Asterisk - The Open Source Telephony Project GIT-master-d856a3e
app_waitforcond.c
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1/*
2 * Asterisk -- An open source telephony toolkit.
3 *
4 * Copyright (C) 2021, Naveen Albert
5 *
6 * Naveen Albert <asterisk@phreaknet.org>
7 *
8 * See http://www.asterisk.org for more information about
9 * the Asterisk project. Please do not directly contact
10 * any of the maintainers of this project for assistance;
11 * the project provides a web site, mailing lists and IRC
12 * channels for your use.
13 *
14 * This program is free software, distributed under the terms of
15 * the GNU General Public License Version 2. See the LICENSE file
16 * at the top of the source tree.
17 */
18
19/*! \file
20 *
21 * \brief Sleep until a condition is true
22 *
23 * \author Naveen Albert <asterisk@phreaknet.org>
24 *
25 * \ingroup applications
26 */
27
28/*** MODULEINFO
29 <support_level>extended</support_level>
30 ***/
31
32#include "asterisk.h"
33
34#include "asterisk/logger.h"
35#include "asterisk/channel.h"
36#include "asterisk/pbx.h"
37#include "asterisk/module.h"
38#include "asterisk/app.h"
39
40/*** DOCUMENTATION
41 <application name="WaitForCondition" language="en_US">
42 <since>
43 <version>16.20.0</version>
44 <version>18.6.0</version>
45 <version>19.0.0</version>
46 </since>
47 <synopsis>
48 Wait (sleep) until the given condition is true.
49 </synopsis>
50 <syntax>
51 <parameter name="replacementchar" required="true">
52 <para>Specifies the character in the expression used to replace the <literal>$</literal>
53 character. This character should not be used anywhere in the expression itself.</para>
54 </parameter>
55 <parameter name="expression" required="true">
56 <para>A modified logical expression with the <literal>$</literal> characters replaced by
57 <replaceable>replacementchar</replaceable>. This is necessary to pass the expression itself
58 into the application, rather than its initial evaluation.</para>
59 </parameter>
60 <parameter name="timeout">
61 <para>The maximum amount of time, in seconds, this application should wait for a condition
62 to become true before dialplan execution continues automatically to the next priority.
63 By default, there is no timeout.</para>
64 </parameter>
65 <parameter name="interval">
66 <para>The frequency, in seconds, of polling the condition, which can be adjusted depending
67 on how time-sensitive execution needs to be. By default, this is 0.05.</para>
68 </parameter>
69 </syntax>
70 <description>
71 <para>Waits until <replaceable>expression</replaceable> evaluates to true, checking every
72 <replaceable>interval</replaceable> seconds for up to <replaceable>timeout</replaceable>. Default
73 is evaluate <replaceable>expression</replaceable> every 50 milliseconds with no timeout.</para>
74 <example title="Wait for condition dialplan variable/function to become 1 for up to 40 seconds, checking every 500ms">
75 same => n,WaitForCondition(#,#["#{condition}"="1"],40,0.5)
76 </example>
77 <para>Sets <variable>WAITFORCONDITIONSTATUS</variable> to one of the following values:</para>
78 <variablelist>
79 <variable name="WAITFORCONDITIONSTATUS">
80 <value name="TRUE">
81 Condition evaluated to true before timeout expired.
82 </value>
83 <value name="FAILURE">
84 Invalid argument.
85 </value>
86 <value name="TIMEOUT">
87 Timeout elapsed without condition evaluating to true.
88 </value>
89 <value name="HANGUP">
90 Channel hung up before condition became true.
91 </value>
92 </variable>
93 </variablelist>
94 </description>
95 </application>
96 ***/
97
98static char *app = "WaitForCondition";
99
100static int waitforcond_exec(struct ast_channel *chan, const char *data)
101{
102 int ms, i;
103 double timeout = 0, poll = 0;
104 int timeout_ms = 0;
105 int poll_ms = 50; /* default is evaluate the condition every 50ms */
106 struct timeval start = ast_tvnow();
107 char dollarsignrep;
108 int brackets = 0;
109 char *pos, *open_bracket, *expression, *optargs = NULL;
110 char condition[512];
111
113 AST_APP_ARG(timeout);
114 AST_APP_ARG(interval);
115 );
116
117 pos = ast_strdupa(data);
118
119 if (ast_strlen_zero(pos)) {
120 ast_log(LOG_ERROR, "WaitForCondition requires a condition\n");
121 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
122 return 0;
123 }
124
125 /* is there at least a [ followed by a ] somewhere ? */
126 if (!(open_bracket = strchr(pos, '[')) || !strchr(open_bracket, ']')) {
127 ast_log(LOG_ERROR, "No expression detected. Did you forget to replace the $ signs?\n");
128 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
129 return 0;
130 }
131
132 dollarsignrep = pos[0];
133 if (dollarsignrep == '$' || dollarsignrep == '[' || dollarsignrep == ']'
134 || dollarsignrep == '{' || dollarsignrep == '}') {
135 ast_log(LOG_ERROR, "Dollar sign replacement cannot be %c.\n", dollarsignrep);
136 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
137 return 0;
138 }
139 ++pos;
140 if (pos[0] != ',') {
141 ast_log(LOG_ERROR, "Invalid separator: %c\n", pos[0]);
142 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
143 return 0;
144 }
145 ++pos;
146 if (pos[0] != dollarsignrep) {
147 ast_log(LOG_ERROR, "Expression start does not match provided replacement: %c\n", pos[0]);
148 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
149 return 0;
150 }
151
152 expression = pos; /* we're at the start of the expression */
153
154 /* commas may appear within the expression, so go until we've encountered as many closing brackets as opening */
155 while (++pos) {
156 if (pos[0] == '\0') {
157 ast_log(LOG_ERROR, "Could not parse end of expression.\n");
158 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "FAILURE");
159 return 0;
160 }
161 if (pos[0] == '[') {
162 brackets++;
163 } else if (pos[0] == ']') {
164 brackets--;
165 }
166 if (brackets == 0) { /* reached end of expression */
167 break;
168 }
169 }
170 ++pos;
171 if (pos[0] != '\0') {
172 ++pos; /* eat comma separator */
173 if (pos[0] != '\0') {
174 optargs = ast_strdupa(pos);
175 AST_STANDARD_APP_ARGS(args, optargs);
176 if (!ast_strlen_zero(args.timeout)) {
177 if (sscanf(args.timeout, "%30lg", &timeout) != 1) {
178 ast_log(LOG_WARNING, "Invalid timeout provided: %s. No timeout set.\n", args.timeout);
179 return -1;
180 }
181 timeout_ms = timeout * 1000.0;
182 }
183
184 if (!ast_strlen_zero(args.interval)) {
185 if (sscanf(args.interval, "%30lg", &poll) != 1) {
186 ast_log(LOG_WARNING, "Invalid polling interval provided: %s. Default unchanged.\n", args.interval);
187 return -1;
188 }
189 if (poll < 0.001) {
190 ast_log(LOG_WARNING, "Polling interval cannot be less than 1ms. Default unchanged.\n");
191 return -1;
192 }
193 poll_ms = poll * 1000.0;
194 }
195 }
196 }
197
198 for (i = 0; expression[i] != '\0'; i++) {
199 if (expression[i] == dollarsignrep) {
200 expression[i] = '$'; /* replace $s back into expression for variable parsing */
201 }
202 }
203
204 if (timeout_ms > 0) {
205 ast_debug(1, "Waiting for condition for %f seconds: %s (checking every %d ms)", timeout, expression, poll_ms);
206 } else {
207 ast_debug(1, "Waiting for condition, forever: %s (checking every %d ms)", expression, poll_ms);
208 }
209
210 while (1) {
211 /* Substitute variables now */
212 pbx_substitute_variables_helper(chan, expression, condition, sizeof(condition) - 1);
213 if (pbx_checkcondition(condition)) {
214 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "TRUE");
215 return 0;
216 }
217 /* If a timeout was specified, check that it hasn't expired */
218 if ((timeout_ms > 0) && !(ms = ast_remaining_ms(start, timeout_ms))) {
219 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "TIMEOUT");
220 return 0;
221 }
222 if (ast_safe_sleep(chan, poll_ms)) { /* don't waste CPU, we don't need a super tight loop */
223 pbx_builtin_setvar_helper(chan, "WAITFORCONDITIONSTATUS", "HANGUP");
224 return -1; /* channel hung up */
225 }
226 }
227}
228
229static int unload_module(void)
230{
232}
233
234static int load_module(void)
235{
237}
238
AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Wait until condition is true")
static char * app
static int waitforcond_exec(struct ast_channel *chan, const char *data)
static int load_module(void)
static int unload_module(void)
Asterisk main include file. File version handling, generic pbx functions.
#define ast_strdupa(s)
duplicate a string in memory from the stack
Definition: astmm.h:298
#define ast_log
Definition: astobj2.c:42
General Asterisk PBX channel definitions.
int ast_safe_sleep(struct ast_channel *chan, int ms)
Wait for a specified amount of time, looking for hangups.
Definition: channel.c:1593
Application convenience functions, designed to give consistent look and feel to Asterisk apps.
#define AST_APP_ARG(name)
Define an application argument.
#define AST_DECLARE_APP_ARGS(name, arglist)
Declare a structure to hold an application's arguments.
#define AST_STANDARD_APP_ARGS(args, parse)
Performs the 'standard' argument separation process for an application.
Support for logging to various files, console and syslog Configuration in file logger....
#define ast_debug(level,...)
Log a DEBUG message.
#define LOG_ERROR
#define LOG_WARNING
Asterisk module definitions.
#define ASTERISK_GPL_KEY
The text the key() function should return.
Definition: module.h:46
int ast_unregister_application(const char *app)
Unregister an application.
Definition: pbx_app.c:392
#define ast_register_application_xml(app, execute)
Register an application using XML documentation.
Definition: module.h:640
Core PBX routines and definitions.
int pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const char *value)
Add a variable to the channel variable stack, removing the most recently set value for the same name.
int pbx_checkcondition(const char *condition)
Evaluate a condition.
Definition: pbx.c:8282
void pbx_substitute_variables_helper(struct ast_channel *c, const char *cp1, char *cp2, int count)
Definition: ael_main.c:211
#define NULL
Definition: resample.c:96
static force_inline int attribute_pure ast_strlen_zero(const char *s)
Definition: strings.h:65
Main Channel structure associated with a channel.
const char * args
int ast_remaining_ms(struct timeval start, int max_ms)
Calculate remaining milliseconds given a starting timestamp and upper bound.
Definition: utils.c:2281
struct timeval ast_tvnow(void)
Returns current timeval. Meant to replace calls to gettimeofday().
Definition: time.h:159