app_dtmfstore.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2021, Naveen Albert
 *
 * 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 Technology independent asynchronous DTMF collection
 *
 * \author Naveen Albert <asterisk@phreaknet.org>
 *
 * \ingroup functions
 *
 */
 
/*** MODULEINFO
    <support_level>extended</support_level>
 ***/
 
#include "asterisk.h"
 
#include "asterisk/module.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/framehook.h"
#include "asterisk/app.h"
#include "asterisk/conversions.h"
 
/*** DOCUMENTATION
    <application name="StoreDTMF" language="en_US">
        <since>
            <version>16.20.0</version>
            <version>18.6.0</version>
        </since>
        <synopsis>
            Stores DTMF digits transmitted or received on a channel.
        </synopsis>
        <syntax>
            <parameter name="direction" required="true">
                <para>Must be <literal>TX</literal> or <literal>RX</literal> to
                store digits, or <literal>remove</literal> to disable.</para>
            </parameter>
        </syntax>
        <description>
            <para>The StoreDTMF function can be used to obtain digits sent in the
            <literal>TX</literal> or <literal>RX</literal> direction of any channel.</para>
            <para>The arguments are:</para>
            <para><replaceable>var_name</replaceable>: Name of variable to which to append
            digits.</para>
            <para><replaceable>max_digits</replaceable>: The maximum number of digits to
            store in the variable. Defaults to 0 (no maximum). After reading <literal>
            maximum</literal> digits, no more digits will be stored.</para>
            <example title="Store digits in CDR variable">
            same => n,StoreDTMF(TX,CDR(digits))
            </example>
            <example title="Store up to 24 digits">
            same => n,StoreDTMF(RX,testvar,24)
            </example>
            <example title="Disable digit collection">
            same => n,StoreDTMF(remove)
            </example>
        </description>
    </application>
 ***/
 
static char *app = "StoreDTMF";
 
/*! \brief Private data structure used with the function's datastore */
struct dtmf_store_data {
    int framehook_id;
    char *rx_var;
    char *tx_var;
    int maxdigits;
};
 
static void datastore_destroy_cb(void *data) {
    struct dtmf_store_data *d;
    d = data;
    if (d) {
        if (d->rx_var) {
            ast_free(d->rx_var);
        }
        if (d->tx_var) {
            ast_free(d->tx_var);
        }
        ast_free(data);
    }
}
 
/*! \brief The channel datastore the function uses to store state */
static const struct ast_datastore_info dtmf_store_datastore = {
    .type = "dtmf_store",
    .destroy = datastore_destroy_cb
};
 
/*! \internal \brief Store digits tx/rx on the channel */
static int remove_dtmf_store(struct ast_channel *chan)
{
    struct ast_datastore *datastore = NULL;
    struct dtmf_store_data *data;
    SCOPED_CHANNELLOCK(chan_lock, chan);
 
    datastore = ast_channel_datastore_find(chan, &dtmf_store_datastore, NULL);
    if (!datastore) {
        ast_log(AST_LOG_WARNING, "Cannot remove StoreDTMF from %s: StoreDTMF not currently enabled\n",
                ast_channel_name(chan));
        return -1;
    }
    data = datastore->data;
 
    if (ast_framehook_detach(chan, data->framehook_id)) {
        ast_log(AST_LOG_WARNING, "Failed to remove StoreDTMF framehook from channel %s\n",
                ast_channel_name(chan));
        return -1;
    }
 
    if (ast_channel_datastore_remove(chan, datastore)) {
        ast_log(AST_LOG_WARNING, "Failed to remove StoreDTMF datastore from channel %s\n",
                ast_channel_name(chan));
        return -1;
    }
    ast_datastore_free(datastore);
 
    return 0;
}
 
/*! \brief Frame hook that is called to intercept digit/undigit */
static struct ast_frame *dtmf_store_framehook(struct ast_channel *chan,
    struct ast_frame *f, enum ast_framehook_event event, void *data)
{
    char currentdata[512];
    char varnamesub[64];
    char *varname = NULL;
    struct dtmf_store_data *framedata = data;
    int len;
 
    if (!f || !framedata) {
        return f;
    }
 
    if ((event != AST_FRAMEHOOK_EVENT_WRITE) && (event != AST_FRAMEHOOK_EVENT_READ)) {
        return f;
    }
 
    if (f->frametype != AST_FRAME_DTMF_END) {
        return f;
    }
 
    /* If this is DTMF then store the digits */
    if (event == AST_FRAMEHOOK_EVENT_READ && framedata->rx_var) { /* coming from source */
        varname = framedata->rx_var;
    } else if (event == AST_FRAMEHOOK_EVENT_WRITE && framedata->tx_var) { /* going to source */
        varname = framedata->tx_var;
    }
 
    if (!varname) {
        return f;
    }
 
    sprintf(varnamesub, "${%s}", varname);
    pbx_substitute_variables_helper(chan, varnamesub, currentdata, 511);
    /* pbx_builtin_getvar_helper works for regular vars but not CDR vars */
    if (ast_strlen_zero(currentdata)) { /* var doesn't exist yet */
        ast_debug(3, "Creating new digit store: %s\n", varname);
    }
    len = strlen(currentdata);
    if (framedata->maxdigits > 0 && len >= framedata->maxdigits) {
        ast_debug(3, "Reached digit limit: %d\n", framedata->maxdigits);
        remove_dtmf_store(chan); /* reached max digit count, stop now */
        return f;
    } else {
        char newdata[len + 2]; /* one more char + terminator */
        if (len > 0) {
            ast_copy_string(newdata, currentdata, len + 2);
        }
        newdata[len] = (unsigned) f->subclass.integer;
        newdata[len + 1] = '\0';
        ast_debug(3, "Appending to digit store: now %s\n", newdata);
        pbx_builtin_setvar_helper(chan, varname, newdata);
    }
    return f;
}
 
/*! \internal \brief Enable digit interception on the channel */
static int dtmfstore_exec(struct ast_channel *chan, const char *appdata)
{
    struct ast_datastore *datastore;
    struct dtmf_store_data *data;
    static struct ast_framehook_interface digit_framehook_interface = {
        .version = AST_FRAMEHOOK_INTERFACE_VERSION,
        .event_cb = dtmf_store_framehook,
        .disable_inheritance = 1,
    };
    char *parse = ast_strdupa(appdata);
    AST_DECLARE_APP_ARGS(args,
        AST_APP_ARG(direction);
        AST_APP_ARG(varname);
        AST_APP_ARG(maxdigits);
    );
    SCOPED_CHANNELLOCK(chan_lock, chan);
    AST_STANDARD_APP_ARGS(args, parse);
 
    if (ast_strlen_zero(appdata)) {
        ast_log(AST_LOG_WARNING, "StoreDTMF requires an argument\n");
        return -1;
    }
 
    if (!strcasecmp(args.direction, "remove")) {
        return remove_dtmf_store(chan);
    }
 
    datastore = ast_channel_datastore_find(chan, &dtmf_store_datastore, NULL);
    if (datastore) {
        ast_log(AST_LOG_WARNING, "StoreDTMF already set on '%s'\n",
                ast_channel_name(chan));
        return 0;
    }
 
    datastore = ast_datastore_alloc(&dtmf_store_datastore, NULL);
    if (!datastore) {
        return -1;
    }
 
    data = ast_calloc(1, sizeof(*data));
    if (!data) {
        ast_datastore_free(datastore);
        return -1;
    }
 
    digit_framehook_interface.data = data;
 
    data->rx_var = NULL;
    data->tx_var = NULL;
    data->maxdigits = 0;
 
    if (!strcasecmp(args.direction, "tx")) {
        data->tx_var = ast_strdup(args.varname);
    } else if (!strcasecmp(args.direction, "rx")) {
        data->rx_var = ast_strdup(args.varname);
    } else {
        ast_log(LOG_ERROR, "Direction must be either RX or TX\n");
        return -1;
    }
 
    if (!ast_strlen_zero(args.maxdigits)) {
        if (ast_str_to_int(args.maxdigits,&(data->maxdigits))) {
            ast_log(LOG_ERROR, "Invalid integer: %s\n", args.maxdigits);
            return -1;
        }
        if (data->maxdigits < 0) {
            ast_log(LOG_ERROR, "Invalid natural number: %d\n", data->maxdigits);
            return -1;
        } else if (data->maxdigits == 0) {
            ast_log(LOG_WARNING, "No maximum digit count set\n");
        }
    }
 
    data->framehook_id = ast_framehook_attach(chan, &digit_framehook_interface);
    if (data->framehook_id < 0) {
        ast_log(AST_LOG_WARNING, "Failed to attach StoreDTMF framehook to '%s'\n",
                ast_channel_name(chan));
        ast_datastore_free(datastore);
        ast_free(data);
        return -1;
    }
    datastore->data = data;
 
    ast_channel_datastore_add(chan, datastore);
 
    return 0;
}
 
static int unload_module(void)
{
    return ast_unregister_application(app);
}
 
static int load_module(void)
{
    return ast_register_application_xml(app, dtmfstore_exec);
}
 
AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Technology independent async DTMF storage");