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
 */
 
/*** 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");