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_scheduler_lib.h"
35 #include "gnunet_datastore_service.h"
39 * How many bytes of overhead will we assume per entry
42 #define GNUNET_DATASTORE_ENTRY_OVERHEAD 256
46 * The datastore service will pass a pointer to a struct
47 * of this type as the first and only argument to the
48 * entry point of each datastore plugin.
50 struct GNUNET_DATASTORE_PluginEnvironment
53 * Configuration to use.
55 const struct GNUNET_CONFIGURATION_Handle *cfg;
60 struct GNUNET_SCHEDULER_Handle *sched;
66 * Function invoked on behalf of a "PluginIterator"
67 * asking the database plugin to call the iterator
70 * @param next_cls whatever argument was given
71 * to the PluginIterator as "next_cls".
72 * @param end_it set to GNUNET_YES if we
73 * should terminate the iteration early
74 * (iterator should be still called once more
75 * to signal the end of the iteration).
77 typedef void (*PluginNextRequest)(void *next_cls,
82 * An iterator over a set of items stored in the datastore.
85 * @param next_cls closure to pass to the "next" function.
86 * @param key key for the content
87 * @param size number of bytes in data
88 * @param data content stored
89 * @param type type of the content
90 * @param priority priority of the content
91 * @param anonymity anonymity-level for the content
92 * @param expiration expiration time for the content
93 * @param uid unique identifier for the datum;
94 * maybe 0 if no unique identifier is available
96 * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue
97 * (continue on call to "next", of course),
98 * GNUNET_NO to delete the item and continue (if supported)
100 typedef int (*PluginIterator) (void *cls,
102 const GNUNET_HashCode * key,
108 struct GNUNET_TIME_Absolute
113 * Get an estimate of how much space the database is
117 * @return number of bytes used on disk
119 typedef unsigned long long (*PluginGetSize) (void *cls);
123 * Store an item in the datastore. If the item is already present,
124 * the priorities are summed up and the higher expiration time and
125 * lower anonymity level is used.
128 * @param key key for the item
129 * @param size number of bytes in data
130 * @param data content stored
131 * @param type type of the content
132 * @param priority priority of the content
133 * @param anonymity anonymity-level for the content
134 * @param expiration expiration time for the content
135 * @param msg set to an error message (on failure)
136 * @return GNUNET_OK on success, GNUNET_NO if the content
137 * was already present (and may have been updated);
138 * GNUNET_SYSERR on failure
140 typedef int (*PluginPut) (void *cls,
141 const GNUNET_HashCode * key,
147 struct GNUNET_TIME_Absolute expiration,
152 * Iterate over the results for a particular key
156 * @param key maybe NULL (to match all entries)
157 * @param vhash hash of the value, maybe NULL (to
158 * match all values that have the right key).
159 * Note that for DBlocks there is no difference
160 * betwen key and vhash, but for other blocks
162 * @param type entries of which type are relevant?
163 * Use 0 for any type.
164 * @param iter function to call on each matching value; however,
165 * after the first call to "iter", the plugin must wait
166 * until "NextRequest" was called before giving the iterator
167 * the next item; finally, the "iter" should be called once
168 * once with a NULL value at the end ("next_cls" should be NULL
169 * for that last call)
170 * @param iter_cls closure for iter
172 typedef void (*PluginGet) (void *cls,
173 const GNUNET_HashCode * key,
174 const GNUNET_HashCode * vhash,
176 PluginIterator iter, void *iter_cls);
180 * Update the priority for a particular key in the datastore. If
181 * the expiration time in value is different than the time found in
182 * the datastore, the higher value should be kept. For the
183 * anonymity level, the lower value is to be used. The specified
184 * priority should be added to the existing priority, ignoring the
187 * Note that it is possible for multiple values to match this put.
188 * In that case, all of the respective values are updated.
191 * @param uid unique identifier of the datum
192 * @param delta by how much should the priority
193 * change? If priority + delta < 0 the
194 * priority should be set to 0 (never go
196 * @param expire new expiration time should be the
197 * MAX of any existing expiration time and
199 * @param msg set to an error message (on error)
200 * @return GNUNET_OK on success
202 typedef int (*PluginUpdate) (void *cls,
204 int delta, struct GNUNET_TIME_Absolute expire,
209 * Select a subset of the items in the datastore and call
210 * the given iterator for each of them.
213 * @param type entries of which type should be considered?
214 * Use 0 for any type.
215 * @param iter function to call on each matching value; however,
216 * after the first call to "iter", the plugin must wait
217 * until "NextRequest" was called before giving the iterator
218 * the next item; finally, the "iter" should be called once
219 * once with a NULL value at the end ("next_cls" should be NULL
220 * for that last call)
221 * @param iter_cls closure for iter
223 typedef void (*PluginSelector) (void *cls,
233 typedef void (*PluginDrop) (void *cls);
238 * Each plugin is required to return a pointer to a struct of this
239 * type as the return value from its entry point.
241 struct GNUNET_DATASTORE_PluginFunctions
245 * Closure to use for all of the following callbacks
246 * (except "next_request").
251 * Get the current on-disk size of the SQ store. Estimates are
252 * fine, if that's the only thing available.
254 PluginGetSize get_size;
257 * Function to store an item in the datastore.
262 * Function called by iterators whenever they want the next value;
263 * note that unlike all of the other callbacks, this one does get a
264 * the "next_cls" closure which is usually different from the "cls"
265 * member of this struct!
267 PluginNextRequest next_request;
270 * Function to iterate over the results for a particular key
276 * Update the priority for a particular key in the datastore. If
277 * the expiration time in value is different than the time found in
278 * the datastore, the higher value should be kept. For the
279 * anonymity level, the lower value is to be used. The specified
280 * priority should be added to the existing priority, ignoring the
286 * Iterate over the items in the datastore in ascending
289 PluginSelector iter_low_priority;
292 * Iterate over content with anonymity zero.
294 PluginSelector iter_zero_anonymity;
297 * Iterate over the items in the datastore in ascending order of
300 PluginSelector iter_ascending_expiration;
303 * Iterate over the items in the datastore in migration
304 * order. Call the given function on the next item only
305 * (and then signal 'end' with a second call). This is
306 * a significant difference from all the other iterators!
308 PluginSelector iter_migration_order;
311 * Iterate over all the items in the datastore
312 * as fast as possible in a single transaction
313 * (can lock datastore while this happens, focus
314 * is on doing it fast).
316 PluginSelector iter_all_now;
319 * Delete the database. The next operation is
320 * guaranteed to be unloading of the module.