2 This file is part of GNUnet
3 (C) 2009, 2011 Christian Grothoff (and other contributing authors)
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22 * @file include/gnunet_datastore_plugin.h
23 * @brief API for the database backend plugins.
24 * @author Christian Grothoff
26 #ifndef PLUGIN_DATASTORE_H
27 #define PLUGIN_DATASTORE_H
29 #include "gnunet_block_lib.h"
30 #include "gnunet_configuration_lib.h"
31 #include "gnunet_datastore_service.h"
32 #include "gnunet_statistics_service.h"
33 #include "gnunet_scheduler_lib.h"
37 * How many bytes of overhead will we assume per entry
38 * in any DB (for reservations)?
40 #define GNUNET_DATASTORE_ENTRY_OVERHEAD 256
44 * Function invoked to notify service of disk utilization
48 * @param delta change in disk utilization,
49 * 0 for "reset to empty"
51 typedef void (*DiskUtilizationChange)(void *cls,
56 * The datastore service will pass a pointer to a struct
57 * of this type as the first and only argument to the
58 * entry point of each datastore plugin.
60 struct GNUNET_DATASTORE_PluginEnvironment
63 * Configuration to use.
65 const struct GNUNET_CONFIGURATION_Handle *cfg;
68 * Function to call on disk utilization change.
70 DiskUtilizationChange duc;
81 * Function invoked on behalf of a "PluginIterator"
82 * asking the database plugin to call the iterator
85 * @param next_cls whatever argument was given
86 * to the PluginIterator as "next_cls".
87 * @param end_it set to GNUNET_YES if we
88 * should terminate the iteration early
89 * (iterator should be still called once more
90 * to signal the end of the iteration).
92 typedef void (*PluginNextRequest)(void *next_cls,
97 * An iterator over a set of items stored in the datastore.
100 * @param next_cls closure to pass to the "next" function.
101 * @param key key for the content
102 * @param size number of bytes in data
103 * @param data content stored
104 * @param type type of the content
105 * @param priority priority of the content
106 * @param anonymity anonymity-level for the content
107 * @param expiration expiration time for the content
108 * @param uid unique identifier for the datum;
109 * maybe 0 if no unique identifier is available
111 * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue
112 * (continue on call to "next", of course),
113 * GNUNET_NO to delete the item and continue (if supported)
115 typedef int (*PluginIterator) (void *cls,
117 const GNUNET_HashCode * key,
120 enum GNUNET_BLOCK_Type type,
123 struct GNUNET_TIME_Absolute
128 * Get an estimate of how much space the database is
132 * @return number of bytes used on disk
134 typedef unsigned long long (*PluginGetSize) (void *cls);
138 * Store an item in the datastore. If the item is already present,
139 * the priorities and replication levels are summed up and the higher
140 * expiration time and lower anonymity level is used.
143 * @param key key for the item
144 * @param size number of bytes in data
145 * @param data content stored
146 * @param type type of the content
147 * @param priority priority of the content
148 * @param anonymity anonymity-level for the content
149 * @param replication replication-level for the content
150 * @param expiration expiration time for the content
151 * @param msg set to an error message (on failure)
152 * @return GNUNET_OK on success, GNUNET_NO if the content
153 * was already present (and may have been updated);
154 * GNUNET_SYSERR on failure
156 typedef int (*PluginPut) (void *cls,
157 const GNUNET_HashCode * key,
160 enum GNUNET_BLOCK_Type type,
163 uint32_t replication,
164 struct GNUNET_TIME_Absolute expiration,
169 * Iterate over the results for a particular key
173 * @param key maybe NULL (to match all entries)
174 * @param vhash hash of the value, maybe NULL (to
175 * match all values that have the right key).
176 * Note that for DBlocks there is no difference
177 * betwen key and vhash, but for other blocks
179 * @param type entries of which type are relevant?
180 * Use 0 for any type.
181 * @param iter function to call on each matching value; however,
182 * after the first call to "iter", the plugin must wait
183 * until "NextRequest" was called before giving the iterator
184 * the next item; finally, the "iter" should be called once
185 * once with a NULL value at the end ("next_cls" should be NULL
186 * for that last call)
187 * @param iter_cls closure for iter
189 typedef void (*PluginGet) (void *cls,
190 const GNUNET_HashCode * key,
191 const GNUNET_HashCode * vhash,
192 enum GNUNET_BLOCK_Type type,
193 PluginIterator iter, void *iter_cls);
198 * Get a random item for replication. Returns a single,
199 * not expired, random item
200 * from those with the highest replication counters. The item's
201 * replication counter is decremented by one IF it was positive before.
202 * Call 'iter' with all values ZERO or NULL if the datastore is empty.
205 * @param iter function to call the value (once only).
206 * @param iter_cls closure for iter
208 typedef void (*PluginReplicationGet) (void *cls,
209 PluginIterator iter, void *iter_cls);
213 * Update the priority for a particular key in the datastore. If
214 * the expiration time in value is different than the time found in
215 * the datastore, the higher value should be kept. For the
216 * anonymity level, the lower value is to be used. The specified
217 * priority should be added to the existing priority, ignoring the
220 * Note that it is possible for multiple values to match this put.
221 * In that case, all of the respective values are updated.
224 * @param uid unique identifier of the datum
225 * @param delta by how much should the priority
226 * change? If priority + delta < 0 the
227 * priority should be set to 0 (never go
229 * @param expire new expiration time should be the
230 * MAX of any existing expiration time and
232 * @param msg set to an error message (on error)
233 * @return GNUNET_OK on success
235 typedef int (*PluginUpdate) (void *cls,
237 int delta, struct GNUNET_TIME_Absolute expire,
242 * Select a subset of the items in the datastore and call
243 * the given iterator for each of them.
246 * @param type entries of which type should be considered?
247 * Use 0 for any type.
248 * @param iter function to call on each matching value; however,
249 * after the first call to "iter", the plugin must wait
250 * until "NextRequest" was called before giving the iterator
251 * the next item; finally, the "iter" should be called once
252 * once with a NULL value at the end ("next_cls" should be NULL
253 * for that last call)
254 * @param iter_cls closure for iter
256 typedef void (*PluginSelector) (void *cls,
257 enum GNUNET_BLOCK_Type type,
266 typedef void (*PluginDrop) (void *cls);
271 * Each plugin is required to return a pointer to a struct of this
272 * type as the return value from its entry point.
274 struct GNUNET_DATASTORE_PluginFunctions
278 * Closure to use for all of the following callbacks
279 * (except "next_request").
284 * Get the current on-disk size of the SQ store. Estimates are
285 * fine, if that's the only thing available.
287 PluginGetSize get_size;
290 * Function to store an item in the datastore.
295 * Function called by iterators whenever they want the next value;
296 * note that unlike all of the other callbacks, this one does get a
297 * the "next_cls" closure which is usually different from the "cls"
298 * member of this struct!
300 PluginNextRequest next_request;
303 * Function to iterate over the results for a particular key
309 * Function to get a random item with high replication score from
310 * the database, lowering the item's replication score.
312 PluginReplicationGet replication_get;
315 * Update the priority for a particular key in the datastore. If
316 * the expiration time in value is different than the time found in
317 * the datastore, the higher value should be kept. For the
318 * anonymity level, the lower value is to be used. The specified
319 * priority should be added to the existing priority, ignoring the
325 * Iterate over the items in the datastore in ascending
328 PluginSelector iter_low_priority;
331 * Iterate over content with anonymity zero.
333 PluginSelector iter_zero_anonymity;
336 * Iterate over the items in the datastore in ascending order of
339 PluginSelector iter_ascending_expiration;
342 * Iterate over the items in the datastore in migration
343 * order. Call the given function on the next item only
344 * (and then signal 'end' with a second call). This is
345 * a significant difference from all the other iterators!
347 PluginSelector iter_migration_order;
350 * Iterate over all the items in the datastore
351 * as fast as possible in a single transaction
352 * (can lock datastore while this happens, focus
353 * is on doing it fast).
355 PluginSelector iter_all_now;
358 * Delete the database. The next operation is
359 * guaranteed to be unloading of the module.