app_dtmfstore.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2021, Naveen Albert
 *
 * Naveen Albert <[email protected]>
 *
 * 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 <[email protected]>
 *
 * \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">
 <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>.</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>
 <para>For example:</para>
 <para>StoreDTMF(TX,CDR(digits))</para>
 <para>StoreDTMF(RX,testvar,24)</para>
 <para>StoreDTMF(remove)</para>
 </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");