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path: root/src/datacache/plugin_datacache_mysql.c
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/*
     This file is part of GNUnet
     (C) 2006, 2009, 2010 Christian Grothoff (and other contributing authors)

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 3, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file datacache/plugin_datacache_mysql.c
 * @brief mysql for an implementation of a database backend for the datacache
 * @author Christian Grothoff
 *
 * SETUP INSTRUCTIONS:
 *
 * 1) Access mysql as root,
 *    <pre>
 *
 *    $ mysql -u root -p
 *
 *    </pre>
 *    and do the following. [You should replace $USER with the username
 *    that will be running the gnunetd process].
 * @verbatim
      CREATE DATABASE gnunet;
      GRANT select,insert,update,delete,create,alter,drop,create temporary tables
         ON gnunet.* TO $USER@localhost;
      SET PASSWORD FOR $USER@localhost=PASSWORD('$the_password_you_like');
      FLUSH PRIVILEGES;
   @endverbatim
 * 2) In the $HOME directory of $USER, create a ".my.cnf" file
 *    with the following lines
 * @verbatim
      [client]
      user=$USER
      password=$the_password_you_like
   @endverbatim
 *
 * Thats it -- now you can configure your datastores in GNUnet to
 * use MySQL. Note that .my.cnf file is a security risk unless its on
 * a safe partition etc. The $HOME/.my.cnf can of course be a symbolic
 * link. Even greater security risk can be achieved by setting no
 * password for $USER.  Luckily $USER has only priviledges to mess
 * up GNUnet's tables, nothing else (unless you give him more,
 * of course).<p>
 *
 * 3) Still, perhaps you should briefly try if the DB connection
 *    works. First, login as $USER. Then use,
 * @verbatim
      $ mysql -u $USER -p $the_password_you_like
      mysql> use gnunet;
   @endverbatim
 *
 *    If you get the message &quot;Database changed&quot; it probably works.
 *
 *    [If you get &quot;ERROR 2002: Can't connect to local MySQL server
 *     through socket '/tmp/mysql.sock' (2)&quot; it may be resolvable by
 *     &quot;ln -s /var/run/mysqld/mysqld.sock /tmp/mysql.sock&quot;
 *     so there may be some additional trouble depending on your mysql setup.]
 *
 * PROBLEMS?
 *
 * If you have problems related to the mysql module, your best
 * friend is probably the mysql manual. The first thing to check
 * is that mysql is basically operational, that you can connect
 * to it, create tables, issue queries etc.
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_datacache_plugin.h"
#include <mysql/mysql.h>

#define DEBUG_DATACACHE_MYSQL GNUNET_NO

/**
 * Estimate of the per-entry overhead (including indices).
 */
#define OVERHEAD ((4*2+4*2+8*2+8*2+sizeof(GNUNET_HashCode)*5+8))

/**
 * Maximum number of supported parameters for a prepared
 * statement.  Increase if needed.
 */
#define MAX_PARAM 16

/**
 * Die with an error message that indicates
 * a failure of the command 'cmd' with the message given
 * by strerror(errno).
 */
#define DIE_MYSQL(cmd, dbh) do { GNUNET_log(GNUNET_ERROR_TYPE__ERROR, _("`%s' failed at %s:%d with error: %s\n"), cmd, __FILE__, __LINE__, mysql_error((dbh)->dbf)); abort(); } while(0);

/**
 * Log an error message at log-level 'level' that indicates
 * a failure of the command 'cmd' on file 'filename'
 * with the message given by strerror(errno).
 */
#define LOG_MYSQL(level, cmd, dbh) do { GNUNET_log(level, _("`%s' failed at %s:%d with error: %s\n"), cmd, __FILE__, __LINE__, mysql_error((dbh)->dbf)); } while(0);

struct GNUNET_MysqlStatementHandle
{
  struct GNUNET_MysqlStatementHandle *next;

  struct GNUNET_MysqlStatementHandle *prev;

  char *query;

  MYSQL_STMT *statement;

  int valid;

};


/**
 * Context for all functions in this plugin.
 */
struct Plugin 
{
  /**
   * Our execution environment.
   */
  struct GNUNET_DATACACHE_PluginEnvironment *env;

  /**
   * Handle to the mysql database.
   */
  MYSQL *dbf;

  struct GNUNET_MysqlStatementHandle *shead;

  struct GNUNET_MysqlStatementHandle *stail;

  /**
   * Filename of "my.cnf" (msyql configuration).
   */
  char *cnffile;

#define SELECT_VALUE_STMT "SELECT value,expire FROM gn080dstore FORCE INDEX (hashidx) WHERE hash=? AND type=? AND expire >= ? LIMIT 1 OFFSET ?"
  struct GNUNET_MysqlStatementHandle *select_value;

#define COUNT_VALUE_STMT "SELECT count(*) FROM gn080dstore FORCE INDEX (hashidx) WHERE hash=? AND type=? AND expire >= ?"
  struct GNUNET_MysqlStatementHandle *count_value;

#define SELECT_OLD_VALUE_STMT "SELECT hash, vhash, type, value FROM gn080dstore FORCE INDEX (expireidx) ORDER BY puttime ASC LIMIT 1"
  struct GNUNET_MysqlStatementHandle *select_old_value;

#define DELETE_VALUE_STMT "DELETE FROM gn080dstore WHERE hash = ? AND vhash = ? AND type = ? AND value = ?"
  struct GNUNET_MysqlStatementHandle *delete_value;

#define INSERT_VALUE_STMT "INSERT INTO gn080dstore (type, puttime, expire, hash, vhash, value) "\
                          "VALUES (?, ?, ?, ?, ?, ?)"
  struct GNUNET_MysqlStatementHandle *insert_value;

#define UPDATE_VALUE_STMT "UPDATE gn080dstore FORCE INDEX (allidx) SET puttime=?, expire=? "\
                          "WHERE hash=? AND vhash=? AND type=?"
  struct GNUNET_MysqlStatementHandle *update_value;

};


/**
 * Obtain the location of ".my.cnf".
 *
 * @param cfg our configuration
 * @return NULL on error
 */
static char *
get_my_cnf_path (const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  char *cnffile;
  char *home_dir;
  struct stat st;
#ifndef WINDOWS
  struct passwd *pw;
#endif
  int configured;

#ifndef WINDOWS
  pw = getpwuid (getuid ());
  if (!pw)
    {
      GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, 
			   "getpwuid");
      return NULL;
    }
  if (GNUNET_YES ==
      GNUNET_CONFIGURATION_have_value (cfg,
				       "datacache-mysql", "CONFIG"))
    {
      GNUNET_assert (GNUNET_OK == 
		     GNUNET_CONFIGURATION_get_value_filename (cfg,
							      "datacache-mysql", "CONFIG", &cnffile));
      configured = GNUNET_YES;
    }
  else
    {
      home_dir = GNUNET_strdup (pw->pw_dir);
#else
      home_dir = (char *) GNUNET_malloc (_MAX_PATH + 1);
      plibc_conv_to_win_path ("~/", home_dir);
#endif
      GNUNET_asprintf (&cnffile, "%s/.my.cnf", home_dir);
      GNUNET_free (home_dir);
      configured = GNUNET_NO;
    }
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
	      _("Trying to use file `%s' for MySQL configuration.\n"),
	      cnffile);
  if ((0 != STAT (cnffile, &st)) ||
      (0 != ACCESS (cnffile, R_OK)) || (!S_ISREG (st.st_mode)))
    {
      if (configured == GNUNET_YES)
	GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
		    _("Could not access file `%s': %s\n"), cnffile,
		    STRERROR (errno));
      GNUNET_free (cnffile);
      return NULL;
    }
  return cnffile;
}


/**
 * Free a prepared statement.
 *
 * @param plugin plugin context
 * @param s prepared statement
 */
static void
prepared_statement_destroy (struct Plugin *plugin, 
			    struct GNUNET_MysqlStatementHandle
			    *s)
{
  GNUNET_CONTAINER_DLL_remove (plugin->shead,
			       plugin->stail,
			       s);
  if (s->valid)
    mysql_stmt_close (s->statement);
  GNUNET_free (s->query);
  GNUNET_free (s);
}


/**
 * Close database connection and all prepared statements (we got a DB
 * disconnect error).
 */
static int
iclose (struct Plugin *plugin)
{
  while (NULL != plugin->shead)
    prepared_statement_destroy (plugin,
				plugin->shead);
  if (plugin->dbf != NULL)
    {
      mysql_close (plugin->dbf);
      plugin->dbf = NULL;
    }
  return GNUNET_OK;
}


/**
 * Open the connection with the database (and initialize
 * our default options).
 *
 * @return GNUNET_OK on success
 */
static int
iopen (struct Plugin *ret)
{
  char *mysql_dbname;
  char *mysql_server;
  char *mysql_user;
  char *mysql_password;
  unsigned long long mysql_port;
  my_bool reconnect;
  unsigned int timeout;

  ret->dbf = mysql_init (NULL);
  if (ret->dbf == NULL)
    return GNUNET_SYSERR;
  if (ret->cnffile != NULL)
    mysql_options (ret->dbf, MYSQL_READ_DEFAULT_FILE, ret->cnffile);
  mysql_options (ret->dbf, MYSQL_READ_DEFAULT_GROUP, "client");
  reconnect = 0;
  mysql_options (ret->dbf, MYSQL_OPT_RECONNECT, &reconnect);
  mysql_options (ret->dbf,
                 MYSQL_OPT_CONNECT_TIMEOUT, (const void *) &timeout);
  mysql_options(ret->dbf, MYSQL_SET_CHARSET_NAME, "UTF8");
  timeout = 60; /* in seconds */
  mysql_options (ret->dbf, MYSQL_OPT_READ_TIMEOUT, (const void *) &timeout);
  mysql_options (ret->dbf, MYSQL_OPT_WRITE_TIMEOUT, (const void *) &timeout);
  mysql_dbname = NULL;
  if (GNUNET_YES == GNUNET_CONFIGURATION_have_value (ret->env->cfg,
						     "datacache-mysql", "DATABASE"))
    GNUNET_assert (GNUNET_OK == 
		   GNUNET_CONFIGURATION_get_value_string (ret->env->cfg,
							  "datacache-mysql", "DATABASE", 
							  &mysql_dbname));
  else
    mysql_dbname = GNUNET_strdup ("gnunet");
  mysql_user = NULL;
  if (GNUNET_YES == GNUNET_CONFIGURATION_have_value (ret->env->cfg,
						     "datacache-mysql", "USER"))
    {
      GNUNET_assert (GNUNET_OK == 
		    GNUNET_CONFIGURATION_get_value_string (ret->env->cfg,
							   "datacache-mysql", "USER", 
							   &mysql_user));
    }
  mysql_password = NULL;
  if (GNUNET_YES == GNUNET_CONFIGURATION_have_value (ret->env->cfg,
						     "datacache-mysql", "PASSWORD"))
    {
      GNUNET_assert (GNUNET_OK ==
		    GNUNET_CONFIGURATION_get_value_string (ret->env->cfg,
							   "datacache-mysql", "PASSWORD",
							   &mysql_password));
    }
  mysql_server = NULL;
  if (GNUNET_YES == GNUNET_CONFIGURATION_have_value (ret->env->cfg,
						     "datacache-mysql", "HOST"))
    {
      GNUNET_assert (GNUNET_OK == 
		    GNUNET_CONFIGURATION_get_value_string (ret->env->cfg,
							   "datacache-mysql", "HOST", 
							   &mysql_server));
    }
  mysql_port = 0;
  if (GNUNET_YES == GNUNET_CONFIGURATION_have_value (ret->env->cfg,
						     "datacache-mysql", "PORT"))
    {
      GNUNET_assert (GNUNET_OK ==
		    GNUNET_CONFIGURATION_get_value_number (ret->env->cfg, "datacache-mysql",
							   "PORT", &mysql_port));
    }

  GNUNET_assert (mysql_dbname != NULL);
  mysql_real_connect (ret->dbf, mysql_server, mysql_user, mysql_password,
                      mysql_dbname, (unsigned int) mysql_port, NULL,
		      CLIENT_IGNORE_SIGPIPE);
  GNUNET_free_non_null (mysql_server);
  GNUNET_free_non_null (mysql_user);
  GNUNET_free_non_null (mysql_password);
  GNUNET_free (mysql_dbname);
  if (mysql_error (ret->dbf)[0])
    {
      LOG_MYSQL (GNUNET_ERROR_TYPE_ERROR,
                 "mysql_real_connect", ret);
      return GNUNET_SYSERR;
    }
  return GNUNET_OK;
}


/**
 * Run the given MySQL statement.
 *
 * @return GNUNET_OK on success, GNUNET_SYSERR on error
 */
static int
run_statement (struct Plugin *plugin,
	       const char *statement)
{
  if ((NULL == plugin->dbf) && (GNUNET_OK != iopen (plugin)))
    return GNUNET_SYSERR;
  mysql_query (plugin->dbf, statement);
  if (mysql_error (plugin->dbf)[0])
    {
      LOG_MYSQL (GNUNET_ERROR_TYPE_ERROR,
                 "mysql_query", plugin);
      iclose (plugin);
      return GNUNET_SYSERR;
    }
  return GNUNET_OK;
}

/**
 * Create a prepared statement.
 *
 * @return NULL on error
 */
static struct GNUNET_MysqlStatementHandle *
prepared_statement_create (struct Plugin *plugin, 
			   const char *statement)
{
  struct GNUNET_MysqlStatementHandle *ret;

  ret = GNUNET_malloc (sizeof (struct GNUNET_MysqlStatementHandle));
  ret->query = GNUNET_strdup (statement);
  GNUNET_CONTAINER_DLL_insert (plugin->shead,
			       plugin->stail,
			       ret);
  return ret;
}


/**
 * Prepare a statement for running.
 *
 * @return GNUNET_OK on success
 */
static int
prepare_statement (struct Plugin *plugin, 
		   struct GNUNET_MysqlStatementHandle *ret)
{
  if (GNUNET_YES == ret->valid)
    return GNUNET_OK;
  if ((NULL == plugin->dbf) && 
      (GNUNET_OK != iopen (plugin)))
    return GNUNET_SYSERR;
  ret->statement = mysql_stmt_init (plugin->dbf);
  if (ret->statement == NULL)
    {
      iclose (plugin);
      return GNUNET_SYSERR;
    }
  if (mysql_stmt_prepare (ret->statement, 
			  ret->query,
			  strlen (ret->query)))
    {
      LOG_MYSQL (GNUNET_ERROR_TYPE_ERROR,
                 "mysql_stmt_prepare", 
		 plugin);
      mysql_stmt_close (ret->statement);
      ret->statement = NULL;
      iclose (plugin);
      return GNUNET_SYSERR;
    }
  ret->valid = GNUNET_YES;
  return GNUNET_OK;

}


/**
 * Bind the parameters for the given MySQL statement
 * and run it.
 *
 * @param plugin plugin context
 * @param s statement to bind and run
 * @param ap arguments for the binding
 * @return GNUNET_SYSERR on error, GNUNET_OK on success
 */
static int
init_params (struct Plugin *plugin,
	     struct GNUNET_MysqlStatementHandle *s,
	     va_list ap)
{
  MYSQL_BIND qbind[MAX_PARAM];
  unsigned int pc;
  unsigned int off;
  enum enum_field_types ft;

  pc = mysql_stmt_param_count (s->statement);
  if (pc > MAX_PARAM)
    {
      /* increase internal constant! */
      GNUNET_break (0);
      return GNUNET_SYSERR;
    }
  memset (qbind, 0, sizeof (qbind));
  off = 0;
  ft = 0;
  while ( (pc > 0) && (-1 != (int) (ft = va_arg (ap, enum enum_field_types))) )
    {
      qbind[off].buffer_type = ft;
      switch (ft)
        {
        case MYSQL_TYPE_FLOAT:
          qbind[off].buffer = va_arg (ap, float *);
          break;
        case MYSQL_TYPE_LONGLONG:
          qbind[off].buffer = va_arg (ap, unsigned long long *);
          qbind[off].is_unsigned = va_arg (ap, int);
          break;
        case MYSQL_TYPE_LONG:
          qbind[off].buffer = va_arg (ap, unsigned int *);
          qbind[off].is_unsigned = va_arg (ap, int);
          break;
        case MYSQL_TYPE_VAR_STRING:
        case MYSQL_TYPE_STRING:
        case MYSQL_TYPE_BLOB:
          qbind[off].buffer = va_arg (ap, void *);
          qbind[off].buffer_length = va_arg (ap, unsigned long);
          qbind[off].length = va_arg (ap, unsigned long *);
          break;
        default:
          /* unsupported type */
          GNUNET_break (0);
          return GNUNET_SYSERR;
        }
      pc--;
      off++;
    }
  if (! ( (pc == 0) && (-1 != (int) ft) && (va_arg (ap, int) == -1)) )
    {
      GNUNET_break (0);
      return GNUNET_SYSERR;
    }
  if (mysql_stmt_bind_param (s->statement, qbind))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
		  _("`%s' failed at %s:%d with error: %s\n"),
		  "mysql_stmt_bind_param",
		  __FILE__, __LINE__, mysql_stmt_error (s->statement));
      iclose (plugin);
      return GNUNET_SYSERR;
    }
  if (mysql_stmt_execute (s->statement))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
		  _("`%s' failed at %s:%d with error: %s\n"),
		  "mysql_stmt_execute",
		  __FILE__, __LINE__, mysql_stmt_error (s->statement));
      iclose (plugin);
      return GNUNET_SYSERR;
    }
  return GNUNET_OK;
}

/**
 * Type of a callback that will be called for each
 * data set returned from MySQL.
 *
 * @param cls user-defined argument
 * @param num_values number of elements in values
 * @param values values returned by MySQL
 * @return GNUNET_OK to continue iterating, GNUNET_SYSERR to abort
 */
typedef int (*GNUNET_MysqlDataProcessor) (void *cls,
                                          unsigned int num_values,
                                          MYSQL_BIND * values);


/**
 * Run a prepared SELECT statement.
 *
 * @param plugin plugin context
 * @param s handle to SELECT statment
 * @param result_size number of elements in results array
 * @param results pointer to already initialized MYSQL_BIND
 *        array (of sufficient size) for passing results
 * @param processor function to call on each result
 * @param processor_cls extra argument to processor
 * @param ... pairs and triplets of "MYSQL_TYPE_XXX" keys and their respective
 *        values (size + buffer-reference for pointers); terminated
 *        with "-1"
 * @return GNUNET_SYSERR on error, otherwise
 *         the number of successfully affected (or queried) rows
 */
static int
prepared_statement_run_select (struct Plugin *plugin,
			       struct GNUNET_MysqlStatementHandle
			       *s,
			       unsigned int result_size,
			       MYSQL_BIND * results,
			       GNUNET_MysqlDataProcessor
			       processor, void *processor_cls,
			       ...)
{
  va_list ap;
  int ret;
  unsigned int rsize;
  int total;

  if (GNUNET_OK != prepare_statement (plugin, s))
    {
      GNUNET_break (0);
      return GNUNET_SYSERR;
    }
  va_start (ap, processor_cls);
  if (GNUNET_OK != init_params (plugin, s, ap))
    {
      GNUNET_break (0);
      va_end (ap);
      return GNUNET_SYSERR;
    }
  va_end (ap);
  rsize = mysql_stmt_field_count (s->statement);
  if (rsize > result_size)
    {
      GNUNET_break (0);
      return GNUNET_SYSERR;
    }
  if (mysql_stmt_bind_result (s->statement, results))
    {
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
		  _("`%s' failed at %s:%d with error: %s\n"),
		  "mysql_stmt_bind_result",
		  __FILE__, __LINE__, mysql_stmt_error (s->statement));
      iclose (plugin);
      return GNUNET_SYSERR;
    }

  total = 0;
  while (1)
    {
      ret = mysql_stmt_fetch (s->statement);
      if (ret == MYSQL_NO_DATA)
        break;
      if (ret != 0)
        {
          GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
		      _("`%s' failed at %s:%d with error: %s\n"),
		      "mysql_stmt_fetch",
		      __FILE__, __LINE__, mysql_stmt_error (s->statement));
          iclose (plugin);
          return GNUNET_SYSERR;
        }
      if (processor != NULL)
        if (GNUNET_OK != processor (processor_cls, rsize, results))
          break;
      total++;
    }
  mysql_stmt_reset (s->statement);
  return total;
}



/**
 * Run a prepared statement that does NOT produce results.
 *
 * @param plugin plugin context
 * @param s handle to SELECT statment
 * @param ... pairs and triplets of "MYSQL_TYPE_XXX" keys and their respective
 *        values (size + buffer-reference for pointers); terminated
 *        with "-1"
 * @param insert_id NULL or address where to store the row ID of whatever
 *        was inserted (only for INSERT statements!)
 * @return GNUNET_SYSERR on error, otherwise
 *         the number of successfully affected rows
 */
static int
prepared_statement_run (struct Plugin *plugin,
			struct GNUNET_MysqlStatementHandle *s,
			unsigned long long *insert_id, ...)
{
  va_list ap;
  int affected;

  if (GNUNET_OK != prepare_statement (plugin, s))
    return GNUNET_SYSERR;
  va_start (ap, insert_id);
  if (GNUNET_OK != init_params (plugin, s, ap))
    {
      va_end (ap);
      return GNUNET_SYSERR;
    }
  va_end (ap);
  affected = mysql_stmt_affected_rows (s->statement);
  if (NULL != insert_id)
    *insert_id = (unsigned long long) mysql_stmt_insert_id (s->statement);
  mysql_stmt_reset (s->statement);
  return affected;
}


/**
 * Create temporary table and prepare statements.
 *
 * @param plugin plugin context
 * @return GNUNET_OK on success
 */
static int
itable (struct Plugin *plugin)
{
#define MRUNS(a) (GNUNET_OK != run_statement (plugin, a) )
  if (MRUNS ("CREATE TEMPORARY TABLE gn080dstore ("
             "  type INT(11) UNSIGNED NOT NULL DEFAULT 0,"
             "  puttime BIGINT UNSIGNED NOT NULL DEFAULT 0,"
             "  expire BIGINT UNSIGNED NOT NULL DEFAULT 0,"
             "  hash BINARY(64) NOT NULL DEFAULT '',"
             "  vhash BINARY(64) NOT NULL DEFAULT '',"
             "  value BLOB NOT NULL DEFAULT '',"
             "  INDEX hashidx (hash(64),type,expire),"
             "  INDEX allidx (hash(64),vhash(64),type),"
             "  INDEX expireidx (puttime)" ") ENGINE=InnoDB") ||
      MRUNS ("SET AUTOCOMMIT = 1"))
    return GNUNET_SYSERR;
#undef MRUNS
#define PINIT(a,b) (NULL == (a = prepared_statement_create(plugin, b)))
  if (PINIT (plugin->select_value, SELECT_VALUE_STMT) ||
      PINIT (plugin->count_value, COUNT_VALUE_STMT) ||
      PINIT (plugin->select_old_value, SELECT_OLD_VALUE_STMT) ||
      PINIT (plugin->delete_value, DELETE_VALUE_STMT) ||
      PINIT (plugin->insert_value, INSERT_VALUE_STMT) ||
      PINIT (plugin->update_value, UPDATE_VALUE_STMT))
    return GNUNET_SYSERR;
#undef PINIT
  return GNUNET_OK;
}


/**
 * Store an item in the datastore.
 *
 * @param cls closure (our "struct Plugin")
 * @param key key to store data under
 * @param size number of bytes in data
 * @param data data to store
 * @param type type of the value
 * @param discard_time when to discard the value in any case
 * @return 0 on error, number of bytes used otherwise
 */
static size_t 
mysql_plugin_put (void *cls,
		  const GNUNET_HashCode * key,
		  size_t size,
		  const char *data,
		  enum GNUNET_BLOCK_Type type,
		  struct GNUNET_TIME_Absolute discard_time)
{
  struct Plugin *plugin = cls;
  struct GNUNET_TIME_Absolute now;
  unsigned long k_length;
  unsigned long h_length;
  unsigned long v_length;
  unsigned long long v_now;
  unsigned long long v_discard_time;
  unsigned int v_type;
  GNUNET_HashCode vhash;
  int ret;

  if (size > GNUNET_SERVER_MAX_MESSAGE_SIZE)
    return GNUNET_SYSERR;
  GNUNET_CRYPTO_hash (data, size, &vhash);
  now = GNUNET_TIME_absolute_get ();

  /* first try UPDATE */
  h_length = sizeof (GNUNET_HashCode);
  k_length = sizeof (GNUNET_HashCode);
  v_length = size;
  v_type = type;
  v_now = (unsigned long long) now.abs_value;
  v_discard_time = (unsigned long long) discard_time.abs_value;
  if (GNUNET_OK ==
      prepared_statement_run (plugin,
			      plugin->update_value,
			      NULL,
			      MYSQL_TYPE_LONGLONG,
			      &v_now,
			      GNUNET_YES,
			      MYSQL_TYPE_LONGLONG,
			      &v_discard_time,
			      GNUNET_YES,
			      MYSQL_TYPE_BLOB,
			      key,
			      sizeof (GNUNET_HashCode),
			      &k_length,
			      MYSQL_TYPE_BLOB,
			      &vhash,
			      sizeof (GNUNET_HashCode),
			      &h_length,
			      MYSQL_TYPE_LONG,
			      &v_type,
			      GNUNET_YES, -1))
    return GNUNET_OK;

  /* now try INSERT */
  h_length = sizeof (GNUNET_HashCode);
  k_length = sizeof (GNUNET_HashCode);
  v_length = size;
  if (GNUNET_OK !=
      (ret = prepared_statement_run (plugin,
				     plugin->insert_value,
				     NULL,
				     MYSQL_TYPE_LONG,
				     &type,
				     GNUNET_YES,
				     MYSQL_TYPE_LONGLONG,
				     &v_now,
				     GNUNET_YES,
				     MYSQL_TYPE_LONGLONG,
				     &v_discard_time,
				     GNUNET_YES,
				     MYSQL_TYPE_BLOB,
				     key,
				     sizeof (GNUNET_HashCode),
				     &k_length,
				     MYSQL_TYPE_BLOB,
				     &vhash,
				     sizeof (GNUNET_HashCode),
				     &h_length,
				     MYSQL_TYPE_BLOB,
				     data,
				     (unsigned long) size,
				     &v_length, -1)))
    {
      if (ret == GNUNET_SYSERR)
        itable (plugin);
      return GNUNET_SYSERR;
    }
  return size + OVERHEAD;
}


static int
return_ok (void *cls, unsigned int num_values, MYSQL_BIND * values)
{
  return GNUNET_OK;
}


/**
 * Iterate over the results for a particular key
 * in the datastore.
 *
 * @param cls closure (our "struct Plugin")
 * @param key
 * @param type entries of which type are relevant?
 * @param iter maybe NULL (to just count)
 * @param iter_cls closure for iter
 * @return the number of results found
 */
static unsigned int 
mysql_plugin_get (void *cls,
		   const GNUNET_HashCode * key,
		   enum GNUNET_BLOCK_Type type,
		   GNUNET_DATACACHE_Iterator iter,
		   void *iter_cls)
{
  struct Plugin *plugin = cls;
  MYSQL_BIND rbind[3];
  unsigned long h_length;
  unsigned long v_length;
  unsigned long long v_expire;
  struct GNUNET_TIME_Absolute now;
  struct GNUNET_TIME_Absolute expire;
  unsigned int cnt;
  unsigned long long total;
  unsigned long long v_now;
  unsigned int off;
  unsigned int v_type;
  int ret;
  char buffer[GNUNET_SERVER_MAX_MESSAGE_SIZE];

  now = GNUNET_TIME_absolute_get ();
  h_length = sizeof (GNUNET_HashCode);
  v_length = sizeof (buffer);
  total = -1;
  memset (rbind, 0, sizeof (rbind));
  rbind[0].buffer_type = MYSQL_TYPE_LONGLONG;
  rbind[0].buffer = &total;
  rbind[0].is_unsigned = GNUNET_YES;
  v_type = type;
  v_now = (unsigned long long) now.abs_value;
  if ((GNUNET_OK !=
       (ret = prepared_statement_run_select (plugin,
					     plugin->count_value,
					     1,
					     rbind,
					     return_ok,
					     NULL,
					     MYSQL_TYPE_BLOB,
					     key,
					     sizeof
					     (GNUNET_HashCode),
					     &h_length,
					     MYSQL_TYPE_LONG,
					     &v_type, GNUNET_YES,
					     MYSQL_TYPE_LONGLONG,
					     &v_now, GNUNET_YES,
					     -1)))
      || (-1 == total))
    {
      if (ret == GNUNET_SYSERR)
        itable (plugin);
      return GNUNET_SYSERR;
    }
  if ((iter == NULL) || (total == 0))
    return (int) total;

  off = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, total);
  cnt = 0;
  while (cnt < total)
    {
      memset (rbind, 0, sizeof (rbind));
      rbind[0].buffer_type = MYSQL_TYPE_BLOB;
      rbind[0].buffer_length = sizeof (buffer);
      rbind[0].length = &v_length;
      rbind[0].buffer = buffer;
      rbind[1].buffer_type = MYSQL_TYPE_LONGLONG;
      rbind[1].is_unsigned = 1;
      rbind[1].buffer = &v_expire;
      off = (off + 1) % total;
      if (GNUNET_OK !=
	  (ret = prepared_statement_run_select (plugin,
						plugin->select_value,
						2,
						rbind,
						return_ok,
						NULL,
						MYSQL_TYPE_BLOB,
						key,
						sizeof
						(GNUNET_HashCode),
						&h_length,
						MYSQL_TYPE_LONG,
						&v_type,
						GNUNET_YES,
						MYSQL_TYPE_LONGLONG,
						&v_now,
						GNUNET_YES,
						MYSQL_TYPE_LONG,
						&off,
						GNUNET_YES,
						-1)))
        {
          if (ret == GNUNET_SYSERR)
            itable (plugin);
          return GNUNET_SYSERR;
        }
      cnt++;
      expire.abs_value = v_expire;
      if (GNUNET_OK != iter (iter_cls, 
			     expire,
			     key, 
			     v_length, buffer,
			     type))
        break;
    }
  return cnt;
}


/**
 * Delete the entry with the lowest expiration value
 * from the datacache right now.
 * 
 * @param cls closure (our "struct Plugin")
 * @return GNUNET_OK on success, GNUNET_SYSERR on error
 */ 
static int 
mysql_plugin_del (void *cls)
{
  struct Plugin *plugin = cls;

  MYSQL_BIND rbind[5];
  unsigned int v_type;
  GNUNET_HashCode v_key;
  GNUNET_HashCode vhash;
  unsigned long k_length;
  unsigned long h_length;
  unsigned long v_length;
  int ret;
  char buffer[GNUNET_SERVER_MAX_MESSAGE_SIZE];

  k_length = sizeof (GNUNET_HashCode);
  h_length = sizeof (GNUNET_HashCode);
  v_length = sizeof (buffer);
  memset (rbind, 0, sizeof (rbind));
  rbind[0].buffer_type = MYSQL_TYPE_BLOB;
  rbind[0].buffer_length = sizeof (GNUNET_HashCode);
  rbind[0].length = &k_length;
  rbind[0].buffer = &v_key;
  rbind[1].buffer_type = MYSQL_TYPE_BLOB;
  rbind[1].buffer_length = sizeof (GNUNET_HashCode);
  rbind[1].length = &h_length;
  rbind[1].buffer = &vhash;
  rbind[2].buffer_type = MYSQL_TYPE_LONG;
  rbind[2].is_unsigned = 1;
  rbind[2].buffer = &v_type;
  rbind[3].buffer_type = MYSQL_TYPE_BLOB;
  rbind[3].buffer_length = sizeof (buffer);
  rbind[3].length = &v_length;
  rbind[3].buffer = buffer;
  if ((GNUNET_OK !=
       (ret = prepared_statement_run_select (plugin,
					     plugin->select_old_value,
					     4,
					     rbind,
					     return_ok,
					     NULL,
					     -1))) ||
      (GNUNET_OK !=
       (ret = prepared_statement_run (plugin,
				      plugin->delete_value,
				      NULL,
				      MYSQL_TYPE_BLOB,
				      &v_key,
				      sizeof (GNUNET_HashCode),
				      &k_length,
				      MYSQL_TYPE_BLOB,
				      &vhash,
				      sizeof (GNUNET_HashCode),
				      &h_length,
				      MYSQL_TYPE_LONG,
				      &v_type,
				      GNUNET_YES,
				      MYSQL_TYPE_BLOB,
				      buffer,
				      (unsigned long)
				      sizeof (buffer),
				      &v_length, -1))))
    {
      if (ret == GNUNET_SYSERR)
        itable (plugin);
      return GNUNET_SYSERR;
    }
  plugin->env->delete_notify (plugin->env->cls,
			      &v_key,
			      v_length + OVERHEAD);

  return GNUNET_OK;
}


/**
 * Entry point for the plugin.
 *
 * @param cls closure (the "struct GNUNET_DATACACHE_PluginEnvironmnet")
 * @return the plugin's closure (our "struct Plugin")
 */
void *
libgnunet_plugin_datacache_mysql_init (void *cls)
{
  struct GNUNET_DATACACHE_PluginEnvironment *env = cls;
  struct GNUNET_DATACACHE_PluginFunctions *api;
  struct Plugin *plugin;

  plugin = GNUNET_malloc (sizeof (struct Plugin));
  plugin->env = env;
  plugin->cnffile = get_my_cnf_path (env->cfg);
  if (GNUNET_OK !=
      iopen (plugin))
    {
      GNUNET_free_non_null (plugin->cnffile);
      GNUNET_free (plugin);
      return NULL;
    }
  if (GNUNET_OK !=
      itable (plugin))
    {
      iclose (plugin);
      GNUNET_free_non_null (plugin->cnffile);
      GNUNET_free (plugin);
      return NULL;
    }
  api = GNUNET_malloc (sizeof (struct GNUNET_DATACACHE_PluginFunctions));
  api->cls = plugin;
  api->get = &mysql_plugin_get;
  api->put = &mysql_plugin_put;
  api->del = &mysql_plugin_del;
  GNUNET_log_from (GNUNET_ERROR_TYPE_INFO,
                   "mysql", _("MySQL datacache running\n"));
  return api;
}


/**
 * Exit point from the plugin.
 *
 * @param cls closure (our "struct Plugin")
 * @return NULL
 */
void *
libgnunet_plugin_datacache_mysql_done (void *cls)
{
  struct GNUNET_DATACACHE_PluginFunctions *api = cls;
  struct Plugin *plugin = api->cls;

  iclose (plugin);
  GNUNET_free_non_null (plugin->cnffile);
  GNUNET_free (plugin);
  GNUNET_free (api);
  mysql_library_end ();
  return NULL;
}


/* end of plugin_datacache_mysql.c */