Wed Aug 18 22:33:43 2010

Asterisk developer's documentation


app_stack.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (c) 2004-2006 Tilghman Lesher <app_stack_v003@the-tilghman.com>.
00005  *
00006  * This code is released by the author with no restrictions on usage.
00007  *
00008  * See http://www.asterisk.org for more information about
00009  * the Asterisk project. Please do not directly contact
00010  * any of the maintainers of this project for assistance;
00011  * the project provides a web site, mailing lists and IRC
00012  * channels for your use.
00013  *
00014  * This program is free software, distributed under the terms of
00015  * the GNU General Public License Version 2. See the LICENSE file
00016  * at the top of the source tree.
00017  */
00018 
00019 /*! \file
00020  *
00021  * \brief Stack applications Gosub, Return, etc.
00022  *
00023  * \author Tilghman Lesher <app_stack_v003@the-tilghman.com>
00024  * 
00025  * \ingroup applications
00026  */
00027 
00028 /*** MODULEINFO
00029    <use>res_agi</use>
00030  ***/
00031 
00032 #include "asterisk.h"
00033  
00034 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 252977 $")
00035 
00036 #include "asterisk/pbx.h"
00037 #include "asterisk/module.h"
00038 #include "asterisk/app.h"
00039 #include "asterisk/manager.h"
00040 #include "asterisk/channel.h"
00041 
00042 /* usage of AGI is optional, so indicate that to the header file */
00043 #define ASTERISK_AGI_OPTIONAL
00044 #include "asterisk/agi.h"
00045 
00046 
00047 static const char *app_gosub = "Gosub";
00048 static const char *app_gosubif = "GosubIf";
00049 static const char *app_return = "Return";
00050 static const char *app_pop = "StackPop";
00051 
00052 static const char *gosub_synopsis = "Jump to label, saving return address";
00053 static const char *gosubif_synopsis = "Conditionally jump to label, saving return address";
00054 static const char *return_synopsis = "Return from gosub routine";
00055 static const char *pop_synopsis = "Remove one address from gosub stack";
00056 
00057 static const char *gosub_descrip =
00058 "  Gosub([[context,]exten,]priority[(arg1[,...][,argN])]):\n"
00059 "Jumps to the label specified, saving the return address.\n";
00060 static const char *gosubif_descrip =
00061 "  GosubIf(condition?labeliftrue[(arg1[,...])][:labeliffalse[(arg1[,...])]]):\n"
00062 "If the condition is true, then jump to labeliftrue.  If false, jumps to\n"
00063 "labeliffalse, if specified.  In either case, a jump saves the return point\n"
00064 "in the dialplan, to be returned to with a Return.\n";
00065 static const char *return_descrip =
00066 "  Return([return-value]):\n"
00067 "Jumps to the last label on the stack, removing it.  The return value, if\n"
00068 "any, is saved in the channel variable GOSUB_RETVAL.\n";
00069 static const char *pop_descrip =
00070 "  StackPop():\n"
00071 "Removes last label on the stack, discarding it.\n";
00072 
00073 static void gosub_free(void *data);
00074 
00075 static struct ast_datastore_info stack_info = {
00076    .type = "GOSUB",
00077    .destroy = gosub_free,
00078 };
00079 
00080 struct gosub_stack_frame {
00081    AST_LIST_ENTRY(gosub_stack_frame) entries;
00082    /* 100 arguments is all that we support anyway, but this will handle up to 255 */
00083    unsigned char arguments;
00084    struct varshead varshead;
00085    int priority;
00086    unsigned int is_agi:1;
00087    char *context;
00088    char extension[0];
00089 };
00090 
00091 static int frame_set_var(struct ast_channel *chan, struct gosub_stack_frame *frame, const char *var, const char *value)
00092 {
00093    struct ast_var_t *variables;
00094    int found = 0;
00095 
00096    /* Does this variable already exist? */
00097    AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
00098       if (!strcmp(var, ast_var_name(variables))) {
00099          found = 1;
00100          break;
00101       }
00102    }
00103 
00104    if (!found) {
00105       variables = ast_var_assign(var, "");
00106       AST_LIST_INSERT_HEAD(&frame->varshead, variables, entries);
00107       pbx_builtin_pushvar_helper(chan, var, value);
00108    } else {
00109       pbx_builtin_setvar_helper(chan, var, value);
00110    }
00111 
00112    manager_event(EVENT_FLAG_DIALPLAN, "VarSet",
00113       "Channel: %s\r\n"
00114       "Variable: LOCAL(%s)\r\n"
00115       "Value: %s\r\n"
00116       "Uniqueid: %s\r\n",
00117       chan->name, var, value, chan->uniqueid);
00118    return 0;
00119 }
00120 
00121 static void gosub_release_frame(struct ast_channel *chan, struct gosub_stack_frame *frame)
00122 {
00123    struct ast_var_t *vardata;
00124 
00125    /* If chan is not defined, then we're calling it as part of gosub_free,
00126     * and the channel variables will be deallocated anyway.  Otherwise, we're
00127     * just releasing a single frame, so we need to clean up the arguments for
00128     * that frame, so that we re-expose the variables from the previous frame
00129     * that were hidden by this one.
00130     */
00131    while ((vardata = AST_LIST_REMOVE_HEAD(&frame->varshead, entries))) {
00132       if (chan)
00133          pbx_builtin_setvar_helper(chan, ast_var_name(vardata), NULL);  
00134       ast_var_delete(vardata);
00135    }
00136 
00137    ast_free(frame);
00138 }
00139 
00140 static struct gosub_stack_frame *gosub_allocate_frame(const char *context, const char *extension, int priority, unsigned char arguments)
00141 {
00142    struct gosub_stack_frame *new = NULL;
00143    int len_extension = strlen(extension), len_context = strlen(context);
00144 
00145    if ((new = ast_calloc(1, sizeof(*new) + 2 + len_extension + len_context))) {
00146       AST_LIST_HEAD_INIT_NOLOCK(&new->varshead);
00147       strcpy(new->extension, extension);
00148       new->context = new->extension + len_extension + 1;
00149       strcpy(new->context, context);
00150       new->priority = priority;
00151       new->arguments = arguments;
00152    }
00153    return new;
00154 }
00155 
00156 static void gosub_free(void *data)
00157 {
00158    AST_LIST_HEAD(, gosub_stack_frame) *oldlist = data;
00159    struct gosub_stack_frame *oldframe;
00160    AST_LIST_LOCK(oldlist);
00161    while ((oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries))) {
00162       gosub_release_frame(NULL, oldframe);
00163    }
00164    AST_LIST_UNLOCK(oldlist);
00165    AST_LIST_HEAD_DESTROY(oldlist);
00166    ast_free(oldlist);
00167 }
00168 
00169 static int pop_exec(struct ast_channel *chan, void *data)
00170 {
00171    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00172    struct gosub_stack_frame *oldframe;
00173    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00174 
00175    if (!stack_store) {
00176       ast_log(LOG_WARNING, "%s called with no gosub stack allocated.\n", app_pop);
00177       return 0;
00178    }
00179 
00180    oldlist = stack_store->data;
00181    AST_LIST_LOCK(oldlist);
00182    oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
00183    AST_LIST_UNLOCK(oldlist);
00184 
00185    if (oldframe) {
00186       gosub_release_frame(chan, oldframe);
00187    } else {
00188       ast_debug(1, "%s called with an empty gosub stack\n", app_pop);
00189    }
00190    return 0;
00191 }
00192 
00193 static int return_exec(struct ast_channel *chan, void *data)
00194 {
00195    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00196    struct gosub_stack_frame *oldframe;
00197    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00198    char *retval = data;
00199    int res = 0;
00200 
00201    if (!stack_store) {
00202       ast_log(LOG_ERROR, "Return without Gosub: stack is unallocated\n");
00203       return -1;
00204    }
00205 
00206    oldlist = stack_store->data;
00207    AST_LIST_LOCK(oldlist);
00208    oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
00209    AST_LIST_UNLOCK(oldlist);
00210 
00211    if (!oldframe) {
00212       ast_log(LOG_ERROR, "Return without Gosub: stack is empty\n");
00213       return -1;
00214    } else if (oldframe->is_agi) {
00215       /* Exit from AGI */
00216       res = -1;
00217    }
00218 
00219    ast_explicit_goto(chan, oldframe->context, oldframe->extension, oldframe->priority);
00220    gosub_release_frame(chan, oldframe);
00221 
00222    /* Set a return value, if any */
00223    pbx_builtin_setvar_helper(chan, "GOSUB_RETVAL", S_OR(retval, ""));
00224    return res;
00225 }
00226 
00227 static int gosub_exec(struct ast_channel *chan, void *data)
00228 {
00229    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00230    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00231    struct gosub_stack_frame *newframe, *lastframe;
00232    char argname[15], *tmp = ast_strdupa(data), *label, *endparen;
00233    int i, max_argc = 0;
00234    AST_DECLARE_APP_ARGS(args2,
00235       AST_APP_ARG(argval)[100];
00236    );
00237 
00238    if (ast_strlen_zero(data)) {
00239       ast_log(LOG_ERROR, "%s requires an argument: %s([[context,]exten,]priority[(arg1[,...][,argN])])\n", app_gosub, app_gosub);
00240       return -1;
00241    }
00242 
00243    if (!stack_store) {
00244       ast_debug(1, "Channel %s has no datastore, so we're allocating one.\n", chan->name);
00245       stack_store = ast_datastore_alloc(&stack_info, NULL);
00246       if (!stack_store) {
00247          ast_log(LOG_ERROR, "Unable to allocate new datastore.  Gosub will fail.\n");
00248          return -1;
00249       }
00250 
00251       oldlist = ast_calloc(1, sizeof(*oldlist));
00252       if (!oldlist) {
00253          ast_log(LOG_ERROR, "Unable to allocate datastore list head.  Gosub will fail.\n");
00254          ast_datastore_free(stack_store);
00255          return -1;
00256       }
00257 
00258       stack_store->data = oldlist;
00259       AST_LIST_HEAD_INIT(oldlist);
00260       ast_channel_datastore_add(chan, stack_store);
00261    } else {
00262       oldlist = stack_store->data;
00263    }
00264 
00265    if ((lastframe = AST_LIST_FIRST(oldlist))) {
00266       max_argc = lastframe->arguments;
00267    }
00268 
00269    /* Separate the arguments from the label */
00270    /* NOTE:  you cannot use ast_app_separate_args for this, because '(' cannot be used as a delimiter. */
00271    label = strsep(&tmp, "(");
00272    if (tmp) {
00273       endparen = strrchr(tmp, ')');
00274       if (endparen)
00275          *endparen = '\0';
00276       else
00277          ast_log(LOG_WARNING, "Ouch.  No closing paren: '%s'?\n", (char *)data);
00278       AST_STANDARD_RAW_ARGS(args2, tmp);
00279    } else
00280       args2.argc = 0;
00281 
00282    /* Mask out previous arguments in this invocation */
00283    if (args2.argc > max_argc) {
00284       max_argc = args2.argc;
00285    }
00286 
00287    /* Create the return address, but don't save it until we know that the Gosub destination exists */
00288    newframe = gosub_allocate_frame(chan->context, chan->exten, chan->priority + 1, max_argc);
00289 
00290    if (!newframe) {
00291       return -1;
00292    }
00293 
00294    if (ast_parseable_goto(chan, label)) {
00295       ast_log(LOG_ERROR, "Gosub address is invalid: '%s'\n", (char *)data);
00296       ast_free(newframe);
00297       return -1;
00298    }
00299 
00300    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)) {
00301       ast_log(LOG_ERROR, "Attempt to reach a non-existent destination for gosub: (Context:%s, Extension:%s, Priority:%d)\n",
00302             chan->context, chan->exten, chan->priority);
00303       ast_copy_string(chan->context, newframe->context, sizeof(chan->context));
00304       ast_copy_string(chan->exten, newframe->extension, sizeof(chan->exten));
00305       chan->priority = newframe->priority;
00306       ast_free(newframe);
00307       return -1;
00308    }
00309 
00310    /* Now that we know for certain that we're going to a new location, set our arguments */
00311    for (i = 0; i < max_argc; i++) {
00312       snprintf(argname, sizeof(argname), "ARG%d", i + 1);
00313       frame_set_var(chan, newframe, argname, i < args2.argc ? args2.argval[i] : "");
00314       ast_debug(1, "Setting '%s' to '%s'\n", argname, i < args2.argc ? args2.argval[i] : "");
00315    }
00316 
00317    /* And finally, save our return address */
00318    oldlist = stack_store->data;
00319    AST_LIST_LOCK(oldlist);
00320    AST_LIST_INSERT_HEAD(oldlist, newframe, entries);
00321    AST_LIST_UNLOCK(oldlist);
00322 
00323    return 0;
00324 }
00325 
00326 static int gosubif_exec(struct ast_channel *chan, void *data)
00327 {
00328    char *args;
00329    int res=0;
00330    AST_DECLARE_APP_ARGS(cond,
00331       AST_APP_ARG(ition);
00332       AST_APP_ARG(labels);
00333    );
00334    AST_DECLARE_APP_ARGS(label,
00335       AST_APP_ARG(iftrue);
00336       AST_APP_ARG(iffalse);
00337    );
00338 
00339    if (ast_strlen_zero(data)) {
00340       ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
00341       return 0;
00342    }
00343 
00344    args = ast_strdupa(data);
00345    AST_NONSTANDARD_RAW_ARGS(cond, args, '?');
00346    if (cond.argc != 2) {
00347       ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
00348       return 0;
00349    }
00350 
00351    AST_NONSTANDARD_RAW_ARGS(label, cond.labels, ':');
00352 
00353    if (pbx_checkcondition(cond.ition)) {
00354       if (!ast_strlen_zero(label.iftrue))
00355          res = gosub_exec(chan, label.iftrue);
00356    } else if (!ast_strlen_zero(label.iffalse)) {
00357       res = gosub_exec(chan, label.iffalse);
00358    }
00359 
00360    return res;
00361 }
00362 
00363 static int local_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
00364 {
00365    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00366    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00367    struct gosub_stack_frame *frame;
00368    struct ast_var_t *variables;
00369 
00370    if (!stack_store)
00371       return -1;
00372 
00373    oldlist = stack_store->data;
00374    AST_LIST_LOCK(oldlist);
00375    if (!(frame = AST_LIST_FIRST(oldlist))) {
00376       /* Not within a Gosub routine */
00377       AST_LIST_UNLOCK(oldlist);
00378       return -1;
00379    }
00380 
00381    AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
00382       if (!strcmp(data, ast_var_name(variables))) {
00383          const char *tmp;
00384          ast_channel_lock(chan);
00385          tmp = pbx_builtin_getvar_helper(chan, data);
00386          ast_copy_string(buf, S_OR(tmp, ""), len);
00387          ast_channel_unlock(chan);
00388          break;
00389       }
00390    }
00391    AST_LIST_UNLOCK(oldlist);
00392    return 0;
00393 }
00394 
00395 static int local_write(struct ast_channel *chan, const char *cmd, char *var, const char *value)
00396 {
00397    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00398    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00399    struct gosub_stack_frame *frame;
00400 
00401    if (!stack_store) {
00402       ast_log(LOG_ERROR, "Tried to set LOCAL(%s), but we aren't within a Gosub routine\n", var);
00403       return -1;
00404    }
00405 
00406    oldlist = stack_store->data;
00407    AST_LIST_LOCK(oldlist);
00408    frame = AST_LIST_FIRST(oldlist);
00409 
00410    if (frame)
00411       frame_set_var(chan, frame, var, value);
00412 
00413    AST_LIST_UNLOCK(oldlist);
00414 
00415    return 0;
00416 }
00417 
00418 static struct ast_custom_function local_function = {
00419    .name = "LOCAL",
00420    .synopsis = "Variables local to the gosub stack frame",
00421    .syntax = "LOCAL(<varname>)",
00422    .write = local_write,
00423    .read = local_read,
00424 };
00425 
00426 static int handle_gosub(struct ast_channel *chan, AGI *agi, int argc, char **argv)
00427 {
00428    int old_priority, priority;
00429    char old_context[AST_MAX_CONTEXT], old_extension[AST_MAX_EXTENSION];
00430    struct ast_app *theapp;
00431    char *gosub_args;
00432 
00433    if (argc < 4 || argc > 5) {
00434       return RESULT_SHOWUSAGE;
00435    }
00436 
00437    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] : "");
00438 
00439    if (sscanf(argv[3], "%30d", &priority) != 1 || priority < 1) {
00440       /* Lookup the priority label */
00441       if ((priority = ast_findlabel_extension(chan, argv[1], argv[2], argv[3], chan->cid.cid_num)) < 0) {
00442          ast_log(LOG_ERROR, "Priority '%s' not found in '%s@%s'\n", argv[3], argv[2], argv[1]);
00443          ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
00444          return RESULT_FAILURE;
00445       }
00446    } else if (!ast_exists_extension(chan, argv[1], argv[2], priority, chan->cid.cid_num)) {
00447       ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
00448       return RESULT_FAILURE;
00449    }
00450 
00451    /* Save previous location, since we're going to change it */
00452    ast_copy_string(old_context, chan->context, sizeof(old_context));
00453    ast_copy_string(old_extension, chan->exten, sizeof(old_extension));
00454    old_priority = chan->priority;
00455 
00456    if (!(theapp = pbx_findapp("Gosub"))) {
00457       ast_log(LOG_ERROR, "Gosub() cannot be found in the list of loaded applications\n");
00458       ast_agi_send(agi->fd, chan, "503 result=-2 Gosub is not loaded\n");
00459       return RESULT_FAILURE;
00460    }
00461 
00462    /* Apparently, if you run ast_pbx_run on a channel that already has a pbx
00463     * structure, you need to add 1 to the priority to get it to go to the
00464     * right place.  But if it doesn't have a pbx structure, then leaving off
00465     * the 1 is the right thing to do.  See how this code differs when we
00466     * call a Gosub for the CALLEE channel in Dial or Queue.
00467     */
00468    if (argc == 5) {
00469       if (asprintf(&gosub_args, "%s,%s,%d(%s)", argv[1], argv[2], priority + (chan->pbx ? 1 : 0), argv[4]) < 0) {
00470          ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
00471          gosub_args = NULL;
00472       }
00473    } else {
00474       if (asprintf(&gosub_args, "%s,%s,%d", argv[1], argv[2], priority + (chan->pbx ? 1 : 0)) < 0) {
00475          ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
00476          gosub_args = NULL;
00477       }
00478    }
00479 
00480    if (gosub_args) {
00481       int res;
00482 
00483       ast_debug(1, "Trying gosub with arguments '%s'\n", gosub_args);
00484 
00485       if ((res = pbx_exec(chan, theapp, gosub_args)) == 0) {
00486          struct ast_pbx *pbx = chan->pbx;
00487          struct ast_pbx_args args;
00488          struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00489          AST_LIST_HEAD(, gosub_stack_frame) *oldlist = stack_store->data;
00490          struct gosub_stack_frame *cur = AST_LIST_FIRST(oldlist);
00491          cur->is_agi = 1;
00492 
00493          memset(&args, 0, sizeof(args));
00494          args.no_hangup_chan = 1;
00495          /* Suppress warning about PBX already existing */
00496          chan->pbx = NULL;
00497          ast_agi_send(agi->fd, chan, "100 result=0 Trying...\n");
00498          ast_pbx_run_args(chan, &args);
00499          ast_agi_send(agi->fd, chan, "200 result=0 Gosub complete\n");
00500          if (chan->pbx) {
00501             ast_free(chan->pbx);
00502          }
00503          chan->pbx = pbx;
00504       } else {
00505          ast_agi_send(agi->fd, chan, "200 result=%d Gosub failed\n", res);
00506       }
00507       ast_free(gosub_args);
00508    } else {
00509       ast_agi_send(agi->fd, chan, "503 result=-2 Memory allocation failure\n");
00510       return RESULT_FAILURE;
00511    }
00512 
00513    /* Restore previous location */
00514    ast_copy_string(chan->context, old_context, sizeof(chan->context));
00515    ast_copy_string(chan->exten, old_extension, sizeof(chan->exten));
00516    chan->priority = old_priority;
00517 
00518    return RESULT_SUCCESS;
00519 }
00520 
00521 static char usage_gosub[] =
00522 " Usage: GOSUB <context> <extension> <priority> [<optional-argument>]\n"
00523 "   Cause the channel to execute the specified dialplan subroutine, returning\n"
00524 " to the dialplan with execution of a Return()\n";
00525 
00526 struct agi_command gosub_agi_command =
00527    { { "gosub", NULL }, handle_gosub, "Execute a dialplan subroutine", usage_gosub , 0 };
00528 
00529 static int unload_module(void)
00530 {
00531    if (ast_agi_unregister) {
00532        ast_agi_unregister(ast_module_info->self, &gosub_agi_command);
00533    }
00534 
00535    ast_unregister_application(app_return);
00536    ast_unregister_application(app_pop);
00537    ast_unregister_application(app_gosubif);
00538    ast_unregister_application(app_gosub);
00539    ast_custom_function_unregister(&local_function);
00540 
00541    return 0;
00542 }
00543 
00544 static int load_module(void)
00545 {
00546    /* usage of AGI is optional, so check to see if the ast_agi_register()
00547       function is available; if so, use it.
00548    */
00549    if (ast_agi_register) {
00550       ast_agi_register(ast_module_info->self, &gosub_agi_command);
00551    }
00552 
00553    ast_register_application(app_pop, pop_exec, pop_synopsis, pop_descrip);
00554    ast_register_application(app_return, return_exec, return_synopsis, return_descrip);
00555    ast_register_application(app_gosubif, gosubif_exec, gosubif_synopsis, gosubif_descrip);
00556    ast_register_application(app_gosub, gosub_exec, gosub_synopsis, gosub_descrip);
00557    ast_custom_function_register(&local_function);
00558 
00559    return 0;
00560 }
00561 
00562 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan subroutines (Gosub, Return, etc)");

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