Asterisk - The Open Source Telephony Project  21.4.1
func_evalexten.c
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1 /*
2  * Asterisk -- An open source telephony toolkit.
3  *
4  * Copyright (C) 2021, Naveen Albert
5  *
6  * See http://www.asterisk.org for more information about
7  * the Asterisk project. Please do not directly contact
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13  * the GNU General Public License Version 2. See the LICENSE file
14  * at the top of the source tree.
15  */
16 
17 /*! \file
18  *
19  * \brief Dialplan extension evaluation function
20  *
21  * \author Naveen Albert <asterisk@phreaknet.org>
22  *
23  * \ingroup functions
24  */
25 
26 /*** MODULEINFO
27  <support_level>extended</support_level>
28  ***/
29 
30 #include "asterisk.h"
31 
32 #include "asterisk/module.h"
33 #include "asterisk/channel.h"
34 #include "asterisk/pbx.h"
35 #include "asterisk/utils.h"
36 #include "asterisk/app.h"
37 
38 /*** DOCUMENTATION
39  <function name="EVAL_EXTEN" language="en_US">
40  <synopsis>
41  Evaluates the contents of a dialplan extension and returns it as a string.
42  </synopsis>
43  <syntax>
44  <parameter name="context" />
45  <parameter name="extensions" />
46  <parameter name="priority" required="true" />
47  </syntax>
48  <description>
49  <para>The EVAL_EXTEN function looks up a dialplan entry by context,extension,priority,
50  evaluates the contents of a Return statement to resolve any variable or function
51  references, and returns the result as a string.</para>
52  <para>You can use this function to create simple user-defined lookup tables or
53  user-defined functions.</para>
54  <example title="Custom dialplan functions">
55  [call-types]
56  exten => _1NNN,1,Return(internal)
57  exten => _NXXNXXXXXX,1,Return(external)
58 
59  [udf]
60  exten => calleridlen,1,Return(${LEN(${CALLERID(num)})})
61 
62  [default]
63  exten => _X!,1,Verbose(Call type ${EVAL_EXTEN(call-types,${EXTEN},1)} - ${EVAL_EXTEN(udf,calleridlen,1)})
64  </example>
65  <para>Any variables in the evaluated data will be resolved in the context of
66  that extension. For example, <literal>${EXTEN}</literal> would refer to the
67  EVAL_EXTEN extension, not the extension in the context invoking the function.
68  This behavior is similar to other applications, e.g. <literal>Gosub</literal>.</para>
69  <example title="Choosing which prompt to use">
70  same => n,Read(input,${EVAL_EXTEN(prompts,${CALLERID(num)},1)})
71 
72  [prompts]
73  exten => _X!,1,Return(default)
74  exten => _20X,1,Return(welcome)
75  exten => _2XX,1,Return(${DB(promptsettings/${EXTEN})})
76  exten => _3XX,1,Return(${ODBC_MYFUNC(${EXTEN})})
77  </example>
78  <para>Extensions on which EVAL_EXTEN is invoked are not different from other
79  extensions. However, the application at that extension is not executed.
80  Only the application data is parsed and evaluated.</para>
81  <para>A limitation of this function is that the application at the specified
82  extension isn't actually executed, and thus unlike a Gosub, you can't pass
83  arguments in the EVAL_EXTEN function.</para>
84  </description>
85  <see-also>
86  <ref type="function">EVAL</ref>
87  </see-also>
88  </function>
89  ***/
90 
91 static int eval_exten_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
92 {
93  char *exten, *pri, *context, *parse;
94  int ipri;
95  char tmpbuf[len];
96 
97  if (ast_strlen_zero(data)) {
98  ast_log(LOG_WARNING, "The EVAL_EXTEN function requires an extension\n");
99  return -1;
100  }
101 
102  parse = ast_strdupa(data);
103  /* Split context,exten,pri */
104  context = strsep(&parse, ",");
105  exten = strsep(&parse, ",");
106  pri = strsep(&parse, ",");
107 
108  if (pbx_parse_location(chan, &context, &exten, &pri, &ipri, NULL, NULL)) {
109  return -1;
110  }
111 
112  if (ast_strlen_zero(exten) || ast_strlen_zero(context)) { /* only lock if we really need to */
113  ast_channel_lock(chan);
114  if (ast_strlen_zero(exten)) {
115  exten = ast_strdupa(ast_channel_exten(chan));
116  }
117  if (ast_strlen_zero(context)) {
118  context = ast_strdupa(ast_channel_context(chan));
119  }
120  ast_channel_unlock(chan);
121  }
122 
123  if (ast_get_extension_data(tmpbuf, len, chan, context, exten, ipri)) {
124  return -1; /* EVAL_EXTEN failed */
125  }
126 
127  pbx_substitute_variables_helper_full_location(chan, (chan) ? ast_channel_varshead(chan) : NULL, tmpbuf, buf, len, NULL, context, exten, ipri);
128 
129  return 0;
130 }
131 
132 static struct ast_custom_function eval_exten_function = {
133  .name = "EVAL_EXTEN",
134  .read = eval_exten_read,
135 };
136 
137 static int unload_module(void)
138 {
139  return ast_custom_function_unregister(&eval_exten_function);
140 }
141 
142 static int load_module(void)
143 {
144  return ast_custom_function_register(&eval_exten_function);
145 }
146 
147 AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Extension evaluation function");
const char * name
Definition: pbx.h:119
Main Channel structure associated with a channel.
Asterisk main include file. File version handling, generic pbx functions.
int pbx_parse_location(struct ast_channel *chan, char **context, char **exten, char **pri, int *ipri, int *mode, char *rest)
Parses a dialplan location into context, extension, priority.
Definition: pbx.c:8791
int ast_get_extension_data(char *buf, int bufsize, struct ast_channel *c, const char *context, const char *exten, int priority)
Fill a string buffer with the data at a dialplan extension.
Definition: pbx.c:8567
void pbx_substitute_variables_helper_full_location(struct ast_channel *c, struct varshead *headp, const char *cp1, char *cp2, int cp2_size, size_t *used, const char *context, const char *exten, int pri)
Substitutes variables, similar to pbx_substitute_variables_helper_full, but allows passing the contex...
int ast_custom_function_unregister(struct ast_custom_function *acf)
Unregister a custom function.
Utility functions.
General Asterisk PBX channel definitions.
#define ast_strdupa(s)
duplicate a string in memory from the stack
Definition: astmm.h:298
Data structure associated with a custom dialplan function.
Definition: pbx.h:118
Core PBX routines and definitions.
#define ASTERISK_GPL_KEY
The text the key() function should return.
Definition: module.h:46
Asterisk module definitions.
Application convenience functions, designed to give consistent look and feel to Asterisk apps...
#define ast_custom_function_register(acf)
Register a custom function.
Definition: pbx.h:1558