Thu Oct 11 06:47:06 2012

Asterisk developer's documentation


astobj2.h

Go to the documentation of this file.
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  * \param debug_msg
00392  * \return A pointer to user-data.
00393  *
00394  * Allocates a struct astobj2 with sufficient space for the
00395  * user-defined structure.
00396  * \note
00397  * - storage is zeroed; XXX maybe we want a flag to enable/disable this.
00398  * - the refcount of the object just created is 1
00399  * - the returned pointer cannot be free()'d or realloc()'ed;
00400  *   rather, we just call ao2_ref(o, -1);
00401  *
00402  * @{
00403  */
00404 
00405 #if defined(REF_DEBUG)
00406 
00407 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) _ao2_alloc_debug((data_size), (destructor_fn), (debug_msg),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00408 #define ao2_alloc(data_size, destructor_fn)              _ao2_alloc_debug((data_size), (destructor_fn), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00409 
00410 #elif defined(__AST_DEBUG_MALLOC)
00411 
00412 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) _ao2_alloc_debug((data_size), (destructor_fn), (debug_msg),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00413 #define ao2_alloc(data_size, destructor_fn)              _ao2_alloc_debug((data_size), (destructor_fn), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00414 
00415 #else
00416 
00417 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) _ao2_alloc((data_size), (destructor_fn))
00418 #define ao2_alloc(data_size, destructor_fn)              _ao2_alloc((data_size), (destructor_fn))
00419 
00420 #endif
00421 
00422 void *_ao2_alloc_debug(const size_t data_size, ao2_destructor_fn destructor_fn, char *tag,
00423          const char *file, int line, const char *funcname, int ref_debug);
00424 void *_ao2_alloc(const size_t data_size, ao2_destructor_fn destructor_fn);
00425 
00426 /*! @} */
00427 
00428 /*! \brief
00429  * Reference/unreference an object and return the old refcount.
00430  *
00431  * \param o A pointer to the object
00432  * \param delta Value to add to the reference counter.
00433  * \return The value of the reference counter before the operation.
00434  *
00435  * Increase/decrease the reference counter according
00436  * the value of delta.
00437  *
00438  * If the refcount goes to zero, the object is destroyed.
00439  *
00440  * \note The object must not be locked by the caller of this function, as
00441  *       it is invalid to try to unlock it after releasing the reference.
00442  *
00443  * \note if we know the pointer to an object, it is because we
00444  * have a reference count to it, so the only case when the object
00445  * can go away is when we release our reference, and it is
00446  * the last one in existence.
00447  *
00448  * @{
00449  */
00450 
00451 #ifdef REF_DEBUG
00452 
00453 #define ao2_t_ref(o,delta,tag) _ao2_ref_debug((o), (delta), (tag),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00454 #define ao2_ref(o,delta)       _ao2_ref_debug((o), (delta), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00455 
00456 #else
00457 
00458 #define ao2_t_ref(o,delta,tag) _ao2_ref((o), (delta))
00459 #define ao2_ref(o,delta)       _ao2_ref((o), (delta))
00460 
00461 #endif
00462 
00463 int _ao2_ref_debug(void *o, int delta, char *tag, char *file, int line, const char *funcname);
00464 int _ao2_ref(void *o, int delta);
00465 /*! @} */
00466 
00467 /*! @} */
00468 
00469 /*! \brief
00470  * Lock an object.
00471  *
00472  * \param a A pointer to the object we want to lock.
00473  * \return 0 on success, other values on error.
00474  */
00475 int ao2_lock(void *a);
00476 int _ao2_lock(void *a, const char *file, const char *func, int line, const char *var);
00477 #ifdef DEBUG_THREADS
00478 #define ao2_lock(a) _ao2_lock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a)
00479 #endif
00480 
00481 /*! \brief
00482  * Unlock an object.
00483  *
00484  * \param a A pointer to the object we want unlock.
00485  * \return 0 on success, other values on error.
00486  */
00487 int ao2_unlock(void *a);
00488 int _ao2_unlock(void *a, const char *file, const char *func, int line, const char *var);
00489 #ifdef DEBUG_THREADS
00490 #define ao2_unlock(a) _ao2_unlock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a)
00491 #endif
00492 
00493 /*! \brief
00494  * Try locking-- (don't block if fail)
00495  *
00496  * \param a A pointer to the object we want to lock.
00497  * \return 0 on success, other values on error.
00498  */
00499 int ao2_trylock(void *a);
00500 int _ao2_trylock(void *a, const char *file, const char *func, int line, const char *var);
00501 #ifdef DEBUG_THREADS
00502 #define ao2_trylock(a) _ao2_trylock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a)
00503 #endif
00504 
00505 /*!
00506  * \brief Return the lock address of an object
00507  *
00508  * \param[in] obj A pointer to the object we want.
00509  * \return the address of the lock, else NULL.
00510  *
00511  * This function comes in handy mainly for debugging locking
00512  * situations, where the locking trace code reports the
00513  * lock address, this allows you to correlate against
00514  * object address, to match objects to reported locks.
00515  *
00516  * \since 1.6.1
00517  */
00518 void *ao2_object_get_lockaddr(void *obj);
00519 
00520 /*!
00521  \page AstObj2_Containers AstObj2 Containers
00522 
00523 Containers are data structures meant to store several objects,
00524 and perform various operations on them.
00525 Internally, objects are stored in lists, hash tables or other
00526 data structures depending on the needs.
00527 
00528 \note NOTA BENE: at the moment the only container we support is the
00529    hash table and its degenerate form, the list.
00530 
00531 Operations on container include:
00532 
00533   -  c = \b ao2_container_alloc(size, hash_fn, cmp_fn)
00534    allocate a container with desired size and default compare
00535    and hash function
00536          -The compare function returns an int, which
00537          can be 0 for not found, CMP_STOP to stop end a traversal,
00538          or CMP_MATCH if they are equal
00539          -The hash function returns an int. The hash function
00540          takes two argument, the object pointer and a flags field,
00541 
00542   -  \b ao2_find(c, arg, flags)
00543    returns zero or more element matching a given criteria
00544    (specified as arg). 'c' is the container pointer. Flags
00545     can be:
00546    OBJ_UNLINK - to remove the object, once found, from the container.
00547    OBJ_NODATA - don't return the object if found (no ref count change)
00548    OBJ_MULTIPLE - don't stop at first match (not fully implemented)
00549    OBJ_POINTER - if set, 'arg' is an object pointer, and a hashtable
00550                   search will be done. If not, a traversal is done.
00551 
00552   -  \b ao2_callback(c, flags, fn, arg)
00553    apply fn(obj, arg) to all objects in the container.
00554    Similar to find. fn() can tell when to stop, and
00555    do anything with the object including unlinking it.
00556      - c is the container;
00557       - flags can be
00558         OBJ_UNLINK   - to remove the object, once found, from the container.
00559         OBJ_NODATA   - don't return the object if found (no ref count change)
00560         OBJ_MULTIPLE - don't stop at first match (not fully implemented)
00561         OBJ_POINTER  - if set, 'arg' is an object pointer, and a hashtable
00562                         search will be done. If not, a traversal is done through
00563                         all the hashtable 'buckets'..
00564       - fn is a func that returns int, and takes 3 args:
00565         (void *obj, void *arg, int flags);
00566           obj is an object
00567           arg is the same as arg passed into ao2_callback
00568           flags is the same as flags passed into ao2_callback
00569          fn returns:
00570            0: no match, keep going
00571            CMP_STOP: stop search, no match
00572            CMP_MATCH: This object is matched.
00573 
00574    Note that the entire operation is run with the container
00575    locked, so noone else can change its content while we work on it.
00576    However, we pay this with the fact that doing
00577    anything blocking in the callback keeps the container
00578    blocked.
00579    The mechanism is very flexible because the callback function fn()
00580    can do basically anything e.g. counting, deleting records, etc.
00581    possibly using arg to store the results.
00582 
00583   -  \b iterate on a container
00584    this is done with the following sequence
00585 
00586 \code
00587 
00588        struct ao2_container *c = ... // our container
00589        struct ao2_iterator i;
00590        void *o;
00591 
00592        i = ao2_iterator_init(c, flags);
00593 
00594        while ((o = ao2_iterator_next(&i))) {
00595       ... do something on o ...
00596       ao2_ref(o, -1);
00597        }
00598 
00599        ao2_iterator_destroy(&i);
00600 \endcode
00601 
00602    The difference with the callback is that the control
00603    on how to iterate is left to us.
00604 
00605     - \b ao2_ref(c, -1)
00606    dropping a reference to a container destroys it, very simple!
00607 
00608 Containers are ao2 objects themselves, and this is why their
00609 implementation is simple too.
00610 
00611 Before declaring containers, we need to declare the types of the
00612 arguments passed to the constructor - in turn, this requires
00613 to define callback and hash functions and their arguments.
00614 
00615 - \ref AstObj2
00616 - \ref astobj2.h
00617  */
00618 
00619 /*! \brief
00620  * Type of a generic callback function
00621  * \param obj  pointer to the (user-defined part) of an object.
00622  * \param arg callback argument from ao2_callback()
00623  * \param flags flags from ao2_callback()
00624  *
00625  * The return values are a combination of enum _cb_results.
00626  * Callback functions are used to search or manipulate objects in a container.
00627  */
00628 typedef int (ao2_callback_fn)(void *obj, void *arg, int flags);
00629 
00630 /*! \brief
00631  * Type of a generic callback function
00632  * \param obj pointer to the (user-defined part) of an object.
00633  * \param arg callback argument from ao2_callback()
00634  * \param data arbitrary data from ao2_callback()
00635  * \param flags flags from ao2_callback()
00636  *
00637  * The return values are a combination of enum _cb_results.
00638  * Callback functions are used to search or manipulate objects in a container.
00639  */
00640 typedef int (ao2_callback_data_fn)(void *obj, void *arg, void *data, int flags);
00641 
00642 /*! \brief a very common callback is one that matches by address. */
00643 ao2_callback_fn ao2_match_by_addr;
00644 
00645 /*! \brief
00646  * A callback function will return a combination of CMP_MATCH and CMP_STOP.
00647  * The latter will terminate the search in a container.
00648  */
00649 enum _cb_results {
00650    CMP_MATCH   = 0x1,   /*!< the object matches the request */
00651    CMP_STOP = 0x2,   /*!< stop the search now */
00652 };
00653 
00654 /*! \brief
00655  * Flags passed to ao2_callback() and ao2_hash_fn() to modify its behaviour.
00656  */
00657 enum search_flags {
00658    /*! Unlink the object for which the callback function
00659     *  returned CMP_MATCH . This is the only way to extract
00660     *  objects from a container. */
00661    OBJ_UNLINK   = (1 << 0),
00662    /*! On match, don't return the object hence do not increase
00663     *  its refcount. */
00664    OBJ_NODATA   = (1 << 1),
00665    /*! Don't stop at the first match in ao2_callback()
00666     *  \note This is not fully implemented.   Using OBJ_MULTIME with OBJ_NODATA
00667     *  is perfectly fine.  The part that is not implemented is the case where
00668     *  multiple objects should be returned by ao2_callback().
00669     */
00670    OBJ_MULTIPLE = (1 << 2),
00671    /*! obj is an object of the same type as the one being searched for,
00672     *  so use the object's hash function for optimized searching.
00673     *  The search function is unaffected (i.e. use the one passed as
00674     *  argument, or match_by_addr if none specified). */
00675    OBJ_POINTER  = (1 << 3),
00676    /*! 
00677     * \brief Continue if a match is not found in the hashed out bucket
00678     *
00679     * This flag is to be used in combination with OBJ_POINTER.  This tells
00680     * the ao2_callback() core to keep searching through the rest of the
00681     * buckets if a match is not found in the starting bucket defined by
00682     * the hash value on the argument.
00683     */
00684    OBJ_CONTINUE     = (1 << 4),
00685 };
00686 
00687 /*!
00688  * Type of a generic function to generate a hash value from an object.
00689  * flags is ignored at the moment. Eventually, it will include the
00690  * value of OBJ_POINTER passed to ao2_callback().
00691  */
00692 typedef int (ao2_hash_fn)(const void *obj, const int flags);
00693 
00694 /*! \name Object Containers
00695  * Here start declarations of containers.
00696  */
00697 /*@{ */
00698 struct ao2_container;
00699 
00700 /*! \brief
00701  * Allocate and initialize a container
00702  * with the desired number of buckets.
00703  *
00704  * We allocate space for a struct astobj_container, struct container
00705  * and the buckets[] array.
00706  *
00707  * \param n_buckets Number of buckets for hash
00708  * \param hash_fn Pointer to a function computing a hash value.
00709  * \param cmp_fn Pointer to a function comparating key-value
00710  *          with a string. (can be NULL)
00711  * \return A pointer to a struct container.
00712  *
00713  * destructor is set implicitly.
00714  */
00715 
00716 #if defined(REF_DEBUG)
00717 
00718 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) _ao2_container_alloc_debug((arg1), (arg2), (arg3), (arg4),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00719 #define ao2_container_alloc(arg1,arg2,arg3)        _ao2_container_alloc_debug((arg1), (arg2), (arg3), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00720 
00721 #elif defined(__AST_DEBUG_MALLOC)
00722 
00723 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) _ao2_container_alloc_debug((arg1), (arg2), (arg3), (arg4),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00724 #define ao2_container_alloc(arg1,arg2,arg3)        _ao2_container_alloc_debug((arg1), (arg2), (arg3), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00725 
00726 #else
00727 
00728 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) _ao2_container_alloc((arg1), (arg2), (arg3))
00729 #define ao2_container_alloc(arg1,arg2,arg3)        _ao2_container_alloc((arg1), (arg2), (arg3))
00730 
00731 #endif
00732 
00733 struct ao2_container *_ao2_container_alloc(const unsigned int n_buckets,
00734                   ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn);
00735 struct ao2_container *_ao2_container_alloc_debug(const unsigned int n_buckets,
00736                    ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn,
00737                    char *tag, char *file, int line, const char *funcname,
00738                    int ref_debug);
00739 
00740 /*! \brief
00741  * Returns the number of elements in a container.
00742  */
00743 int ao2_container_count(struct ao2_container *c);
00744 
00745 /*@} */
00746 
00747 /*! \name Object Management
00748  * Here we have functions to manage objects.
00749  *
00750  * We can use the functions below on any kind of
00751  * object defined by the user.
00752  */
00753 /*@{ */
00754 
00755 /*!
00756  * \brief Add an object to a container.
00757  *
00758  * \param c the container to operate on.
00759  * \param newobj the object to be added.
00760  *
00761  * \retval NULL on errors
00762  * \retval newobj on success.
00763  *
00764  * This function inserts an object in a container according its key.
00765  *
00766  * \note Remember to set the key before calling this function.
00767  *
00768  * \note This function automatically increases the reference count to account
00769  *       for the reference that the container now holds to the object.
00770  */
00771 #ifdef REF_DEBUG
00772 
00773 #define ao2_t_link(arg1, arg2, arg3) _ao2_link_debug((arg1), (arg2), (arg3),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00774 #define ao2_link(arg1, arg2)         _ao2_link_debug((arg1), (arg2), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00775 
00776 #else
00777 
00778 #define ao2_t_link(arg1, arg2, arg3) _ao2_link((arg1), (arg2))
00779 #define ao2_link(arg1, arg2)         _ao2_link((arg1), (arg2))
00780 
00781 #endif
00782 
00783 void *_ao2_link_debug(struct ao2_container *c, void *new_obj, char *tag, char *file, int line, const char *funcname);
00784 void *_ao2_link(struct ao2_container *c, void *newobj);
00785 
00786 /*!
00787  * \brief Remove an object from a container
00788  *
00789  * \param c the container
00790  * \param obj the object to unlink
00791  *
00792  * \retval NULL, always
00793  *
00794  * \note The object requested to be unlinked must be valid.  However, if it turns
00795  *       out that it is not in the container, this function is still safe to
00796  *       be called.
00797  *
00798  * \note If the object gets unlinked from the container, the container's
00799  *       reference to the object will be automatically released. (The
00800  *       refcount will be decremented).
00801  */
00802 #ifdef REF_DEBUG
00803 
00804 #define ao2_t_unlink(arg1, arg2, arg3) _ao2_unlink_debug((arg1), (arg2), (arg3),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00805 #define ao2_unlink(arg1, arg2)         _ao2_unlink_debug((arg1), (arg2), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00806 
00807 #else
00808 
00809 #define ao2_t_unlink(arg1, arg2, arg3) _ao2_unlink((arg1), (arg2))
00810 #define ao2_unlink(arg1, arg2)         _ao2_unlink((arg1), (arg2))
00811 
00812 #endif
00813 
00814 void *_ao2_unlink_debug(struct ao2_container *c, void *obj, char *tag, char *file, int line, const char *funcname);
00815 void *_ao2_unlink(struct ao2_container *c, void *obj);
00816 
00817 
00818 /*! \brief Used as return value if the flag OBJ_MULTIPLE is set */
00819 struct ao2_list {
00820    struct ao2_list *next;
00821    void *obj;  /* pointer to the user portion of the object */
00822 };
00823 
00824 /*@} */
00825 
00826 /*! \brief
00827  * ao2_callback() is a generic function that applies cb_fn() to all objects
00828  * in a container, as described below.
00829  *
00830  * \param c A pointer to the container to operate on.
00831  * \param flags A set of flags specifying the operation to perform,
00832    partially used by the container code, but also passed to
00833    the callback.
00834      - If OBJ_NODATA is set, ao2_callback will return NULL. No refcounts
00835        of any of the traversed objects will be incremented.
00836        On the converse, if it is NOT set (the default), The ref count
00837        of each object for which CMP_MATCH was set will be incremented,
00838        and you will have no way of knowing which those are, until
00839        the multiple-object-return functionality is implemented.
00840      - If OBJ_POINTER is set, the traversed items will be restricted
00841        to the objects in the bucket that the object key hashes to.
00842  * \param cb_fn A function pointer, that will be called on all
00843     objects, to see if they match. This function returns CMP_MATCH
00844     if the object is matches the criteria; CMP_STOP if the traversal
00845     should immediately stop, or both (via bitwise ORing), if you find a
00846     match and want to end the traversal, and 0 if the object is not a match,
00847     but the traversal should continue. This is the function that is applied
00848     to each object traversed. It's arguments are:
00849         (void *obj, void *arg, int flags), where:
00850           obj is an object
00851           arg is the same as arg passed into ao2_callback
00852           flags is the same as flags passed into ao2_callback (flags are
00853            also used by ao2_callback).
00854  * \param arg passed to the callback.
00855  * \return  A pointer to the object found/marked,
00856  *       a pointer to a list of objects matching comparison function,
00857  *       NULL if not found.
00858  *
00859  * If the function returns any objects, their refcount is incremented,
00860  * and the caller is in charge of decrementing them once done.
00861  * Also, in case of multiple values returned, the list used
00862  * to store the objects must be freed by the caller.
00863  *
00864  * Typically, ao2_callback() is used for two purposes:
00865  * - to perform some action (including removal from the container) on one
00866  *   or more objects; in this case, cb_fn() can modify the object itself,
00867  *   and to perform deletion should set CMP_MATCH on the matching objects,
00868  *   and have OBJ_UNLINK set in flags.
00869  * - to look for a specific object in a container; in this case, cb_fn()
00870  *   should not modify the object, but just return a combination of
00871  *   CMP_MATCH and CMP_STOP on the desired object.
00872  * Other usages are also possible, of course.
00873 
00874  * This function searches through a container and performs operations
00875  * on objects according on flags passed.
00876  * XXX describe better
00877  * The comparison is done calling the compare function set implicitly.
00878  * The p pointer can be a pointer to an object or to a key,
00879  * we can say this looking at flags value.
00880  * If p points to an object we will search for the object pointed
00881  * by this value, otherwise we serch for a key value.
00882  * If the key is not uniq we only find the first matching valued.
00883  * If we use the OBJ_MARK flags, we mark all the objects matching
00884  * the condition.
00885  *
00886  * The use of flags argument is the follow:
00887  *
00888  * OBJ_UNLINK     unlinks the object found
00889  * OBJ_NODATA     on match, do return an object
00890  *          Callbacks use OBJ_NODATA as a default
00891  *          functions such as find() do
00892  * OBJ_MULTIPLE      return multiple matches
00893  *          Default for _find() is no.
00894  *          to a key (not yet supported)
00895  * OBJ_POINTER       the pointer is an object pointer
00896  *
00897  * In case we return a list, the callee must take care to destroy
00898  * that list when no longer used.
00899  *
00900  * \note When the returned object is no longer in use, ao2_ref() should
00901  * be used to free the additional reference possibly created by this function.
00902  *
00903  * @{
00904  */
00905 #ifdef REF_DEBUG
00906 
00907 #define ao2_t_callback(c,flags,cb_fn,arg,tag) _ao2_callback_debug((c), (flags), (cb_fn), (arg), (tag), __FILE__, __LINE__, __PRETTY_FUNCTION__)
00908 #define ao2_callback(c,flags,cb_fn,arg)       _ao2_callback_debug((c), (flags), (cb_fn), (arg), "", __FILE__, __LINE__, __PRETTY_FUNCTION__)
00909 
00910 #else
00911 
00912 #define ao2_t_callback(c,flags,cb_fn,arg,tag) _ao2_callback((c), (flags), (cb_fn), (arg))
00913 #define ao2_callback(c,flags,cb_fn,arg)       _ao2_callback((c), (flags), (cb_fn), (arg))
00914 
00915 #endif
00916 
00917 void *_ao2_callback_debug(struct ao2_container *c, enum search_flags flags,
00918                     ao2_callback_fn *cb_fn, void *arg, char *tag,
00919                     char *file, int line, const char *funcname);
00920 void *_ao2_callback(struct ao2_container *c,
00921                enum search_flags flags,
00922                ao2_callback_fn *cb_fn, void *arg);
00923 /*! @} */
00924 
00925 /*! \brief
00926  * ao2_callback_data() is a generic function that applies cb_fn() to all objects
00927  * in a container.  It is functionally identical to ao2_callback() except that
00928  * instead of taking an ao2_callback_fn *, it takes an ao2_callback_data_fn *, and
00929  * allows the caller to pass in arbitrary data.
00930  *
00931  * This call would be used instead of ao2_callback() when the caller needs to pass
00932  * OBJ_POINTER as part of the flags argument (which in turn requires passing in a
00933  * prototype ao2 object for 'arg') and also needs access to other non-global data
00934  * to complete it's comparison or task.
00935  *
00936  * See the documentation for ao2_callback() for argument descriptions.
00937  *
00938  * \see ao2_callback()
00939  */
00940 #ifdef REF_DEBUG
00941 #define ao2_t_callback_data(arg1,arg2,arg3,arg4,arg5,arg6) _ao2_callback_data_debug((arg1), (arg2), (arg3), (arg4), (arg5), (arg6), __FILE__, __LINE__, __PRETTY_FUNCTION__)
00942 #define ao2_callback_data(arg1,arg2,arg3,arg4,arg5)        _ao2_callback_data_debug((arg1), (arg2), (arg3), (arg4), (arg5), "", __FILE__, __LINE__, __PRETTY_FUNCTION__)
00943 #else
00944 #define ao2_t_callback_data(arg1,arg2,arg3,arg4,arg5,arg6) _ao2_callback_data((arg1), (arg2), (arg3), (arg4), (arg5))
00945 #define ao2_callback_data(arg1,arg2,arg3,arg4,arg5)        _ao2_callback_data((arg1), (arg2), (arg3), (arg4), (arg5))
00946 #endif
00947 void *_ao2_callback_data_debug(struct ao2_container *c, enum search_flags flags,
00948                     ao2_callback_data_fn *cb_fn, void *arg, void *data, char *tag,
00949                     char *file, int line, const char *funcname);
00950 void *_ao2_callback_data(struct ao2_container *c,
00951                enum search_flags flags,
00952                ao2_callback_data_fn *cb_fn, void *arg, void *data);
00953 
00954 /*! ao2_find() is a short hand for ao2_callback(c, flags, c->cmp_fn, arg)
00955  * XXX possibly change order of arguments ?
00956  */
00957 #ifdef REF_DEBUG
00958 
00959 #define ao2_t_find(arg1,arg2,arg3,arg4) _ao2_find_debug((arg1), (arg2), (arg3), (arg4), __FILE__, __LINE__, __PRETTY_FUNCTION__)
00960 #define ao2_find(arg1,arg2,arg3)        _ao2_find_debug((arg1), (arg2), (arg3), "", __FILE__, __LINE__, __PRETTY_FUNCTION__)
00961 
00962 #else
00963 
00964 #define ao2_t_find(arg1,arg2,arg3,arg4) _ao2_find((arg1), (arg2), (arg3))
00965 #define ao2_find(arg1,arg2,arg3)        _ao2_find((arg1), (arg2), (arg3))
00966 
00967 #endif
00968 
00969 void *_ao2_find_debug(struct ao2_container *c, void *arg, enum search_flags flags, char *tag, char *file, int line, const char *funcname);
00970 void *_ao2_find(struct ao2_container *c, void *arg, enum search_flags flags);
00971 
00972 /*! \brief
00973  *
00974  *
00975  * When we need to walk through a container, we use an
00976  * ao2_iterator to keep track of the current position.
00977  *
00978  * Because the navigation is typically done without holding the
00979  * lock on the container across the loop, objects can be inserted or deleted
00980  * or moved while we work. As a consequence, there is no guarantee that
00981  * we manage to touch all the elements in the container, and it is possible
00982  * that we touch the same object multiple times.
00983  *
00984  * However, within the current hash table container, the following is true:
00985  *  - It is not possible to miss an object in the container while iterating
00986  *    unless it gets added after the iteration begins and is added to a bucket
00987  *    that is before the one the current object is in.  In this case, even if
00988  *    you locked the container around the entire iteration loop, you still would
00989  *    not see this object, because it would still be waiting on the container
00990  *    lock so that it can be added.
00991  *  - It would be extremely rare to see an object twice.  The only way this can
00992  *    happen is if an object got unlinked from the container and added again
00993  *    during the same iteration.  Furthermore, when the object gets added back,
00994  *    it has to be in the current or later bucket for it to be seen again.
00995  *
00996  * An iterator must be first initialized with ao2_iterator_init(),
00997  * then we can use o = ao2_iterator_next() to move from one
00998  * element to the next. Remember that the object returned by
00999  * ao2_iterator_next() has its refcount incremented,
01000  * and the reference must be explicitly released when done with it.
01001  *
01002  * In addition, ao2_iterator_init() will hold a reference to the container
01003  * being iterated, which will be freed when ao2_iterator_destroy() is called
01004  * to free up the resources used by the iterator (if any).
01005  *
01006  * Example:
01007  *
01008  *  \code
01009  *
01010  *  struct ao2_container *c = ... // the container we want to iterate on
01011  *  struct ao2_iterator i;
01012  *  struct my_obj *o;
01013  *
01014  *  i = ao2_iterator_init(c, flags);
01015  *
01016  *  while ((o = ao2_iterator_next(&i))) {
01017  *     ... do something on o ...
01018  *     ao2_ref(o, -1);
01019  *  }
01020  *
01021  *  ao2_iterator_destroy(&i);
01022  *
01023  *  \endcode
01024  *
01025  */
01026 
01027 /*! \brief
01028  * The astobj2 iterator
01029  *
01030  * \note You are not supposed to know the internals of an iterator!
01031  * We would like the iterator to be opaque, unfortunately
01032  * its size needs to be known if we want to store it around
01033  * without too much trouble.
01034  * Anyways...
01035  * The iterator has a pointer to the container, and a flags
01036  * field specifying various things e.g. whether the container
01037  * should be locked or not while navigating on it.
01038  * The iterator "points" to the current object, which is identified
01039  * by three values:
01040  *
01041  * - a bucket number;
01042  * - the object_id, which is also the container version number
01043  *   when the object was inserted. This identifies the object
01044  *   uniquely, however reaching the desired object requires
01045  *   scanning a list.
01046  * - a pointer, and a container version when we saved the pointer.
01047  *   If the container has not changed its version number, then we
01048  *   can safely follow the pointer to reach the object in constant time.
01049  *
01050  * Details are in the implementation of ao2_iterator_next()
01051  * A freshly-initialized iterator has bucket=0, version=0.
01052  */
01053 struct ao2_iterator {
01054    /*! the container */
01055    struct ao2_container *c;
01056    /*! operation flags */
01057    int flags;
01058    /*! current bucket */
01059    int bucket;
01060    /*! container version */
01061    unsigned int c_version;
01062    /*! pointer to the current object */
01063    void *obj;
01064    /*! container version when the object was created */
01065    unsigned int version;
01066 };
01067 
01068 /*! Flags that can be passed to ao2_iterator_init() to modify the behavior
01069  * of the iterator.
01070  */
01071 enum ao2_iterator_flags {
01072    /*! Prevents ao2_iterator_next() from locking the container
01073     * while retrieving the next object from it.
01074     */
01075    AO2_ITERATOR_DONTLOCK = (1 << 0),
01076 };
01077 
01078 /*!
01079  * \brief Create an iterator for a container
01080  *
01081  * \param c the container
01082  * \param flags one or more flags from ao2_iterator_flags
01083  *
01084  * \retval the constructed iterator
01085  *
01086  * \note This function does \b not take a pointer to an iterator;
01087  *       rather, it returns an iterator structure that should be
01088  *       assigned to (overwriting) an existing iterator structure
01089  *       allocated on the stack or on the heap.
01090  *
01091  * This function will take a reference on the container being iterated.
01092  *
01093  */
01094 struct ao2_iterator ao2_iterator_init(struct ao2_container *c, int flags);
01095 
01096 /*!
01097  * \brief Destroy a container iterator
01098  *
01099  * \param i the iterator to destroy
01100  *
01101  * \retval none
01102  *
01103  * This function will release the container reference held by the iterator
01104  * and any other resources it may be holding.
01105  *
01106  */
01107 void ao2_iterator_destroy(struct ao2_iterator *i);
01108 
01109 #ifdef REF_DEBUG
01110 
01111 #define ao2_t_iterator_next(arg1, arg2) _ao2_iterator_next_debug((arg1), (arg2),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
01112 #define ao2_iterator_next(arg1)         _ao2_iterator_next_debug((arg1), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
01113 
01114 #else
01115 
01116 #define ao2_t_iterator_next(arg1, arg2) _ao2_iterator_next((arg1))
01117 #define ao2_iterator_next(arg1)         _ao2_iterator_next((arg1))
01118 
01119 #endif
01120 
01121 void *_ao2_iterator_next_debug(struct ao2_iterator *a, char *tag, char *file, int line, const char *funcname);
01122 void *_ao2_iterator_next(struct ao2_iterator *a);
01123 
01124 /* extra functions */
01125 void ao2_bt(void);   /* backtrace */
01126 
01127 #endif /* _ASTERISK_ASTOBJ2_H */

Generated on Thu Oct 11 06:47:06 2012 for Asterisk - the Open Source PBX by  doxygen 1.5.6