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, 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,
96 const GNUNET_HashCode * key,
99 enum GNUNET_BLOCK_Type type,
102 struct GNUNET_TIME_Absolute
103 expiration, uint64_t uid);
106 * Get an estimate of how much space the database is
110 * @return number of bytes used on disk
112 typedef unsigned long long (*PluginEstimateSize) (void *cls);
116 * Store an item in the datastore. If the item is already present,
117 * the priorities and replication levels are summed up and the higher
118 * expiration time and lower anonymity level is used.
121 * @param key key for the item
122 * @param size number of bytes in data
123 * @param data content stored
124 * @param type type of the content
125 * @param priority priority of the content
126 * @param anonymity anonymity-level for the content
127 * @param replication replication-level for the content
128 * @param expiration expiration time for the content
129 * @param msg set to an error message (on failure)
130 * @return GNUNET_OK on success,
131 * GNUNET_SYSERR on failure
133 typedef int (*PluginPut) (void *cls,
134 const GNUNET_HashCode * key,
137 enum GNUNET_BLOCK_Type type,
140 uint32_t replication,
141 struct GNUNET_TIME_Absolute expiration, char **msg);
145 * Get one of the results for a particular key in the datastore.
148 * @param offset offset of the result (modulo num-results);
149 * specific ordering does not matter for the offset
150 * @param key key to match, never NULL
151 * @param vhash hash of the value, maybe NULL (to
152 * match all values that have the right key).
153 * Note that for DBlocks there is no difference
154 * betwen key and vhash, but for other blocks
156 * @param type entries of which type are relevant?
157 * Use 0 for any type.
158 * @param proc function to call on the matching value;
159 * proc should be called with NULL if there is no result
160 * @param proc_cls closure for proc
162 typedef void (*PluginGetKey) (void *cls,
164 const GNUNET_HashCode * key,
165 const GNUNET_HashCode * vhash,
166 enum GNUNET_BLOCK_Type type,
167 PluginDatumProcessor proc, void *proc_cls);
172 * Get a random item (additional constraints may apply depending on
173 * the specific implementation). Calls 'proc' with all values ZERO or
174 * NULL if no item applies, otherwise 'proc' is called once and only
178 * @param proc function to call the value (once only).
179 * @param proc_cls closure for proc
181 typedef void (*PluginGetRandom) (void *cls,
182 PluginDatumProcessor proc, void *proc_cls);
186 * Update the priority for a particular key in the datastore. If
187 * the expiration time in value is different than the time found in
188 * the datastore, the higher value should be kept. For the
189 * anonymity level, the lower value is to be used. The specified
190 * priority should be added to the existing priority, ignoring the
193 * Note that it is possible for multiple values to match this put.
194 * In that case, all of the respective values are updated.
197 * @param uid unique identifier of the datum
198 * @param delta by how much should the priority
199 * change? If priority + delta < 0 the
200 * priority should be set to 0 (never go
202 * @param expire new expiration time should be the
203 * MAX of any existing expiration time and
205 * @param msg set to an error message (on error)
206 * @return GNUNET_OK on success
208 typedef int (*PluginUpdate) (void *cls,
211 struct GNUNET_TIME_Absolute expire, char **msg);
215 * Select a single item from the datastore at the specified offset
216 * (among those applicable).
219 * @param offset offset of the result (modulo num-results);
220 * specific ordering does not matter for the offset
221 * @param type entries of which type should be considered?
222 * Must not be zero (ANY).
223 * @param proc function to call on the matching value
224 * @param proc_cls closure for proc
226 typedef void (*PluginGetType) (void *cls,
228 enum GNUNET_BLOCK_Type type,
229 PluginDatumProcessor proc, void *proc_cls);
237 typedef void (*PluginDrop) (void *cls);
242 * Each plugin is required to return a pointer to a struct of this
243 * type as the return value from its entry point.
245 struct GNUNET_DATASTORE_PluginFunctions
249 * Closure to use for all of the following callbacks
250 * (except "next_request").
255 * Calculate the current on-disk size of the SQ store. Estimates
256 * are fine, if that's the only thing available.
258 PluginEstimateSize estimate_size;
261 * Function to store an item in the datastore.
266 * Update the priority for a particular key in the datastore. If
267 * the expiration time in value is different than the time found in
268 * the datastore, the higher value should be kept. For the
269 * anonymity level, the lower value is to be used. The specified
270 * priority should be added to the existing priority, ignoring the
276 * Get a particular datum matching a given hash from the datastore.
278 PluginGetKey get_key;
281 * Get datum (of the specified type) with anonymity level zero.
282 * This function is allowed to ignore the 'offset' argument
283 * and instead return a random result (with zero anonymity of
284 * the correct type) if implementing an offset is expensive.
286 PluginGetType get_zero_anonymity;
289 * Function to get a random item with high replication score from
290 * the database, lowering the item's replication score. Returns a
291 * single random item from those with the highest replication
292 * counters. The item's replication counter is decremented by one
293 * IF it was positive before.
295 PluginGetRandom get_replication;
298 * Function to get a random expired item or, if none are expired,
299 * either the oldest entry or one with a low priority (depending
300 * on what was efficiently implementable).
302 PluginGetRandom get_expiration;
305 * Delete the database. The next operation is
306 * guaranteed to be unloading of the module.