2 This file is part of GNUnet
3 (C) 2009, 2011 Christian Grothoff (and other contributing authors)
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13 General Public License for more details.
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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, int delta);
55 * The datastore service will pass a pointer to a struct
56 * of this type as the first and only argument to the
57 * entry point of each datastore plugin.
59 struct GNUNET_DATASTORE_PluginEnvironment
62 * Configuration to use.
64 const struct GNUNET_CONFIGURATION_Handle *cfg;
67 * Function to call on disk utilization change.
69 DiskUtilizationChange duc;
80 * An processor over a set of items stored in the datastore.
83 * @param key key for the content
84 * @param size number of bytes in data
85 * @param data content stored
86 * @param type type of the content
87 * @param priority priority of the content
88 * @param anonymity anonymity-level for the content
89 * @param expiration expiration time for the content
90 * @param uid unique identifier for the datum
92 * @return GNUNET_OK to keep the item
93 * GNUNET_NO to delete the item
95 typedef int (*PluginDatumProcessor) (void *cls, const struct GNUNET_HashCode * key,
96 uint32_t size, const void *data,
97 enum GNUNET_BLOCK_Type type,
98 uint32_t priority, uint32_t anonymity,
99 struct GNUNET_TIME_Absolute expiration,
103 * Get an estimate of how much space the database is
107 * @return number of bytes used on disk
109 typedef unsigned long long (*PluginEstimateSize) (void *cls);
113 * Store an item in the datastore. If the item is already present,
114 * the priorities and replication levels are summed up and the higher
115 * expiration time and lower anonymity level is used.
118 * @param key key for the item
119 * @param size number of bytes in data
120 * @param data content stored
121 * @param type type of the content
122 * @param priority priority of the content
123 * @param anonymity anonymity-level for the content
124 * @param replication replication-level for the content
125 * @param expiration expiration time for the content
126 * @param msg set to an error message (on failure)
127 * @return GNUNET_OK on success,
128 * GNUNET_SYSERR on failure
130 typedef int (*PluginPut) (void *cls, const struct GNUNET_HashCode * key, uint32_t size,
131 const void *data, enum GNUNET_BLOCK_Type type,
132 uint32_t priority, uint32_t anonymity,
133 uint32_t replication,
134 struct GNUNET_TIME_Absolute expiration, char **msg);
138 * An processor over a set of keys stored in the datastore.
141 * @param key key in the data store
142 * @param count how many values are stored under this key in the datastore
144 typedef void (*PluginKeyProcessor) (void *cls,
145 const struct GNUNET_HashCode *key,
150 * Get all of the keys in the datastore.
153 * @param proc function to call on each key
154 * @param proc_cls closure for proc
156 typedef void (*PluginGetKeys) (void *cls,
157 PluginKeyProcessor proc, void *proc_cls);
161 * Get one of the results for a particular key in the datastore.
164 * @param offset offset of the result (modulo num-results);
165 * specific ordering does not matter for the offset
166 * @param key key to match, never NULL
167 * @param vhash hash of the value, maybe NULL (to
168 * match all values that have the right key).
169 * Note that for DBlocks there is no difference
170 * betwen key and vhash, but for other blocks
172 * @param type entries of which type are relevant?
173 * Use 0 for any type.
174 * @param min find the smallest key that is larger than the given min,
175 * NULL for no minimum (return smallest key)
176 * @param proc function to call on the matching value;
177 * proc should be called with NULL if there is no result
178 * @param proc_cls closure for proc
180 typedef void (*PluginGetKey) (void *cls, uint64_t offset,
181 const struct GNUNET_HashCode * key,
182 const struct GNUNET_HashCode * vhash,
183 enum GNUNET_BLOCK_Type type,
184 PluginDatumProcessor proc, void *proc_cls);
188 * Get a random item (additional constraints may apply depending on
189 * the specific implementation). Calls 'proc' with all values ZERO or
190 * NULL if no item applies, otherwise 'proc' is called once and only
194 * @param proc function to call the value (once only).
195 * @param proc_cls closure for proc
197 typedef void (*PluginGetRandom) (void *cls, PluginDatumProcessor proc,
204 * Update the priority for a particular key in the datastore. If
205 * the expiration time in value is different than the time found in
206 * the datastore, the higher value should be kept. For the
207 * anonymity level, the lower value is to be used. The specified
208 * priority should be added to the existing priority, ignoring the
212 * @param uid unique identifier of the datum
213 * @param delta by how much should the priority
214 * change? If priority + delta < 0 the
215 * priority should be set to 0 (never go
217 * @param expire new expiration time should be the
218 * MAX of any existing expiration time and
220 * @param msg set to an error message (on error)
221 * @return GNUNET_OK on success
223 typedef int (*PluginUpdate) (void *cls, uint64_t uid, int delta,
224 struct GNUNET_TIME_Absolute expire, char **msg);
228 * Select a single item from the datastore at the specified offset
229 * (among those applicable).
232 * @param offset offset of the result (modulo num-results);
233 * specific ordering does not matter for the offset
234 * @param type entries of which type should be considered?
235 * Must not be zero (ANY).
236 * @param proc function to call on the matching value
237 * @param proc_cls closure for proc
239 typedef void (*PluginGetType) (void *cls, uint64_t offset,
240 enum GNUNET_BLOCK_Type type,
241 PluginDatumProcessor proc, void *proc_cls);
249 typedef void (*PluginDrop) (void *cls);
254 * Each plugin is required to return a pointer to a struct of this
255 * type as the return value from its entry point.
257 struct GNUNET_DATASTORE_PluginFunctions
261 * Closure to use for all of the following callbacks
262 * (except "next_request").
267 * Calculate the current on-disk size of the SQ store. Estimates
268 * are fine, if that's the only thing available.
270 PluginEstimateSize estimate_size;
273 * Function to store an item in the datastore.
278 * Update the priority for a particular key in the datastore. If
279 * the expiration time in value is different than the time found in
280 * the datastore, the higher value should be kept. For the
281 * anonymity level, the lower value is to be used. The specified
282 * priority should be added to the existing priority, ignoring the
288 * Get a particular datum matching a given hash from the datastore.
290 PluginGetKey get_key;
293 * Get datum (of the specified type) with anonymity level zero.
294 * This function is allowed to ignore the 'offset' argument
295 * and instead return a random result (with zero anonymity of
296 * the correct type) if implementing an offset is expensive.
298 PluginGetType get_zero_anonymity;
301 * Function to get a random item with high replication score from
302 * the database, lowering the item's replication score. Returns a
303 * single random item from those with the highest replication
304 * counters. The item's replication counter is decremented by one
305 * IF it was positive before.
307 PluginGetRandom get_replication;
310 * Function to get a random expired item or, if none are expired,
311 * either the oldest entry or one with a low priority (depending
312 * on what was efficiently implementable).
314 PluginGetRandom get_expiration;
317 * Delete the database. The next operation is
318 * guaranteed to be unloading of the module.
323 * Iterate over all keys in the database.
325 PluginGetKeys get_keys;