aboutsummaryrefslogtreecommitdiff
path: root/src/include/gnunet_datastore_plugin.h
blob: f499cb82786a767a02bacd1c5b4cd2a1439cc75f (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
/*
     This file is part of GNUnet
     (C) 2009, 2011 Christian Grothoff (and other contributing authors)

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 2, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file include/gnunet_datastore_plugin.h
 * @brief API for the database backend plugins.
 * @author Christian Grothoff
 */
#ifndef PLUGIN_DATASTORE_H
#define PLUGIN_DATASTORE_H

#include "gnunet_block_lib.h"
#include "gnunet_configuration_lib.h"
#include "gnunet_datastore_service.h"
#include "gnunet_statistics_service.h"
#include "gnunet_scheduler_lib.h"


/**
 * How many bytes of overhead will we assume per entry
 * in any DB (for reservations)?
 */
#define GNUNET_DATASTORE_ENTRY_OVERHEAD 256


/**
 * Function invoked to notify service of disk utilization
 * changes.
 *
 * @param cls closure
 * @param delta change in disk utilization, 
 *        0 for "reset to empty"
 */
typedef void (*DiskUtilizationChange)(void *cls,
				      int delta);


/**
 * The datastore service will pass a pointer to a struct
 * of this type as the first and only argument to the
 * entry point of each datastore plugin.
 */
struct GNUNET_DATASTORE_PluginEnvironment
{
  /**
   * Configuration to use.
   */
  const struct GNUNET_CONFIGURATION_Handle *cfg;

  /**
   * Function to call on disk utilization change.
   */
  DiskUtilizationChange duc;

  /**
   * Closure.
   */
  void *cls;

};


/**
 * Function invoked on behalf of a "PluginIterator"
 * asking the database plugin to call the iterator
 * with the next item.
 *
 * @param next_cls whatever argument was given
 *        to the PluginIterator as "next_cls".
 * @param end_it set to GNUNET_YES if we
 *        should terminate the iteration early
 *        (iterator should be still called once more
 *         to signal the end of the iteration).
 */
typedef void (*PluginNextRequest)(void *next_cls,
				  int end_it);


/**
 * An iterator over a set of items stored in the datastore.
 *
 * @param cls closure
 * @param next_cls closure to pass to the "next" function.
 * @param key key for the content
 * @param size number of bytes in data
 * @param data content stored
 * @param type type of the content
 * @param priority priority of the content
 * @param anonymity anonymity-level for the content
 * @param expiration expiration time for the content
 * @param uid unique identifier for the datum;
 *        maybe 0 if no unique identifier is available
 *
 * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue
 *         (continue on call to "next", of course),
 *         GNUNET_NO to delete the item and continue (if supported)
 */
typedef int (*PluginIterator) (void *cls,
			       void *next_cls,
			       const GNUNET_HashCode * key,
			       uint32_t size,
			       const void *data,
			       enum GNUNET_BLOCK_Type type,
			       uint32_t priority,
			       uint32_t anonymity,
			       struct GNUNET_TIME_Absolute
			       expiration, 
			       uint64_t uid);

/**
 * Get an estimate of how much space the database is
 * currently using.
 *
 * @param cls closure
 * @return number of bytes used on disk
 */
typedef unsigned long long (*PluginGetSize) (void *cls);


/**
 * Store an item in the datastore.  If the item is already present,
 * the priorities and replication levels are summed up and the higher
 * expiration time and lower anonymity level is used.
 *
 * @param cls closure
 * @param key key for the item
 * @param size number of bytes in data
 * @param data content stored
 * @param type type of the content
 * @param priority priority of the content
 * @param anonymity anonymity-level for the content
 * @param replication replication-level for the content
 * @param expiration expiration time for the content
 * @param msg set to an error message (on failure)
 * @return GNUNET_OK on success,
 *         GNUNET_SYSERR on failure
 */
typedef int (*PluginPut) (void *cls,
			  const GNUNET_HashCode * key,
			  uint32_t size,
			  const void *data,
			  enum GNUNET_BLOCK_Type type,
			  uint32_t priority,
			  uint32_t anonymity,
			  uint32_t replication,
			  struct GNUNET_TIME_Absolute expiration,
			  char **msg);


/**
 * Iterate over the results for a particular key
 * in the datastore.
 *
 * @param cls closure
 * @param key key to match, never NULL
 * @param vhash hash of the value, maybe NULL (to
 *        match all values that have the right key).
 *        Note that for DBlocks there is no difference
 *        betwen key and vhash, but for other blocks
 *        there may be!
 * @param type entries of which type are relevant?
 *     Use 0 for any type.
 * @param iter function to call on each matching value; however,
 *        after the first call to "iter", the plugin must wait
 *        until "NextRequest" was called before giving the iterator
 *        the next item; finally, the "iter" should be called once
 *        once with a NULL value at the end ("next_cls" should be NULL
 *        for that last call)
 * @param iter_cls closure for iter
 */
typedef void (*PluginGet) (void *cls,
			   const GNUNET_HashCode *key,
			   const GNUNET_HashCode *vhash,
			   enum GNUNET_BLOCK_Type type,
			   PluginIterator iter, void *iter_cls);



/**
 * Get a random item (additional constraints may apply depending on
 * the specific implementation).  Calls 'iter' with all values ZERO or
 * NULL if no item applies, otherwise 'iter' is called once and only
 * once with an item, with the 'next_cls' argument being NULL.
 *
 * @param cls closure
 * @param iter function to call the value (once only).
 * @param iter_cls closure for iter
 */
typedef void (*PluginRandomGet) (void *cls,
				 PluginIterator iter, void *iter_cls);


/**
 * Update the priority for a particular key in the datastore.  If
 * the expiration time in value is different than the time found in
 * the datastore, the higher value should be kept.  For the
 * anonymity level, the lower value is to be used.  The specified
 * priority should be added to the existing priority, ignoring the
 * priority in value.
 *
 * Note that it is possible for multiple values to match this put.
 * In that case, all of the respective values are updated.
 *
 * @param cls closure
 * @param uid unique identifier of the datum
 * @param delta by how much should the priority
 *     change?  If priority + delta < 0 the
 *     priority should be set to 0 (never go
 *     negative).
 * @param expire new expiration time should be the
 *     MAX of any existing expiration time and
 *     this value
 * @param msg set to an error message (on error)
 * @return GNUNET_OK on success
 */
typedef int (*PluginUpdate) (void *cls,
			     uint64_t uid,
			     int delta, 
			     struct GNUNET_TIME_Absolute expire,
			     char **msg);


/**
 * Select a subset of the items in the datastore and call the given
 * iterator for the first item; then allow getting more items by
 * calling the 'next_request' callback with the given 'next_cls'
 * argument passed to 'iter'.
 *
 * @param cls closure
 * @param type entries of which type should be considered?
 *        Myst not be zero (ANY).
 * @param iter function to call on each matching value; however,
 *        after the first call to "iter", the plugin must wait
 *        until "NextRequest" was called before giving the iterator
 *        the next item; finally, the "iter" should be called once
 *        once with a NULL value at the end ("next_cls" should be NULL
 *        for that last call)
 * @param iter_cls closure for iter
 */
typedef void (*PluginSelector) (void *cls,
                                enum GNUNET_BLOCK_Type type,
                                PluginIterator iter,
                                void *iter_cls);


/**
 * Drop database.
 *
 * @param cls closure
 */
typedef void (*PluginDrop) (void *cls);



/**
 * Each plugin is required to return a pointer to a struct of this
 * type as the return value from its entry point.
 */
struct GNUNET_DATASTORE_PluginFunctions
{

  /**
   * Closure to use for all of the following callbacks
   * (except "next_request").
   */
  void *cls;

  /**
   * Get the current on-disk size of the SQ store.  Estimates are
   * fine, if that's the only thing available.
   */
  PluginGetSize get_size;

  /**
   * Function to store an item in the datastore.
   */
  PluginPut put;

  /**
   * Update the priority for a particular key in the datastore.  If
   * the expiration time in value is different than the time found in
   * the datastore, the higher value should be kept.  For the
   * anonymity level, the lower value is to be used.  The specified
   * priority should be added to the existing priority, ignoring the
   * priority in value.
   */
  PluginUpdate update;

  /**
   * Function called by iterators whenever they want the next value;
   * note that unlike all of the other callbacks, this one does get a
   * the "next_cls" closure which is usually different from the "cls"
   * member of this struct!
   */
  PluginNextRequest next_request;

  /**
   * Function to iterate over the results for a particular key
   * in the datastore.
   */
  PluginGet get;

  /**
   * Iterate over content with anonymity level zero.
   */
  PluginSelector iter_zero_anonymity;

  /**
   * Function to get a random item with high replication score from
   * the database, lowering the item's replication score.  Returns a
   * single, not expired, random item from those with the highest
   * replication counters.  The item's replication counter is
   * decremented by one IF it was positive before.
   */
  PluginRandomGet replication_get;

  /**
   * Function to get a random expired item or, if none are expired, one
   * with a low priority.
   */
  PluginRandomGet expiration_get;

  /**
   * Delete the database.  The next operation is
   * guaranteed to be unloading of the module.
   */
  PluginDrop drop;

};


#endif