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 * An processor over a set of items stored in the datastore.
84 * @param key key for the content
85 * @param size number of bytes in data
86 * @param data content stored
87 * @param type type of the content
88 * @param priority priority of the content
89 * @param anonymity anonymity-level for the content
90 * @param expiration expiration time for the content
91 * @param uid unique identifier for the datum
93 * @return GNUNET_OK to keep the item
94 * GNUNET_NO to delete the item
96 typedef int (*PluginDatumProcessor) (void *cls,
97 const GNUNET_HashCode * key,
100 enum GNUNET_BLOCK_Type type,
103 struct GNUNET_TIME_Absolute
108 * Get an estimate of how much space the database is
112 * @return number of bytes used on disk
114 typedef unsigned long long (*PluginEstimateSize) (void *cls);
118 * Store an item in the datastore. If the item is already present,
119 * the priorities and replication levels are summed up and the higher
120 * expiration time and lower anonymity level is used.
123 * @param key key for the item
124 * @param size number of bytes in data
125 * @param data content stored
126 * @param type type of the content
127 * @param priority priority of the content
128 * @param anonymity anonymity-level for the content
129 * @param replication replication-level for the content
130 * @param expiration expiration time for the content
131 * @param msg set to an error message (on failure)
132 * @return GNUNET_OK on success,
133 * GNUNET_SYSERR on failure
135 typedef int (*PluginPut) (void *cls,
136 const GNUNET_HashCode * key,
139 enum GNUNET_BLOCK_Type type,
142 uint32_t replication,
143 struct GNUNET_TIME_Absolute expiration,
148 * Get one of the results for a particular key in the datastore.
151 * @param offset offset of the result (modulo num-results);
152 * specific ordering does not matter for the offset
153 * @param key key to match, never NULL
154 * @param vhash hash of the value, maybe NULL (to
155 * match all values that have the right key).
156 * Note that for DBlocks there is no difference
157 * betwen key and vhash, but for other blocks
159 * @param type entries of which type are relevant?
160 * Use 0 for any type.
161 * @param proc function to call on the matching value;
162 * proc should be called with NULL if there is no result
163 * @param proc_cls closure for proc
165 typedef void (*PluginGetKey) (void *cls,
167 const GNUNET_HashCode *key,
168 const GNUNET_HashCode *vhash,
169 enum GNUNET_BLOCK_Type type,
170 PluginDatumProcessor proc, void *proc_cls);
175 * Get a random item (additional constraints may apply depending on
176 * the specific implementation). Calls 'proc' with all values ZERO or
177 * NULL if no item applies, otherwise 'proc' is called once and only
181 * @param proc function to call the value (once only).
182 * @param proc_cls closure for proc
184 typedef void (*PluginGetRandom) (void *cls,
185 PluginDatumProcessor proc, void *proc_cls);
189 * Update the priority for a particular key in the datastore. If
190 * the expiration time in value is different than the time found in
191 * the datastore, the higher value should be kept. For the
192 * anonymity level, the lower value is to be used. The specified
193 * priority should be added to the existing priority, ignoring the
196 * Note that it is possible for multiple values to match this put.
197 * In that case, all of the respective values are updated.
200 * @param uid unique identifier of the datum
201 * @param delta by how much should the priority
202 * change? If priority + delta < 0 the
203 * priority should be set to 0 (never go
205 * @param expire new expiration time should be the
206 * MAX of any existing expiration time and
208 * @param msg set to an error message (on error)
209 * @return GNUNET_OK on success
211 typedef int (*PluginUpdate) (void *cls,
214 struct GNUNET_TIME_Absolute expire,
219 * Select a single item from the datastore at the specified offset
220 * (among those applicable).
223 * @param offset offset of the result (modulo num-results);
224 * specific ordering does not matter for the offset
225 * @param type entries of which type should be considered?
226 * Must not be zero (ANY).
227 * @param proc function to call on the matching value
228 * @param proc_cls closure for proc
230 typedef void (*PluginGetType) (void *cls,
232 enum GNUNET_BLOCK_Type type,
233 PluginDatumProcessor proc,
242 typedef void (*PluginDrop) (void *cls);
247 * Each plugin is required to return a pointer to a struct of this
248 * type as the return value from its entry point.
250 struct GNUNET_DATASTORE_PluginFunctions
254 * Closure to use for all of the following callbacks
255 * (except "next_request").
260 * Calculate the current on-disk size of the SQ store. Estimates
261 * are fine, if that's the only thing available.
263 PluginEstimateSize estimate_size;
266 * Function to store an item in the datastore.
271 * Update the priority for a particular key in the datastore. If
272 * the expiration time in value is different than the time found in
273 * the datastore, the higher value should be kept. For the
274 * anonymity level, the lower value is to be used. The specified
275 * priority should be added to the existing priority, ignoring the
281 * Get a particular datum matching a given hash from the datastore.
283 PluginGetKey get_key;
286 * Get datum (of the specified type) with anonymity level zero.
288 PluginGetType get_zero_anonymity;
291 * Function to get a random item with high replication score from
292 * the database, lowering the item's replication score. Returns a
293 * single random item from those with the highest replication
294 * counters. The item's replication counter is decremented by one
295 * IF it was positive before.
297 PluginGetRandom get_replication;
300 * Function to get a random expired item or, if none are expired, one
301 * with a low priority.
303 PluginGetRandom get_expiration;
306 * Delete the database. The next operation is
307 * guaranteed to be unloading of the module.