res_config_sqlite3.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2011, Terry Wilson
 *
 * Terry Wilson <[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.
 *
 * Please follow coding guidelines
 * http://svn.digium.com/view/asterisk/trunk/doc/CODING-GUIDELINES
 */

/*! \file
 *
 * \brief SQLite 3 configuration engine
 *
 * \author\verbatim Terry Wilson <[email protected]> \endverbatim
 *
 * This is a realtime configuration engine for the SQLite 3 Database
 * \ingroup resources
 */

/*! \li \ref res_config_sqlite3.c uses the configuration file \ref res_config_sqlite3.conf
 * \addtogroup configuration_file Configuration Files
 */

/*!
 * \page res_config_sqlite3.conf res_config_sqlite3.conf
 * \verbinclude res_config_sqlite3.conf.sample
 */

/*** MODULEINFO
   <depend>sqlite3</depend>
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <sqlite3.h>

#include "asterisk/module.h"
#include "asterisk/config.h"
#include "asterisk/paths.h"
#include "asterisk/astobj2.h"
#include "asterisk/lock.h"
#include "asterisk/utils.h"
#include "asterisk/app.h"

/*** DOCUMENTATION
 ***/

static int has_explicit_like_escaping;

static struct ast_config *realtime_sqlite3_load(const char *database, const char *table, const char *configfile, struct ast_config *config, struct ast_flags flags, const char *suggested_include_file, const char *who_asked);
static struct ast_variable *realtime_sqlite3(const char *database, const char *table, const struct ast_variable *fields);
static struct ast_config *realtime_sqlite3_multi(const char *database, const char *table, const struct ast_variable *fields);
static int realtime_sqlite3_update(const char *database, const char *table, const char *keyfield, const char *entity, const struct ast_variable *fields);
static int realtime_sqlite3_update2(const char *database, const char *table, const struct ast_variable *lookup_fields, const struct ast_variable *update_fields);
static int realtime_sqlite3_store(const char *database, const char *table, const struct ast_variable *fields);
static int realtime_sqlite3_destroy(const char *database, const char *table, const char *keyfield, const char *entity, const struct ast_variable *fields);
static int realtime_sqlite3_require(const char *database, const char *table, va_list ap);
static int realtime_sqlite3_unload(const char *database, const char *table);

struct ast_config_engine sqlite3_config_engine = {
   .name = "sqlite3",
   .load_func = realtime_sqlite3_load,
   .realtime_func = realtime_sqlite3,
   .realtime_multi_func = realtime_sqlite3_multi,
   .update_func = realtime_sqlite3_update,
   .update2_func = realtime_sqlite3_update2,
   .store_func = realtime_sqlite3_store,
   .destroy_func = realtime_sqlite3_destroy,
   .require_func = realtime_sqlite3_require,
   .unload_func = realtime_sqlite3_unload,
};

enum {
   REALTIME_SQLITE3_REQ_WARN,
   REALTIME_SQLITE3_REQ_CLOSE,
   REALTIME_SQLITE3_REQ_CHAR,
};

struct realtime_sqlite3_db {
   AST_DECLARE_STRING_FIELDS(
      AST_STRING_FIELD(name);
      AST_STRING_FIELD(filename);
   );
   sqlite3 *handle;
   pthread_t syncthread;
   ast_cond_t cond;
   unsigned int requirements:2;
   unsigned int dirty:1;
   unsigned int debug:1;
   unsigned int exiting:1;
   unsigned int wakeup:1;
   unsigned int has_batch_thread:1;
   unsigned int batch;
   int busy_timeout;
};

struct ao2_container *databases;
#define DB_BUCKETS 7

AST_MUTEX_DEFINE_STATIC(config_lock);

/* We need a separate buffer for each field we might use concurrently */
AST_THREADSTORAGE(escape_table_buf);
AST_THREADSTORAGE(escape_column_buf);
AST_THREADSTORAGE(escape_value_buf);

typedef int (*callback_t)(void*, int, char **, char **);

static int realtime_sqlite3_exec_query_with_handle(struct realtime_sqlite3_db *, const char *, callback_t, void *);
static int realtime_sqlite3_exec_query(const char *, const char *, callback_t, void *);
static int realtime_sqlite3_exec_update_with_handle(struct realtime_sqlite3_db *, const char *);
static int realtime_sqlite3_exec_update(const char *, const char *);

void db_start_batch(struct realtime_sqlite3_db *db);
void db_stop_batch(struct realtime_sqlite3_db *db);

static inline const char *sqlite3_escape_string_helper(struct ast_threadstorage *ts, const char *param)
{
   size_t maxlen = strlen(param) * 2 + sizeof("\"\"");
   /* It doesn't appear that sqlite3_snprintf will do more than double the
    * length of a string with %q as an option. %Q could double and possibly
    * add two quotes, and convert NULL pointers to the word "NULL", but we
    * don't allow those anyway. Just going to use %q for now. */
   struct ast_str *buf = ast_str_thread_get(ts, maxlen);
   char q = ts == &escape_value_buf ? '\'' : '"';
   char *tmp;

   if (ast_str_size(buf) < maxlen) {
      /* realloc if buf is too small */
      ast_str_make_space(&buf, maxlen);
   }
   tmp = ast_str_buffer(buf);

   ast_str_reset(buf);
   *tmp++ = q; /* Initial quote */
   while ((*tmp++ = *param++)) {
      /* Did we just copy a quote? Then double it. */
      if (*(tmp - 1) == q) {
         *tmp++ = q;
      }
   }
   *tmp = '\0'; /* Terminate past NULL from copy */
   *(tmp - 1) = q; /* Replace original NULL with the quote */
   ast_str_update(buf);

   return ast_str_buffer(buf);
}

static inline const char *sqlite3_escape_table(const char *param)
{
   return sqlite3_escape_string_helper(&escape_table_buf, param);
}

static inline const char *sqlite3_escape_column(const char *param)
{
   return sqlite3_escape_string_helper(&escape_column_buf, param);
}

/* Not inlining this function because it uses strdupa and I don't know if the compiler would be dumb */
static const char *sqlite3_escape_column_op(const char *param)
{
   size_t maxlen = strlen(param) * 2 + sizeof("\"\" =");
   struct ast_str *buf = ast_str_thread_get(&escape_column_buf, maxlen);
   char *tmp;
   int space = 0;

   if (ast_str_size(buf) < maxlen) {
      /* realloc if buf is too small */
      ast_str_make_space(&buf, maxlen);
   }
   tmp = ast_str_buffer(buf);

   ast_str_reset(buf);
   *tmp++ = '"';
   while ((*tmp++ = *param++)) {
      /* If we have seen a space, don't double quotes. XXX If we ever make the column/op field
       * available to users via an API, we will definitely need to avoid allowing special
       * characters like ';' in the data past the space as it will be unquoted data */
      if (space) {
         continue;
      }
      if (*(tmp - 1) == ' ') {
         *(tmp - 1) = '"';
         *tmp++ = ' ';
         space = 1;
      } else if (*(tmp - 1) == '"') {
         *tmp++ = '"';
      }
   }
   if (!space) {
      strcpy(tmp - 1, "\" =");
   }

   ast_str_update(buf);

   return ast_str_buffer(buf);
}

static inline const char *sqlite3_escape_value(const char *param)
{
   return sqlite3_escape_string_helper(&escape_value_buf, param);
}

static int db_hash_fn(const void *obj, const int flags)
{
   const struct realtime_sqlite3_db *db = obj;

   return ast_str_hash(flags & OBJ_KEY ? (const char *) obj : db->name);
}

static int db_cmp_fn(void *obj, void *arg, int flags) {
   struct realtime_sqlite3_db *db = obj, *other = arg;
   const char *name = arg;

   return !strcasecmp(db->name, flags & OBJ_KEY ? name : other->name) ? CMP_MATCH | CMP_STOP : 0;
}

static void db_destructor(void *obj)
{
   struct realtime_sqlite3_db *db = obj;

   ast_debug(1, "Destroying db: %s\n", db->name);
   ast_string_field_free_memory(db);
   db_stop_batch(db);
   if (db->handle) {
      ao2_lock(db);
      sqlite3_close(db->handle);
      ao2_unlock(db);
   }
}

static struct realtime_sqlite3_db *find_database(const char *database)
{
   return ao2_find(databases, database, OBJ_KEY);
}

static void unref_db(struct realtime_sqlite3_db **db)
{
   ao2_ref(*db, -1);
   *db = NULL;
}

static int stop_batch_cb(void *obj, void *arg, int flags)
{
   struct realtime_sqlite3_db *db = obj;

   db_stop_batch(db);
   return CMP_MATCH;
}

static int mark_dirty_cb(void *obj, void *arg, int flags)
{
   struct realtime_sqlite3_db *db = obj;
   db->dirty = 1;
   return CMP_MATCH;
}

static void mark_all_databases_dirty(void)
{
   ao2_callback(databases, OBJ_MULTIPLE | OBJ_NODATA, mark_dirty_cb, NULL);
}

static int is_dirty_cb(void *obj, void *arg, int flags)
{
   struct realtime_sqlite3_db *db = obj;
   if (db->dirty) {
      db_stop_batch(db);
      return CMP_MATCH;
   }
   return 0;
}

static void unlink_dirty_databases(void)
{
   ao2_callback(databases, OBJ_MULTIPLE | OBJ_NODATA | OBJ_UNLINK, is_dirty_cb, NULL);
}

static int str_to_requirements(const char *data)
{
   if (!strcasecmp(data, "createclose")) {
      return REALTIME_SQLITE3_REQ_CLOSE;
   } else if (!strcasecmp(data, "createchar")) {
      return REALTIME_SQLITE3_REQ_CHAR;
   }
   /* default */
   return REALTIME_SQLITE3_REQ_WARN;
}

/*! \note Since this is called while a query is executing, we should already hold the db lock */
static void trace_cb(void *arg, const char *sql)
{
   struct realtime_sqlite3_db *db = arg;
   ast_debug(3, "DB: %s SQL: %s\n", db->name, sql);
}

/*! \brief Wrap commands in transactions increased write performance */
static void *db_sync_thread(void *data)
{
   struct realtime_sqlite3_db *db = data;
   ao2_lock(db);
   realtime_sqlite3_exec_query_with_handle(db, "BEGIN TRANSACTION", NULL, NULL);
   for (;;) {
      if (!db->wakeup) {
         ast_cond_wait(&db->cond, ao2_object_get_lockaddr(db));
      }
      db->wakeup = 0;
      if (realtime_sqlite3_exec_query_with_handle(db, "COMMIT", NULL, NULL) < 0) {
         realtime_sqlite3_exec_query_with_handle(db, "ROLLBACK", NULL, NULL);
      }
      if (db->exiting) {
         ao2_unlock(db);
         break;
      }
      realtime_sqlite3_exec_query_with_handle(db, "BEGIN TRANSACTION", NULL, NULL);
      ao2_unlock(db);
      usleep(1000 * db->batch);
      ao2_lock(db);
   }

   unref_db(&db);

   return NULL;
}

/*! \brief Open a database and appropriately set debugging on the db handle */
static int db_open(struct realtime_sqlite3_db *db)
{
   ao2_lock(db);
   if (sqlite3_open(db->filename, &db->handle) != SQLITE_OK) {
      ast_log(LOG_WARNING, "Could not open %s: %s\n", db->filename, sqlite3_errmsg(db->handle));
      ao2_unlock(db);
      return -1;
   }
   sqlite3_busy_timeout(db->handle, db->busy_timeout);

   if (db->debug) {
      sqlite3_trace(db->handle, trace_cb, db);
   } else {
      sqlite3_trace(db->handle, NULL, NULL);
   }

   ao2_unlock(db);

   return 0;
}

static void db_sync(struct realtime_sqlite3_db *db)
{
   db->wakeup = 1;
   ast_cond_signal(&db->cond);
}

void db_start_batch(struct realtime_sqlite3_db *db)
{
   if (db->batch) {
      ast_cond_init(&db->cond, NULL);
      ao2_ref(db, +1);
      db->has_batch_thread = !ast_pthread_create_background(&db->syncthread, NULL, db_sync_thread, db);
   }
}

void db_stop_batch(struct realtime_sqlite3_db *db)
{
   if (db->has_batch_thread) {
      db->has_batch_thread = 0;
      db->exiting = 1;
      db_sync(db);
      pthread_join(db->syncthread, NULL);
   }
}

/*! \brief Create a db object based on a config category
 * \note Opening the db handle and linking to databases must be handled outside of this function
 */
static struct realtime_sqlite3_db *new_realtime_sqlite3_db(struct ast_config *config, const char *cat)
{
   struct ast_variable *var;
   struct realtime_sqlite3_db *db;

   if (!(db = ao2_alloc(sizeof(*db), db_destructor))) {
      return NULL;
   }

   if (ast_string_field_init(db, 64)) {
      unref_db(&db);
      return NULL;
   }

   /* Set defaults */
   db->requirements = REALTIME_SQLITE3_REQ_WARN;
   db->batch = 100;
   ast_string_field_set(db, name, cat);
   db->busy_timeout = 1000;

   for (var = ast_variable_browse(config, cat); var; var = var->next) {
      if (!strcasecmp(var->name, "dbfile")) {
         ast_string_field_set(db, filename, var->value);
      } else if (!strcasecmp(var->name, "requirements")) {
         db->requirements = str_to_requirements(var->value);
      } else if (!strcasecmp(var->name, "batch")) {
         ast_app_parse_timelen(var->value, (int *) &db->batch, TIMELEN_MILLISECONDS);
      } else if (!strcasecmp(var->name, "debug")) {
         db->debug = ast_true(var->value);
      } else if (!strcasecmp(var->name, "busy_timeout")) {
         if (ast_parse_arg(var->value, PARSE_INT32|PARSE_DEFAULT, &(db->busy_timeout), 1000) != 0) {
            ast_log(LOG_WARNING, "Invalid busy_timeout value '%s' at res_config_sqlite3.conf:%d. Using 1000 instead.\n", var->value, var->lineno);
         }
      }
   }

   if (ast_strlen_zero(db->filename)) {
      ast_log(LOG_WARNING, "Must specify dbfile in res_config_sqlite3.conf\n");
      unref_db(&db);
      return NULL;
   }

   return db;
}

/*! \brief Update an existing db object based on config data
 * \param db The database object to update
 * \param config The configuration data with which to update the db
 * \param cat The config category (which becomes db->name)
 */
static int update_realtime_sqlite3_db(struct realtime_sqlite3_db *db, struct ast_config *config, const char *cat)
{
   struct realtime_sqlite3_db *new;

   if (!(new = new_realtime_sqlite3_db(config, cat))) {
      return -1;
   }

   /* Copy fields that don't need anything special done on change */
   db->requirements = new->requirements;

   /* Handle changes that require immediate behavior modification */
   if (db->debug != new->debug) {
      if (db->debug) {
         sqlite3_trace(db->handle, NULL, NULL);
      } else {
         sqlite3_trace(db->handle, trace_cb, db);
      }
      db->debug = new->debug;
   }

   if (strcmp(db->filename, new->filename)) {
      sqlite3_close(db->handle);
      ast_string_field_set(db, filename, new->filename);
      db_open(db); /* Also handles setting appropriate debug on new handle */
   }

   if (db->busy_timeout != new->busy_timeout) {
      db->busy_timeout = new->busy_timeout;
      sqlite3_busy_timeout(db->handle, db->busy_timeout);
   }

   if (db->batch != new->batch) {
      if (db->batch == 0) {
         db->batch = new->batch;
         db_start_batch(db);
      } else if (new->batch == 0) {
         db->batch = new->batch;
         db_stop_batch(db);
      }
      db->batch = new->batch;
   }

   db->dirty = 0;
   unref_db(&new);

   return 0;
}

/*! \brief Create a varlist from a single sqlite3 result row */
static int row_to_varlist(void *arg, int num_columns, char **values, char **columns)
{
   struct ast_variable **head = arg, *tail;
   int i;
   struct ast_variable *new;

   if (!(new = ast_variable_new(columns[0], S_OR(values[0], ""), ""))) {
      return SQLITE_ABORT;
   }
   *head = tail = new;

   for (i = 1; i < num_columns; i++) {
      if (!(new = ast_variable_new(columns[i], S_OR(values[i], ""), ""))) {
         ast_variables_destroy(*head);
         *head = NULL;
         return SQLITE_ABORT;
      }
      tail->next = new;
      tail = new;
   }

   return 0;
}

/*! \brief Callback for creating an ast_config from a successive sqlite3 result rows */
static int append_row_to_cfg(void *arg, int num_columns, char **values, char **columns)
{
   struct ast_config *cfg = arg;
   struct ast_category *cat;
   int i;

   cat = ast_category_new_anonymous();
   if (!cat) {
      return SQLITE_ABORT;
   }

   for (i = 0; i < num_columns; i++) {
      struct ast_variable *var;
      if (!(var = ast_variable_new(columns[i], S_OR(values[i], ""), ""))) {
         ast_log(LOG_ERROR, "Could not create new variable for '%s: %s', throwing away list\n", columns[i], values[i]);
         continue;
      }
      ast_variable_append(cat, var);
   }
   ast_category_append(cfg, cat);

   return 0;
}

/*!
 * Structure sent to the SQLite 3 callback function for static configuration.
 *
 * \see static_realtime_cb()
 */
struct cfg_entry_args {
   struct ast_config *cfg;
   struct ast_category *cat;
   char *cat_name;
   struct ast_flags flags;
   const char *who_asked;
};

/*!
 * Structure passed to row counting SQLite callback.
 */
struct row_counter_args {
   callback_t wrapped_callback;
   void *wrapped_arg;
   int row_count;
};

/*!
 * \internal
 * \brief SQLite3 callback that counts rows of a result set.
 *
 * \details
 * This is used to decorate existing callbacks so that we can count the number
 * of rows returned from a SELECT statement and still process each row
 * independently.
 *
 * \param data user data pointer passed in via sqlite3_exec()
 * \param num_columns number of columns in the result
 * \param values array of pointers to column values
 * \param columns array of pointers of to column names
 *
 * \return the return value of the wrapped callback, or 0 if no wrapped callback
 *         is provided.
 */
static int row_counter_wrapper(void *arg, int num_columns, char **values, char **columns)
{
   struct row_counter_args *wrapped = arg;
   wrapped->row_count++;
   if (wrapped->wrapped_callback) {
      return wrapped->wrapped_callback(wrapped->wrapped_arg, num_columns, values, columns);
   }
   return 0;
}

/*!
 * \internal
 * \brief Execute a SQL SELECT statement using a database handle
 *
 * \param db the database handle to use for the query
 * \param sql the SQL statement to execute
 * \param callback a user defined callback that will be called for each row of
 *        the result set
 * \param arg data to be passed to the user defined callback
 *
 * \return if successful, the number of rows returned from the provided SELECT
 *         statement. -1 on failure.
 */
static int realtime_sqlite3_exec_query_with_handle(struct realtime_sqlite3_db *db, const char *sql, callback_t callback, void *arg)
{
   int res = 0;
   char *errmsg;
   struct row_counter_args wrapper = {
      .wrapped_callback = callback,
      .wrapped_arg = arg,
      .row_count = 0,
   };

   ao2_lock(db);
   if (sqlite3_exec(db->handle, sql, row_counter_wrapper, &wrapper, &errmsg) != SQLITE_OK) {
      ast_log(LOG_WARNING, "Could not execute '%s': %s\n", sql, errmsg);
      sqlite3_free(errmsg);
      res = -1;
   }
   ao2_unlock(db);

   return res == 0 ? wrapper.row_count : res;
}

/*!
 * \internal
 * \brief Execute a SQL SELECT statement on the specified database
 *
 * \param database the name of the database to query
 * \param sql the SQL statement to execute
 * \param callback a user defined callback that will be called for each row of
 *        the result set
 * \param arg data to be passed to the user defined callback
 *
 * \return if successful, the number of rows returned from the provided SELECT
 *         statement. -1 on failure.
 */
static int realtime_sqlite3_exec_query(const char *database, const char *sql, callback_t callback, void *arg)
{
   struct realtime_sqlite3_db *db;
   int res;

   if (!(db = find_database(database))) {
      ast_log(LOG_WARNING, "Could not find database: %s\n", database);
      return -1;
   }

   res = realtime_sqlite3_exec_query_with_handle(db, sql, callback, arg);
   ao2_ref(db, -1);

   return res;
}

/*!
 * \internal
 * \brief Execute a SQL INSERT/UPDATE/DELETE statement using a database handle
 *
 * \note A database sync operation is always performed after a statement
 *       is executed.
 *
 * \param db the database handle to use for the query
 * \param sql the SQL statement to execute
 *
 * \return if successful, the number of rows modified by the provided SQL
 *         statement. -1 on failure.
 */
static int realtime_sqlite3_exec_update_with_handle(struct realtime_sqlite3_db *db, const char *sql)
{
   int res = 0;
   char *errmsg;

   ao2_lock(db);
   if (sqlite3_exec(db->handle, sql, NULL, NULL, &errmsg) != SQLITE_OK) {
      ast_log(LOG_WARNING, "Could not execute '%s': %s\n", sql, errmsg);
      sqlite3_free(errmsg);
      res = -1;
   } else {
      res = sqlite3_changes(db->handle);
   }
   ao2_unlock(db);

   db_sync(db);

   return res;
}

/*!
 * \internal
 * \brief Execute a SQL INSERT/UPDATE/DELETE statement using a database handle
 *
 * \note A database sync operation is always performed after a statement
 *       is executed.
 *
 * \param database the name of the database to query
 * \param sql the SQL statement to execute
 *
 * \return if successful, the number of rows modified by the provided SQL
 *         statement. -1 on failure.
 */
static int realtime_sqlite3_exec_update(const char *database, const char *sql)
{
   struct realtime_sqlite3_db *db;
   int res;

   if (!(db = find_database(database))) {
      ast_log(LOG_WARNING, "Could not find database: %s\n", database);
      return -1;
   }

   res = realtime_sqlite3_exec_update_with_handle(db, sql);
   ao2_ref(db, -1);

   return res;
}

/*! \note It is important that the COL_* enum matches the order of the columns selected in static_sql */
static const char *static_sql = "SELECT category, var_name, var_val FROM \"%q\" WHERE filename = %Q AND commented = 0 ORDER BY cat_metric ASC, var_metric ASC";
enum {
   COL_CATEGORY,
   COL_VAR_NAME,
   COL_VAR_VAL,
   COL_COLUMNS,
};

static int static_realtime_cb(void *arg, int num_columns, char **values, char **columns)
{
   struct cfg_entry_args *args = arg;
   struct ast_variable *var;

   if (!strcmp(values[COL_VAR_NAME], "#include")) {
      struct ast_config *cfg;
      char *val;

      val = values[COL_VAR_VAL];
      if (!(cfg = ast_config_internal_load(val, args->cfg, args->flags, "", args->who_asked))) {
         ast_log(LOG_WARNING, "Unable to include %s\n", val);
         return SQLITE_ABORT;
      } else {
         args->cfg = cfg;
         return 0;
      }
   }

   if (!args->cat_name || strcmp(args->cat_name, values[COL_CATEGORY])) {
      args->cat = ast_category_new_dynamic(values[COL_CATEGORY]);
      if (!args->cat) {
         return SQLITE_ABORT;
      }

      ast_free(args->cat_name);

      if (!(args->cat_name = ast_strdup(values[COL_CATEGORY]))) {
         ast_category_destroy(args->cat);
         return SQLITE_ABORT;
      }

      ast_category_append(args->cfg, args->cat);
   }

   if (!(var = ast_variable_new(values[COL_VAR_NAME], values[COL_VAR_VAL], ""))) {
      ast_log(LOG_WARNING, "Unable to allocate variable\n");
      return SQLITE_ABORT;
   }

   ast_variable_append(args->cat, var);

   return 0;
}

/*! \brief Realtime callback for static realtime
 * \return ast_config on success, NULL on failure
 */
static struct ast_config *realtime_sqlite3_load(const char *database, const char *table, const char *configfile, struct ast_config *config, struct ast_flags flags, const char *suggested_include_file, const char *who_asked)
{
   char *sql;
   struct cfg_entry_args args;

   if (ast_strlen_zero(table)) {
      ast_log(LOG_WARNING, "Must have a table to query!\n");
      return NULL;
   }

   if (!(sql = sqlite3_mprintf(static_sql, table, configfile))) {
      ast_log(LOG_WARNING, "Couldn't allocate query\n");
      return NULL;
   };

   args.cfg = config;
   args.cat = NULL;
   args.cat_name = NULL;
   args.flags = flags;
   args.who_asked = who_asked;

   realtime_sqlite3_exec_query(database, sql, static_realtime_cb, &args);

   sqlite3_free(sql);

   return config;
}

#define IS_SQL_LIKE_CLAUSE(x) ((x) && ast_ends_with(x, " LIKE"))

/*! \brief Helper function for single and multi-row realtime load functions */
static int realtime_sqlite3_helper(const char *database, const char *table, const struct ast_variable *fields, int is_multi, void *arg)
{
   struct ast_str *sql;
   const struct ast_variable *field;
   int first = 1;

   if (ast_strlen_zero(table)) {
      ast_log(LOG_WARNING, "Must have a table to query!\n");
      return -1;
   }

   if (!(sql = ast_str_create(128))) {
      return -1;
   }

   for (field = fields; field; field = field->next) {
      if (first) {
         ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s %s", sqlite3_escape_table(table),
                sqlite3_escape_column_op(field->name), sqlite3_escape_value(field->value));
         first = 0;
      } else {
         ast_str_append(&sql, 0, " AND %s %s", sqlite3_escape_column_op(field->name),
               sqlite3_escape_value(field->value));
      }

      if (has_explicit_like_escaping && IS_SQL_LIKE_CLAUSE(field->name)) {
         /*
          * The realtime framework is going to pre-escape these
          * for us with a backslash. We just need to make sure
          * to tell SQLite about it
          */
         ast_str_append(&sql, 0, " ESCAPE '\\'");
      }
   }

   if (!is_multi) {
      ast_str_append(&sql, 0, "%s", " LIMIT 1");
   }

   if (realtime_sqlite3_exec_query(database, ast_str_buffer(sql), is_multi ? append_row_to_cfg : row_to_varlist, arg) < 0) {
      ast_free(sql);
      return -1;
   }

   ast_free(sql);

   return 0;
}

/*! \brief Realtime callback for a single row query
 * \return ast_variable list for single result on success, NULL on empty/failure
 */
static struct ast_variable *realtime_sqlite3(const char *database, const char *table, const struct ast_variable *fields)
{
   struct ast_variable *result_row = NULL;

   realtime_sqlite3_helper(database, table, fields, 0, &result_row);

   return result_row;
}

/*! \brief Realtime callback for a multi-row query
 * \return ast_config containing possibly many results on success, NULL on empty/failure
 */
static struct ast_config *realtime_sqlite3_multi(const char *database, const char *table, const struct ast_variable *fields)
{
   struct ast_config *cfg;

   if (!(cfg = ast_config_new())) {
      return NULL;
   }

   if (realtime_sqlite3_helper(database, table, fields, 1, cfg)) {
      ast_config_destroy(cfg);
      return NULL;
   }

   return cfg;
}

/*! \brief Realtime callback for updating a row based on a single criteria
 * \return Number of rows affected or -1 on error
 */
static int realtime_sqlite3_update(const char *database, const char *table, const char *keyfield, const char *entity, const struct ast_variable *fields)
{
   struct ast_str *sql;
   const struct ast_variable *field;
   int first = 1, res;

   if (ast_strlen_zero(table)) {
      ast_log(LOG_WARNING, "Must have a table to query!\n");
      return -1;
   }

   if (!(sql = ast_str_create(128))) {
      return -1;
   }

   for (field = fields; field; field = field->next) {
      if (first) {
         ast_str_set(&sql, 0, "UPDATE %s SET %s = %s",
               sqlite3_escape_table(table), sqlite3_escape_column(field->name), sqlite3_escape_value(field->value));
         first = 0;
      } else {
         ast_str_append(&sql, 0, ", %s = %s", sqlite3_escape_column(field->name), sqlite3_escape_value(field->value));
      }
   }

   ast_str_append(&sql, 0, " WHERE %s %s", sqlite3_escape_column_op(keyfield), sqlite3_escape_value(entity));

   res = realtime_sqlite3_exec_update(database, ast_str_buffer(sql));
   ast_free(sql);

   return res;
}

/*! \brief Realtime callback for updating a row based on multiple criteria
 * \return Number of rows affected or -1 on error
 */
static int realtime_sqlite3_update2(const char *database, const char *table, const struct ast_variable *lookup_fields, const struct ast_variable *update_fields)
{
   struct ast_str *sql;
   struct ast_str *where_clause;
   const struct ast_variable *field;
   int first = 1, res;

   if (ast_strlen_zero(table)) {
      ast_log(LOG_WARNING, "Must have a table to query!\n");
      return -1;
   }

   if (!(sql = ast_str_create(128))) {
      return -1;
   }

   if (!(where_clause = ast_str_create(128))) {
      ast_free(sql);
      return -1;
   }

   for (field = lookup_fields; field; field = field->next) {
      if (first) {
         ast_str_set(&where_clause, 0, " WHERE %s %s", sqlite3_escape_column_op(field->name), sqlite3_escape_value(field->value));
         first = 0;
      } else {
         ast_str_append(&where_clause, 0, " AND %s %s", sqlite3_escape_column_op(field->name), sqlite3_escape_value(field->value));
      }
   }

   first = 1;
   for (field = update_fields; field; field = field->next) {
      if (first) {
         ast_str_set(&sql, 0, "UPDATE %s SET %s = %s", sqlite3_escape_table(table), sqlite3_escape_column(field->name), sqlite3_escape_value(field->value));
         first = 0;
      } else {
         ast_str_append(&sql, 0, ", %s = %s", sqlite3_escape_column(field->name), sqlite3_escape_value(field->value));
      }
   }

   ast_str_append(&sql, 0, "%s", ast_str_buffer(where_clause));

   res = realtime_sqlite3_exec_update(database, ast_str_buffer(sql));

   ast_free(sql);
   ast_free(where_clause);

   return res;
}

/*! \brief Realtime callback for inserting a row
 * \return Number of rows affected or -1 on error
 */
static int realtime_sqlite3_store(const char *database, const char *table, const struct ast_variable *fields)
{
   struct ast_str *sql, *values;
   const struct ast_variable *field;
   int first = 1, res;

   if (ast_strlen_zero(table)) {
      ast_log(LOG_WARNING, "Must have a table to query!\n");
      return -1;
   }

   if (!(sql = ast_str_create(128))) {
      return -1;
   }

   if (!(values = ast_str_create(128))) {
      ast_free(sql);
      return -1;
   }

   for (field = fields; field; field = field->next) {
      if (first) {
         ast_str_set(&sql, 0, "INSERT INTO %s (%s", sqlite3_escape_table(table), sqlite3_escape_column(field->name));
         ast_str_set(&values, 0, ") VALUES (%s", sqlite3_escape_value(field->value));
         first = 0;
      } else {
         ast_str_append(&sql, 0, ", %s", sqlite3_escape_column(field->name));
         ast_str_append(&values, 0, ", %s", sqlite3_escape_value(field->value));
      }
   }

   ast_str_append(&sql, 0, "%s)", ast_str_buffer(values));

   res = realtime_sqlite3_exec_update(database, ast_str_buffer(sql));

   ast_free(sql);
   ast_free(values);

   return res;
}

/*! \brief Realtime callback for deleting a row
 * \return Number of rows affected or -1 on error
 */
static int realtime_sqlite3_destroy(const char *database, const char *table, const char *keyfield, const char *entity, const struct ast_variable *fields)
{
   struct ast_str *sql;
   const struct ast_variable *field;
   int first = 1, res;

   if (ast_strlen_zero(table)) {
      ast_log(LOG_WARNING, "Must have a table to query!\n");
      return -1;
   }

   if (!(sql = ast_str_create(128))) {
      return -1;
   }

   for (field = fields; field; field = field->next) {
      if (first) {
         ast_str_set(&sql, 0, "DELETE FROM %s WHERE %s %s", sqlite3_escape_table(table),
               sqlite3_escape_column_op(field->name), sqlite3_escape_value(field->value));
         first = 0;
      } else {
         ast_str_append(&sql, 0, " AND %s %s", sqlite3_escape_column_op(field->name), sqlite3_escape_value(field->value));
      }
   }

   res = realtime_sqlite3_exec_update(database, ast_str_buffer(sql));

   ast_free(sql);

   return res;
}

/*! \brief Convert Asterisk realtime types to SQLite 3 types
 * \note SQLite 3 has NULL, INTEGER, REAL, TEXT, and BLOB types. Any column other than
 * an INTEGER PRIMARY KEY will actually store any kind of data due to its dynamic
 * typing. When we create columns, we'll go ahead and use these base types instead
 * of messing with column widths, etc. */

static const char *get_sqlite_column_type(int type)
{
   switch(type) {
   case RQ_INTEGER1 :
   case RQ_UINTEGER1 :
   case RQ_INTEGER2 :
   case RQ_UINTEGER2 :
   case RQ_INTEGER3 :
   case RQ_UINTEGER3 :
   case RQ_INTEGER4 :
   case RQ_UINTEGER4 :
   case RQ_INTEGER8 :
      return "INTEGER";
   case RQ_UINTEGER8 : /* SQLite3 stores INTEGER as signed 8-byte */
   case RQ_CHAR :
   case RQ_DATE :
   case RQ_DATETIME :
      return "TEXT";
   case RQ_FLOAT :
      return "REAL";
   default :
      return "TEXT";
   }

   return "TEXT";
}

/*! \brief Create a table if ast_realtime_require shows that we are configured to handle the data
 */
static int handle_missing_table(struct realtime_sqlite3_db *db, const char *table, va_list ap)
{
   const char *column;
   int type, first = 1, res;
   size_t sz;
   struct ast_str *sql;

   if (!(sql = ast_str_create(128))) {
      return -1;
   }

   while ((column = va_arg(ap, typeof(column)))) {
      type = va_arg(ap, typeof(type));
      sz = va_arg(ap, typeof(sz));
      if (first) {
         ast_str_set(&sql, 0, "CREATE TABLE IF NOT EXISTS %s (%s %s", sqlite3_escape_table(table),
               sqlite3_escape_column(column), get_sqlite_column_type(type));
         first = 0;
      } else {
         ast_str_append(&sql, 0, ", %s %s", sqlite3_escape_column(column), get_sqlite_column_type(type));
      }
   }

   ast_str_append(&sql, 0, ")");

   res = realtime_sqlite3_exec_update_with_handle(db, ast_str_buffer(sql)) < 0 ? -1 : 0;
   ast_free(sql);

   return res;
}

/*! \brief If ast_realtime_require sends info about a column we don't have, create it
 */
static int handle_missing_column(struct realtime_sqlite3_db *db, const char *table, const char *column, int type, size_t sz)
{
   char *sql;
   const char *sqltype = get_sqlite_column_type(type);
   int res;

   if (db->requirements == REALTIME_SQLITE3_REQ_WARN) {
      ast_log(LOG_WARNING, "Missing column '%s' of type '%s' in %s.%s\n", column, sqltype, db->name, table);
      return -1;
   } else if (db->requirements == REALTIME_SQLITE3_REQ_CHAR) {
      sqltype = "TEXT";
   }

   if (!(sql = sqlite3_mprintf("ALTER TABLE \"%q\" ADD COLUMN \"%q\" %s", table, column, sqltype))) {
      return -1;
   }

   if (!(res = (realtime_sqlite3_exec_update_with_handle(db, sql) < 0 ? -1 : 0))) {
      ast_log(LOG_NOTICE, "Creating column '%s' type %s for table %s\n", column, sqltype, table);
   }

   sqlite3_free(sql);

   return res;
}

static int str_hash_fn(const void *obj, const int flags)
{
   return ast_str_hash((const char *) obj);
}

static int str_cmp_fn(void *obj, void *arg, int flags) {
   return !strcasecmp((const char *) obj, (const char *) arg);
}

/*! \brief Callback for creating a hash of column names for comparison in realtime_sqlite3_require
 */
static int add_column_name(void *arg, int num_columns, char **values, char **columns)
{
   char *column;
   struct ao2_container *cnames = arg;


   if (!(column = ao2_alloc(strlen(values[1]) + 1, NULL))) {
      return -1;
   }

   strcpy(column, values[1]);

   ao2_link(cnames, column);
   ao2_ref(column, -1);

   return 0;
}

/*! \brief Callback for ast_realtime_require
 * \retval 0 Required fields met specified standards
 * \retval -1 One or more fields was missing or insufficient
 */
static int realtime_sqlite3_require(const char *database, const char *table, va_list ap)
{
   const char *column;
   char *sql;
   int type;
   int res;
   size_t sz;
   struct ao2_container *columns;
   struct realtime_sqlite3_db *db;

   /* SQLite3 columns are dynamically typed, with type affinity. Built-in functions will
    * return the results as char * anyway. The only field that cannot contain text
    * data is an INTEGER PRIMARY KEY, which must be a 64-bit signed integer. So, for
    * the purposes here we really only care whether the column exists and not what its
    * type or length is. */

   if (ast_strlen_zero(table)) {
      ast_log(LOG_WARNING, "Must have a table to query!\n");
      return -1;
   }

   if (!(db = find_database(database))) {
      return -1;
   }

   columns = ao2_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0, 31,
      str_hash_fn, NULL, str_cmp_fn);
   if (!columns) {
      unref_db(&db);
      return -1;
   }

   if (!(sql = sqlite3_mprintf("PRAGMA table_info(\"%q\")", table))) {
      unref_db(&db);
      ao2_ref(columns, -1);
      return -1;
   }

   if ((res = realtime_sqlite3_exec_query_with_handle(db, sql, add_column_name, columns)) < 0) {
      unref_db(&db);
      ao2_ref(columns, -1);
      sqlite3_free(sql);
      return -1;
   } else if (res == 0) {
      /* Table does not exist */
      sqlite3_free(sql);
      res = handle_missing_table(db, table, ap);
      ao2_ref(columns, -1);
      unref_db(&db);
      return res;
   }

   sqlite3_free(sql);

   while ((column = va_arg(ap, typeof(column)))) {
      char *found;
      type = va_arg(ap, typeof(type));
      sz = va_arg(ap, typeof(sz));
      if (!(found = ao2_find(columns, column, OBJ_POINTER | OBJ_UNLINK))) {
         if (handle_missing_column(db, table, column, type, sz)) {
            unref_db(&db);
            ao2_ref(columns, -1);
            return -1;
         }
      } else {
         ao2_ref(found, -1);
      }
   }

   ao2_ref(columns, -1);
   unref_db(&db);

   return 0;
}

/*! \brief Callback for clearing any cached info
 * \note We don't currently cache anything
 * \retval 0 If any cache was purged
 * \retval -1 If no cache was found
 */
static int realtime_sqlite3_unload(const char *database, const char *table)
{
   /* We currently do no caching */
   return -1;
}

/*! \brief Parse the res_config_sqlite3 config file
 */
static int parse_config(int reload)
{
   struct ast_config *config;
   struct ast_flags config_flags = { CONFIG_FLAG_NOREALTIME | (reload ? CONFIG_FLAG_FILEUNCHANGED : 0) };
   static const char *config_filename = "res_config_sqlite3.conf";

   config = ast_config_load(config_filename, config_flags);

   if (config == CONFIG_STATUS_FILEUNCHANGED) {
      ast_debug(1, "%s was unchanged, skipping parsing\n", config_filename);
      return 0;
   }

   ast_mutex_lock(&config_lock);

   if (config == CONFIG_STATUS_FILEMISSING || config == CONFIG_STATUS_FILEINVALID) {
      ast_log(LOG_ERROR, "%s config file '%s'\n",
         config == CONFIG_STATUS_FILEMISSING ? "Missing" : "Invalid", config_filename);
      ast_mutex_unlock(&config_lock);
      return 0;
   } else {
      const char *cat;
      struct realtime_sqlite3_db *db;

      mark_all_databases_dirty();
      for (cat = ast_category_browse(config, NULL); cat; cat = ast_category_browse(config, cat)) {
         if (!strcasecmp(cat, "general")) {
            continue;
         }
         if (!(db = find_database(cat))) {
            if (!(db = new_realtime_sqlite3_db(config, cat))) {
               ast_log(LOG_WARNING, "Could not allocate new db for '%s' - skipping.\n", cat);
               continue;
            }
            if (db_open(db)) {
               unref_db(&db);
               continue;
            }
            db_start_batch(db);
            ao2_link(databases, db);
            unref_db(&db);
         } else  {
            if (update_realtime_sqlite3_db(db, config, cat)) {
               unref_db(&db);
               continue;
            }
            unref_db(&db);
         }
      }
      unlink_dirty_databases();
   }

   ast_mutex_unlock(&config_lock);

   ast_config_destroy(config);

   return 0;
}

static int reload(void)
{
   parse_config(1);
   return 0;
}

static int unload_module(void)
{
   ast_mutex_lock(&config_lock);
   ao2_callback(databases, OBJ_MULTIPLE | OBJ_NODATA | OBJ_UNLINK, stop_batch_cb, NULL);
   ao2_ref(databases, -1);
   databases = NULL;
   ast_config_engine_deregister(&sqlite3_config_engine);
   ast_mutex_unlock(&config_lock);

   return 0;
}

static void discover_sqlite3_caps(void)
{
   /*
    * So we cheat a little bit here. SQLite3 added support for the
    * 'ESCAPE' keyword in 3.1.0. They added SQLITE_VERSION_NUMBER
    * in 3.1.2. So if we run into 3.1.0 or 3.1.1 in the wild, we
    * just treat it like < 3.1.0.
    *
    * For reference: 3.1.0, 3.1.1, and 3.1.2 were all released
    * within 30 days of each other in Jan/Feb 2005, so I don't
    * imagine we'll be finding something pre-3.1.2 that often in
    * practice.
    */
#if defined(SQLITE_VERSION_NUMBER)
   has_explicit_like_escaping = 1;
#else
   has_explicit_like_escaping = 0;
#endif

   ast_debug(3, "SQLite3 has 'LIKE ... ESCAPE ...' support? %s\n",
         has_explicit_like_escaping ? "Yes" : "No");
}

/*!
 * \brief Load the module
 *
 * Module loading including tests for configuration or dependencies.
 * This function can return AST_MODULE_LOAD_FAILURE, AST_MODULE_LOAD_DECLINE,
 * or AST_MODULE_LOAD_SUCCESS. If a dependency or environment variable fails
 * tests return AST_MODULE_LOAD_FAILURE. If the module can not load the
 * configuration file or other non-critical problem return
 * AST_MODULE_LOAD_DECLINE. On success return AST_MODULE_LOAD_SUCCESS.
 */
static int load_module(void)
{
   discover_sqlite3_caps();

   databases = ao2_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0, DB_BUCKETS,
      db_hash_fn, NULL, db_cmp_fn);
   if (!databases) {
      return AST_MODULE_LOAD_DECLINE;
   }

   if (parse_config(0)) {
      ao2_ref(databases, -1);
      return AST_MODULE_LOAD_DECLINE;
   }

   if (!(ast_config_engine_register(&sqlite3_config_engine))) {
      ast_log(LOG_ERROR, "The config API must have changed, this shouldn't happen.\n");
      ao2_ref(databases, -1);
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "SQLite 3 realtime config engine",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .reload = reload,
   .load_pri = AST_MODPRI_REALTIME_DRIVER,
   .requires = "extconfig",
);