func_config.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008, Digium, Inc.
 *
 * Russell Bryant <russell@digium.com>
 * Tilghman Lesher <func_config__200803@the-tilghman.com>
 *
 * 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 <russell@digium.com>
 * \author Tilghman Lesher <func_config__200803@the-tilghman.com>
 * 
 * \ingroup functions
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 136302 $")

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

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 };
   const char *val;
   char *parse;
   struct config_item *cur;
   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 (!(cfg = ast_config_load(args.filename, cfg_flags))) {
      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_malloc(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))) {
            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_malloc(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;
      }
   }

   if (!(val = ast_variable_retrieve(cfg, args.category, args.variable))) {
      ast_log(LOG_ERROR, "'%s' not found in [%s] of '%s'\n", args.variable, 
         args.category, args.filename);
      AST_RWLIST_UNLOCK(&configs);
      return -1;
   }

   ast_copy_string(buf, val, 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",
   .syntax = "AST_CONFIG(config_file,category,variable_name)",
   .synopsis = "Retrieve a variable from a configuration file",
   .desc = 
   "   This function reads a variable from an Asterisk configuration file.\n"
   "",
   .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");