[Asterisk-code-review] app_waitforcond: New application (asterisk[master])
Friendly Automation
asteriskteam at digium.com
Thu Jul 8 09:50:44 CDT 2021
Friendly Automation has submitted this change. ( https://gerrit.asterisk.org/c/asterisk/+/15946 )
Change subject: app_waitforcond: New application
......................................................................
app_waitforcond: New application
While several applications exist to wait for
a certain event to occur, none allow waiting
for any generic expression to become true.
This application allows for waiting for a condition
to become true, with configurable timeout and
checking interval.
ASTERISK-29444
Change-Id: I08adf2824b8bc63405778cf355963b5005612f41
---
A apps/app_waitforcond.c
A doc/CHANGES-staging/app_waitforcond.txt
2 files changed, 239 insertions(+), 0 deletions(-)
Approvals:
Joshua Colp: Looks good to me, but someone else must approve
George Joseph: Looks good to me, approved
Friendly Automation: Approved for Submit
diff --git a/apps/app_waitforcond.c b/apps/app_waitforcond.c
new file mode 100644
index 0000000..7bc254c
--- /dev/null
+++ b/apps/app_waitforcond.c
@@ -0,0 +1,234 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2021, Naveen Albert
+ *
+ * Naveen Albert <asterisk at 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 Sleep until a condition is true
+ *
+ * \author Naveen Albert <asterisk at phreaknet.org>
+ *
+ * \ingroup applications
+ */
+
+/*** MODULEINFO
+ <support_level>extended</support_level>
+ ***/
+
+#include "asterisk.h"
+
+#include "asterisk/logger.h"
+#include "asterisk/channel.h"
+#include "asterisk/pbx.h"
+#include "asterisk/module.h"
+#include "asterisk/app.h"
+
+/*** DOCUMENTATION
+ <application name="WaitForCondition" language="en_US">
+ <synopsis>
+ Wait (sleep) until the given condition is true.
+ </synopsis>
+ <syntax>
+ <parameter name="replacementchar" required="true">
+ <para>Specifies the character in the expression used to replace the <literal>$</literal>
+ character. This character should not be used anywhere in the expression itself.</para>
+ </parameter>
+ <parameter name="expression" required="true">
+ <para>A modified logical expression with the <literal>$</literal> characters replaced by
+ <replaceable>replacementchar</replaceable>. This is necessary to pass the expression itself
+ into the application, rather than its initial evaluation.</para>
+ </parameter>
+ <parameter name="timeout">
+ <para>The maximum amount of time, in seconds, this application should wait for a condition
+ to become true before dialplan execution continues automatically to the next priority.
+ By default, there is no timeout.</para>
+ </parameter>
+ <parameter name="interval">
+ <para>The frequency, in seconds, of polling the condition, which can be adjusted depending
+ on how time-sensitive execution needs to be. By default, this is 0.05.</para>
+ </parameter>
+ </syntax>
+ <description>
+ <para>Waits until <replaceable>expression</replaceable> evaluates to true, checking every
+ <replaceable>interval</replaceable> seconds for up to <replaceable>timeout</replaceable>. Default
+ is evaluate <replaceable>expression</replaceable> every 50 milliseconds with no timeout.</para>
+ <example title="Wait for ${condition} to become 1 for up to 40 seconds, checking every 500ms">
+ same => n,WaitForCondition(#,#["#{condition}"="1"],40,0.5)
+ </example>
+ <para>Sets <variable>WAITFORCONDITIONSTATUS</variable> to one of the following values:</para>
+ <variablelist>
+ <variable name="WAITFORCONDITIONSTATUS">
+ <value name="TRUE">
+ Condition evaluated to true before timeout expired.
+ </value>
+ <value name="FAILURE">
+ Invalid argument.
+ </value>
+ <value name="TIMEOUT">
+ Timeout elapsed without condition evaluating to true.
+ </value>
+ <value name="HANGUP">
+ Channel hung up before condition became true.
+ </value>
+ </variable>
+ </variablelist>
+ </description>
+ </application>
+ ***/
+
+static char *app = "WaitForCondition";
+
+static int waitforcond_exec(struct ast_channel *chan, const char *data)
+{
+ int ms, i;
+ double timeout = 0, poll = 0;
+ int timeout_ms = 0;
+ int poll_ms = 50; /* default is evaluate the condition every 50ms */
+ struct timeval start = ast_tvnow();
+ char dollarsignrep;
+ int brackets = 0;
+ char *pos, *open_bracket, *expression, *optargs = NULL;
+ char condition[512];
+
+ AST_DECLARE_APP_ARGS(args,
+ AST_APP_ARG(timeout);
+ AST_APP_ARG(interval);
+ );
+
+ pos = ast_strdupa(data);
+
+ if (ast_strlen_zero(pos)) {
+ ast_log(LOG_ERROR, "WaitForCondition requires a condition\n");
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
+ return 0;
+ }
+
+ /* is there at least a [ followed by a ] somewhere ? */
+ if (!(open_bracket = strchr(pos, '[')) || !strchr(open_bracket, ']')) {
+ ast_log(LOG_ERROR, "No expression detected. Did you forget to replace the $ signs?\n");
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
+ return 0;
+ }
+
+ dollarsignrep = pos[0];
+ if (dollarsignrep == '$' || dollarsignrep == '[' || dollarsignrep == ']'
+ || dollarsignrep == '{' || dollarsignrep == '}') {
+ ast_log(LOG_ERROR, "Dollar sign replacement cannot be %c.\n", dollarsignrep);
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
+ return 0;
+ }
+ ++pos;
+ if (pos[0] != ',') {
+ ast_log(LOG_ERROR, "Invalid separator: %c\n", pos[0]);
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
+ return 0;
+ }
+ ++pos;
+ if (pos[0] != dollarsignrep) {
+ ast_log(LOG_ERROR, "Expression start does not match provided replacement: %c\n", pos[0]);
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
+ return 0;
+ }
+
+ expression = pos; /* we're at the start of the expression */
+
+ /* commas may appear within the expression, so go until we've encountered as many closing brackets as opening */
+ while (++pos) {
+ if (pos[0] == '\0') {
+ ast_log(LOG_ERROR, "Could not parse end of expression.\n");
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
+ return 0;
+ }
+ if (pos[0] == '[') {
+ brackets++;
+ } else if (pos[0] == ']') {
+ brackets--;
+ }
+ if (brackets == 0) { /* reached end of expression */
+ break;
+ }
+ }
+ ++pos;
+ if (pos[0] != '\0') {
+ ++pos; /* eat comma separator */
+ if (pos[0] != '\0') {
+ optargs = ast_strdupa(pos);
+ AST_STANDARD_APP_ARGS(args, optargs);
+ if (!ast_strlen_zero(args.timeout)) {
+ if (sscanf(args.timeout, "%30lg", &timeout) != 1) {
+ ast_log(LOG_WARNING, "Invalid timeout provided: %s. No timeout set.\n", args.timeout);
+ return -1;
+ }
+ timeout_ms = timeout * 1000.0;
+ }
+
+ if (!ast_strlen_zero(args.interval)) {
+ if (sscanf(args.interval, "%30lg", &poll) != 1) {
+ ast_log(LOG_WARNING, "Invalid polling interval provided: %s. Default unchanged.\n", args.interval);
+ return -1;
+ }
+ if (poll < 0.001) {
+ ast_log(LOG_WARNING, "Polling interval cannot be less than 1ms. Default unchanged.\n");
+ return -1;
+ }
+ poll_ms = poll * 1000.0;
+ }
+ }
+ }
+
+ for (i = 0; expression[i] != '\0'; i++) {
+ if (expression[i] == dollarsignrep) {
+ expression[i] = '$'; /* replace $s back into expression for variable parsing */
+ }
+ }
+
+ if (timeout_ms > 0) {
+ ast_debug(1, "Waiting for condition for %f seconds: %s (checking every %d ms)", timeout, expression, poll_ms);
+ } else {
+ ast_debug(1, "Waiting for condition, forever: %s (checking every %d ms)", expression, poll_ms);
+ }
+
+ while (1) {
+ /* Substitute variables now */
+ pbx_substitute_variables_helper(chan, expression, condition, sizeof(condition) - 1);
+ if (pbx_checkcondition(condition)) {
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "TRUE");
+ return 0;
+ }
+ /* If a timeout was specified, check that it hasn't expired */
+ if ((timeout_ms > 0) && !(ms = ast_remaining_ms(start, timeout_ms))) {
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "TIMEOUT");
+ return 0;
+ }
+ if (ast_safe_sleep(chan, poll_ms)) { /* don't waste CPU, we don't need a super tight loop */
+ pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "HANGUP");
+ return -1; /* channel hung up */
+ }
+ }
+}
+
+static int unload_module(void)
+{
+ return ast_unregister_application(app);
+}
+
+static int load_module(void)
+{
+ return ast_register_application_xml(app, waitforcond_exec);
+}
+
+AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Wait until condition is true");
diff --git a/doc/CHANGES-staging/app_waitforcond.txt b/doc/CHANGES-staging/app_waitforcond.txt
new file mode 100644
index 0000000..a7ab600
--- /dev/null
+++ b/doc/CHANGES-staging/app_waitforcond.txt
@@ -0,0 +1,5 @@
+Subject: WaitForCondition application
+
+This application provides a way to halt
+dialplan execution until a provided
+condition evaluates to true.
--
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Gerrit-Project: asterisk
Gerrit-Branch: master
Gerrit-Change-Id: I08adf2824b8bc63405778cf355963b5005612f41
Gerrit-Change-Number: 15946
Gerrit-PatchSet: 12
Gerrit-Owner: N A <mail at interlinked.x10host.com>
Gerrit-Reviewer: Friendly Automation
Gerrit-Reviewer: George Joseph <gjoseph at digium.com>
Gerrit-Reviewer: Joshua Colp <jcolp at sangoma.com>
Gerrit-Reviewer: Kevin Harwell <kharwell at digium.com>
Gerrit-Reviewer: Richard Mudgett <rmudgett at digium.com>
Gerrit-MessageType: merged
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