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
27 * - consider defining enumeration or at least typedef
28 * for the type of "type" (instead of using uint32_t)
30 #ifndef PLUGIN_DATASTORE_H
31 #define PLUGIN_DATASTORE_H
33 #include "gnunet_configuration_lib.h"
34 #include "gnunet_datastore_service.h"
35 #include "gnunet_statistics_service.h"
36 #include "gnunet_scheduler_lib.h"
40 * How many bytes of overhead will we assume per entry
43 #define GNUNET_DATASTORE_ENTRY_OVERHEAD 256
47 * The datastore service will pass a pointer to a struct
48 * of this type as the first and only argument to the
49 * entry point of each datastore plugin.
51 struct GNUNET_DATASTORE_PluginEnvironment
54 * Configuration to use.
56 const struct GNUNET_CONFIGURATION_Handle *cfg;
61 struct GNUNET_SCHEDULER_Handle *sched;
67 * Function invoked on behalf of a "PluginIterator"
68 * asking the database plugin to call the iterator
71 * @param next_cls whatever argument was given
72 * to the PluginIterator as "next_cls".
73 * @param end_it set to GNUNET_YES if we
74 * should terminate the iteration early
75 * (iterator should be still called once more
76 * to signal the end of the iteration).
78 typedef void (*PluginNextRequest)(void *next_cls,
83 * An iterator over a set of items stored in the datastore.
86 * @param next_cls closure to pass to the "next" function.
87 * @param key key for the content
88 * @param size number of bytes in data
89 * @param data content stored
90 * @param type type of the content
91 * @param priority priority of the content
92 * @param anonymity anonymity-level for the content
93 * @param expiration expiration time for the content
94 * @param uid unique identifier for the datum;
95 * maybe 0 if no unique identifier is available
97 * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue
98 * (continue on call to "next", of course),
99 * GNUNET_NO to delete the item and continue (if supported)
101 typedef int (*PluginIterator) (void *cls,
103 const GNUNET_HashCode * key,
109 struct GNUNET_TIME_Absolute
114 * Get an estimate of how much space the database is
118 * @return number of bytes used on disk
120 typedef unsigned long long (*PluginGetSize) (void *cls);
124 * Store an item in the datastore. If the item is already present,
125 * the priorities are summed up and the higher expiration time and
126 * lower anonymity level is used.
129 * @param key key for the item
130 * @param size number of bytes in data
131 * @param data content stored
132 * @param type type of the content
133 * @param priority priority of the content
134 * @param anonymity anonymity-level for the content
135 * @param expiration expiration time for the content
136 * @param msg set to an error message (on failure)
137 * @return GNUNET_OK on success, GNUNET_NO if the content
138 * was already present (and may have been updated);
139 * GNUNET_SYSERR on failure
141 typedef int (*PluginPut) (void *cls,
142 const GNUNET_HashCode * key,
148 struct GNUNET_TIME_Absolute expiration,
153 * Iterate over the results for a particular key
157 * @param key maybe NULL (to match all entries)
158 * @param vhash hash of the value, maybe NULL (to
159 * match all values that have the right key).
160 * Note that for DBlocks there is no difference
161 * betwen key and vhash, but for other blocks
163 * @param type entries of which type are relevant?
164 * Use 0 for any type.
165 * @param iter function to call on each matching value; however,
166 * after the first call to "iter", the plugin must wait
167 * until "NextRequest" was called before giving the iterator
168 * the next item; finally, the "iter" should be called once
169 * once with a NULL value at the end ("next_cls" should be NULL
170 * for that last call)
171 * @param iter_cls closure for iter
173 typedef void (*PluginGet) (void *cls,
174 const GNUNET_HashCode * key,
175 const GNUNET_HashCode * vhash,
177 PluginIterator iter, void *iter_cls);
181 * Update the priority for a particular key in the datastore. If
182 * the expiration time in value is different than the time found in
183 * the datastore, the higher value should be kept. For the
184 * anonymity level, the lower value is to be used. The specified
185 * priority should be added to the existing priority, ignoring the
188 * Note that it is possible for multiple values to match this put.
189 * In that case, all of the respective values are updated.
192 * @param uid unique identifier of the datum
193 * @param delta by how much should the priority
194 * change? If priority + delta < 0 the
195 * priority should be set to 0 (never go
197 * @param expire new expiration time should be the
198 * MAX of any existing expiration time and
200 * @param msg set to an error message (on error)
201 * @return GNUNET_OK on success
203 typedef int (*PluginUpdate) (void *cls,
205 int delta, struct GNUNET_TIME_Absolute expire,
210 * Select a subset of the items in the datastore and call
211 * the given iterator for each of them.
214 * @param type entries of which type should be considered?
215 * Use 0 for any type.
216 * @param iter function to call on each matching value; however,
217 * after the first call to "iter", the plugin must wait
218 * until "NextRequest" was called before giving the iterator
219 * the next item; finally, the "iter" should be called once
220 * once with a NULL value at the end ("next_cls" should be NULL
221 * for that last call)
222 * @param iter_cls closure for iter
224 typedef void (*PluginSelector) (void *cls,
234 typedef void (*PluginDrop) (void *cls);
239 * Each plugin is required to return a pointer to a struct of this
240 * type as the return value from its entry point.
242 struct GNUNET_DATASTORE_PluginFunctions
246 * Closure to use for all of the following callbacks
247 * (except "next_request").
252 * Get the current on-disk size of the SQ store. Estimates are
253 * fine, if that's the only thing available.
255 PluginGetSize get_size;
258 * Function to store an item in the datastore.
263 * Function called by iterators whenever they want the next value;
264 * note that unlike all of the other callbacks, this one does get a
265 * the "next_cls" closure which is usually different from the "cls"
266 * member of this struct!
268 PluginNextRequest next_request;
271 * Function to iterate over the results for a particular key
277 * Update the priority for a particular key in the datastore. If
278 * the expiration time in value is different than the time found in
279 * the datastore, the higher value should be kept. For the
280 * anonymity level, the lower value is to be used. The specified
281 * priority should be added to the existing priority, ignoring the
287 * Iterate over the items in the datastore in ascending
290 PluginSelector iter_low_priority;
293 * Iterate over content with anonymity zero.
295 PluginSelector iter_zero_anonymity;
298 * Iterate over the items in the datastore in ascending order of
301 PluginSelector iter_ascending_expiration;
304 * Iterate over the items in the datastore in migration
305 * order. Call the given function on the next item only
306 * (and then signal 'end' with a second call). This is
307 * a significant difference from all the other iterators!
309 PluginSelector iter_migration_order;
312 * Iterate over all the items in the datastore
313 * as fast as possible in a single transaction
314 * (can lock datastore while this happens, focus
315 * is on doing it fast).
317 PluginSelector iter_all_now;
320 * Delete the database. The next operation is
321 * guaranteed to be unloading of the module.