/* This file is part of GNUnet (C) 2009 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 2, 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 datastore/plugin_datastore.h * @brief API for the database backend plugins. * @author Christian Grothoff * * TODO: * - consider defining enumeration or at least typedef * for the type of "type" (instead of using uint32_t) */ #ifndef PLUGIN_DATASTORE_H #define PLUGIN_DATASTORE_H #include "gnunet_configuration_lib.h" #include "gnunet_scheduler_lib.h" #include "gnunet_datastore_service.h" /** * How many bytes of overhead will we assume per entry * in the SQlite DB? */ #define GNUNET_DATASTORE_ENTRY_OVERHEAD 256 /** * The datastore service will pass a pointer to a struct * of this type as the first and only argument to the * entry point of each datastore plugin. */ struct GNUNET_DATASTORE_PluginEnvironment { /** * Configuration to use. */ const struct GNUNET_CONFIGURATION_Handle *cfg; /** * Scheduler to use. */ struct GNUNET_SCHEDULER_Handle *sched; }; /** * Function invoked on behalf of a "PluginIterator" * asking the database plugin to call the iterator * with the next item. * * @param next_cls whatever argument was given * to the PluginIterator as "next_cls". * @param end_it set to GNUNET_YES if we * should terminate the iteration early * (iterator should be still called once more * to signal the end of the iteration). */ typedef void (*PluginNextRequest)(void *next_cls, int end_it); /** * An iterator over a set of items stored in the datastore. * * @param cls closure * @param next_cls closure to pass to the "next" function. * @param key key for the content * @param size number of bytes in data * @param data content stored * @param type type of the content * @param priority priority of the content * @param anonymity anonymity-level for the content * @param expiration expiration time for the content * @param uid unique identifier for the datum; * maybe 0 if no unique identifier is available * * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue * (continue on call to "next", of course), * GNUNET_NO to delete the item and continue (if supported) */ typedef int (*PluginIterator) (void *cls, void *next_cls, const GNUNET_HashCode * key, uint32_t size, const void *data, uint32_t type, uint32_t priority, uint32_t anonymity, struct GNUNET_TIME_Absolute expiration, uint64_t uid); /** * Get an estimate of how much space the database is * currently using. * * @param cls closure * @return number of bytes used on disk */ typedef unsigned long long (*PluginGetSize) (void *cls); /** * Store an item in the datastore. If the item is already present, * the priorities are summed up and the higher expiration time and * lower anonymity level is used. * * @param cls closure * @param key key for the item * @param size number of bytes in data * @param data content stored * @param type type of the content * @param priority priority of the content * @param anonymity anonymity-level for the content * @param expiration expiration time for the content * @param msg set to an error message (on failure) * @return GNUNET_OK on success, GNUNET_NO if the content * was already present (and may have been updated); * GNUNET_SYSERR on failure */ typedef int (*PluginPut) (void *cls, const GNUNET_HashCode * key, uint32_t size, const void *data, uint32_t type, uint32_t priority, uint32_t anonymity, struct GNUNET_TIME_Absolute expiration, char **msg); /** * Iterate over the results for a particular key * in the datastore. * * @param cls closure * @param key maybe NULL (to match all entries) * @param vhash hash of the value, maybe NULL (to * match all values that have the right key). * Note that for DBlocks there is no difference * betwen key and vhash, but for other blocks * there may be! * @param type entries of which type are relevant? * Use 0 for any type. * @param iter function to call on each matching value; however, * after the first call to "iter", the plugin must wait * until "NextRequest" was called before giving the iterator * the next item; finally, the "iter" should be called once * once with a NULL value at the end ("next_cls" should be NULL * for that last call) * @param iter_cls closure for iter */ typedef void (*PluginGet) (void *cls, const GNUNET_HashCode * key, const GNUNET_HashCode * vhash, uint32_t type, PluginIterator iter, void *iter_cls); /** * Update the priority for a particular key in the datastore. If * the expiration time in value is different than the time found in * the datastore, the higher value should be kept. For the * anonymity level, the lower value is to be used. The specified * priority should be added to the existing priority, ignoring the * priority in value. * * Note that it is possible for multiple values to match this put. * In that case, all of the respective values are updated. * * @param cls closure * @param uid unique identifier of the datum * @param delta by how much should the priority * change? If priority + delta < 0 the * priority should be set to 0 (never go * negative). * @param expire new expiration time should be the * MAX of any existing expiration time and * this value * @param msg set to an error message (on error) * @return GNUNET_OK on success */ typedef int (*PluginUpdate) (void *cls, uint64_t uid, int delta, struct GNUNET_TIME_Absolute expire, char **msg); /** * Select a subset of the items in the datastore and call * the given iterator for each of them. * * @param cls closure * @param type entries of which type should be considered? * Use 0 for any type. * @param iter function to call on each matching value; however, * after the first call to "iter", the plugin must wait * until "NextRequest" was called before giving the iterator * the next item; finally, the "iter" should be called once * once with a NULL value at the end ("next_cls" should be NULL * for that last call) * @param iter_cls closure for iter */ typedef void (*PluginSelector) (void *cls, uint32_t type, PluginIterator iter, void *iter_cls); /** * Drop database. * * @param cls closure */ typedef void (*PluginDrop) (void *cls); /** * Each plugin is required to return a pointer to a struct of this * type as the return value from its entry point. */ struct GNUNET_DATASTORE_PluginFunctions { /** * Closure to use for all of the following callbacks * (except "next_request"). */ void *cls; /** * Get the current on-disk size of the SQ store. Estimates are * fine, if that's the only thing available. */ PluginGetSize get_size; /** * Function to store an item in the datastore. */ PluginPut put; /** * Function called by iterators whenever they want the next value; * note that unlike all of the other callbacks, this one does get a * the "next_cls" closure which is usually different from the "cls" * member of this struct! */ PluginNextRequest next_request; /** * Function to iterate over the results for a particular key * in the datastore. */ PluginGet get; /** * Update the priority for a particular key in the datastore. If * the expiration time in value is different than the time found in * the datastore, the higher value should be kept. For the * anonymity level, the lower value is to be used. The specified * priority should be added to the existing priority, ignoring the * priority in value. */ PluginUpdate update; /** * Iterate over the items in the datastore in ascending * order of priority. */ PluginSelector iter_low_priority; /** * Iterate over content with anonymity zero. */ PluginSelector iter_zero_anonymity; /** * Iterate over the items in the datastore in ascending order of * expiration time. */ PluginSelector iter_ascending_expiration; /** * Iterate over the items in the datastore in migration * order. Call the given function on the next item only * (and then signal 'end' with a second call). This is * a significant difference from all the other iterators! */ PluginSelector iter_migration_order; /** * Iterate over all the items in the datastore * as fast as possible in a single transaction * (can lock datastore while this happens, focus * is on doing it fast). */ PluginSelector iter_all_now; /** * Delete the database. The next operation is * guaranteed to be unloading of the module. */ PluginDrop drop; }; #endif