/* This file is part of GNUnet (C) 2009, 2011 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 include/gnunet_datastore_plugin.h * @brief API for the database backend plugins. * @author Christian Grothoff */ #ifndef PLUGIN_DATASTORE_H #define PLUGIN_DATASTORE_H #include "gnunet_block_lib.h" #include "gnunet_configuration_lib.h" #include "gnunet_datastore_service.h" #include "gnunet_statistics_service.h" #include "gnunet_scheduler_lib.h" /** * How many bytes of overhead will we assume per entry * in any DB (for reservations)? */ #define GNUNET_DATASTORE_ENTRY_OVERHEAD 256 /** * Function invoked to notify service of disk utilization * changes. * * @param cls closure * @param delta change in disk utilization, * 0 for "reset to empty" */ typedef void (*DiskUtilizationChange)(void *cls, int delta); /** * 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; /** * Function to call on disk utilization change. */ DiskUtilizationChange duc; /** * Closure. */ void *cls; }; /** * 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, enum GNUNET_BLOCK_Type 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 and replication levels 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 replication replication-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_SYSERR on failure */ typedef int (*PluginPut) (void *cls, const GNUNET_HashCode * key, uint32_t size, const void *data, enum GNUNET_BLOCK_Type type, uint32_t priority, uint32_t anonymity, uint32_t replication, 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, enum GNUNET_BLOCK_Type type, PluginIterator iter, void *iter_cls); /** * Get a random item (additional constraints may apply depending on * the specific implementation). Calls 'iter' with all values ZERO or * NULL if no item applies, otherwise 'iter' is called once and only * once with an item, with the 'next_cls' argument being NULL. * * @param cls closure * @param iter function to call the value (once only). * @param iter_cls closure for iter */ typedef void (*PluginRandomGet) (void *cls, 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 the first item; then allow getting more items by * calling the 'next_request' callback with the given 'next_cls' * argument passed to 'iter'. * * @param cls closure * @param type entries of which type should be considered? * Myst not be zero (ANY). * @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, enum GNUNET_BLOCK_Type 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; /** * 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; /** * 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; /** * Iterate over content with anonymity level zero. */ PluginSelector iter_zero_anonymity; /** * Function to get a random item with high replication score from * the database, lowering the item's replication score. Returns a * single, not expired, random item from those with the highest * replication counters. The item's replication counter is * decremented by one IF it was positive before. */ PluginRandomGet replication_get; /** * Function to get a random expired item or, if none are expired, one * with a low priority. */ PluginRandomGet expiration_get; /** * Delete the database. The next operation is * guaranteed to be unloading of the module. */ PluginDrop drop; }; #endif