func_config.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008, Digium, Inc.
 *
 * Russell Bryant <[email protected]>
 * Tilghman Lesher <[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 A function to retrieve variables from an Asterisk configuration file
 *
 * \author Russell Bryant <[email protected]>
 * \author Tilghman Lesher <[email protected]>
 *
 * \ingroup functions
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/module.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/app.h"

/*** DOCUMENTATION
   <function name="AST_CONFIG" language="en_US">
      <synopsis>
         Retrieve a variable from a configuration file.
      </synopsis>
      <syntax>
         <parameter name="config_file" required="true" />
         <parameter name="category" required="true" />
         <parameter name="variable_name" required="true" />
         <parameter name="index" required="false">
            <para>If there are multiple variables with the same name, you can specify
            <literal>0</literal> for the first item (default), <literal>-1</literal> for the last
            item, or any other number for that specific item.  <literal>-1</literal> is useful
            when the variable is derived from a template and you want the effective value (the last
            occurrence), not the value from the template (the first occurrence).</para>
         </parameter>
      </syntax>
      <description>
         <para>This function reads a variable from an Asterisk configuration file.</para>
      </description>
   </function>

***/

struct config_item {
   AST_RWLIST_ENTRY(config_item) entry;
   struct ast_config *cfg;
   char filename[0];
};

static AST_RWLIST_HEAD_STATIC(configs, config_item);

static int config_function_read(struct ast_channel *chan, const char *cmd, char *data,
   char *buf, size_t len)
{
   struct ast_config *cfg;
   struct ast_flags cfg_flags = { CONFIG_FLAG_FILEUNCHANGED };
   char *parse;
   struct config_item *cur;
   int index = 0;
   struct ast_variable *var;
   struct ast_variable *found = NULL;
   int ix = 0;
   AST_DECLARE_APP_ARGS(args,
      AST_APP_ARG(filename);
      AST_APP_ARG(category);
      AST_APP_ARG(variable);
      AST_APP_ARG(index);
   );

   if (ast_strlen_zero(data)) {
      ast_log(LOG_ERROR, "AST_CONFIG() requires an argument\n");
      return -1;
   }

   parse = ast_strdupa(data);
   AST_STANDARD_APP_ARGS(args, parse);

   if (ast_strlen_zero(args.filename)) {
      ast_log(LOG_ERROR, "AST_CONFIG() requires a filename\n");
      return -1;
   }

   if (ast_strlen_zero(args.category)) {
      ast_log(LOG_ERROR, "AST_CONFIG() requires a category\n");
      return -1;
   }

   if (ast_strlen_zero(args.variable)) {
      ast_log(LOG_ERROR, "AST_CONFIG() requires a variable\n");
      return -1;
   }

   if (!ast_strlen_zero(args.index)) {
      if (!sscanf(args.index, "%d", &index)) {
         ast_log(LOG_ERROR, "AST_CONFIG() index must be an integer\n");
         return -1;
      }
   }

   if (!(cfg = ast_config_load(args.filename, cfg_flags)) || cfg == CONFIG_STATUS_FILEINVALID) {
      return -1;
   }

   if (cfg == CONFIG_STATUS_FILEUNCHANGED) {
      /* Retrieve cfg from list */
      AST_RWLIST_RDLOCK(&configs);
      AST_RWLIST_TRAVERSE(&configs, cur, entry) {
         if (!strcmp(cur->filename, args.filename)) {
            break;
         }
      }

      if (!cur) {
         /* At worst, we might leak an entry while upgrading locks */
         AST_RWLIST_UNLOCK(&configs);
         AST_RWLIST_WRLOCK(&configs);
         if (!(cur = ast_calloc(1, sizeof(*cur) + strlen(args.filename) + 1))) {
            AST_RWLIST_UNLOCK(&configs);
            return -1;
         }

         strcpy(cur->filename, args.filename);

         ast_clear_flag(&cfg_flags, CONFIG_FLAG_FILEUNCHANGED);
         if (!(cfg = ast_config_load(args.filename, cfg_flags)) || cfg == CONFIG_STATUS_FILEINVALID) {
            ast_free(cur);
            AST_RWLIST_UNLOCK(&configs);
            return -1;
         }

         cur->cfg = cfg;
         AST_RWLIST_INSERT_TAIL(&configs, cur, entry);
      }

      cfg = cur->cfg;
   } else {
      /* Replace cfg in list */
      AST_RWLIST_WRLOCK(&configs);
      AST_RWLIST_TRAVERSE(&configs, cur, entry) {
         if (!strcmp(cur->filename, args.filename)) {
            break;
         }
      }

      if (!cur) {
         if (!(cur = ast_calloc(1, sizeof(*cur) + strlen(args.filename) + 1))) {
            AST_RWLIST_UNLOCK(&configs);
            return -1;
         }

         strcpy(cur->filename, args.filename);
         cur->cfg = cfg;

         AST_RWLIST_INSERT_TAIL(&configs, cur, entry);
      } else {
         ast_config_destroy(cur->cfg);
         cur->cfg = cfg;
      }
   }

   for (var = ast_category_root(cfg, args.category); var; var = var->next) {
      if (strcasecmp(args.variable, var->name)) {
         continue;
      }
      found = var;
      if (index == -1) {
         continue;
      }
      if (ix == index) {
         break;
      }
      found = NULL;
      ix++;
   }

   if (!found) {
      ast_debug(1, "'%s' not found at index %d in [%s] of '%s'.  Maximum index found: %d\n",
         args.variable, index, args.category, args.filename, ix);
      AST_RWLIST_UNLOCK(&configs);
      return -1;
   }

   ast_copy_string(buf, found->value, len);

   /* Unlock down here, so there's no chance the struct goes away while we're using it. */
   AST_RWLIST_UNLOCK(&configs);

   return 0;
}

static struct ast_custom_function config_function = {
   .name = "AST_CONFIG",
   .read = config_function_read,
};

static int unload_module(void)
{
   struct config_item *current;
   int res = ast_custom_function_unregister(&config_function);

   AST_RWLIST_WRLOCK(&configs);
   while ((current = AST_RWLIST_REMOVE_HEAD(&configs, entry))) {
      ast_config_destroy(current->cfg);
      ast_free(current);
   }
   AST_RWLIST_UNLOCK(&configs);

   return res;
}

static int load_module(void)
{
   return ast_custom_function_register(&config_function);
}

AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Asterisk configuration file variable access");