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82bef2ed90
Also updates the 'since' of applications/functions that existed before XML documentation was introduced (1.6.2.0).
251 lines
9.1 KiB
C
251 lines
9.1 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2021, 2024, Naveen Albert
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief Dialplan extension evaluation function
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*
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* \author Naveen Albert <asterisk@phreaknet.org>
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*
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* \ingroup functions
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*/
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/*** MODULEINFO
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<support_level>extended</support_level>
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***/
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#include "asterisk.h"
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#include "asterisk/module.h"
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#include "asterisk/channel.h"
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#include "asterisk/pbx.h"
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#include "asterisk/utils.h"
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#include "asterisk/app.h"
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/*** DOCUMENTATION
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<function name="EVAL_EXTEN" language="en_US">
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<since>
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<version>16.26.0</version>
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<version>18.12.0</version>
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<version>19.4.0</version>
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</since>
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<synopsis>
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Evaluates the contents of a dialplan extension and returns it as a string.
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</synopsis>
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<syntax>
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<parameter name="context" />
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<parameter name="extensions" />
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<parameter name="priority" required="true" />
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</syntax>
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<description>
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<para>The EVAL_EXTEN function looks up a dialplan entry by context,extension,priority,
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evaluates the contents of a Return statement to resolve any variable or function
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references, and returns the result as a string.</para>
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<para>You can use this function to create simple user-defined lookup tables or
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user-defined functions.</para>
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<example title="Custom dialplan functions">
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[call-types]
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exten => _1NNN,1,Return(internal)
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exten => _NXXNXXXXXX,1,Return(external)
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[udf]
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exten => calleridlen,1,Return(${LEN(${CALLERID(num)})})
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[default]
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exten => _X!,1,Verbose(Call type ${EVAL_EXTEN(call-types,${EXTEN},1)} - ${EVAL_EXTEN(udf,calleridlen,1)})
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</example>
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<para>Any variables in the evaluated data will be resolved in the context of
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that extension. For example, <literal>${EXTEN}</literal> would refer to the
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EVAL_EXTEN extension, not the extension in the context invoking the function.
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This behavior is similar to other applications, e.g. <literal>Gosub</literal>.</para>
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<example title="Choosing which prompt to use">
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same => n,Read(input,${EVAL_EXTEN(prompts,${CALLERID(num)},1)})
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[prompts]
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exten => _X!,1,Return(default)
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exten => _20X,1,Return(welcome)
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exten => _2XX,1,Return(${DB(promptsettings/${EXTEN})})
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exten => _3XX,1,Return(${ODBC_MYFUNC(${EXTEN})})
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</example>
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<para>Extensions on which EVAL_EXTEN is invoked are not different from other
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extensions. However, the application at that extension is not executed.
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Only the application data is parsed and evaluated.</para>
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<para>A limitation of this function is that the application at the specified
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extension isn't actually executed, and thus unlike a Gosub, you can't pass
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arguments in the EVAL_EXTEN function.</para>
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<para>If you need the ability to evaluate more complex logic that cannot be done
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purely using functions, see <literal>EVAL_SUB</literal>.</para>
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</description>
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<see-also>
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<ref type="function">EVAL</ref>
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<ref type="function">EVAL_SUB</ref>
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</see-also>
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</function>
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<function name="EVAL_SUB" language="en_US">
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<since>
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<version>20.11.0</version>
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<version>21.6.0</version>
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<version>22.1.0</version>
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</since>
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<synopsis>
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Executes a Gosub and provides its return value as a string
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</synopsis>
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<syntax>
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<parameter name="context" />
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<parameter name="extensions" />
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<parameter name="priority" required="true" />
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</syntax>
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<description>
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<para>The EVAL_SUB function executes up a dialplan location by context,extension,priority, with optional arguments
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and returns the contents of the Return statement. The arguments to <literal>EVAL_SUB</literal>
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are exactly like they are with <literal>Gosub</literal>.</para>
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<para>This function is complementary to <literal>EVAL_EXTEN</literal>. However, it is more powerful,
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since it allows executing arbitrary dialplan and capturing some outcome as a dialplan function's
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return value, allowing it to be used in a variety of scenarios that do not allow executing dialplan
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directly but allow variables and functions to be used, and where using <literal>EVAL_EXTEN</literal>
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would be difficult or impossible.</para>
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<para>Consequently, this function also allows you to implement your own arbitrary functions
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in dialplan, which can then be wrapped using the Asterisk function interface using <literal>EVAL_SUB</literal>.</para>
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<para>While this function is primarily intended to be used for executing Gosub routines that are quick
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and do not interact with the channel, it is safe to execute arbitrary, even blocking, dialplan in the
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called subroutine. That said, this kind of usage is not recommended.</para>
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<para>This function will always return, even if the channel is hung up.</para>
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<example title="Record whether a PSTN call is local">
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[islocal]
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exten => _X!,1,ExecIf($[${LEN(${EXTEN})}<10]?Return(1))
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same => n,Set(LOCAL(npanxx)=${EXTEN:-10:6})
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same => n,ReturnIf(${EXISTS(${DB(localcall/${npanxx})})}?${DB(localcall/${npanxx})})
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same => n,Set(LOCAL(islocal)=${SHELL(curl "https://example.com/islocal?npanxx=${EXTEN:-10:6}")})
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same => n,Set(LOCAL(islocal)=${FILTER(A-Z,${islocal})})
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same => n,Set(DB(localcall/${npanxx})=${islocal})
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same => n,Return(${islocal})
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[outgoing]
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exten => _1NXXNXXXXXX,1,Set(CDR(toll)=${IF($["${EVAL_SUB(islocal,${EXTEN},1)}"="Y"]?0:1)})
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same => n,Dial(DAHDI/1/${EXTEN})
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same => n,Hangup()
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</example>
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<para>This example illustrates an example of logic that would be difficult to capture
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in a way that a single call to <literal>EVAL_EXTEN</literal> would return the same result. For one, conditionals
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are involved, and due to the way Asterisk parses dialplan, all functions in an application call are evaluated all the
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time, which may be undesirable if they cause side effects (e.g. making a cURL request) that should only happen in certain circumstances.</para>
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<para>The above example, of course, does not require the use of this function, as it could have been invoked
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using the Gosub application directly. However, if constrained to just using variables or functions,
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<literal>EVAL_SUB</literal> would be required.</para>
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</description>
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<see-also>
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<ref type="function">EVAL_EXTEN</ref>
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<ref type="application">Return</ref>
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</see-also>
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</function>
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***/
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static int eval_exten_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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char *exten, *pri, *context, *parse;
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int ipri;
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char tmpbuf[len];
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if (ast_strlen_zero(data)) {
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ast_log(LOG_WARNING, "The EVAL_EXTEN function requires an extension\n");
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return -1;
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}
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parse = ast_strdupa(data);
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/* Split context,exten,pri */
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context = strsep(&parse, ",");
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exten = strsep(&parse, ",");
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pri = strsep(&parse, ",");
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if (pbx_parse_location(chan, &context, &exten, &pri, &ipri, NULL, NULL)) {
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return -1;
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}
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if (ast_strlen_zero(exten) || ast_strlen_zero(context)) { /* only lock if we really need to */
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ast_channel_lock(chan);
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if (ast_strlen_zero(exten)) {
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exten = ast_strdupa(ast_channel_exten(chan));
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}
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if (ast_strlen_zero(context)) {
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context = ast_strdupa(ast_channel_context(chan));
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}
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ast_channel_unlock(chan);
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}
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if (ast_get_extension_data(tmpbuf, len, chan, context, exten, ipri)) {
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return -1; /* EVAL_EXTEN failed */
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}
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pbx_substitute_variables_helper_full_location(chan, (chan) ? ast_channel_varshead(chan) : NULL, tmpbuf, buf, len, NULL, context, exten, ipri);
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return 0;
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}
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static int eval_sub_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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int gosub_res;
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const char *retval;
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if (ast_strlen_zero(data)) {
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ast_log(LOG_WARNING, "The EVAL_SUB function requires an extension\n");
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*buf = '\0';
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return -1;
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}
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/* Ignore hangups since we want to retrieve a value, and this function could be called at hangup time */
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gosub_res = ast_app_exec_sub(NULL, chan, data, 1);
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if (gosub_res) {
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ast_log(LOG_WARNING, "Failed to execute Gosub(%s)\n", data);
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*buf = '\0';
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return -1;
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}
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ast_channel_lock(chan);
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retval = pbx_builtin_getvar_helper(chan, "GOSUB_RETVAL");
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ast_copy_string(buf, S_OR(retval, ""), len); /* Overwrite, even if empty, to ensure a stale GOSUB_RETVAL isn't returned as our value */
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ast_channel_unlock(chan);
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return 0;
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}
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static struct ast_custom_function eval_exten_function = {
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.name = "EVAL_EXTEN",
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.read = eval_exten_read,
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};
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static struct ast_custom_function eval_sub_function = {
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.name = "EVAL_SUB",
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.read = eval_sub_read,
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};
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static int unload_module(void)
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{
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int res = 0;
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res |= ast_custom_function_unregister(&eval_exten_function);
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res |= ast_custom_function_unregister(&eval_sub_function);
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return res;
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}
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static int load_module(void)
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{
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int res = 0;
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res |= ast_custom_function_register(&eval_exten_function);
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res |= ast_custom_function_register(&eval_sub_function);
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return res;
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}
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AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Extension evaluation function");
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