack_store)
      return -1;

   oldlist = stack_store->data;
   AST_LIST_LOCK(oldlist);
   if (!(frame = AST_LIST_FIRST(oldlist))) {
      /* Not within a Gosub routine */
      AST_LIST_UNLOCK(oldlist);
      return -1;
   }

   AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
      if (!strcmp(data, ast_var_name(variables))) {
         const char *tmp;
         ast_channel_lock(chan);
         tmp = pbx_builtin_getvar_helper(chan, data);
         ast_copy_string(buf, S_OR(tmp, ""), len);
         ast_channel_unlock(chan);
         break;
      }
   }
   AST_LIST_UNLOCK(oldlist);
   return 0;
}

static int local_write(struct ast_channel *chan, const char *cmd, char *var, const char *value)
{
   struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
   AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
   struct gosub_stack_frame *frame;

   if (!stack_store) {
      ast_log(LOG_ERROR, "Tried to set LOCAL(%s), but we aren't within a Gosub routine\n", var);
      return -1;
   }

   oldlist = stack_store->data;
   AST_LIST_LOCK(oldlist);
   frame = AST_LIST_FIRST(oldlist);

   if (frame)
      frame_set_var(chan, frame, var, value);

   AST_LIST_UNLOCK(oldlist);

   return 0;
}

static struct ast_custom_function local_function = {
   .name = "LOCAL",
   .write = local_write,
   .read = local_read,
};

static int peek_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
{
   int found = 0, n;
   struct ast_var_t *variables;
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(n);
      AST_APP_ARG(name);
   );

   if (!chan) {
      ast_log(LOG_ERROR, "LOCAL_PEEK must be called on an active channel\n");
      return -1;
   }

   AST_STANDARD_RAW_ARGS(args, data);
   n = atoi(args.n);
   *buf = '\0';

   ast_channel_lock(chan);
   AST_LIST_TRAVERSE(&chan->varshead, variables, entries) {
      if (!strcmp(args.name, ast_var_name(variables)) && ++found > n) {
         ast_copy_string(buf, ast_var_value(variables), len);
         break;
      }
   }
   ast_channel_unlock(chan);
   return 0;
}

static struct ast_custom_function peek_function = {
   .name = "LOCAL_PEEK",
   .read = peek_read,
};

static int handle_gosub(struct ast_channel *chan, AGI *agi, int argc, char **argv)
{
   int old_priority, priority;
   char old_context[AST_MAX_CONTEXT], old_extension[AST_MAX_EXTENSION];
   struct ast_app *theapp;
   char *gosub_args;

   if (argc < 4 || argc > 5) {
      return RESULT_SHOWUSAGE;
   }

   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] : "");

   if (sscanf(argv[3], "%30d", &priority) != 1 || priority < 1) {
      /* Lookup the priority label */
      if ((priority = ast_findlabel_extension(chan, argv[1], argv[2], argv[3], chan->cid.cid_num)) < 0) {
         ast_log(LOG_ERROR, "Priority '%s' not found in '%s@%s'\n", argv[3], argv[2], argv[1]);
         ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
         return RESULT_FAILURE;
      }
   } else if (!ast_exists_extension(chan, argv[1], argv[2], priority, chan->cid.cid_num)) {
      ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
      return RESULT_FAILURE;
   }

   /* Save previous location, since we're going to change it */
   ast_copy_string(old_context, chan->context, sizeof(old_context));
   ast_copy_string(old_extension, chan->exten, sizeof(old_extension));
   old_priority = chan->priority;

   if (!(theapp = pbx_findapp("Gosub"))) {
      ast_log(LOG_ERROR, "Gosub() cannot be found in the list of loaded applications\n");
      ast_agi_send(agi->fd, chan, "503 result=-2 Gosub is not loaded\n");
      return RESULT_FAILURE;
   }

   /* Apparently, if you run ast_pbx_run on a channel that already has a pbx
    * structure, you need to add 1 to the priority to get it to go to the
    * right place.  But if it doesn't have a pbx structure, then leaving off
    * the 1 is the right thing to do.  See how this code differs when we
    * call a Gosub for the CALLEE channel in Dial or Queue.
    */
   if (argc == 5) {
      if (asprintf(&gosub_args, "%s,%s,%d(%s)", argv[1], argv[2], priority + (chan->pbx ? 1 : 0), argv[4]) < 0) {
         ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
         gosub_args = NULL;
      }
   } else {
      if (asprintf(&gosub_args, "%s,%s,%d", argv[1], argv[2], priority + (chan->pbx ? 1 : 0)) < 0) {
         ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
         gosub_args = NULL;
      }
   }

   if (gosub_args) {
      int res;

      ast_debug(1, "Trying gosub with arguments '%s'\n", gosub_args);

      if ((res = pbx_exec(chan, theapp, gosub_args)) == 0) {
         struct ast_pbx *pbx = chan->pbx;
         struct ast_pbx_args args;
         struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
         AST_LIST_HEAD(, gosub_stack_frame) *oldlist = stack_store->data;
         struct gosub_stack_frame *cur = AST_LIST_FIRST(oldlist);
         cur->is_agi = 1;

         memset(&args, 0, sizeof(args));
         args.no_hangup_chan = 1;
         /* Suppress warning about PBX already existing */
         chan->pbx = NULL;
         ast_agi_send(agi->fd, chan, "100 result=0 Trying...\n");
         ast_pbx_run_args(chan, &args);
         ast_agi_send(agi->fd, chan, "200 result=0 Gosub complete\n");
         if (chan->pbx) {
            ast_free(chan->pbx);
         }
         chan->pbx = pbx;
      } else {
         ast_agi_send(agi->fd, chan, "200 result=%d Gosub failed\n", res);
      }
      ast_free(gosub_args);
   } else {
      ast_agi_send(agi->fd, chan, "503 result=-2 Memory allocation failure\n");
      return RESULT_FAILURE;
   }

   /* Restore previous location */
   ast_copy_string(chan->context, old_context, sizeof(chan->context));
   ast_copy_string(chan->exten, old_extension, sizeof(chan->exten));
   chan->priority = old_priority;

   return RESULT_SUCCESS;
}

static char usage_gosub[] =
" Usage: GOSUB <context> <extension> <priority> [<optional-argument>]\n"
"   Cause the channel to execute the specified dialplan subroutine, returning\n"
" to the dialplan with execution of a Return()\n";

struct agi_command gosub_agi_command =
   { { "gosub", NULL }, handle_gosub, "Execute a dialplan subroutine", usage_gosub , 0 };

static int unload_module(void)
{
   if (ast_agi_unregister) {
       ast_agi_unregister(ast_module_info->self, &gosub_agi_command);
   }

   ast_unregister_application(app_return);
   ast_unregister_application(app_pop);
   ast_unregister_application(app_gosubif);
   ast_unregister_application(app_gosub);
   ast_custom_function_unregister(&local_function);
   ast_custom_function_unregister(&peek_function);

   return 0;
}

static int load_module(void)
{
   if (ast_agi_register) {
       ast_agi_register(ast_module_info->self, &gosub_agi_command);
   }

   ast_register_application_xml(app_pop, pop_exec);
   ast_register_application_xml(app_return, return_exec);
   ast_register_application_xml(app_gosubif, gosubif_exec);
   ast_register_application_xml(app_gosub, gosub_exec);
   ast_custom_function_register(&local_function);
   ast_custom_function_register(&peek_function);

   return 0;
}

AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan subroutines (Gosub, Return, etc)");