Thu Jul 9 13:40:20 2009

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: 195840 $")
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    char *context;
00087    char extension[0];
00088 };
00089 
00090 static int frame_set_var(struct ast_channel *chan, struct gosub_stack_frame *frame, const char *var, const char *value)
00091 {
00092    struct ast_var_t *variables;
00093    int found = 0;
00094 
00095    /* Does this variable already exist? */
00096    AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
00097       if (!strcmp(var, ast_var_name(variables))) {
00098          found = 1;
00099          break;
00100       }
00101    }
00102 
00103    if (!found) {
00104       variables = ast_var_assign(var, "");
00105       AST_LIST_INSERT_HEAD(&frame->varshead, variables, entries);
00106       pbx_builtin_pushvar_helper(chan, var, value);
00107    } else {
00108       pbx_builtin_setvar_helper(chan, var, value);
00109    }
00110 
00111    manager_event(EVENT_FLAG_DIALPLAN, "VarSet",
00112       "Channel: %s\r\n"
00113       "Variable: LOCAL(%s)\r\n"
00114       "Value: %s\r\n"
00115       "Uniqueid: %s\r\n",
00116       chan->name, var, value, chan->uniqueid);
00117    return 0;
00118 }
00119 
00120 static void gosub_release_frame(struct ast_channel *chan, struct gosub_stack_frame *frame)
00121 {
00122    struct ast_var_t *vardata;
00123 
00124    /* If chan is not defined, then we're calling it as part of gosub_free,
00125     * and the channel variables will be deallocated anyway.  Otherwise, we're
00126     * just releasing a single frame, so we need to clean up the arguments for
00127     * that frame, so that we re-expose the variables from the previous frame
00128     * that were hidden by this one.
00129     */
00130    while ((vardata = AST_LIST_REMOVE_HEAD(&frame->varshead, entries))) {
00131       if (chan)
00132          pbx_builtin_setvar_helper(chan, ast_var_name(vardata), NULL);  
00133       ast_var_delete(vardata);
00134    }
00135 
00136    ast_free(frame);
00137 }
00138 
00139 static struct gosub_stack_frame *gosub_allocate_frame(const char *context, const char *extension, int priority, unsigned char arguments)
00140 {
00141    struct gosub_stack_frame *new = NULL;
00142    int len_extension = strlen(extension), len_context = strlen(context);
00143 
00144    if ((new = ast_calloc(1, sizeof(*new) + 2 + len_extension + len_context))) {
00145       AST_LIST_HEAD_INIT_NOLOCK(&new->varshead);
00146       strcpy(new->extension, extension);
00147       new->context = new->extension + len_extension + 1;
00148       strcpy(new->context, context);
00149       new->priority = priority;
00150       new->arguments = arguments;
00151    }
00152    return new;
00153 }
00154 
00155 static void gosub_free(void *data)
00156 {
00157    AST_LIST_HEAD(, gosub_stack_frame) *oldlist = data;
00158    struct gosub_stack_frame *oldframe;
00159    AST_LIST_LOCK(oldlist);
00160    while ((oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries))) {
00161       gosub_release_frame(NULL, oldframe);
00162    }
00163    AST_LIST_UNLOCK(oldlist);
00164    AST_LIST_HEAD_DESTROY(oldlist);
00165    ast_free(oldlist);
00166 }
00167 
00168 static int pop_exec(struct ast_channel *chan, void *data)
00169 {
00170    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00171    struct gosub_stack_frame *oldframe;
00172    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00173 
00174    if (!stack_store) {
00175       ast_log(LOG_WARNING, "%s called with no gosub stack allocated.\n", app_pop);
00176       return 0;
00177    }
00178 
00179    oldlist = stack_store->data;
00180    AST_LIST_LOCK(oldlist);
00181    oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
00182    AST_LIST_UNLOCK(oldlist);
00183 
00184    if (oldframe) {
00185       gosub_release_frame(chan, oldframe);
00186    } else {
00187       ast_debug(1, "%s called with an empty gosub stack\n", app_pop);
00188    }
00189    return 0;
00190 }
00191 
00192 static int return_exec(struct ast_channel *chan, void *data)
00193 {
00194    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00195    struct gosub_stack_frame *oldframe;
00196    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00197    char *retval = data;
00198 
00199    if (!stack_store) {
00200       ast_log(LOG_ERROR, "Return without Gosub: stack is unallocated\n");
00201       return -1;
00202    }
00203 
00204    oldlist = stack_store->data;
00205    AST_LIST_LOCK(oldlist);
00206    oldframe = AST_LIST_REMOVE_HEAD(oldlist, entries);
00207    AST_LIST_UNLOCK(oldlist);
00208 
00209    if (!oldframe) {
00210       ast_log(LOG_ERROR, "Return without Gosub: stack is empty\n");
00211       return -1;
00212    }
00213 
00214    ast_explicit_goto(chan, oldframe->context, oldframe->extension, oldframe->priority);
00215    gosub_release_frame(chan, oldframe);
00216 
00217    /* Set a return value, if any */
00218    pbx_builtin_setvar_helper(chan, "GOSUB_RETVAL", S_OR(retval, ""));
00219    return 0;
00220 }
00221 
00222 static int gosub_exec(struct ast_channel *chan, void *data)
00223 {
00224    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00225    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00226    struct gosub_stack_frame *newframe;
00227    char argname[15], *tmp = ast_strdupa(data), *label, *endparen;
00228    int i;
00229    AST_DECLARE_APP_ARGS(args2,
00230       AST_APP_ARG(argval)[100];
00231    );
00232 
00233    if (ast_strlen_zero(data)) {
00234       ast_log(LOG_ERROR, "%s requires an argument: %s([[context,]exten,]priority[(arg1[,...][,argN])])\n", app_gosub, app_gosub);
00235       return -1;
00236    }
00237 
00238    if (!stack_store) {
00239       ast_debug(1, "Channel %s has no datastore, so we're allocating one.\n", chan->name);
00240       stack_store = ast_channel_datastore_alloc(&stack_info, NULL);
00241       if (!stack_store) {
00242          ast_log(LOG_ERROR, "Unable to allocate new datastore.  Gosub will fail.\n");
00243          return -1;
00244       }
00245 
00246       oldlist = ast_calloc(1, sizeof(*oldlist));
00247       if (!oldlist) {
00248          ast_log(LOG_ERROR, "Unable to allocate datastore list head.  Gosub will fail.\n");
00249          ast_channel_datastore_free(stack_store);
00250          return -1;
00251       }
00252 
00253       stack_store->data = oldlist;
00254       AST_LIST_HEAD_INIT(oldlist);
00255       ast_channel_datastore_add(chan, stack_store);
00256    }
00257 
00258    /* Separate the arguments from the label */
00259    /* NOTE:  you cannot use ast_app_separate_args for this, because '(' cannot be used as a delimiter. */
00260    label = strsep(&tmp, "(");
00261    if (tmp) {
00262       endparen = strrchr(tmp, ')');
00263       if (endparen)
00264          *endparen = '\0';
00265       else
00266          ast_log(LOG_WARNING, "Ouch.  No closing paren: '%s'?\n", (char *)data);
00267       AST_STANDARD_APP_ARGS(args2, tmp);
00268    } else
00269       args2.argc = 0;
00270 
00271    /* Create the return address, but don't save it until we know that the Gosub destination exists */
00272    newframe = gosub_allocate_frame(chan->context, chan->exten, chan->priority + 1, args2.argc);
00273 
00274    if (!newframe) {
00275       return -1;
00276    }
00277 
00278    if (ast_parseable_goto(chan, label)) {
00279       ast_log(LOG_ERROR, "Gosub address is invalid: '%s'\n", (char *)data);
00280       ast_free(newframe);
00281       return -1;
00282    }
00283 
00284    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)) {
00285       ast_log(LOG_ERROR, "Attempt to reach a non-existent destination for gosub: (Context:%s, Extension:%s, Priority:%d)\n",
00286             chan->context, chan->exten, chan->priority);
00287       ast_copy_string(chan->context, newframe->context, sizeof(chan->context));
00288       ast_copy_string(chan->exten, newframe->extension, sizeof(chan->exten));
00289       chan->priority = newframe->priority;
00290       ast_free(newframe);
00291       return -1;
00292    }
00293 
00294    /* Now that we know for certain that we're going to a new location, set our arguments */
00295    for (i = 0; i < args2.argc; i++) {
00296       snprintf(argname, sizeof(argname), "ARG%d", i + 1);
00297       frame_set_var(chan, newframe, argname, args2.argval[i]);
00298       ast_debug(1, "Setting '%s' to '%s'\n", argname, args2.argval[i]);
00299    }
00300 
00301    /* And finally, save our return address */
00302    oldlist = stack_store->data;
00303    AST_LIST_LOCK(oldlist);
00304    AST_LIST_INSERT_HEAD(oldlist, newframe, entries);
00305    AST_LIST_UNLOCK(oldlist);
00306 
00307    return 0;
00308 }
00309 
00310 static int gosubif_exec(struct ast_channel *chan, void *data)
00311 {
00312    char *args;
00313    int res=0;
00314    AST_DECLARE_APP_ARGS(cond,
00315       AST_APP_ARG(ition);
00316       AST_APP_ARG(labels);
00317    );
00318    AST_DECLARE_APP_ARGS(label,
00319       AST_APP_ARG(iftrue);
00320       AST_APP_ARG(iffalse);
00321    );
00322 
00323    if (ast_strlen_zero(data)) {
00324       ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
00325       return 0;
00326    }
00327 
00328    args = ast_strdupa(data);
00329    AST_NONSTANDARD_APP_ARGS(cond, args, '?');
00330    if (cond.argc != 2) {
00331       ast_log(LOG_WARNING, "GosubIf requires an argument: GosubIf(cond?label1(args):label2(args)\n");
00332       return 0;
00333    }
00334 
00335    AST_NONSTANDARD_APP_ARGS(label, cond.labels, ':');
00336 
00337    if (pbx_checkcondition(cond.ition)) {
00338       if (!ast_strlen_zero(label.iftrue))
00339          res = gosub_exec(chan, label.iftrue);
00340    } else if (!ast_strlen_zero(label.iffalse)) {
00341       res = gosub_exec(chan, label.iffalse);
00342    }
00343 
00344    return res;
00345 }
00346 
00347 static int local_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
00348 {
00349    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00350    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00351    struct gosub_stack_frame *frame;
00352    struct ast_var_t *variables;
00353 
00354    if (!stack_store)
00355       return -1;
00356 
00357    oldlist = stack_store->data;
00358    AST_LIST_LOCK(oldlist);
00359    frame = AST_LIST_FIRST(oldlist);
00360    AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
00361       if (!strcmp(data, ast_var_name(variables))) {
00362          const char *tmp = pbx_builtin_getvar_helper(chan, data);
00363          ast_copy_string(buf, S_OR(tmp, ""), len);
00364          break;
00365       }
00366    }
00367    AST_LIST_UNLOCK(oldlist);
00368    return 0;
00369 }
00370 
00371 static int local_write(struct ast_channel *chan, const char *cmd, char *var, const char *value)
00372 {
00373    struct ast_datastore *stack_store = ast_channel_datastore_find(chan, &stack_info, NULL);
00374    AST_LIST_HEAD(, gosub_stack_frame) *oldlist;
00375    struct gosub_stack_frame *frame;
00376 
00377    if (!stack_store) {
00378       ast_log(LOG_ERROR, "Tried to set LOCAL(%s), but we aren't within a Gosub routine\n", var);
00379       return -1;
00380    }
00381 
00382    oldlist = stack_store->data;
00383    AST_LIST_LOCK(oldlist);
00384    frame = AST_LIST_FIRST(oldlist);
00385 
00386    if (frame)
00387       frame_set_var(chan, frame, var, value);
00388 
00389    AST_LIST_UNLOCK(oldlist);
00390 
00391    return 0;
00392 }
00393 
00394 static struct ast_custom_function local_function = {
00395    .name = "LOCAL",
00396    .synopsis = "Variables local to the gosub stack frame",
00397    .syntax = "LOCAL(<varname>)",
00398    .write = local_write,
00399    .read = local_read,
00400 };
00401 
00402 static int handle_gosub(struct ast_channel *chan, AGI *agi, int argc, char **argv)
00403 {
00404    int old_priority, priority;
00405    char old_context[AST_MAX_CONTEXT], old_extension[AST_MAX_EXTENSION];
00406    struct ast_app *theapp;
00407    char *gosub_args;
00408 
00409    if (argc < 4 || argc > 5) {
00410       return RESULT_SHOWUSAGE;
00411    }
00412 
00413    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] : "");
00414 
00415    if (sscanf(argv[3], "%d", &priority) != 1 || priority < 1) {
00416       /* Lookup the priority label */
00417       if ((priority = ast_findlabel_extension(chan, argv[1], argv[2], argv[3], chan->cid.cid_num)) < 0) {
00418          ast_log(LOG_ERROR, "Priority '%s' not found in '%s@%s'\n", argv[3], argv[2], argv[1]);
00419          ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
00420          return RESULT_FAILURE;
00421       }
00422    } else if (!ast_exists_extension(chan, argv[1], argv[2], priority, chan->cid.cid_num)) {
00423       ast_agi_send(agi->fd, chan, "200 result=-1 Gosub label not found\n");
00424       return RESULT_FAILURE;
00425    }
00426 
00427    /* Save previous location, since we're going to change it */
00428    ast_copy_string(old_context, chan->context, sizeof(old_context));
00429    ast_copy_string(old_extension, chan->exten, sizeof(old_extension));
00430    old_priority = chan->priority;
00431 
00432    if (!(theapp = pbx_findapp("Gosub"))) {
00433       ast_log(LOG_ERROR, "Gosub() cannot be found in the list of loaded applications\n");
00434       ast_agi_send(agi->fd, chan, "503 result=-2 Gosub is not loaded\n");
00435       return RESULT_FAILURE;
00436    }
00437 
00438    /* Apparently, if you run ast_pbx_run on a channel that already has a pbx
00439     * structure, you need to add 1 to the priority to get it to go to the
00440     * right place.  But if it doesn't have a pbx structure, then leaving off
00441     * the 1 is the right thing to do.  See how this code differs when we
00442     * call a Gosub for the CALLEE channel in Dial or Queue.
00443     */
00444    if (argc == 5) {
00445       if (asprintf(&gosub_args, "%s,%s,%d(%s)", argv[1], argv[2], priority + 1, argv[4]) < 0) {
00446          ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
00447          gosub_args = NULL;
00448       }
00449    } else {
00450       if (asprintf(&gosub_args, "%s,%s,%d", argv[1], argv[2], priority + 1) < 0) {
00451          ast_log(LOG_WARNING, "asprintf() failed: %s\n", strerror(errno));
00452          gosub_args = NULL;
00453       }
00454    }
00455 
00456    if (gosub_args) {
00457       int res;
00458 
00459       ast_debug(1, "Trying gosub with arguments '%s'\n", gosub_args);
00460       ast_copy_string(chan->context, "app_stack_gosub_virtual_context", sizeof(chan->context));
00461       ast_copy_string(chan->exten, "s", sizeof(chan->exten));
00462       chan->priority = 0;
00463 
00464       if ((res = pbx_exec(chan, theapp, gosub_args)) == 0) {
00465          struct ast_pbx *pbx = chan->pbx;
00466          struct ast_pbx_args args;
00467          memset(&args, 0, sizeof(args));
00468          args.no_hangup_chan = 1;
00469          /* Suppress warning about PBX already existing */
00470          chan->pbx = NULL;
00471          ast_agi_send(agi->fd, chan, "100 result=0 Trying...\n");
00472          ast_pbx_run_args(chan, &args);
00473          ast_agi_send(agi->fd, chan, "200 result=0 Gosub complete\n");
00474          if (chan->pbx) {
00475             ast_free(chan->pbx);
00476          }
00477          chan->pbx = pbx;
00478       } else {
00479          ast_agi_send(agi->fd, chan, "200 result=%d Gosub failed\n", res);
00480       }
00481       ast_free(gosub_args);
00482    } else {
00483       ast_agi_send(agi->fd, chan, "503 result=-2 Memory allocation failure\n");
00484       return RESULT_FAILURE;
00485    }
00486 
00487    /* Restore previous location */
00488    ast_copy_string(chan->context, old_context, sizeof(chan->context));
00489    ast_copy_string(chan->exten, old_extension, sizeof(chan->exten));
00490    chan->priority = old_priority;
00491 
00492    return RESULT_SUCCESS;
00493 }
00494 
00495 static char usage_gosub[] =
00496 " Usage: GOSUB <context> <extension> <priority> [<optional-argument>]\n"
00497 "   Cause the channel to execute the specified dialplan subroutine, returning\n"
00498 " to the dialplan with execution of a Return()\n";
00499 
00500 struct agi_command gosub_agi_command =
00501    { { "gosub", NULL }, handle_gosub, "Execute a dialplan subroutine", usage_gosub , 0 };
00502 
00503 static int unload_module(void)
00504 {
00505    if (ast_agi_unregister) {
00506       ast_agi_unregister(ast_module_info->self, &gosub_agi_command);
00507    }
00508 
00509    ast_unregister_application(app_return);
00510    ast_unregister_application(app_pop);
00511    ast_unregister_application(app_gosubif);
00512    ast_unregister_application(app_gosub);
00513    ast_custom_function_unregister(&local_function);
00514 
00515    return 0;
00516 }
00517 
00518 static int load_module(void)
00519 {
00520    /* usage of AGI is optional, so check to see if the ast_agi_register()
00521       function is available; if so, use it.
00522    */
00523    if (ast_agi_register) {
00524       ast_agi_register(ast_module_info->self, &gosub_agi_command);
00525    }
00526 
00527    ast_register_application(app_pop, pop_exec, pop_synopsis, pop_descrip);
00528    ast_register_application(app_return, return_exec, return_synopsis, return_descrip);
00529    ast_register_application(app_gosubif, gosubif_exec, gosubif_synopsis, gosubif_descrip);
00530    ast_register_application(app_gosub, gosub_exec, gosub_synopsis, gosub_descrip);
00531    ast_custom_function_register(&local_function);
00532 
00533    return 0;
00534 }
00535 
00536 AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan subroutines (Gosub, Return, etc)");

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