app_if.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright 2022, Naveen Albert <asterisk@phreaknet.org>
 *
 * Naveen Albert <asterisk@phreaknet.org>
 *
 * 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 If Branch Implementation
 *
 * \author Naveen Albert <asterisk@phreaknet.org>
 *
 * \ingroup applications
 */
 
/*** MODULEINFO
    <support_level>extended</support_level>
 ***/
 
#include "asterisk.h"
 
#include "asterisk/pbx.h"
#include "asterisk/module.h"
#include "asterisk/channel.h"
 
/*** DOCUMENTATION
    <application name="If" language="en_US">
        <synopsis>
            Start an if branch.
        </synopsis>
        <syntax>
            <parameter name="expr" required="true" />
        </syntax>
        <description>
            <para>Start an If branch.  Execution will continue inside the branch
            if expr is true.</para>
            <note><para>This application (and related applications) set variables
            internally during execution.</para></note>
        </description>
        <see-also>
            <ref type="application">ElseIf</ref>
            <ref type="application">Else</ref>
            <ref type="application">EndIf</ref>
            <ref type="application">ExitIf</ref>
        </see-also>
    </application>
    <application name="ElseIf" language="en_US">
        <synopsis>
            Start an else if branch.
        </synopsis>
        <syntax>
            <parameter name="expr" required="true" />
        </syntax>
        <description>
            <para>Start an optional ElseIf branch. Execution will continue inside the branch
            if expr is true and if previous If and ElseIf branches evaluated to false.</para>
            <para>Please note that execution inside a true If branch will fallthrough into
            ElseIf unless the If segment is terminated with an ExitIf call. This is only
            necessary with ElseIf but not with Else.</para>
        </description>
        <see-also>
            <ref type="application">If</ref>
            <ref type="application">Else</ref>
            <ref type="application">EndIf</ref>
            <ref type="application">ExitIf</ref>
        </see-also>
    </application>
    <application name="Else" language="en_US">
        <synopsis>
            Define an optional else branch.
        </synopsis>
        <syntax>
            <parameter name="expr" required="true" />
        </syntax>
        <description>
            <para>Start an Else branch. Execution will jump here if all previous
            If and ElseIf branches evaluated to false.</para>
        </description>
        <see-also>
            <ref type="application">If</ref>
            <ref type="application">ElseIf</ref>
            <ref type="application">EndIf</ref>
            <ref type="application">ExitIf</ref>
        </see-also>
    </application>
    <application name="EndIf" language="en_US">
        <synopsis>
            End an if branch.
        </synopsis>
        <syntax />
        <description>
            <para>Ends the branch begun by the preceding <literal>If()</literal> application.</para>
        </description>
        <see-also>
            <ref type="application">If</ref>
            <ref type="application">ElseIf</ref>
            <ref type="application">Else</ref>
            <ref type="application">ExitIf</ref>
        </see-also>
    </application>
    <application name="ExitIf" language="en_US">
        <synopsis>
            End an If branch.
        </synopsis>
        <syntax />
        <description>
            <para>Exits an <literal>If()</literal> branch, whether or not it has completed.</para>
        </description>
        <see-also>
            <ref type="application">If</ref>
            <ref type="application">ElseIf</ref>
            <ref type="application">Else</ref>
            <ref type="application">EndIf</ref>
        </see-also>
    </application>
 ***/
 
static char *if_app = "If";
static char *elseif_app = "ElseIf";
static char *else_app = "Else";
static char *stop_app = "EndIf";
static char *exit_app = "ExitIf";
 
#define VAR_SIZE 64
 
static const char *get_index(struct ast_channel *chan, const char *prefix, int idx)
{
    char varname[VAR_SIZE];
 
    snprintf(varname, VAR_SIZE, "%s_%d", prefix, idx);
    return pbx_builtin_getvar_helper(chan, varname);
}
 
static struct ast_exten *find_matching_priority(struct ast_context *c, const char *exten, int priority, const char *callerid)
{
    struct ast_exten *e;
    struct ast_context *c2;
    int idx;
 
    for (e = ast_walk_context_extensions(c, NULL); e; e = ast_walk_context_extensions(c, e)) {
        if (ast_extension_match(ast_get_extension_name(e), exten)) {
            int needmatch = ast_get_extension_matchcid(e);
            if ((needmatch && ast_extension_match(ast_get_extension_cidmatch(e), callerid)) ||
                (!needmatch)) {
                /* This is the matching extension we want */
                struct ast_exten *p;
                for (p = ast_walk_extension_priorities(e, NULL); p; p = ast_walk_extension_priorities(e, p)) {
                    if (priority != ast_get_extension_priority(p))
                        continue;
                    return p;
                }
            }
        }
    }
 
    /* No match; run through includes */
    for (idx = 0; idx < ast_context_includes_count(c); idx++) {
        const struct ast_include *i = ast_context_includes_get(c, idx);
 
        for (c2 = ast_walk_contexts(NULL); c2; c2 = ast_walk_contexts(c2)) {
            if (!strcmp(ast_get_context_name(c2), ast_get_include_name(i))) {
                e = find_matching_priority(c2, exten, priority, callerid);
                if (e)
                    return e;
            }
        }
    }
    return NULL;
}
 
static int find_matching_endif(struct ast_channel *chan, const char *otherapp)
{
    struct ast_context *c;
    int res = -1;
 
    if (ast_rdlock_contexts()) {
        ast_log(LOG_ERROR, "Failed to lock contexts list\n");
        return -1;
    }
 
    for (c = ast_walk_contexts(NULL); c; c = ast_walk_contexts(c)) {
        struct ast_exten *e;
 
        if (!ast_rdlock_context(c)) {
            if (!strcmp(ast_get_context_name(c), ast_channel_context(chan))) {
                /* This is the matching context we want */
 
                int cur_priority = ast_channel_priority(chan) + 1, level = 1;
 
                for (e = find_matching_priority(c, ast_channel_exten(chan), cur_priority,
                    S_COR(ast_channel_caller(chan)->id.number.valid, ast_channel_caller(chan)->id.number.str, NULL));
                    e;
                    e = find_matching_priority(c, ast_channel_exten(chan), ++cur_priority,
                        S_COR(ast_channel_caller(chan)->id.number.valid, ast_channel_caller(chan)->id.number.str, NULL))) {
 
                    if (!strcasecmp(ast_get_extension_app(e), "IF")) {
                        level++;
                    } else if (!strcasecmp(ast_get_extension_app(e), "ENDIF")) {
                        level--;
                    }
 
                    if (!otherapp && level == 0) {
                        res = cur_priority;
                        break;
                    } else if (otherapp && level == 1 && !strcasecmp(ast_get_extension_app(e), otherapp)) {
                        res = cur_priority;
                        break;
                    }
                }
            }
            ast_unlock_context(c);
            if (res > 0) {
                break;
            }
        }
    }
    ast_unlock_contexts();
    return res;
}
 
static int if_helper(struct ast_channel *chan, const char *data, int end)
{
    int res = 0;
    const char *if_pri = NULL;
    char *my_name = NULL;
    const char *label = NULL;
    char varname[VAR_SIZE + 3]; /* + IF_ */
    char end_varname[sizeof(varname) + 4]; /* + END_ + sizeof(varname) */
    const char *prefix = "IF";
    size_t size = 0;
    int used_index_i = -1, x = 0;
    char used_index[VAR_SIZE] = "0", new_index[VAR_SIZE] = "0";
 
    if (!chan) {
        return -1;
    }
 
    for (x = 0 ;; x++) {
        if (get_index(chan, prefix, x)) {
            used_index_i = x;
        } else {
            break;
        }
    }
 
    snprintf(used_index, sizeof(used_index), "%d", used_index_i);
    snprintf(new_index, sizeof(new_index), "%d", used_index_i + 1);
 
    size = strlen(ast_channel_context(chan)) + strlen(ast_channel_exten(chan)) + 32;
    my_name = ast_alloca(size);
    memset(my_name, 0, size);
    snprintf(my_name, size, "%s_%s_%d", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan));
 
    ast_channel_lock(chan);
    if (end > 1) {
        label = used_index;
    } else if (!(label = pbx_builtin_getvar_helper(chan, my_name))) {
        label = new_index;
        pbx_builtin_setvar_helper(chan, my_name, label);
    }
    snprintf(varname, sizeof(varname), "%s_%s", prefix, label);
    if ((if_pri = pbx_builtin_getvar_helper(chan, varname)) && !end) {
        if_pri = ast_strdupa(if_pri);
        snprintf(end_varname,sizeof(end_varname),"END_%s",varname);
    }
    ast_channel_unlock(chan);
 
    if ((end <= 1 && !pbx_checkcondition(ast_strdupa(data))) || (end > 1)) {
        /* Condition Met (clean up helper vars) */
        const char *goto_str;
        int pri, endifpri;
        pbx_builtin_setvar_helper(chan, varname, NULL);
        pbx_builtin_setvar_helper(chan, my_name, NULL);
        snprintf(end_varname,sizeof(end_varname),"END_%s",varname);
        ast_channel_lock(chan);
        /* For EndIf, simply go to the next priority.
         * We do not add 1 to ast_channel_priority because the dialplan will
         * auto-increment the priority when we return, so just keep the priority as is.
         * For ExitIf or false If() condition, we need to find the end of the current
         * If branch (at same indentation) and branch there. */
        endifpri = end == 2 ? ast_channel_priority(chan) : find_matching_endif(chan, NULL);
        if ((goto_str = pbx_builtin_getvar_helper(chan, end_varname))) {
            ast_parseable_goto(chan, goto_str);
            pbx_builtin_setvar_helper(chan, end_varname, NULL);
        } else if (end <= 1 && (pri = find_matching_endif(chan, "ElseIf")) > 0 && pri < endifpri) {
            pri--; /* back up a priority, since it returned the priority after the ElseIf */
            /* If is false, and ElseIf exists, so jump to ElseIf */
            ast_verb(3, "Taking conditional false branch, jumping to priority %d\n", pri);
            ast_channel_priority_set(chan, pri);
        } else if (end <= 1 && (pri = find_matching_endif(chan, "Else")) > 0 && pri < endifpri) {
            /* don't need to back up a priority, because we don't actually need to execute Else, just jump to the priority after. Directly executing Else will exit the conditional. */
            /* If is false, and Else exists, so jump to Else */
            ast_verb(3, "Taking absolute false branch, jumping to priority %d\n", pri);
            ast_channel_priority_set(chan, pri);
        } else {
            pri = endifpri;
            if (pri > 0) {
                ast_verb(3, "Exiting conditional, jumping to priority %d\n", pri);
                ast_channel_priority_set(chan, pri);
            } else if (end == 4) { /* Condition added because of end > 0 instead of end == 4 */
                ast_log(LOG_WARNING, "Couldn't find matching EndIf? (If at %s@%s priority %d)\n", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan));
            }
        }
        ast_channel_unlock(chan);
        return res;
    }
 
    if (end <= 1 && !if_pri) {
        char *goto_str;
        size = strlen(ast_channel_context(chan)) + strlen(ast_channel_exten(chan)) + 32;
        goto_str = ast_alloca(size);
        memset(goto_str, 0, size);
        snprintf(goto_str, size, "%s,%s,%d", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan));
        pbx_builtin_setvar_helper(chan, varname, goto_str);
    } else if (end > 1 && if_pri) {
        /* END of branch */
        snprintf(end_varname, sizeof(end_varname), "END_%s", varname);
        if (!pbx_builtin_getvar_helper(chan, end_varname)) {
            char *goto_str;
            size = strlen(ast_channel_context(chan)) + strlen(ast_channel_exten(chan)) + 32;
            goto_str = ast_alloca(size);
            memset(goto_str, 0, size);
            snprintf(goto_str, size, "%s,%s,%d", ast_channel_context(chan), ast_channel_exten(chan), ast_channel_priority(chan)+1);
            pbx_builtin_setvar_helper(chan, end_varname, goto_str);
        }
        ast_parseable_goto(chan, if_pri);
    }
 
    return res;
}
 
static int if_exec(struct ast_channel *chan, const char *data) {
    return if_helper(chan, data, 0);
}
 
static int elseif_exec(struct ast_channel *chan, const char *data) {
    return if_helper(chan, data, 1);
}
 
static int end_exec(struct ast_channel *chan, const char *data) {
    return if_helper(chan, data, 2);
}
 
static int else_exec(struct ast_channel *chan, const char *data) {
    return if_helper(chan, data, 3);
}
 
static int exit_exec(struct ast_channel *chan, const char *data) {
    return if_helper(chan, data, 4);
}
 
static int unload_module(void)
{
    int res;
 
    res = ast_unregister_application(if_app);
    res |= ast_unregister_application(elseif_app);
    res |= ast_unregister_application(stop_app);
    res |= ast_unregister_application(else_app);
    res |= ast_unregister_application(exit_app);
 
    return res;
}
 
static int load_module(void)
{
    int res;
 
    res = ast_register_application_xml(if_app, if_exec);
    res |= ast_register_application_xml(elseif_app, elseif_exec);
    res |= ast_register_application_xml(stop_app, end_exec);
    res |= ast_register_application_xml(else_app, else_exec);
    res |= ast_register_application_xml(exit_app, exit_exec);
 
    return res;
}
 
AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "If Branch and Conditional Execution");