2 This file is part of GNUnet
3 (C) 2009 Christian Grothoff (and other contributing authors)
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22 * @file datastore/plugin_datastore.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;
70 struct GNUNET_SCHEDULER_Handle *sched;
73 * Function to call on disk utilization change.
75 DiskUtilizationChange duc;
86 * Function invoked on behalf of a "PluginIterator"
87 * asking the database plugin to call the iterator
90 * @param next_cls whatever argument was given
91 * to the PluginIterator as "next_cls".
92 * @param end_it set to GNUNET_YES if we
93 * should terminate the iteration early
94 * (iterator should be still called once more
95 * to signal the end of the iteration).
97 typedef void (*PluginNextRequest)(void *next_cls,
102 * An iterator over a set of items stored in the datastore.
105 * @param next_cls closure to pass to the "next" function.
106 * @param key key for the content
107 * @param size number of bytes in data
108 * @param data content stored
109 * @param type type of the content
110 * @param priority priority of the content
111 * @param anonymity anonymity-level for the content
112 * @param expiration expiration time for the content
113 * @param uid unique identifier for the datum;
114 * maybe 0 if no unique identifier is available
116 * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue
117 * (continue on call to "next", of course),
118 * GNUNET_NO to delete the item and continue (if supported)
120 typedef int (*PluginIterator) (void *cls,
122 const GNUNET_HashCode * key,
125 enum GNUNET_BLOCK_Type type,
128 struct GNUNET_TIME_Absolute
133 * Get an estimate of how much space the database is
137 * @return number of bytes used on disk
139 typedef unsigned long long (*PluginGetSize) (void *cls);
143 * Store an item in the datastore. If the item is already present,
144 * the priorities are summed up and the higher expiration time and
145 * lower anonymity level is used.
148 * @param key key for the item
149 * @param size number of bytes in data
150 * @param data content stored
151 * @param type type of the content
152 * @param priority priority of the content
153 * @param anonymity anonymity-level for the content
154 * @param expiration expiration time for the content
155 * @param msg set to an error message (on failure)
156 * @return GNUNET_OK on success, GNUNET_NO if the content
157 * was already present (and may have been updated);
158 * GNUNET_SYSERR on failure
160 typedef int (*PluginPut) (void *cls,
161 const GNUNET_HashCode * key,
164 enum GNUNET_BLOCK_Type type,
167 struct GNUNET_TIME_Absolute expiration,
172 * Iterate over the results for a particular key
176 * @param key maybe NULL (to match all entries)
177 * @param vhash hash of the value, maybe NULL (to
178 * match all values that have the right key).
179 * Note that for DBlocks there is no difference
180 * betwen key and vhash, but for other blocks
182 * @param type entries of which type are relevant?
183 * Use 0 for any type.
184 * @param iter function to call on each matching value; however,
185 * after the first call to "iter", the plugin must wait
186 * until "NextRequest" was called before giving the iterator
187 * the next item; finally, the "iter" should be called once
188 * once with a NULL value at the end ("next_cls" should be NULL
189 * for that last call)
190 * @param iter_cls closure for iter
192 typedef void (*PluginGet) (void *cls,
193 const GNUNET_HashCode * key,
194 const GNUNET_HashCode * vhash,
195 enum GNUNET_BLOCK_Type type,
196 PluginIterator iter, void *iter_cls);
200 * Update the priority for a particular key in the datastore. If
201 * the expiration time in value is different than the time found in
202 * the datastore, the higher value should be kept. For the
203 * anonymity level, the lower value is to be used. The specified
204 * priority should be added to the existing priority, ignoring the
207 * Note that it is possible for multiple values to match this put.
208 * In that case, all of the respective values are updated.
211 * @param uid unique identifier of the datum
212 * @param delta by how much should the priority
213 * change? If priority + delta < 0 the
214 * priority should be set to 0 (never go
216 * @param expire new expiration time should be the
217 * MAX of any existing expiration time and
219 * @param msg set to an error message (on error)
220 * @return GNUNET_OK on success
222 typedef int (*PluginUpdate) (void *cls,
224 int delta, struct GNUNET_TIME_Absolute expire,
229 * Select a subset of the items in the datastore and call
230 * the given iterator for each of them.
233 * @param type entries of which type should be considered?
234 * Use 0 for any type.
235 * @param iter function to call on each matching value; however,
236 * after the first call to "iter", the plugin must wait
237 * until "NextRequest" was called before giving the iterator
238 * the next item; finally, the "iter" should be called once
239 * once with a NULL value at the end ("next_cls" should be NULL
240 * for that last call)
241 * @param iter_cls closure for iter
243 typedef void (*PluginSelector) (void *cls,
244 enum GNUNET_BLOCK_Type type,
253 typedef void (*PluginDrop) (void *cls);
258 * Each plugin is required to return a pointer to a struct of this
259 * type as the return value from its entry point.
261 struct GNUNET_DATASTORE_PluginFunctions
265 * Closure to use for all of the following callbacks
266 * (except "next_request").
271 * Get the current on-disk size of the SQ store. Estimates are
272 * fine, if that's the only thing available.
274 PluginGetSize get_size;
277 * Function to store an item in the datastore.
282 * Function called by iterators whenever they want the next value;
283 * note that unlike all of the other callbacks, this one does get a
284 * the "next_cls" closure which is usually different from the "cls"
285 * member of this struct!
287 PluginNextRequest next_request;
290 * Function to iterate over the results for a particular key
296 * Update the priority for a particular key in the datastore. If
297 * the expiration time in value is different than the time found in
298 * the datastore, the higher value should be kept. For the
299 * anonymity level, the lower value is to be used. The specified
300 * priority should be added to the existing priority, ignoring the
306 * Iterate over the items in the datastore in ascending
309 PluginSelector iter_low_priority;
312 * Iterate over content with anonymity zero.
314 PluginSelector iter_zero_anonymity;
317 * Iterate over the items in the datastore in ascending order of
320 PluginSelector iter_ascending_expiration;
323 * Iterate over the items in the datastore in migration
324 * order. Call the given function on the next item only
325 * (and then signal 'end' with a second call). This is
326 * a significant difference from all the other iterators!
328 PluginSelector iter_migration_order;
331 * Iterate over all the items in the datastore
332 * as fast as possible in a single transaction
333 * (can lock datastore while this happens, focus
334 * is on doing it fast).
336 PluginSelector iter_all_now;
339 * Delete the database. The next operation is
340 * guaranteed to be unloading of the module.