1registry(3)                   C Library Functions                  registry(3)
2
3
4

NAME

6       registry - Store and back up key-value pairs.
7

DESCRIPTION

9   Note:
10       This  functionality  is deprecated as of OTP 23, and will be removed in
11       OTP 24. Reasonably new gcc compilers will issue  deprecation  warnings.
12       In order to disable these warnings, define the macro EI_NO_DEPR_WARN.
13
14
15       This  module  provides  support  for storing key-value pairs in a table
16       known as a registry, backing up registries to Mnesia in an atomic  man‐
17       ner, and later restoring the contents of a registry from Mnesia.
18

EXPORTS

20       int ei_reg_close(reg)
21
22              Types:
23
24                 ei_reg *reg;
25
26              A  registry  that has previously been created with ei_reg_open()
27              is closed, and all the objects it contains are freed.
28
29              reg is the registry to close.
30
31              Returns 0.
32
33       int ei_reg_delete(reg,key)
34
35              Types:
36
37                 ei_reg *reg;
38                 const char *key;
39
40              Deletes an object from the registry. The object is  not  removed
41              from  the  registry, it is only marked for later removal so that
42              on later backups to Mnesia,  the  corresponding  object  can  be
43              removed  from  the  Mnesia  table  as well. If another object is
44              later created with the same key, the object will be reused.
45
46              The object  is  removed  from  the  registry  after  a  call  to
47              ei_reg_dump() or ei_reg_purge().
48
49                * reg is the registry containing key.
50
51                * key is the object to remove.
52
53              Returns 0 on success, otherwise -1.
54
55       int ei_reg_dump(fd,reg,mntab,flags)
56
57              Types:
58
59                 int fd;
60                 ei_reg *reg;
61                 const char *mntab;
62                 int flags;
63
64              Dumps  the contents of a registry to a Mnesia table in an atomic
65              manner, that is, either all data or no data is updated.  If  any
66              errors  are  encountered  while  backing up the data, the entire
67              operation is aborted.
68
69                * fd is an open connection to Erlang. Mnesia 3.0 or later must
70                  be running on the Erlang node.
71
72                * reg is the registry to back up.
73
74                * mntab  is  the  name of the Mnesia table where the backed up
75                  data is to be placed. If the table does  not  exist,  it  is
76                  created   automatically  using  configurable  defaults.  For
77                  information about configuring this behavior, see Mnesia.
78
79              If flags is 0, the backup includes only those objects that  have
80              been  created,  modified,  or  deleted  since the last backup or
81              restore (that is, an incremental backup). After the backup,  any
82              objects  that  were  marked dirty are now clean, and any objects
83              that had been marked for deletion are deleted.
84
85              Alternatively, setting flags to EI_FORCE causes a full backup to
86              be done, and EI_NOPURGE causes the deleted objects to be left in
87              the registry afterwards. These can be bitwise OR'ed together  if
88              both   behaviors  are  desired.  If  EI_NOPURGE  was  specified,
89              ei_reg_purge() can be used  to  explicitly  remove  the  deleted
90              items from the registry later.
91
92              Returns 0 on success, otherwise -1.
93
94       double ei_reg_getfval(reg,key)
95
96              Types:
97
98                 ei_reg *reg;
99                 const char *key;
100
101              Gets  the  value  associated with key in the registry. The value
102              must be a floating point type.
103
104                * reg is the registry where the object will be looked up.
105
106                * key is the name of the object to look up.
107
108              On success, the function returns the value associated with  key.
109              If  the  object  is  not  found or if it is not a floating point
110              object, -1.0 is returned. To avoid problems with  in-band  error
111              reporting (that is, if you cannot distinguish between -1.0 and a
112              valid result), use the  more  general  function  ei_reg_getval()
113              instead.
114
115       int ei_reg_getival(reg,key)
116
117              Types:
118
119                 ei_reg *reg;
120                 const char *key;
121
122              Gets  the  value  associated with key in the registry. The value
123              must be an integer.
124
125                * reg is the registry where the object will be looked up.
126
127                * key is the name of the object to look up.
128
129              On success, the function returns the value associated with  key.
130              If the object is not found or if it is not an integer object, -1
131              is returned. To avoid  problems  with  in-band  error  reporting
132              (that  is,  if  you  cannot  distinguish  between -1 and a valid
133              result), use the more general function ei_reg_getval() instead.
134
135       const void *ei_reg_getpval(reg,key,size)
136
137              Types:
138
139                 ei_reg *reg;
140                 const char *key;
141                 int size;
142
143              Gets the value associated with key in the  registry.  The  value
144              must be a binary (pointer) type.
145
146                * reg is the registry where the object will be looked up.
147
148                * key is the name of the object to look up.
149
150                * size  is  initialized  to contain the length in bytes of the
151                  object, if it is found.
152
153              On success, the function returns the value associated  with  key
154              and  indicates its length in size. If the object is not found or
155              if it is not a binary object, NULL is returned. To  avoid  prob‐
156              lems  with  in-band error reporting (that is, if you cannot dis‐
157              tinguish between NULL and a valid result), use the more  general
158              function ei_reg_getval() instead.
159
160       const char *ei_reg_getsval(reg,key)
161
162              Types:
163
164                 ei_reg *reg;
165                 const char *key;
166
167              Gets  the  value  associated with key in the registry. The value
168              must be a string.
169
170                * reg is the registry where the object will be looked up.
171
172                * key is the name of the object to look up.
173
174              On success, the function returns the value associated with  key.
175              If  the  object  is  not found or if it is not a string, NULL is
176              returned. To avoid problems with in-band error  reporting  (that
177              is,  if you cannot distinguish between NULL and a valid result),
178              use the more general function ei_reg_getval() instead.
179
180       int ei_reg_getval(reg,key,flags,v,...)
181
182              Types:
183
184                 ei_reg *reg;
185                 const char *key;
186                 int flags;
187                 void *v (see below)
188
189              A general function for retrieving any kind of  object  from  the
190              registry.
191
192                * reg is the registry where the object will be looked up.
193
194                * key is the name of the object to look up.
195
196                * flags indicates the type of object that you are looking for.
197                  If flags is 0, any kind of object is returned. If  flags  is
198                  EI_INT,  EI_FLT, EI_STR, or EI_BIN, then only values of that
199                  kind are returned.
200
201                  The buffer pointed to by v must be large enough to hold  the
202                  return  data,  that  is, it must be a pointer to one of int,
203                  double, char*, or void*, respectively.
204
205                  If flags is EI_BIN, a fifth argument int *size is  required,
206                  so that the size of the object can be returned.
207
208              On  success, v (and size if the object is binary) is initialized
209              with the value associated with key,  and  the  function  returns
210              EI_INT,  EI_FLT,  EI_STR,  or  EI_BIN,  indicating  the  type of
211              object. On failure, -1 is returned and  the  arguments  are  not
212              updated.
213
214       int ei_reg_markdirty(reg,key)
215
216              Types:
217
218                 ei_reg *reg;
219                 const char *key;
220
221              Marks  a  registry  object  as  dirty.  This  ensures that it is
222              included in the next backup to Mnesia. Normally  this  operation
223              is  not necessary, as all of the normal registry 'set' functions
224              do this automatically. However, if you have retrieved the  value
225              of  a string or binary object from the registry and modified the
226              contents, then the change is invisible to the registry  and  the
227              object  is assumed to be unmodified. This function allows you to
228              make such modifications and then let  the  registry  know  about
229              them.
230
231                * reg is the registry containing the object.
232
233                * key is the name of the object to mark.
234
235              Returns 0 on success, otherwise -1.
236
237       ei_reg *ei_reg_open(size)
238
239              Types:
240
241                 int size;
242
243              Opens  (creates)  a registry, which initially is empty. To close
244              the registry later, use ei_reg_close().
245
246              size is the approximate number of objects you intend to store in
247              the  registry.  As the registry uses a hash table with collision
248              chaining, no absolute  upper  limit  exists  on  the  number  of
249              objects  that can be stored in it. However, for reasons of effi‐
250              ciency, it is a good idea to choose a number that is appropriate
251              for  your  needs. To change the size later, use ei_reg_resize().
252              Notice that the number you provide is increased to  the  nearest
253              larger prime number.
254
255              Returns an empty registry on success, otherwise NULL.
256
257       int ei_reg_purge(reg)
258
259              Types:
260
261                 ei_reg *reg;
262
263              Removes  all  objects  marked  for  deletion.  When  objects are
264              deleted with ei_reg_delete() they are not removed from the  reg‐
265              istry,  only marked for later removal. On a later backup to Mne‐
266              sia, the objects can also be removed from the Mnesia  table.  If
267              you  are  not  backing  up to Mnesia, you may wish to remove the
268              objects manually with this function.
269
270              reg is a registry containing objects marked for deletion.
271
272              Returns 0 on success, otherwise -1.
273
274       int ei_reg_resize(reg,newsize)
275
276              Types:
277
278                 ei_reg *reg;
279                 int newsize;
280
281              Changes the size of a registry.
282
283              newsize is the new size to make  the  registry.  The  number  is
284              increased to the nearest larger prime number.
285
286              On  success, the registry is resized, all contents rehashed, and
287              0 is returned. On failure, the registry is left unchanged and -1
288              is returned.
289
290       int ei_reg_restore(fd,reg,mntab)
291
292              Types:
293
294                 int fd;
295                 ei_reg *reg;
296                 const char *mntab;
297
298              The contents of a Mnesia table are read into the registry.
299
300                * fd is an open connection to Erlang. Mnesia 3.0 or later must
301                  be running on the Erlang node.
302
303                * reg is the registry where the data is to be placed.
304
305                * mntab is the name of the Mnesia table to read data from.
306
307              Notice that only tables of a certain  format  can  be  restored,
308              that  is,  those  that  have  been created and backed up to with
309              ei_reg_dump(). If the registry was not empty before  the  opera‐
310              tion, the contents of the table are added to the contents of the
311              registry. If the table contains objects with the  same  keys  as
312              those  already  in  the registry, the registry objects are over‐
313              written with the new values. If the  registry  contains  objects
314              that  were  not  in the table, they are unchanged by this opera‐
315              tion.
316
317              After the restore operation, the entire contents of the registry
318              is  marked  as unmodified. Notice that this includes any objects
319              that were modified before the restore and not overwritten by the
320              restore.
321
322              Returns 0 on success, otherwise -1.
323
324       int ei_reg_setfval(reg,key,f)
325
326              Types:
327
328                 ei_reg *reg;
329                 const char *key;
330                 double f;
331
332              Creates  a  key-value  pair  with the specified key and floating
333              point value f. If an object already exists with  the  same  key,
334              the  new value replaces the old one. If the previous value was a
335              binary or string, it is freed with free().
336
337                * reg is the registry where the object is to be placed.
338
339                * key is the object name.
340
341                * f is the floating point value to assign.
342
343              Returns 0 on success, otherwise -1.
344
345       int ei_reg_setival(reg,key,i)
346
347              Types:
348
349                 ei_reg *reg;
350                 const char *key;
351                 int i;
352
353              Creates a key-value pair with  the  specified  key  and  integer
354              value  i. If an object already exists with the same key, the new
355              value replaces the old one. If the previous value was  a  binary
356              or string, it is freed with free().
357
358                * reg is the registry where the object is to be placed.
359
360                * key is the object name.
361
362                * i is the integer value to assign.
363
364              Returns 0 on success, otherwise -1.
365
366       int ei_reg_setpval(reg,key,p,size)
367
368              Types:
369
370                 ei_reg *reg;
371                 const char *key;
372                 const void *p;
373                 int size;
374
375              Creates a key-value pair with the specified key whose "value" is
376              the binary object pointed to by p. If an object  already  exists
377              with  the  same  key, the new value replaces the old one. If the
378              previous value was a binary or string, it is freed with free().
379
380                * reg is the registry where the object is to be placed.
381
382                * key is the object name.
383
384                * p is a pointer to the binary object. The object itself  must
385                  have  been  created  through  a single call to malloc() or a
386                  similar function, so that the registry can later  delete  it
387                  if necessary by calling free().
388
389                * size is the length in bytes of the binary object.
390
391              Returns 0 on success, otherwise -1.
392
393       int ei_reg_setsval(reg,key,s)
394
395              Types:
396
397                 ei_reg *reg;
398                 const char *key;
399                 const char *s;
400
401              Creates a key-value pair with the specified key whose "value" is
402              the specified string s. If an object  already  exists  with  the
403              same  key,  the  new value replaces the old one. If the previous
404              value was a binary or string, it is freed with free().
405
406                * reg is the registry where the object is to be placed.
407
408                * key is the object name.
409
410                * s is the string to assign. The string itself must have  been
411                  created through a single call to malloc() or similar a func‐
412                  tion, so that the registry can later delete it if  necessary
413                  by calling free().
414
415              Returns 0 on success, otherwise -1.
416
417       int ei_reg_setval(reg,key,flags,v,...)
418
419              Types:
420
421                 ei_reg *reg;
422                 const char *key;
423                 int flags;
424                 v (see below)
425
426              Creates  a  key-value pair with the specified key whose value is
427              specified by v. If an object already exists with the  same  key,
428              the  new value replaces the old one. If the previous value was a
429              binary or string, it is freed with free().
430
431                * reg is the registry where the object is to be placed.
432
433                * key is the object name.
434
435                * flags indicates the type of the object specified by v. Flags
436                  must  be one of EI_INT, EI_FLT, EI_STR, and EI_BIN, indicat‐
437                  ing whether v is int, double, char*, or void*.
438
439                  If flags is EI_BIN, a fifth argument size is required, indi‐
440                  cating the size in bytes of the object pointed to by v.
441
442              If you wish to store an arbitrary pointer in the registry, spec‐
443              ify a size of 0. In this case, the object itself is  not  trans‐
444              ferred by an ei_reg_dump() operation, only the pointer value.
445
446              Returns 0 on success, otherwise -1.
447
448       int ei_reg_stat(reg,key,obuf)
449
450              Types:
451
452                 ei_reg *reg;
453                 const char *key;
454                 struct ei_reg_stat *obuf;
455
456              Returns information about an object.
457
458                * reg is the registry containing the object.
459
460                * key is the object name.
461
462                * obuf  is  a  pointer to an ei_reg_stat structure, defined as
463                  follows:
464
465              struct ei_reg_stat {
466                int attr;
467                int size;
468              };
469
470
471              In attr the attributes of the object are stored as  the  logical
472              OR  of  its  type  (one  of EI_INT, EI_FLT, EI_BIN, and EI_STR),
473              whether it is marked for deletion (EI_DELET), and whether it has
474              been modified since the last backup to Mnesia (EI_DIRTY).
475
476              Field  size indicates the size in bytes required to store EI_STR
477              (including the terminating 0)  and  EI_BIN  objects,  or  0  for
478              EI_INT and EI_FLT.
479
480              Returns 0 and initializes obuf on success, otherwise -1.
481
482       int ei_reg_tabstat(reg,obuf)
483
484              Types:
485
486                 ei_reg *reg;
487                 struct ei_reg_tabstat *obuf;
488
489              Returns information about a registry. Using information returned
490              by this function, you can see whether the size of  the  registry
491              is suitable for the amount of data it contains.
492
493                * reg is the registry to return information about.
494
495                * obuf is a pointer to an ei_reg_tabstat structure, defined as
496                  follows:
497
498              struct ei_reg_tabstat {
499                int size;
500                int nelem;
501                int npos;
502                int collisions;
503              };
504
505
506              Field size indicates the number of hash positions  in  the  reg‐
507              istry.  This is the number you provided when you created or last
508              resized the registry, rounded up to the nearest prime number.
509
510                * nelem indicates the number of elements stored  in  the  reg‐
511                  istry. It includes objects that are deleted but not purged.
512
513                * npos indicates the number of unique positions that are occu‐
514                  pied in the registry.
515
516                * collisions indicates how many elements are sharing positions
517                  in the registry.
518
519              On success, 0 is returned and obuf is initialized to contain ta‐
520              ble statistics, otherwise -1 is returned.
521
522
523
524Ericsson AB                   erl_interface 4.0.2                  registry(3)
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