00001 /* 00002 * astobj2 - replacement containers for asterisk data structures. 00003 * 00004 * Copyright (C) 2006 Marta Carbone, Luigi Rizzo - Univ. di Pisa, Italy 00005 * 00006 * See http://www.asterisk.org for more information about 00007 * the Asterisk project. Please do not directly contact 00008 * any of the maintainers of this project for assistance; 00009 * the project provides a web site, mailing lists and IRC 00010 * channels for your use. 00011 * 00012 * This program is free software, distributed under the terms of 00013 * the GNU General Public License Version 2. See the LICENSE file 00014 * at the top of the source tree. 00015 */ 00016 00017 #ifndef _ASTERISK_ASTOBJ2_H 00018 #define _ASTERISK_ASTOBJ2_H 00019 00020 #include "asterisk/compat.h" 00021 00022 /*! \file 00023 * \ref AstObj2 00024 * 00025 * \page AstObj2 Object Model implementing objects and containers. 00026 00027 This module implements an abstraction for objects (with locks and 00028 reference counts), and containers for these user-defined objects, 00029 also supporting locking, reference counting and callbacks. 00030 00031 The internal implementation of objects and containers is opaque to the user, 00032 so we can use different data structures as needs arise. 00033 00034 \section AstObj2_UsageObjects USAGE - OBJECTS 00035 00036 An ao2 object is a block of memory that the user code can access, 00037 and for which the system keeps track (with a bit of help from the 00038 programmer) of the number of references around. When an object has 00039 no more references (refcount == 0), it is destroyed, by first 00040 invoking whatever 'destructor' function the programmer specifies 00041 (it can be NULL if none is necessary), and then freeing the memory. 00042 This way objects can be shared without worrying who is in charge 00043 of freeing them. 00044 As an additional feature, ao2 objects are associated to individual 00045 locks. 00046 00047 Creating an object requires the size of the object and 00048 and a pointer to the destructor function: 00049 00050 struct foo *o; 00051 00052 o = ao2_alloc(sizeof(struct foo), my_destructor_fn); 00053 00054 The value returned points to the user-visible portion of the objects 00055 (user-data), but is also used as an identifier for all object-related 00056 operations such as refcount and lock manipulations. 00057 00058 On return from ao2_alloc(): 00059 00060 - the object has a refcount = 1; 00061 - the memory for the object is allocated dynamically and zeroed; 00062 - we cannot realloc() the object itself; 00063 - we cannot call free(o) to dispose of the object. Rather, we 00064 tell the system that we do not need the reference anymore: 00065 00066 ao2_ref(o, -1) 00067 00068 causing the destructor to be called (and then memory freed) when 00069 the refcount goes to 0. 00070 00071 - ao2_ref(o, +1) can be used to modify the refcount on the 00072 object in case we want to pass it around. 00073 00074 - ao2_lock(obj), ao2_unlock(obj), ao2_trylock(obj) can be used 00075 to manipulate the lock associated with the object. 00076 00077 00078 \section AstObj2_UsageContainers USAGE - CONTAINERS 00079 00080 An ao2 container is an abstract data structure where we can store 00081 ao2 objects, search them (hopefully in an efficient way), and iterate 00082 or apply a callback function to them. A container is just an ao2 object 00083 itself. 00084 00085 A container must first be allocated, specifying the initial 00086 parameters. At the moment, this is done as follows: 00087 00088 <b>Sample Usage:</b> 00089 \code 00090 00091 struct ao2_container *c; 00092 00093 c = ao2_container_alloc(MAX_BUCKETS, my_hash_fn, my_cmp_fn); 00094 \endcode 00095 00096 where 00097 00098 - MAX_BUCKETS is the number of buckets in the hash table, 00099 - my_hash_fn() is the (user-supplied) function that returns a 00100 hash key for the object (further reduced modulo MAX_BUCKETS 00101 by the container's code); 00102 - my_cmp_fn() is the default comparison function used when doing 00103 searches on the container, 00104 00105 A container knows little or nothing about the objects it stores, 00106 other than the fact that they have been created by ao2_alloc(). 00107 All knowledge of the (user-defined) internals of the objects 00108 is left to the (user-supplied) functions passed as arguments 00109 to ao2_container_alloc(). 00110 00111 If we want to insert an object in a container, we should 00112 initialize its fields -- especially, those used by my_hash_fn() -- 00113 to compute the bucket to use. 00114 Once done, we can link an object to a container with 00115 00116 ao2_link(c, o); 00117 00118 The function returns NULL in case of errors (and the object 00119 is not inserted in the container). Other values mean success 00120 (we are not supposed to use the value as a pointer to anything). 00121 Linking an object to a container increases its refcount by 1 00122 automatically. 00123 00124 \note While an object o is in a container, we expect that 00125 my_hash_fn(o) will always return the same value. The function 00126 does not lock the object to be computed, so modifications of 00127 those fields that affect the computation of the hash should 00128 be done by extracting the object from the container, and 00129 reinserting it after the change (this is not terribly expensive). 00130 00131 \note A container with a single buckets is effectively a linked 00132 list. However there is no ordering among elements. 00133 00134 - \ref AstObj2_Containers 00135 - \ref astobj2.h All documentation for functions and data structures 00136 00137 */ 00138 00139 /* 00140 \note DEBUGGING REF COUNTS BIBLE: 00141 An interface to help debug refcounting is provided 00142 in this package. It is dependent on the REF_DEBUG macro being 00143 defined in a source file, before the #include of astobj2.h, 00144 and in using variants of the normal ao2_xxxx functions 00145 that are named ao2_t_xxxx instead, with an extra argument, a string, 00146 that will be printed out into /tmp/refs when the refcount for an 00147 object is changed. 00148 00149 these ao2_t_xxxx variants are provided: 00150 00151 ao2_t_alloc(arg1, arg2, arg3) 00152 ao2_t_ref(arg1,arg2,arg3) 00153 ao2_t_container_alloc(arg1,arg2,arg3,arg4) 00154 ao2_t_link(arg1, arg2, arg3) 00155 ao2_t_unlink(arg1, arg2, arg3) 00156 ao2_t_callback(arg1,arg2,arg3,arg4,arg5) 00157 ao2_t_find(arg1,arg2,arg3,arg4) 00158 ao2_t_iterator_next(arg1, arg2) 00159 00160 If you study each argument list, you will see that these functions all have 00161 one extra argument that their ao2_xxx counterpart. The last argument in 00162 each case is supposed to be a string pointer, a "tag", that should contain 00163 enough of an explanation, that you can pair operations that increment the 00164 ref count, with operations that are meant to decrement the refcount. 00165 00166 Each of these calls will generate at least one line of output in /tmp/refs. 00167 These lines look like this: 00168 ... 00169 0x8756f00 =1 chan_sip.c:22240:load_module (allocate users) 00170 0x86e3408 =1 chan_sip.c:22241:load_module (allocate peers) 00171 0x86dd380 =1 chan_sip.c:22242:load_module (allocate peers_by_ip) 00172 0x822d020 =1 chan_sip.c:22243:load_module (allocate dialogs) 00173 0x8930fd8 =1 chan_sip.c:20025:build_peer (allocate a peer struct) 00174 0x8930fd8 +1 chan_sip.c:21467:reload_config (link peer into peer table) [@1] 00175 0x8930fd8 -1 chan_sip.c:2370:unref_peer (unref_peer: from reload_config) [@2] 00176 0x89318b0 =1 chan_sip.c:20025:build_peer (allocate a peer struct) 00177 0x89318b0 +1 chan_sip.c:21467:reload_config (link peer into peer table) [@1] 00178 0x89318b0 -1 chan_sip.c:2370:unref_peer (unref_peer: from reload_config) [@2] 00179 0x8930218 =1 chan_sip.c:20025:build_peer (allocate a peer struct) 00180 0x8930218 +1 chan_sip.c:21539:reload_config (link peer into peers table) [@1] 00181 0x868c040 -1 chan_sip.c:2424:dialog_unlink_all (unset the relatedpeer->call field in tandem with relatedpeer field itself) [@2] 00182 0x868c040 -1 chan_sip.c:2443:dialog_unlink_all (Let's unbump the count in the unlink so the poor pvt can disappear if it is time) [@1] 00183 0x868c040 **call destructor** chan_sip.c:2443:dialog_unlink_all (Let's unbump the count in the unlink so the poor pvt can disappear if it is time) 00184 0x8cc07e8 -1 chan_sip.c:2370:unref_peer (unsetting a dialog relatedpeer field in sip_destroy) [@3] 00185 0x8cc07e8 +1 chan_sip.c:3876:find_peer (ao2_find in peers table) [@2] 00186 0x8cc07e8 -1 chan_sip.c:2370:unref_peer (unref_peer, from sip_devicestate, release ref from find_peer) [@3] 00187 ... 00188 00189 The first column is the object address. 00190 The second column reflects how the operation affected the ref count 00191 for that object. Creation sets the ref count to 1 (=1). 00192 increment or decrement and amount are specified (-1/+1). 00193 The remainder of the line specifies where in the file the call was made, 00194 and the function name, and the tag supplied in the function call. 00195 00196 The **call destructor** is specified when the the destroy routine is 00197 run for an object. It does not affect the ref count, but is important 00198 in debugging, because it is possible to have the astobj2 system run it 00199 multiple times on the same object, commonly fatal to asterisk. 00200 00201 Sometimes you have some helper functions to do object ref/unref 00202 operations. Using these normally hides the place where these 00203 functions were called. To get the location where these functions 00204 were called to appear in /tmp/refs, you can do this sort of thing: 00205 00206 #ifdef REF_DEBUG 00207 #define dialog_ref(arg1,arg2) dialog_ref_debug((arg1),(arg2), __FILE__, __LINE__, __PRETTY_FUNCTION__) 00208 #define dialog_unref(arg1,arg2) dialog_unref_debug((arg1),(arg2), __FILE__, __LINE__, __PRETTY_FUNCTION__) 00209 static struct sip_pvt *dialog_ref_debug(struct sip_pvt *p, char *tag, char *file, int line, const char *func) 00210 { 00211 if (p) 00212 ao2_ref_debug(p, 1, tag, file, line, func); 00213 else 00214 ast_log(LOG_ERROR, "Attempt to Ref a null pointer\n"); 00215 return p; 00216 } 00217 00218 static struct sip_pvt *dialog_unref_debug(struct sip_pvt *p, char *tag, char *file, int line, const char *func) 00219 { 00220 if (p) 00221 ao2_ref_debug(p, -1, tag, file, line, func); 00222 return NULL; 00223 } 00224 #else 00225 static struct sip_pvt *dialog_ref(struct sip_pvt *p, char *tag) 00226 { 00227 if (p) 00228 ao2_ref(p, 1); 00229 else 00230 ast_log(LOG_ERROR, "Attempt to Ref a null pointer\n"); 00231 return p; 00232 } 00233 00234 static struct sip_pvt *dialog_unref(struct sip_pvt *p, char *tag) 00235 { 00236 if (p) 00237 ao2_ref(p, -1); 00238 return NULL; 00239 } 00240 #endif 00241 00242 In the above code, note that the "normal" helper funcs call ao2_ref() as 00243 normal, and the "helper" functions call ao2_ref_debug directly with the 00244 file, function, and line number info provided. You might find this 00245 well worth the effort to help track these function calls in the code. 00246 00247 To find out why objects are not destroyed (a common bug), you can 00248 edit the source file to use the ao2_t_* variants, add the #define REF_DEBUG 1 00249 before the #include "asterisk/astobj2.h" line, and add a descriptive 00250 tag to each call. Recompile, and run Asterisk, exit asterisk with 00251 "stop gracefully", which should result in every object being destroyed. 00252 Then, you can "sort -k 1 /tmp/refs > x1" to get a sorted list of 00253 all the objects, or you can use "util/refcounter" to scan the file 00254 for you and output any problems it finds. 00255 00256 The above may seem astronomically more work than it is worth to debug 00257 reference counts, which may be true in "simple" situations, but for 00258 more complex situations, it is easily worth 100 times this effort to 00259 help find problems. 00260 00261 To debug, pair all calls so that each call that increments the 00262 refcount is paired with a corresponding call that decrements the 00263 count for the same reason. Hopefully, you will be left with one 00264 or more unpaired calls. This is where you start your search! 00265 00266 For instance, here is an example of this for a dialog object in 00267 chan_sip, that was not getting destroyed, after I moved the lines around 00268 to pair operations: 00269 00270 0x83787a0 =1 chan_sip.c:5733:sip_alloc (allocate a dialog(pvt) struct) 00271 0x83787a0 -1 chan_sip.c:19173:sip_poke_peer (unref dialog at end of sip_poke_peer, obtained from sip_alloc, just before it goes out of scope) [@4] 00272 00273 0x83787a0 +1 chan_sip.c:5854:sip_alloc (link pvt into dialogs table) [@1] 00274 0x83787a0 -1 chan_sip.c:19150:sip_poke_peer (About to change the callid -- remove the old name) [@3] 00275 0x83787a0 +1 chan_sip.c:19152:sip_poke_peer (Linking in under new name) [@2] 00276 0x83787a0 -1 chan_sip.c:2399:dialog_unlink_all (unlinking dialog via ao2_unlink) [@5] 00277 00278 0x83787a0 +1 chan_sip.c:19130:sip_poke_peer (copy sip alloc from p to peer->call) [@2] 00279 00280 00281 0x83787a0 +1 chan_sip.c:2996:__sip_reliable_xmit (__sip_reliable_xmit: setting pkt->owner) [@3] 00282 0x83787a0 -1 chan_sip.c:2425:dialog_unlink_all (remove all current packets in this dialog, and the pointer to the dialog too as part of __sip_destroy) [@4] 00283 00284 0x83787a0 +1 chan_sip.c:22356:unload_module (iterate thru dialogs) [@4] 00285 0x83787a0 -1 chan_sip.c:22359:unload_module (toss dialog ptr from iterator_next) [@5] 00286 00287 00288 0x83787a0 +1 chan_sip.c:22373:unload_module (iterate thru dialogs) [@3] 00289 0x83787a0 -1 chan_sip.c:22375:unload_module (throw away iterator result) [@2] 00290 00291 0x83787a0 +1 chan_sip.c:2397:dialog_unlink_all (Let's bump the count in the unlink so it doesn't accidentally become dead before we are done) [@4] 00292 0x83787a0 -1 chan_sip.c:2436:dialog_unlink_all (Let's unbump the count in the unlink so the poor pvt can disappear if it is time) [@3] 00293 00294 As you can see, only one unbalanced operation is in the list, a ref count increment when 00295 the peer->call was set, but no corresponding decrement was made... 00296 00297 Hopefully this helps you narrow your search and find those bugs. 00298 00299 THE ART OF REFERENCE COUNTING 00300 (by Steve Murphy) 00301 SOME TIPS for complicated code, and ref counting: 00302 00303 1. Theoretically, passing a refcounted object pointer into a function 00304 call is an act of copying the reference, and could be refcounted. 00305 But, upon examination, this sort of refcounting will explode the amount 00306 of code you have to enter, and for no tangible benefit, beyond 00307 creating more possible failure points/bugs. It will even 00308 complicate your code and make debugging harder, slow down your program 00309 doing useless increments and decrements of the ref counts. 00310 00311 2. It is better to track places where a ref counted pointer 00312 is copied into a structure or stored. Make sure to decrement the refcount 00313 of any previous pointer that might have been there, if setting 00314 this field might erase a previous pointer. ao2_find and iterate_next 00315 internally increment the ref count when they return a pointer, so 00316 you need to decrement the count before the pointer goes out of scope. 00317 00318 3. Any time you decrement a ref count, it may be possible that the 00319 object will be destroyed (freed) immediately by that call. If you 00320 are destroying a series of fields in a refcounted object, and 00321 any of the unref calls might possibly result in immediate destruction, 00322 you can first increment the count to prevent such behavior, then 00323 after the last test, decrement the pointer to allow the object 00324 to be destroyed, if the refcount would be zero. 00325 00326 Example: 00327 00328 dialog_ref(dialog, "Let's bump the count in the unlink so it doesn't accidentally become dead before we are done"); 00329 00330 ao2_t_unlink(dialogs, dialog, "unlinking dialog via ao2_unlink"); 00331 00332 *//* Unlink us from the owner (channel) if we have one *//* 00333 if (dialog->owner) { 00334 if (lockowner) 00335 ast_channel_lock(dialog->owner); 00336 ast_debug(1, "Detaching from channel %s\n", dialog->owner->name); 00337 dialog->owner->tech_pvt = dialog_unref(dialog->owner->tech_pvt, "resetting channel dialog ptr in unlink_all"); 00338 if (lockowner) 00339 ast_channel_unlock(dialog->owner); 00340 } 00341 if (dialog->registry) { 00342 if (dialog->registry->call == dialog) 00343 dialog->registry->call = dialog_unref(dialog->registry->call, "nulling out the registry's call dialog field in unlink_all"); 00344 dialog->registry = registry_unref(dialog->registry, "delete dialog->registry"); 00345 } 00346 ... 00347 dialog_unref(dialog, "Let's unbump the count in the unlink so the poor pvt can disappear if it is time"); 00348 00349 In the above code, the ao2_t_unlink could end up destroying the dialog 00350 object; if this happens, then the subsequent usages of the dialog 00351 pointer could result in a core dump. So, we 'bump' the 00352 count upwards before beginning, and then decrementing the count when 00353 we are finished. This is analogous to 'locking' or 'protecting' operations 00354 for a short while. 00355 00356 4. One of the most insidious problems I've run into when converting 00357 code to do ref counted automatic destruction, is in the destruction 00358 routines. Where a "destroy" routine had previously been called to 00359 get rid of an object in non-refcounted code, the new regime demands 00360 that you tear that "destroy" routine into two pieces, one that will 00361 tear down the links and 'unref' them, and the other to actually free 00362 and reset fields. A destroy routine that does any reference deletion 00363 for its own object, will never be called. Another insidious problem 00364 occurs in mutually referenced structures. As an example, a dialog contains 00365 a pointer to a peer, and a peer contains a pointer to a dialog. Watch 00366 out that the destruction of one doesn't depend on the destruction of the 00367 other, as in this case a dependency loop will result in neither being 00368 destroyed! 00369 00370 Given the above, you should be ready to do a good job! 00371 00372 murf 00373 00374 */ 00375 00376 00377 00378 /*! \brief 00379 * Typedef for an object destructor. This is called just before freeing 00380 * the memory for the object. It is passed a pointer to the user-defined 00381 * data of the object. 00382 */ 00383 typedef void (*ao2_destructor_fn)(void *); 00384 00385 00386 /*! \brief 00387 * Allocate and initialize an object. 00388 * 00389 * \param data_size The sizeof() of the user-defined structure. 00390 * \param destructor_fn The destructor function (can be NULL) 00391 * \return A pointer to user-data. 00392 * 00393 * Allocates a struct astobj2 with sufficient space for the 00394 * user-defined structure. 00395 * \note 00396 * - storage is zeroed; XXX maybe we want a flag to enable/disable this. 00397 * - the refcount of the object just created is 1 00398 * - the returned pointer cannot be free()'d or realloc()'ed; 00399 * rather, we just call ao2_ref(o, -1); 00400 */ 00401 00402 #if defined(REF_DEBUG) 00403 00404 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) _ao2_alloc_debug((data_size), (destructor_fn), (debug_msg), __FILE__, __LINE__, __PRETTY_FUNCTION__, 1) 00405 #define ao2_alloc(data_size, destructor_fn) _ao2_alloc_debug((data_size), (destructor_fn), "", __FILE__, __LINE__, __PRETTY_FUNCTION__, 1) 00406 00407 #elif defined(__AST_DEBUG_MALLOC) 00408 00409 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) _ao2_alloc_debug((data_size), (destructor_fn), (debug_msg), __FILE__, __LINE__, __PRETTY_FUNCTION__, 0) 00410 #define ao2_alloc(data_size, destructor_fn) _ao2_alloc_debug((data_size), (destructor_fn), "", __FILE__, __LINE__, __PRETTY_FUNCTION__, 0) 00411 00412 #else 00413 00414 #define ao2_t_alloc(arg1,arg2,arg3) _ao2_alloc((arg1), (arg2)) 00415 #define ao2_alloc(arg1,arg2) _ao2_alloc((arg1), (arg2)) 00416 00417 #endif 00418 00419 void *_ao2_alloc_debug(const size_t data_size, ao2_destructor_fn destructor_fn, char *tag, 00420 const char *file, int line, const char *funcname, int ref_debug); 00421 void *_ao2_alloc(const size_t data_size, ao2_destructor_fn destructor_fn); 00422 00423 /*! @} */ 00424 00425 00426 /*! \brief 00427 * Reference/unreference an object and return the old refcount. 00428 * 00429 * \param o A pointer to the object 00430 * \param delta Value to add to the reference counter. 00431 * \return The value of the reference counter before the operation. 00432 * 00433 * Increase/decrease the reference counter according 00434 * the value of delta. 00435 * 00436 * If the refcount goes to zero, the object is destroyed. 00437 * 00438 * \note The object must not be locked by the caller of this function, as 00439 * it is invalid to try to unlock it after releasing the reference. 00440 * 00441 * \note if we know the pointer to an object, it is because we 00442 * have a reference count to it, so the only case when the object 00443 * can go away is when we release our reference, and it is 00444 * the last one in existence. 00445 */ 00446 00447 #ifdef REF_DEBUG 00448 00449 #define ao2_t_ref(arg1,arg2,arg3) _ao2_ref_debug((arg1), (arg2), (arg3), __FILE__, __LINE__, __PRETTY_FUNCTION__) 00450 #define ao2_ref(arg1,arg2) _ao2_ref_debug((arg1), (arg2), "", __FILE__, __LINE__, __PRETTY_FUNCTION__) 00451 00452 #else 00453 00454 #define ao2_t_ref(arg1,arg2,arg3) _ao2_ref((arg1), (arg2)) 00455 #define ao2_ref(arg1,arg2) _ao2_ref((arg1), (arg2)) 00456 00457 #endif 00458 00459 int _ao2_ref_debug(void *o, int delta, char *tag, char *file, int line, const char *funcname); 00460 int _ao2_ref(void *o, int delta); 00461 00462 /*! @} */ 00463 00464 /*! \brief 00465 * Lock an object. 00466 * 00467 * \param a A pointer to the object we want to lock. 00468 * \return 0 on success, other values on error. 00469 */ 00470 int ao2_lock(void *a); 00471 int _ao2_lock(void *a, const char *file, const char *func, int line, const char *var); 00472 #ifdef DEBUG_THREADS 00473 #define ao2_lock(a) _ao2_lock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a) 00474 #endif 00475 00476 /*! \brief 00477 * Unlock an object. 00478 * 00479 * \param a A pointer to the object we want unlock. 00480 * \return 0 on success, other values on error. 00481 */ 00482 int ao2_unlock(void *a); 00483 int _ao2_unlock(void *a, const char *file, const char *func, int line, const char *var); 00484 #ifdef DEBUG_THREADS 00485 #define ao2_unlock(a) _ao2_unlock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a) 00486 #endif 00487 00488 /*! \brief 00489 * Try locking-- (don't block if fail) 00490 * 00491 * \param a A pointer to the object we want to lock. 00492 * \return 0 on success, other values on error. 00493 */ 00494 int ao2_trylock(void *a); 00495 int _ao2_trylock(void *a, const char *file, const char *func, int line, const char *var); 00496 #ifdef DEBUG_THREADS 00497 #define ao2_trylock(a) _ao2_trylock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a) 00498 #endif 00499 00500 /*! 00501 * \brief Return the lock address of an object 00502 * 00503 * \param[in] obj A pointer to the object we want. 00504 * \return the address of the lock, else NULL. 00505 * 00506 * This function comes in handy mainly for debugging locking 00507 * situations, where the locking trace code reports the 00508 * lock address, this allows you to correlate against 00509 * object address, to match objects to reported locks. 00510 * 00511 * \since 1.6.1 00512 */ 00513 void *ao2_object_get_lockaddr(void *obj); 00514 00515 /*! 00516 \page AstObj2_Containers AstObj2 Containers 00517 00518 Containers are data structures meant to store several objects, 00519 and perform various operations on them. 00520 Internally, objects are stored in lists, hash tables or other 00521 data structures depending on the needs. 00522 00523 \note NOTA BENE: at the moment the only container we support is the 00524 hash table and its degenerate form, the list. 00525 00526 Operations on container include: 00527 00528 - c = \b ao2_container_alloc(size, cmp_fn, hash_fn) 00529 allocate a container with desired size and default compare 00530 and hash function 00531 -The compare function returns an int, which 00532 can be 0 for not found, CMP_STOP to stop end a traversal, 00533 or CMP_MATCH if they are equal 00534 -The hash function returns an int. The hash function 00535 takes two argument, the object pointer and a flags field, 00536 00537 - \b ao2_find(c, arg, flags) 00538 returns zero or more element matching a given criteria 00539 (specified as arg). 'c' is the container pointer. Flags 00540 can be: 00541 OBJ_UNLINK - to remove the object, once found, from the container. 00542 OBJ_NODATA - don't return the object if found (no ref count change) 00543 OBJ_MULTIPLE - don't stop at first match (not fully implemented) 00544 OBJ_POINTER - if set, 'arg' is an object pointer, and a hashtable 00545 search will be done. If not, a traversal is done. 00546 00547 - \b ao2_callback(c, flags, fn, arg) 00548 apply fn(obj, arg) to all objects in the container. 00549 Similar to find. fn() can tell when to stop, and 00550 do anything with the object including unlinking it. 00551 - c is the container; 00552 - flags can be 00553 OBJ_UNLINK - to remove the object, once found, from the container. 00554 OBJ_NODATA - don't return the object if found (no ref count change) 00555 OBJ_MULTIPLE - don't stop at first match (not fully implemented) 00556 OBJ_POINTER - if set, 'arg' is an object pointer, and a hashtable 00557 search will be done. If not, a traversal is done through 00558 all the hashtable 'buckets'.. 00559 - fn is a func that returns int, and takes 3 args: 00560 (void *obj, void *arg, int flags); 00561 obj is an object 00562 arg is the same as arg passed into ao2_callback 00563 flags is the same as flags passed into ao2_callback 00564 fn returns: 00565 0: no match, keep going 00566 CMP_STOP: stop search, no match 00567 CMP_MATCH: This object is matched. 00568 00569 Note that the entire operation is run with the container 00570 locked, so noone else can change its content while we work on it. 00571 However, we pay this with the fact that doing 00572 anything blocking in the callback keeps the container 00573 blocked. 00574 The mechanism is very flexible because the callback function fn() 00575 can do basically anything e.g. counting, deleting records, etc. 00576 possibly using arg to store the results. 00577 00578 - \b iterate on a container 00579 this is done with the following sequence 00580 00581 \code 00582 00583 struct ao2_container *c = ... // our container 00584 struct ao2_iterator i; 00585 void *o; 00586 00587 i = ao2_iterator_init(c, flags); 00588 00589 while ( (o = ao2_iterator_next(&i)) ) { 00590 ... do something on o ... 00591 ao2_ref(o, -1); 00592 } 00593 00594 ao2_iterator_destroy(&i); 00595 \endcode 00596 00597 The difference with the callback is that the control 00598 on how to iterate is left to us. 00599 00600 - \b ao2_ref(c, -1) 00601 dropping a reference to a container destroys it, very simple! 00602 00603 Containers are ao2 objects themselves, and this is why their 00604 implementation is simple too. 00605 00606 Before declaring containers, we need to declare the types of the 00607 arguments passed to the constructor - in turn, this requires 00608 to define callback and hash functions and their arguments. 00609 00610 - \ref AstObj2 00611 - \ref astobj2.h 00612 */ 00613 00614 /*! \brief 00615 * Type of a generic callback function 00616 * \param obj pointer to the (user-defined part) of an object. 00617 * \param arg callback argument from ao2_callback() 00618 * \param flags flags from ao2_callback() 00619 * 00620 * The return values are a combination of enum _cb_results. 00621 * Callback functions are used to search or manipulate objects in a container, 00622 */ 00623 typedef int (ao2_callback_fn)(void *obj, void *arg, int flags); 00624 00625 /*! \brief a very common callback is one that matches by address. */ 00626 ao2_callback_fn ao2_match_by_addr; 00627 00628 /*! \brief 00629 * A callback function will return a combination of CMP_MATCH and CMP_STOP. 00630 * The latter will terminate the search in a container. 00631 */ 00632 enum _cb_results { 00633 CMP_MATCH = 0x1, /*!< the object matches the request */ 00634 CMP_STOP = 0x2, /*!< stop the search now */ 00635 }; 00636 00637 /*! \brief 00638 * Flags passed to ao2_callback() and ao2_hash_fn() to modify its behaviour. 00639 */ 00640 enum search_flags { 00641 /*! Unlink the object for which the callback function 00642 * returned CMP_MATCH . This is the only way to extract 00643 * objects from a container. */ 00644 OBJ_UNLINK = (1 << 0), 00645 /*! On match, don't return the object hence do not increase 00646 * its refcount. */ 00647 OBJ_NODATA = (1 << 1), 00648 /*! Don't stop at the first match in ao2_callback() 00649 * \note This is not fully implemented. Using OBJ_MULTIME with OBJ_NODATA 00650 * is perfectly fine. The part that is not implemented is the case where 00651 * multiple objects should be returned by ao2_callback(). 00652 */ 00653 OBJ_MULTIPLE = (1 << 2), 00654 /*! obj is an object of the same type as the one being searched for, 00655 * so use the object's hash function for optimized searching. 00656 * The search function is unaffected (i.e. use the one passed as 00657 * argument, or match_by_addr if none specified). */ 00658 OBJ_POINTER = (1 << 3), 00659 /*! 00660 * \brief Continue if a match is not found in the hashed out bucket 00661 * 00662 * This flag is to be used in combination with OBJ_POINTER. This tells 00663 * the ao2_callback() core to keep searching through the rest of the 00664 * buckets if a match is not found in the starting bucket defined by 00665 * the hash value on the argument. 00666 */ 00667 OBJ_CONTINUE = (1 << 4), 00668 }; 00669 00670 /*! 00671 * Type of a generic function to generate a hash value from an object. 00672 * flags is ignored at the moment. Eventually, it will include the 00673 * value of OBJ_POINTER passed to ao2_callback(). 00674 */ 00675 typedef int (ao2_hash_fn)(const void *obj, const int flags); 00676 00677 /*! \name Object Containers 00678 * Here start declarations of containers. 00679 */ 00680 /*@{ */ 00681 struct ao2_container; 00682 00683 /*! \brief 00684 * Allocate and initialize a container 00685 * with the desired number of buckets. 00686 * 00687 * We allocate space for a struct astobj_container, struct container 00688 * and the buckets[] array. 00689 * 00690 * \param n_buckets Number of buckets for hash 00691 * \param hash_fn Pointer to a function computing a hash value. 00692 * \param cmp_fn Pointer to a function comparating key-value 00693 * with a string. (can be NULL) 00694 * \return A pointer to a struct container. 00695 * 00696 * destructor is set implicitly. 00697 */ 00698 00699 #if defined(REF_DEBUG) 00700 00701 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) _ao2_container_alloc_debug((arg1), (arg2), (arg3), (arg4), __FILE__, __LINE__, __PRETTY_FUNCTION__, 1) 00702 #define ao2_container_alloc(arg1,arg2,arg3) _ao2_container_alloc_debug((arg1), (arg2), (arg3), "", __FILE__, __LINE__, __PRETTY_FUNCTION__, 1) 00703 00704 #elif defined(__AST_DEBUG_MALLOC) 00705 00706 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) _ao2_container_alloc_debug((arg1), (arg2), (arg3), (arg4), __FILE__, __LINE__, __PRETTY_FUNCTION__, 0) 00707 #define ao2_container_alloc(arg1,arg2,arg3) _ao2_container_alloc_debug((arg1), (arg2), (arg3), "", __FILE__, __LINE__, __PRETTY_FUNCTION__, 0) 00708 00709 #else 00710 00711 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) _ao2_container_alloc((arg1), (arg2), (arg3)) 00712 #define ao2_container_alloc(arg1,arg2,arg3) _ao2_container_alloc((arg1), (arg2), (arg3)) 00713 00714 #endif 00715 00716 struct ao2_container *_ao2_container_alloc(const unsigned int n_buckets, 00717 ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn); 00718 struct ao2_container *_ao2_container_alloc_debug(const unsigned int n_buckets, 00719 ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn, 00720 char *tag, char *file, int line, const char *funcname, 00721 int ref_debug); 00722 00723 /*! \brief 00724 * Returns the number of elements in a container. 00725 */ 00726 int ao2_container_count(struct ao2_container *c); 00727 00728 /*@} */ 00729 00730 /*! \name Object Management 00731 * Here we have functions to manage objects. 00732 * 00733 * We can use the functions below on any kind of 00734 * object defined by the user. 00735 */ 00736 /*@{ */ 00737 00738 /*! 00739 * \brief Add an object to a container. 00740 * 00741 * \param c the container to operate on. 00742 * \param newobj the object to be added. 00743 * 00744 * \retval NULL on errors 00745 * \retval newobj on success. 00746 * 00747 * This function inserts an object in a container according its key. 00748 * 00749 * \note Remember to set the key before calling this function. 00750 * 00751 * \note This function automatically increases the reference count to account 00752 * for the reference that the container now holds to the object. 00753 */ 00754 #ifdef REF_DEBUG 00755 00756 #define ao2_t_link(arg1, arg2, arg3) _ao2_link_debug((arg1), (arg2), (arg3), __FILE__, __LINE__, __PRETTY_FUNCTION__) 00757 #define ao2_link(arg1, arg2) _ao2_link_debug((arg1), (arg2), "", __FILE__, __LINE__, __PRETTY_FUNCTION__) 00758 00759 #else 00760 00761 #define ao2_t_link(arg1, arg2, arg3) _ao2_link((arg1), (arg2)) 00762 #define ao2_link(arg1, arg2) _ao2_link((arg1), (arg2)) 00763 00764 #endif 00765 00766 void *_ao2_link_debug(struct ao2_container *c, void *new_obj, char *tag, char *file, int line, const char *funcname); 00767 void *_ao2_link(struct ao2_container *c, void *newobj); 00768 00769 /*! 00770 * \brief Remove an object from a container 00771 * 00772 * \param c the container 00773 * \param obj the object to unlink 00774 * 00775 * \retval NULL, always 00776 * 00777 * \note The object requested to be unlinked must be valid. However, if it turns 00778 * out that it is not in the container, this function is still safe to 00779 * be called. 00780 * 00781 * \note If the object gets unlinked from the container, the container's 00782 * reference to the object will be automatically released. (The 00783 * refcount will be decremented). 00784 */ 00785 #ifdef REF_DEBUG 00786 00787 #define ao2_t_unlink(arg1, arg2, arg3) _ao2_unlink_debug((arg1), (arg2), (arg3), __FILE__, __LINE__, __PRETTY_FUNCTION__) 00788 #define ao2_unlink(arg1, arg2) _ao2_unlink_debug((arg1), (arg2), "", __FILE__, __LINE__, __PRETTY_FUNCTION__) 00789 00790 #else 00791 00792 #define ao2_t_unlink(arg1, arg2, arg3) _ao2_unlink((arg1), (arg2)) 00793 #define ao2_unlink(arg1, arg2) _ao2_unlink((arg1), (arg2)) 00794 00795 #endif 00796 00797 void *_ao2_unlink_debug(struct ao2_container *c, void *obj, char *tag, char *file, int line, const char *funcname); 00798 void *_ao2_unlink(struct ao2_container *c, void *obj); 00799 00800 00801 /*! \brief Used as return value if the flag OBJ_MULTIPLE is set */ 00802 struct ao2_list { 00803 struct ao2_list *next; 00804 void *obj; /* pointer to the user portion of the object */ 00805 }; 00806 00807 /*@} */ 00808 00809 /*! \brief 00810 * ao2_callback() is a generic function that applies cb_fn() to all objects 00811 * in a container, as described below. 00812 * 00813 * \param c A pointer to the container to operate on. 00814 * \param flags A set of flags specifying the operation to perform, 00815 partially used by the container code, but also passed to 00816 the callback. 00817 - If OBJ_NODATA is set, ao2_callback will return NULL. No refcounts 00818 of any of the traversed objects will be incremented. 00819 On the converse, if it is NOT set (the default), The ref count 00820 of each object for which CMP_MATCH was set will be incremented, 00821 and you will have no way of knowing which those are, until 00822 the multiple-object-return functionality is implemented. 00823 - If OBJ_POINTER is set, the traversed items will be restricted 00824 to the objects in the bucket that the object key hashes to. 00825 * \param cb_fn A function pointer, that will be called on all 00826 objects, to see if they match. This function returns CMP_MATCH 00827 if the object is matches the criteria; CMP_STOP if the traversal 00828 should immediately stop, or both (via bitwise ORing), if you find a 00829 match and want to end the traversal, and 0 if the object is not a match, 00830 but the traversal should continue. This is the function that is applied 00831 to each object traversed. It's arguments are: 00832 (void *obj, void *arg, int flags), where: 00833 obj is an object 00834 arg is the same as arg passed into ao2_callback 00835 flags is the same as flags passed into ao2_callback (flags are 00836 also used by ao2_callback). 00837 * \param arg passed to the callback. 00838 * \return A pointer to the object found/marked, 00839 * a pointer to a list of objects matching comparison function, 00840 * NULL if not found. 00841 * 00842 * If the function returns any objects, their refcount is incremented, 00843 * and the caller is in charge of decrementing them once done. 00844 * Also, in case of multiple values returned, the list used 00845 * to store the objects must be freed by the caller. 00846 * 00847 * Typically, ao2_callback() is used for two purposes: 00848 * - to perform some action (including removal from the container) on one 00849 * or more objects; in this case, cb_fn() can modify the object itself, 00850 * and to perform deletion should set CMP_MATCH on the matching objects, 00851 * and have OBJ_UNLINK set in flags. 00852 * - to look for a specific object in a container; in this case, cb_fn() 00853 * should not modify the object, but just return a combination of 00854 * CMP_MATCH and CMP_STOP on the desired object. 00855 * Other usages are also possible, of course. 00856 00857 * This function searches through a container and performs operations 00858 * on objects according on flags passed. 00859 * XXX describe better 00860 * The comparison is done calling the compare function set implicitly. 00861 * The p pointer can be a pointer to an object or to a key, 00862 * we can say this looking at flags value. 00863 * If p points to an object we will search for the object pointed 00864 * by this value, otherwise we serch for a key value. 00865 * If the key is not uniq we only find the first matching valued. 00866 * If we use the OBJ_MARK flags, we mark all the objects matching 00867 * the condition. 00868 * 00869 * The use of flags argument is the follow: 00870 * 00871 * OBJ_UNLINK unlinks the object found 00872 * OBJ_NODATA on match, do return an object 00873 * Callbacks use OBJ_NODATA as a default 00874 * functions such as find() do 00875 * OBJ_MULTIPLE return multiple matches 00876 * Default for _find() is no. 00877 * to a key (not yet supported) 00878 * OBJ_POINTER the pointer is an object pointer 00879 * 00880 * In case we return a list, the callee must take care to destroy 00881 * that list when no longer used. 00882 * 00883 * \note When the returned object is no longer in use, ao2_ref() should 00884 * be used to free the additional reference possibly created by this function. 00885 */ 00886 #ifdef REF_DEBUG 00887 00888 #define ao2_t_callback(arg1,arg2,arg3,arg4,arg5) _ao2_callback_debug((arg1), (arg2), (arg3), (arg4), (arg5), __FILE__, __LINE__, __PRETTY_FUNCTION__) 00889 #define ao2_callback(arg1,arg2,arg3,arg4) _ao2_callback_debug((arg1), (arg2), (arg3), (arg4), "", __FILE__, __LINE__, __PRETTY_FUNCTION__) 00890 00891 #else 00892 00893 #define ao2_t_callback(arg1,arg2,arg3,arg4,arg5) _ao2_callback((arg1), (arg2), (arg3), (arg4)) 00894 #define ao2_callback(arg1,arg2,arg3,arg4) _ao2_callback((arg1), (arg2), (arg3), (arg4)) 00895 00896 #endif 00897 00898 void *_ao2_callback_debug(struct ao2_container *c, enum search_flags flags, 00899 ao2_callback_fn *cb_fn, void *arg, char *tag, 00900 char *file, int line, const char *funcname); 00901 void *_ao2_callback(struct ao2_container *c, 00902 enum search_flags flags, 00903 ao2_callback_fn *cb_fn, void *arg); 00904 00905 /*! ao2_find() is a short hand for ao2_callback(c, flags, c->cmp_fn, arg) 00906 * XXX possibly change order of arguments ? 00907 */ 00908 #ifdef REF_DEBUG 00909 00910 #define ao2_t_find(arg1,arg2,arg3,arg4) _ao2_find_debug((arg1), (arg2), (arg3), (arg4), __FILE__, __LINE__, __PRETTY_FUNCTION__) 00911 #define ao2_find(arg1,arg2,arg3) _ao2_find_debug((arg1), (arg2), (arg3), "", __FILE__, __LINE__, __PRETTY_FUNCTION__) 00912 00913 #else 00914 00915 #define ao2_t_find(arg1,arg2,arg3,arg4) _ao2_find((arg1), (arg2), (arg3)) 00916 #define ao2_find(arg1,arg2,arg3) _ao2_find((arg1), (arg2), (arg3)) 00917 00918 #endif 00919 00920 void *_ao2_find_debug(struct ao2_container *c, void *arg, enum search_flags flags, char *tag, char *file, int line, const char *funcname); 00921 void *_ao2_find(struct ao2_container *c, void *arg, enum search_flags flags); 00922 00923 /*! \brief 00924 * 00925 * 00926 * When we need to walk through a container, we use an 00927 * ao2_iterator to keep track of the current position. 00928 * 00929 * Because the navigation is typically done without holding the 00930 * lock on the container across the loop, objects can be inserted or deleted 00931 * or moved while we work. As a consequence, there is no guarantee that 00932 * we manage to touch all the elements in the container, and it is possible 00933 * that we touch the same object multiple times. 00934 * 00935 * However, within the current hash table container, the following is true: 00936 * - It is not possible to miss an object in the container while iterating 00937 * unless it gets added after the iteration begins and is added to a bucket 00938 * that is before the one the current object is in. In this case, even if 00939 * you locked the container around the entire iteration loop, you still would 00940 * not see this object, because it would still be waiting on the container 00941 * lock so that it can be added. 00942 * - It would be extremely rare to see an object twice. The only way this can 00943 * happen is if an object got unlinked from the container and added again 00944 * during the same iteration. Furthermore, when the object gets added back, 00945 * it has to be in the current or later bucket for it to be seen again. 00946 * 00947 * An iterator must be first initialized with ao2_iterator_init(), 00948 * then we can use o = ao2_iterator_next() to move from one 00949 * element to the next. Remember that the object returned by 00950 * ao2_iterator_next() has its refcount incremented, 00951 * and the reference must be explicitly released when done with it. 00952 * 00953 * In addition, ao2_iterator_init() will hold a reference to the container 00954 * being iterated, which will be freed when ao2_iterator_destroy() is called 00955 * to free up the resources used by the iterator (if any). 00956 * 00957 * Example: 00958 * 00959 * \code 00960 * 00961 * struct ao2_container *c = ... // the container we want to iterate on 00962 * struct ao2_iterator i; 00963 * struct my_obj *o; 00964 * 00965 * i = ao2_iterator_init(c, flags); 00966 * 00967 * while ( (o = ao2_iterator_next(&i)) ) { 00968 * ... do something on o ... 00969 * ao2_ref(o, -1); 00970 * } 00971 * 00972 * ao2_iterator_destroy(&i); 00973 * 00974 * \endcode 00975 * 00976 */ 00977 00978 /*! \brief 00979 * The astobj2 iterator 00980 * 00981 * \note You are not supposed to know the internals of an iterator! 00982 * We would like the iterator to be opaque, unfortunately 00983 * its size needs to be known if we want to store it around 00984 * without too much trouble. 00985 * Anyways... 00986 * The iterator has a pointer to the container, and a flags 00987 * field specifying various things e.g. whether the container 00988 * should be locked or not while navigating on it. 00989 * The iterator "points" to the current object, which is identified 00990 * by three values: 00991 * 00992 * - a bucket number; 00993 * - the object_id, which is also the container version number 00994 * when the object was inserted. This identifies the object 00995 * uniquely, however reaching the desired object requires 00996 * scanning a list. 00997 * - a pointer, and a container version when we saved the pointer. 00998 * If the container has not changed its version number, then we 00999 * can safely follow the pointer to reach the object in constant time. 01000 * 01001 * Details are in the implementation of ao2_iterator_next() 01002 * A freshly-initialized iterator has bucket=0, version=0. 01003 */ 01004 struct ao2_iterator { 01005 /*! the container */ 01006 struct ao2_container *c; 01007 /*! operation flags */ 01008 int flags; 01009 /*! current bucket */ 01010 int bucket; 01011 /*! container version */ 01012 unsigned int c_version; 01013 /*! pointer to the current object */ 01014 void *obj; 01015 /*! container version when the object was created */ 01016 unsigned int version; 01017 }; 01018 01019 /*! Flags that can be passed to ao2_iterator_init() to modify the behavior 01020 * of the iterator. 01021 */ 01022 enum ao2_iterator_flags { 01023 /*! Prevents ao2_iterator_next() from locking the container 01024 * while retrieving the next object from it. 01025 */ 01026 AO2_ITERATOR_DONTLOCK = (1 << 0), 01027 }; 01028 01029 /*! 01030 * \brief Create an iterator for a container 01031 * 01032 * \param c the container 01033 * \param flags one or more flags from ao2_iterator_flags 01034 * 01035 * \retval the constructed iterator 01036 * 01037 * \note This function does \b not take a pointer to an iterator; 01038 * rather, it returns an iterator structure that should be 01039 * assigned to (overwriting) an existing iterator structure 01040 * allocated on the stack or on the heap. 01041 * 01042 * This function will take a reference on the container being iterated. 01043 * 01044 */ 01045 struct ao2_iterator ao2_iterator_init(struct ao2_container *c, int flags); 01046 01047 /*! 01048 * \brief Destroy a container iterator 01049 * 01050 * \param i the iterator to destroy 01051 * 01052 * \retval none 01053 * 01054 * This function will release the container reference held by the iterator 01055 * and any other resources it may be holding. 01056 * 01057 */ 01058 void ao2_iterator_destroy(struct ao2_iterator *i); 01059 01060 #ifdef REF_DEBUG 01061 01062 #define ao2_t_iterator_next(arg1, arg2) _ao2_iterator_next_debug((arg1), (arg2), __FILE__, __LINE__, __PRETTY_FUNCTION__) 01063 #define ao2_iterator_next(arg1) _ao2_iterator_next_debug((arg1), "", __FILE__, __LINE__, __PRETTY_FUNCTION__) 01064 01065 #else 01066 01067 #define ao2_t_iterator_next(arg1, arg2) _ao2_iterator_next((arg1)) 01068 #define ao2_iterator_next(arg1) _ao2_iterator_next((arg1)) 01069 01070 #endif 01071 01072 void *_ao2_iterator_next_debug(struct ao2_iterator *a, char *tag, char *file, int line, const char *funcname); 01073 void *_ao2_iterator_next(struct ao2_iterator *a); 01074 01075 /* extra functions */ 01076 void ao2_bt(void); /* backtrace */ 01077 01078 #endif /* _ASTERISK_ASTOBJ2_H */