Wed Apr 6 11:29:40 2011

Asterisk developer's documentation


astobj2.h

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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 #include "asterisk/linkedlists.h"
00022 
00023 /*! \file
00024  * \ref AstObj2
00025  *
00026  * \page AstObj2 Object Model implementing objects and containers.
00027 
00028 This module implements an abstraction for objects (with locks and
00029 reference counts), and containers for these user-defined objects,
00030 also supporting locking, reference counting and callbacks.
00031 
00032 The internal implementation of objects and containers is opaque to the user,
00033 so we can use different data structures as needs arise.
00034 
00035 \section AstObj2_UsageObjects USAGE - OBJECTS
00036 
00037 An ao2 object is a block of memory that the user code can access,
00038 and for which the system keeps track (with a bit of help from the
00039 programmer) of the number of references around.  When an object has
00040 no more references (refcount == 0), it is destroyed, by first
00041 invoking whatever 'destructor' function the programmer specifies
00042 (it can be NULL if none is necessary), and then freeing the memory.
00043 This way objects can be shared without worrying who is in charge
00044 of freeing them.
00045 As an additional feature, ao2 objects are associated to individual
00046 locks.
00047 
00048 Creating an object requires the size of the object and
00049 and a pointer to the destructor function:
00050 
00051     struct foo *o;
00052 
00053     o = ao2_alloc(sizeof(struct foo), my_destructor_fn);
00054 
00055 The value returned points to the user-visible portion of the objects
00056 (user-data), but is also used as an identifier for all object-related
00057 operations such as refcount and lock manipulations.
00058 
00059 On return from ao2_alloc():
00060 
00061  - the object has a refcount = 1;
00062  - the memory for the object is allocated dynamically and zeroed;
00063  - we cannot realloc() the object itself;
00064  - we cannot call free(o) to dispose of the object. Rather, we
00065    tell the system that we do not need the reference anymore:
00066 
00067     ao2_ref(o, -1)
00068 
00069   causing the destructor to be called (and then memory freed) when
00070   the refcount goes to 0.
00071 
00072 - ao2_ref(o, +1) can be used to modify the refcount on the
00073   object in case we want to pass it around.
00074 
00075 - ao2_lock(obj), ao2_unlock(obj), ao2_trylock(obj) can be used
00076   to manipulate the lock associated with the object.
00077 
00078 
00079 \section AstObj2_UsageContainers USAGE - CONTAINERS
00080 
00081 An ao2 container is an abstract data structure where we can store
00082 ao2 objects, search them (hopefully in an efficient way), and iterate
00083 or apply a callback function to them. A container is just an ao2 object
00084 itself.
00085 
00086 A container must first be allocated, specifying the initial
00087 parameters. At the moment, this is done as follows:
00088 
00089     <b>Sample Usage:</b>
00090     \code
00091 
00092     struct ao2_container *c;
00093 
00094     c = ao2_container_alloc(MAX_BUCKETS, my_hash_fn, my_cmp_fn);
00095     \endcode
00096 
00097 where
00098 
00099 - MAX_BUCKETS is the number of buckets in the hash table,
00100 - my_hash_fn() is the (user-supplied) function that returns a
00101   hash key for the object (further reduced modulo MAX_BUCKETS
00102   by the container's code);
00103 - my_cmp_fn() is the default comparison function used when doing
00104   searches on the container,
00105 
00106 A container knows little or nothing about the objects it stores,
00107 other than the fact that they have been created by ao2_alloc().
00108 All knowledge of the (user-defined) internals of the objects
00109 is left to the (user-supplied) functions passed as arguments
00110 to ao2_container_alloc().
00111 
00112 If we want to insert an object in a container, we should
00113 initialize its fields -- especially, those used by my_hash_fn() --
00114 to compute the bucket to use.
00115 Once done, we can link an object to a container with
00116 
00117     ao2_link(c, o);
00118 
00119 The function returns NULL in case of errors (and the object
00120 is not inserted in the container). Other values mean success
00121 (we are not supposed to use the value as a pointer to anything).
00122 Linking an object to a container increases its refcount by 1
00123 automatically.
00124 
00125 \note While an object o is in a container, we expect that
00126 my_hash_fn(o) will always return the same value. The function
00127 does not lock the object to be computed, so modifications of
00128 those fields that affect the computation of the hash should
00129 be done by extracting the object from the container, and
00130 reinserting it after the change (this is not terribly expensive).
00131 
00132 \note A container with a single buckets is effectively a linked
00133 list. However there is no ordering among elements.
00134 
00135 - \ref AstObj2_Containers
00136 - \ref astobj2.h All documentation for functions and data structures
00137 
00138  */
00139 
00140 /*
00141 \note DEBUGGING REF COUNTS BIBLE:
00142 An interface to help debug refcounting is provided
00143 in this package. It is dependent on the REF_DEBUG macro being
00144 defined in a source file, before the #include of astobj2.h,
00145 and in using variants of the normal ao2_xxxx functions
00146 that are named ao2_t_xxxx instead, with an extra argument, a string,
00147 that will be printed out into /tmp/refs when the refcount for an
00148 object is changed.
00149 
00150   these ao2_t_xxxx variants are provided:
00151 
00152 ao2_t_alloc(arg1, arg2, arg3)
00153 ao2_t_ref(arg1,arg2,arg3)
00154 ao2_t_container_alloc(arg1,arg2,arg3,arg4)
00155 ao2_t_link(arg1, arg2, arg3)
00156 ao2_t_unlink(arg1, arg2, arg3)
00157 ao2_t_callback(arg1,arg2,arg3,arg4,arg5)
00158 ao2_t_find(arg1,arg2,arg3,arg4)
00159 ao2_t_iterator_next(arg1, arg2)
00160 
00161 If you study each argument list, you will see that these functions all have
00162 one extra argument that their ao2_xxx counterpart. The last argument in
00163 each case is supposed to be a string pointer, a "tag", that should contain
00164 enough of an explanation, that you can pair operations that increment the
00165 ref count, with operations that are meant to decrement the refcount.
00166 
00167 Each of these calls will generate at least one line of output in /tmp/refs.
00168 These lines look like this:
00169 ...
00170 0x8756f00 =1   chan_sip.c:22240:load_module (allocate users)
00171 0x86e3408 =1   chan_sip.c:22241:load_module (allocate peers)
00172 0x86dd380 =1   chan_sip.c:22242:load_module (allocate peers_by_ip)
00173 0x822d020 =1   chan_sip.c:22243:load_module (allocate dialogs)
00174 0x8930fd8 =1   chan_sip.c:20025:build_peer (allocate a peer struct)
00175 0x8930fd8 +1   chan_sip.c:21467:reload_config (link peer into peer table) [@1]
00176 0x8930fd8 -1   chan_sip.c:2370:unref_peer (unref_peer: from reload_config) [@2]
00177 0x89318b0 =1   chan_sip.c:20025:build_peer (allocate a peer struct)
00178 0x89318b0 +1   chan_sip.c:21467:reload_config (link peer into peer table) [@1]
00179 0x89318b0 -1   chan_sip.c:2370:unref_peer (unref_peer: from reload_config) [@2]
00180 0x8930218 =1   chan_sip.c:20025:build_peer (allocate a peer struct)
00181 0x8930218 +1   chan_sip.c:21539:reload_config (link peer into peers table) [@1]
00182 0x868c040 -1   chan_sip.c:2424:dialog_unlink_all (unset the relatedpeer->call field in tandem with relatedpeer field itself) [@2]
00183 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]
00184 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)
00185 0x8cc07e8 -1   chan_sip.c:2370:unref_peer (unsetting a dialog relatedpeer field in sip_destroy) [@3]
00186 0x8cc07e8 +1   chan_sip.c:3876:find_peer (ao2_find in peers table) [@2]
00187 0x8cc07e8 -1   chan_sip.c:2370:unref_peer (unref_peer, from sip_devicestate, release ref from find_peer) [@3]
00188 ...
00189 
00190 The first column is the object address.
00191 The second column reflects how the operation affected the ref count
00192     for that object. Creation sets the ref count to 1 (=1).
00193     increment or decrement and amount are specified (-1/+1).
00194 The remainder of the line specifies where in the file the call was made,
00195     and the function name, and the tag supplied in the function call.
00196 
00197 The **call destructor** is specified when the the destroy routine is
00198 run for an object. It does not affect the ref count, but is important
00199 in debugging, because it is possible to have the astobj2 system run it
00200 multiple times on the same object, commonly fatal to asterisk.
00201 
00202 Sometimes you have some helper functions to do object ref/unref
00203 operations. Using these normally hides the place where these
00204 functions were called. To get the location where these functions
00205 were called to appear in /tmp/refs, you can do this sort of thing:
00206 
00207 #ifdef REF_DEBUG
00208 #define dialog_ref(arg1,arg2) dialog_ref_debug((arg1),(arg2), __FILE__, __LINE__, __PRETTY_FUNCTION__)
00209 #define dialog_unref(arg1,arg2) dialog_unref_debug((arg1),(arg2), __FILE__, __LINE__, __PRETTY_FUNCTION__)
00210 static struct sip_pvt *dialog_ref_debug(struct sip_pvt *p, char *tag, const char *file, int line, const char *func)
00211 {
00212    if (p)
00213       ao2_ref_debug(p, 1, tag, file, line, func);
00214    else
00215       ast_log(LOG_ERROR, "Attempt to Ref a null pointer\n");
00216    return p;
00217 }
00218 
00219 static struct sip_pvt *dialog_unref_debug(struct sip_pvt *p, char *tag, const char *file, int line, const char *func)
00220 {
00221    if (p)
00222       ao2_ref_debug(p, -1, tag, file, line, func);
00223    return NULL;
00224 }
00225 #else
00226 static struct sip_pvt *dialog_ref(struct sip_pvt *p, char *tag)
00227 {
00228    if (p)
00229       ao2_ref(p, 1);
00230    else
00231       ast_log(LOG_ERROR, "Attempt to Ref a null pointer\n");
00232    return p;
00233 }
00234 
00235 static struct sip_pvt *dialog_unref(struct sip_pvt *p, char *tag)
00236 {
00237    if (p)
00238       ao2_ref(p, -1);
00239    return NULL;
00240 }
00241 #endif
00242 
00243 In the above code, note that the "normal" helper funcs call ao2_ref() as
00244 normal, and the "helper" functions call ao2_ref_debug directly with the
00245 file, function, and line number info provided. You might find this
00246 well worth the effort to help track these function calls in the code.
00247 
00248 To find out why objects are not destroyed (a common bug), you can
00249 edit the source file to use the ao2_t_* variants, add the #define REF_DEBUG 1
00250 before the #include "asterisk/astobj2.h" line, and add a descriptive
00251 tag to each call. Recompile, and run Asterisk, exit asterisk with
00252 "stop gracefully", which should result in every object being destroyed.
00253 Then, you can "sort -k 1 /tmp/refs > x1" to get a sorted list of
00254 all the objects, or you can use "util/refcounter" to scan the file
00255 for you and output any problems it finds.
00256 
00257 The above may seem astronomically more work than it is worth to debug
00258 reference counts, which may be true in "simple" situations, but for
00259 more complex situations, it is easily worth 100 times this effort to
00260 help find problems.
00261 
00262 To debug, pair all calls so that each call that increments the
00263 refcount is paired with a corresponding call that decrements the
00264 count for the same reason. Hopefully, you will be left with one
00265 or more unpaired calls. This is where you start your search!
00266 
00267 For instance, here is an example of this for a dialog object in
00268 chan_sip, that was not getting destroyed, after I moved the lines around
00269 to pair operations:
00270 
00271    0x83787a0 =1   chan_sip.c:5733:sip_alloc (allocate a dialog(pvt) struct)
00272    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]
00273 
00274    0x83787a0 +1   chan_sip.c:5854:sip_alloc (link pvt into dialogs table) [@1]
00275    0x83787a0 -1   chan_sip.c:19150:sip_poke_peer (About to change the callid -- remove the old name) [@3]
00276    0x83787a0 +1   chan_sip.c:19152:sip_poke_peer (Linking in under new name) [@2]
00277    0x83787a0 -1   chan_sip.c:2399:dialog_unlink_all (unlinking dialog via ao2_unlink) [@5]
00278 
00279    0x83787a0 +1   chan_sip.c:19130:sip_poke_peer (copy sip alloc from p to peer->call) [@2]
00280 
00281 
00282    0x83787a0 +1   chan_sip.c:2996:__sip_reliable_xmit (__sip_reliable_xmit: setting pkt->owner) [@3]
00283    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]
00284 
00285    0x83787a0 +1   chan_sip.c:22356:unload_module (iterate thru dialogs) [@4]
00286    0x83787a0 -1   chan_sip.c:22359:unload_module (toss dialog ptr from iterator_next) [@5]
00287 
00288 
00289    0x83787a0 +1   chan_sip.c:22373:unload_module (iterate thru dialogs) [@3]
00290    0x83787a0 -1   chan_sip.c:22375:unload_module (throw away iterator result) [@2]
00291 
00292    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]
00293    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]
00294 
00295 As you can see, only one unbalanced operation is in the list, a ref count increment when
00296 the peer->call was set, but no corresponding decrement was made...
00297 
00298 Hopefully this helps you narrow your search and find those bugs.
00299 
00300 THE ART OF REFERENCE COUNTING
00301 (by Steve Murphy)
00302 SOME TIPS for complicated code, and ref counting:
00303 
00304 1. Theoretically, passing a refcounted object pointer into a function
00305 call is an act of copying the reference, and could be refcounted.
00306 But, upon examination, this sort of refcounting will explode the amount
00307 of code you have to enter, and for no tangible benefit, beyond
00308 creating more possible failure points/bugs. It will even
00309 complicate your code and make debugging harder, slow down your program
00310 doing useless increments and decrements of the ref counts.
00311 
00312 2. It is better to track places where a ref counted pointer
00313 is copied into a structure or stored. Make sure to decrement the refcount
00314 of any previous pointer that might have been there, if setting
00315 this field might erase a previous pointer. ao2_find and iterate_next
00316 internally increment the ref count when they return a pointer, so
00317 you need to decrement the count before the pointer goes out of scope.
00318 
00319 3. Any time you decrement a ref count, it may be possible that the
00320 object will be destroyed (freed) immediately by that call. If you
00321 are destroying a series of fields in a refcounted object, and
00322 any of the unref calls might possibly result in immediate destruction,
00323 you can first increment the count to prevent such behavior, then
00324 after the last test, decrement the pointer to allow the object
00325 to be destroyed, if the refcount would be zero.
00326 
00327 Example:
00328 
00329    dialog_ref(dialog, "Let's bump the count in the unlink so it doesn't accidentally become dead before we are done");
00330 
00331    ao2_t_unlink(dialogs, dialog, "unlinking dialog via ao2_unlink");
00332 
00333    *//* Unlink us from the owner (channel) if we have one *//*
00334    if (dialog->owner) {
00335       if (lockowner)
00336          ast_channel_lock(dialog->owner);
00337       ast_debug(1, "Detaching from channel %s\n", dialog->owner->name);
00338       dialog->owner->tech_pvt = dialog_unref(dialog->owner->tech_pvt, "resetting channel dialog ptr in unlink_all");
00339       if (lockowner)
00340          ast_channel_unlock(dialog->owner);
00341    }
00342    if (dialog->registry) {
00343       if (dialog->registry->call == dialog)
00344          dialog->registry->call = dialog_unref(dialog->registry->call, "nulling out the registry's call dialog field in unlink_all");
00345       dialog->registry = registry_unref(dialog->registry, "delete dialog->registry");
00346    }
00347     ...
00348    dialog_unref(dialog, "Let's unbump the count in the unlink so the poor pvt can disappear if it is time");
00349 
00350 In the above code, the ao2_t_unlink could end up destroying the dialog
00351 object; if this happens, then the subsequent usages of the dialog
00352 pointer could result in a core dump. So, we 'bump' the
00353 count upwards before beginning, and then decrementing the count when
00354 we are finished. This is analogous to 'locking' or 'protecting' operations
00355 for a short while.
00356 
00357 4. One of the most insidious problems I've run into when converting
00358 code to do ref counted automatic destruction, is in the destruction
00359 routines. Where a "destroy" routine had previously been called to
00360 get rid of an object in non-refcounted code, the new regime demands
00361 that you tear that "destroy" routine into two pieces, one that will
00362 tear down the links and 'unref' them, and the other to actually free
00363 and reset fields. A destroy routine that does any reference deletion
00364 for its own object, will never be called. Another insidious problem
00365 occurs in mutually referenced structures. As an example, a dialog contains
00366 a pointer to a peer, and a peer contains a pointer to a dialog. Watch
00367 out that the destruction of one doesn't depend on the destruction of the
00368 other, as in this case a dependency loop will result in neither being
00369 destroyed!
00370 
00371 Given the above, you should be ready to do a good job!
00372 
00373 murf
00374 
00375 */
00376 
00377 
00378 
00379 /*! \brief
00380  * Typedef for an object destructor. This is called just before freeing
00381  * the memory for the object. It is passed a pointer to the user-defined
00382  * data of the object.
00383  */
00384 typedef void (*ao2_destructor_fn)(void *);
00385 
00386 
00387 /*! \brief
00388  * Allocate and initialize an object.
00389  *
00390  * \param data_size The sizeof() of the user-defined structure.
00391  * \param destructor_fn The destructor function (can be NULL)
00392  * \param debug_msg
00393  * \return A pointer to user-data.
00394  *
00395  * Allocates a struct astobj2 with sufficient space for the
00396  * user-defined structure.
00397  * \note
00398  * - storage is zeroed; XXX maybe we want a flag to enable/disable this.
00399  * - the refcount of the object just created is 1
00400  * - the returned pointer cannot be free()'d or realloc()'ed;
00401  *   rather, we just call ao2_ref(o, -1);
00402  *
00403  * @{
00404  */
00405 
00406 #if defined(REF_DEBUG)
00407 
00408 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) __ao2_alloc_debug((data_size), (destructor_fn), (debug_msg),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00409 #define ao2_alloc(data_size, destructor_fn)              __ao2_alloc_debug((data_size), (destructor_fn), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00410 
00411 #elif defined(__AST_DEBUG_MALLOC)
00412 
00413 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) __ao2_alloc_debug((data_size), (destructor_fn), (debug_msg),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00414 #define ao2_alloc(data_size, destructor_fn)              __ao2_alloc_debug((data_size), (destructor_fn), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00415 
00416 #else
00417 
00418 #define ao2_t_alloc(data_size, destructor_fn, debug_msg) __ao2_alloc((data_size), (destructor_fn))
00419 #define ao2_alloc(data_size, destructor_fn)              __ao2_alloc((data_size), (destructor_fn))
00420 
00421 #endif
00422 
00423 void *__ao2_alloc_debug(const size_t data_size, ao2_destructor_fn destructor_fn, char *tag,
00424          const char *file, int line, const char *funcname, int ref_debug);
00425 void *__ao2_alloc(const size_t data_size, ao2_destructor_fn destructor_fn);
00426 
00427 /*! @} */
00428 
00429 /*! \brief
00430  * Reference/unreference an object and return the old refcount.
00431  *
00432  * \param o A pointer to the object
00433  * \param delta Value to add to the reference counter.
00434  * \param tag used for debugging
00435  * \return The value of the reference counter before the operation.
00436  *
00437  * Increase/decrease the reference counter according
00438  * the value of delta.
00439  *
00440  * If the refcount goes to zero, the object is destroyed.
00441  *
00442  * \note The object must not be locked by the caller of this function, as
00443  *       it is invalid to try to unlock it after releasing the reference.
00444  *
00445  * \note if we know the pointer to an object, it is because we
00446  * have a reference count to it, so the only case when the object
00447  * can go away is when we release our reference, and it is
00448  * the last one in existence.
00449  *
00450  * @{
00451  */
00452 
00453 #ifdef REF_DEBUG
00454 
00455 #define ao2_t_ref(o,delta,tag) __ao2_ref_debug((o), (delta), (tag),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00456 #define ao2_ref(o,delta)       __ao2_ref_debug((o), (delta), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00457 
00458 #else
00459 
00460 #define ao2_t_ref(o,delta,tag) __ao2_ref((o), (delta))
00461 #define ao2_ref(o,delta)       __ao2_ref((o), (delta))
00462 
00463 #endif
00464 
00465 int __ao2_ref_debug(void *o, int delta, char *tag, char *file, int line, const char *funcname);
00466 int __ao2_ref(void *o, int delta);
00467 
00468 /*! @} */
00469 
00470 /*! \brief
00471  * Lock an object.
00472  *
00473  * \param a A pointer to the object we want to lock.
00474  * \return 0 on success, other values on error.
00475  */
00476 int __ao2_lock(void *a, const char *file, const char *func, int line, const char *var);
00477 #define ao2_lock(a) __ao2_lock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a)
00478 
00479 /*! \brief
00480  * Unlock an object.
00481  *
00482  * \param a A pointer to the object we want unlock.
00483  * \return 0 on success, other values on error.
00484  */
00485 int __ao2_unlock(void *a, const char *file, const char *func, int line, const char *var);
00486 #define ao2_unlock(a) __ao2_unlock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a)
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, const char *file, const char *func, int line, const char *var);
00495 #define ao2_trylock(a) __ao2_trylock(a, __FILE__, __PRETTY_FUNCTION__, __LINE__, #a)
00496 
00497 /*!
00498  * \brief Return the lock address of an object
00499  *
00500  * \param[in] obj A pointer to the object we want.
00501  * \return the address of the lock, else NULL.
00502  *
00503  * This function comes in handy mainly for debugging locking
00504  * situations, where the locking trace code reports the
00505  * lock address, this allows you to correlate against
00506  * object address, to match objects to reported locks.
00507  *
00508  * \since 1.6.1
00509  */
00510 void *ao2_object_get_lockaddr(void *obj);
00511 
00512 /*!
00513  \page AstObj2_Containers AstObj2 Containers
00514 
00515 Containers are data structures meant to store several objects,
00516 and perform various operations on them.
00517 Internally, objects are stored in lists, hash tables or other
00518 data structures depending on the needs.
00519 
00520 \note NOTA BENE: at the moment the only container we support is the
00521    hash table and its degenerate form, the list.
00522 
00523 Operations on container include:
00524 
00525   -  c = \b ao2_container_alloc(size, hash_fn, cmp_fn)
00526    allocate a container with desired size and default compare
00527    and hash function
00528          -The compare function returns an int, which
00529          can be 0 for not found, CMP_STOP to stop end a traversal,
00530          or CMP_MATCH if they are equal
00531          -The hash function returns an int. The hash function
00532          takes two argument, the object pointer and a flags field,
00533 
00534   -  \b ao2_find(c, arg, flags)
00535    returns zero or more element matching a given criteria
00536    (specified as arg). 'c' is the container pointer. Flags
00537     can be:
00538    OBJ_UNLINK - to remove the object, once found, from the container.
00539    OBJ_NODATA - don't return the object if found (no ref count change)
00540    OBJ_MULTIPLE - don't stop at first match
00541    OBJ_POINTER - if set, 'arg' is an object pointer, and a hashtable
00542                   search will be done. If not, a traversal is done.
00543 
00544   -  \b ao2_callback(c, flags, fn, arg)
00545    apply fn(obj, arg) to all objects in the container.
00546    Similar to find. fn() can tell when to stop, and
00547    do anything with the object including unlinking it.
00548      - c is the container;
00549       - flags can be
00550         OBJ_UNLINK   - to remove the object, once found, from the container.
00551         OBJ_NODATA   - don't return the object if found (no ref count change)
00552         OBJ_MULTIPLE - don't stop at first match
00553         OBJ_POINTER  - if set, 'arg' is an object pointer, and a hashtable
00554                         search will be done. If not, a traversal is done through
00555                         all the hashtable 'buckets'..
00556       - fn is a func that returns int, and takes 3 args:
00557         (void *obj, void *arg, int flags);
00558           obj is an object
00559           arg is the same as arg passed into ao2_callback
00560           flags is the same as flags passed into ao2_callback
00561          fn returns:
00562            0: no match, keep going
00563            CMP_STOP: stop search, no match
00564            CMP_MATCH: This object is matched.
00565 
00566    Note that the entire operation is run with the container
00567    locked, so noone else can change its content while we work on it.
00568    However, we pay this with the fact that doing
00569    anything blocking in the callback keeps the container
00570    blocked.
00571    The mechanism is very flexible because the callback function fn()
00572    can do basically anything e.g. counting, deleting records, etc.
00573    possibly using arg to store the results.
00574 
00575   -  \b iterate on a container
00576    this is done with the following sequence
00577 
00578 \code
00579 
00580        struct ao2_container *c = ... // our container
00581        struct ao2_iterator i;
00582        void *o;
00583 
00584        i = ao2_iterator_init(c, flags);
00585 
00586        while ((o = ao2_iterator_next(&i))) {
00587       ... do something on o ...
00588       ao2_ref(o, -1);
00589        }
00590 
00591        ao2_iterator_destroy(&i);
00592 \endcode
00593 
00594    The difference with the callback is that the control
00595    on how to iterate is left to us.
00596 
00597     - \b ao2_ref(c, -1)
00598    dropping a reference to a container destroys it, very simple!
00599 
00600 Containers are ao2 objects themselves, and this is why their
00601 implementation is simple too.
00602 
00603 Before declaring containers, we need to declare the types of the
00604 arguments passed to the constructor - in turn, this requires
00605 to define callback and hash functions and their arguments.
00606 
00607 - \ref AstObj2
00608 - \ref astobj2.h
00609  */
00610 
00611 /*! \brief
00612  * Type of a generic callback function
00613  * \param obj  pointer to the (user-defined part) of an object.
00614  * \param arg callback argument from ao2_callback()
00615  * \param flags flags from ao2_callback()
00616  *
00617  * The return values are a combination of enum _cb_results.
00618  * Callback functions are used to search or manipulate objects in a container.
00619  */
00620 typedef int (ao2_callback_fn)(void *obj, void *arg, int flags);
00621 
00622 /*! \brief
00623  * Type of a generic callback function
00624  * \param obj pointer to the (user-defined part) of an object.
00625  * \param arg callback argument from ao2_callback()
00626  * \param data arbitrary data from ao2_callback()
00627  * \param flags flags from ao2_callback()
00628  *
00629  * The return values are a combination of enum _cb_results.
00630  * Callback functions are used to search or manipulate objects in a container.
00631  */
00632 typedef int (ao2_callback_data_fn)(void *obj, void *arg, void *data, int flags);
00633 
00634 /*! \brief a very common callback is one that matches by address. */
00635 ao2_callback_fn ao2_match_by_addr;
00636 
00637 /*! \brief
00638  * A callback function will return a combination of CMP_MATCH and CMP_STOP.
00639  * The latter will terminate the search in a container.
00640  */
00641 enum _cb_results {
00642    CMP_MATCH   = 0x1,   /*!< the object matches the request */
00643    CMP_STOP = 0x2,   /*!< stop the search now */
00644 };
00645 
00646 /*! \brief
00647  * Flags passed to ao2_callback() and ao2_hash_fn() to modify its behaviour.
00648  */
00649 enum search_flags {
00650    /*! Unlink the object for which the callback function
00651     *  returned CMP_MATCH.
00652     */
00653    OBJ_UNLINK   = (1 << 0),
00654    /*! On match, don't return the object hence do not increase
00655     *  its refcount.
00656     */
00657    OBJ_NODATA   = (1 << 1),
00658    /*! Don't stop at the first match in ao2_callback() unless the result of
00659     *  of the callback function == (CMP_STOP | CMP_MATCH).
00660     */
00661    OBJ_MULTIPLE = (1 << 2),
00662    /*! obj is an object of the same type as the one being searched for,
00663     *  so use the object's hash function for optimized searching.
00664     *  The search function is unaffected (i.e. use the one passed as
00665     *  argument, or match_by_addr if none specified).
00666     */
00667    OBJ_POINTER  = (1 << 3),
00668    /*! 
00669     * \brief Continue if a match is not found in the hashed out bucket
00670     *
00671     * This flag is to be used in combination with OBJ_POINTER.  This tells
00672     * the ao2_callback() core to keep searching through the rest of the
00673     * buckets if a match is not found in the starting bucket defined by
00674     * the hash value on the argument.
00675     */
00676    OBJ_CONTINUE     = (1 << 4),
00677 };
00678 
00679 /*!
00680  * Type of a generic function to generate a hash value from an object.
00681  * flags is ignored at the moment. Eventually, it will include the
00682  * value of OBJ_POINTER passed to ao2_callback().
00683  */
00684 typedef int (ao2_hash_fn)(const void *obj, const int flags);
00685 
00686 /*! \name Object Containers
00687  * Here start declarations of containers.
00688  */
00689 /*@{ */
00690 struct ao2_container;
00691 
00692 /*! \brief
00693  * Allocate and initialize a container
00694  * with the desired number of buckets.
00695  *
00696  * We allocate space for a struct astobj_container, struct container
00697  * and the buckets[] array.
00698  *
00699  * \param arg1 Number of buckets for hash
00700  * \param arg2 Pointer to a function computing a hash value.
00701  * \param arg3 Pointer to a function comparating key-value
00702  *          with a string. (can be NULL)
00703  * \param arg4
00704  *
00705  * \return A pointer to a struct container.
00706  *
00707  * \note Destructor is set implicitly.
00708  */
00709 
00710 #if defined(REF_DEBUG)
00711 
00712 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) __ao2_container_alloc_debug((arg1), (arg2), (arg3), (arg4),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00713 #define ao2_container_alloc(arg1,arg2,arg3)        __ao2_container_alloc_debug((arg1), (arg2), (arg3), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 1)
00714 
00715 #elif defined(__AST_DEBUG_MALLOC)
00716 
00717 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) __ao2_container_alloc_debug((arg1), (arg2), (arg3), (arg4),  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00718 #define ao2_container_alloc(arg1,arg2,arg3)        __ao2_container_alloc_debug((arg1), (arg2), (arg3), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__, 0)
00719 
00720 #else
00721 
00722 #define ao2_t_container_alloc(arg1,arg2,arg3,arg4) __ao2_container_alloc((arg1), (arg2), (arg3))
00723 #define ao2_container_alloc(arg1,arg2,arg3)        __ao2_container_alloc((arg1), (arg2), (arg3))
00724 
00725 #endif
00726 
00727 struct ao2_container *__ao2_container_alloc(const unsigned int n_buckets,
00728                    ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn);
00729 struct ao2_container *__ao2_container_alloc_debug(const unsigned int n_buckets,
00730                     ao2_hash_fn *hash_fn, ao2_callback_fn *cmp_fn,
00731                     char *tag, char *file, int line, const char *funcname,
00732                     int ref_debug);
00733 
00734 /*! \brief
00735  * Returns the number of elements in a container.
00736  */
00737 int ao2_container_count(struct ao2_container *c);
00738 
00739 /*@} */
00740 
00741 /*! \name Object Management
00742  * Here we have functions to manage objects.
00743  *
00744  * We can use the functions below on any kind of
00745  * object defined by the user.
00746  */
00747 /*@{ */
00748 
00749 /*!
00750  * \brief Add an object to a container.
00751  *
00752  * \param arg1 the container to operate on.
00753  * \param arg2 the object to be added.
00754  * \param arg3 used for debuging.
00755  *
00756  * \retval NULL on errors.
00757  * \retval newobj on success.
00758  *
00759  * This function inserts an object in a container according its key.
00760  *
00761  * \note Remember to set the key before calling this function.
00762  *
00763  * \note This function automatically increases the reference count to account
00764  *       for the reference that the container now holds to the object.
00765  */
00766 #ifdef REF_DEBUG
00767 
00768 #define ao2_t_link(arg1, arg2, arg3) __ao2_link_debug((arg1), (arg2), (arg3),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00769 #define ao2_link(arg1, arg2)         __ao2_link_debug((arg1), (arg2), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00770 
00771 #else
00772 
00773 #define ao2_t_link(arg1, arg2, arg3) __ao2_link((arg1), (arg2))
00774 #define ao2_link(arg1, arg2)         __ao2_link((arg1), (arg2))
00775 
00776 #endif
00777 
00778 void *__ao2_link_debug(struct ao2_container *c, void *new_obj, char *tag, char *file, int line, const char *funcname);
00779 void *__ao2_link(struct ao2_container *c, void *newobj);
00780 
00781 /*!
00782  * \brief Remove an object from a container
00783  *
00784  * \param arg1 the container
00785  * \param arg2 the object to unlink
00786  * \param arg3 tag for debugging
00787  *
00788  * \retval NULL, always
00789  *
00790  * \note The object requested to be unlinked must be valid.  However, if it turns
00791  *       out that it is not in the container, this function is still safe to
00792  *       be called.
00793  *
00794  * \note If the object gets unlinked from the container, the container's
00795  *       reference to the object will be automatically released. (The
00796  *       refcount will be decremented).
00797  */
00798 #ifdef REF_DEBUG
00799 
00800 #define ao2_t_unlink(arg1, arg2, arg3) __ao2_unlink_debug((arg1), (arg2), (arg3),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00801 #define ao2_unlink(arg1, arg2)         __ao2_unlink_debug((arg1), (arg2), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
00802 
00803 #else
00804 
00805 #define ao2_t_unlink(arg1, arg2, arg3) __ao2_unlink((arg1), (arg2))
00806 #define ao2_unlink(arg1, arg2)         __ao2_unlink((arg1), (arg2))
00807 
00808 #endif
00809 
00810 void *__ao2_unlink_debug(struct ao2_container *c, void *obj, char *tag, char *file, int line, const char *funcname);
00811 void *__ao2_unlink(struct ao2_container *c, void *obj);
00812 
00813 
00814 /*@} */
00815 
00816 /*! \brief
00817  * ao2_callback() is a generic function that applies cb_fn() to all objects
00818  * in a container, as described below.
00819  *
00820  * \param c A pointer to the container to operate on.
00821  * \param flags A set of flags specifying the operation to perform,
00822    partially used by the container code, but also passed to
00823    the callback.
00824      - If OBJ_NODATA is set, ao2_callback will return NULL. No refcounts
00825        of any of the traversed objects will be incremented.
00826        On the converse, if it is NOT set (the default), The ref count
00827        of each object for which CMP_MATCH was set will be incremented,
00828        and you will have no way of knowing which those are, until
00829        the multiple-object-return functionality is implemented.
00830      - If OBJ_POINTER is set, the traversed items will be restricted
00831        to the objects in the bucket that the object key hashes to.
00832  * \param cb_fn A function pointer, that will be called on all
00833     objects, to see if they match. This function returns CMP_MATCH
00834     if the object is matches the criteria; CMP_STOP if the traversal
00835     should immediately stop, or both (via bitwise ORing), if you find a
00836     match and want to end the traversal, and 0 if the object is not a match,
00837     but the traversal should continue. This is the function that is applied
00838     to each object traversed. Its arguments are:
00839         (void *obj, void *arg, int flags), where:
00840           obj is an object
00841           arg is the same as arg passed into ao2_callback
00842           flags is the same as flags passed into ao2_callback (flags are
00843            also used by ao2_callback).
00844  * \param arg passed to the callback.
00845  * \param tag used for debuging.
00846  * \return when OBJ_MULTIPLE is not included in the flags parameter,
00847  *         the return value will be either the object found or NULL if no
00848  *         no matching object was found. if OBJ_MULTIPLE is included,
00849  *         the return value will be a pointer to an ao2_iterator object,
00850  *         which must be destroyed with ao2_iterator_destroy() when the
00851  *         caller no longer needs it.
00852  *
00853  * If the function returns any objects, their refcount is incremented,
00854  * and the caller is in charge of decrementing them once done.
00855  *
00856  * Typically, ao2_callback() is used for two purposes:
00857  * - to perform some action (including removal from the container) on one
00858  *   or more objects; in this case, cb_fn() can modify the object itself,
00859  *   and to perform deletion should set CMP_MATCH on the matching objects,
00860  *   and have OBJ_UNLINK set in flags.
00861  * - to look for a specific object in a container; in this case, cb_fn()
00862  *   should not modify the object, but just return a combination of
00863  *   CMP_MATCH and CMP_STOP on the desired object.
00864  * Other usages are also possible, of course.
00865 
00866  * This function searches through a container and performs operations
00867  * on objects according on flags passed.
00868  * XXX describe better
00869  * The comparison is done calling the compare function set implicitly.
00870  * The p pointer can be a pointer to an object or to a key,
00871  * we can say this looking at flags value.
00872  * If p points to an object we will search for the object pointed
00873  * by this value, otherwise we serch for a key value.
00874  * If the key is not unique we only find the first matching valued.
00875  *
00876  * The use of flags argument is the follow:
00877  *
00878  * OBJ_UNLINK     unlinks the object found
00879  * OBJ_NODATA     on match, do return an object
00880  *          Callbacks use OBJ_NODATA as a default
00881  *          functions such as find() do
00882  * OBJ_MULTIPLE      return multiple matches
00883  *          Default is no.
00884  * OBJ_POINTER       the pointer is an object pointer
00885  *
00886  * \note When the returned object is no longer in use, ao2_ref() should
00887  * be used to free the additional reference possibly created by this function.
00888  *
00889  * @{
00890  */
00891 #ifdef REF_DEBUG
00892 
00893 #define ao2_t_callback(c,flags,cb_fn,arg,tag) __ao2_callback_debug((c), (flags), (cb_fn), (arg), (tag), __FILE__, __LINE__, __PRETTY_FUNCTION__)
00894 #define ao2_callback(c,flags,cb_fn,arg)       __ao2_callback_debug((c), (flags), (cb_fn), (arg), "", __FILE__, __LINE__, __PRETTY_FUNCTION__)
00895 
00896 #else
00897 
00898 #define ao2_t_callback(c,flags,cb_fn,arg,tag) __ao2_callback((c), (flags), (cb_fn), (arg))
00899 #define ao2_callback(c,flags,cb_fn,arg)       __ao2_callback((c), (flags), (cb_fn), (arg))
00900 
00901 #endif
00902 
00903 void *__ao2_callback_debug(struct ao2_container *c, enum search_flags flags, ao2_callback_fn *cb_fn,
00904             void *arg, char *tag, char *file, int line, const char *funcname);
00905 void *__ao2_callback(struct ao2_container *c, enum search_flags flags, ao2_callback_fn *cb_fn, void *arg);
00906 
00907 /*! @} */
00908 
00909 /*! \brief
00910  * ao2_callback_data() is a generic function that applies cb_fn() to all objects
00911  * in a container.  It is functionally identical to ao2_callback() except that
00912  * instead of taking an ao2_callback_fn *, it takes an ao2_callback_data_fn *, and
00913  * allows the caller to pass in arbitrary data.
00914  *
00915  * This call would be used instead of ao2_callback() when the caller needs to pass
00916  * OBJ_POINTER as part of the flags argument (which in turn requires passing in a
00917  * prototype ao2 object for 'arg') and also needs access to other non-global data
00918  * to complete it's comparison or task.
00919  *
00920  * See the documentation for ao2_callback() for argument descriptions.
00921  *
00922  * \see ao2_callback()
00923  */
00924 #ifdef REF_DEBUG
00925 
00926 #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__)
00927 #define ao2_callback_data(arg1,arg2,arg3,arg4,arg5)        __ao2_callback_data_debug((arg1), (arg2), (arg3), (arg4), (arg5), "", __FILE__, __LINE__, __PRETTY_FUNCTION__)
00928 
00929 #else
00930 
00931 #define ao2_t_callback_data(arg1,arg2,arg3,arg4,arg5,arg6) __ao2_callback_data((arg1), (arg2), (arg3), (arg4), (arg5))
00932 #define ao2_callback_data(arg1,arg2,arg3,arg4,arg5)        __ao2_callback_data((arg1), (arg2), (arg3), (arg4), (arg5))
00933 
00934 #endif
00935 
00936 void *__ao2_callback_data_debug(struct ao2_container *c, enum search_flags flags,
00937             ao2_callback_data_fn *cb_fn, void *arg, void *data, char *tag,
00938             char *file, int line, const char *funcname);
00939 void *__ao2_callback_data(struct ao2_container *c, enum search_flags flags,
00940            ao2_callback_data_fn *cb_fn, void *arg, void *data);
00941 
00942 /*! ao2_find() is a short hand for ao2_callback(c, flags, c->cmp_fn, arg)
00943  * XXX possibly change order of arguments ?
00944  */
00945 #ifdef REF_DEBUG
00946 
00947 #define ao2_t_find(arg1,arg2,arg3,arg4) __ao2_find_debug((arg1), (arg2), (arg3), (arg4), __FILE__, __LINE__, __PRETTY_FUNCTION__)
00948 #define ao2_find(arg1,arg2,arg3)        __ao2_find_debug((arg1), (arg2), (arg3), "", __FILE__, __LINE__, __PRETTY_FUNCTION__)
00949 
00950 #else
00951 
00952 #define ao2_t_find(arg1,arg2,arg3,arg4) __ao2_find((arg1), (arg2), (arg3))
00953 #define ao2_find(arg1,arg2,arg3)        __ao2_find((arg1), (arg2), (arg3))
00954 
00955 #endif
00956 
00957 void *__ao2_find_debug(struct ao2_container *c, void *arg, enum search_flags flags, char *tag,
00958              char *file, int line, const char *funcname);
00959 void *__ao2_find(struct ao2_container *c, void *arg, enum search_flags flags);
00960 
00961 /*! \brief
00962  *
00963  *
00964  * When we need to walk through a container, we use an
00965  * ao2_iterator to keep track of the current position.
00966  *
00967  * Because the navigation is typically done without holding the
00968  * lock on the container across the loop, objects can be inserted or deleted
00969  * or moved while we work. As a consequence, there is no guarantee that
00970  * we manage to touch all the elements in the container, and it is possible
00971  * that we touch the same object multiple times.
00972  *
00973  * However, within the current hash table container, the following is true:
00974  *  - It is not possible to miss an object in the container while iterating
00975  *    unless it gets added after the iteration begins and is added to a bucket
00976  *    that is before the one the current object is in.  In this case, even if
00977  *    you locked the container around the entire iteration loop, you still would
00978  *    not see this object, because it would still be waiting on the container
00979  *    lock so that it can be added.
00980  *  - It would be extremely rare to see an object twice.  The only way this can
00981  *    happen is if an object got unlinked from the container and added again
00982  *    during the same iteration.  Furthermore, when the object gets added back,
00983  *    it has to be in the current or later bucket for it to be seen again.
00984  *
00985  * An iterator must be first initialized with ao2_iterator_init(),
00986  * then we can use o = ao2_iterator_next() to move from one
00987  * element to the next. Remember that the object returned by
00988  * ao2_iterator_next() has its refcount incremented,
00989  * and the reference must be explicitly released when done with it.
00990  *
00991  * In addition, ao2_iterator_init() will hold a reference to the container
00992  * being iterated, which will be freed when ao2_iterator_destroy() is called
00993  * to free up the resources used by the iterator (if any).
00994  *
00995  * Example:
00996  *
00997  *  \code
00998  *
00999  *  struct ao2_container *c = ... // the container we want to iterate on
01000  *  struct ao2_iterator i;
01001  *  struct my_obj *o;
01002  *
01003  *  i = ao2_iterator_init(c, flags);
01004  *
01005  *  while ((o = ao2_iterator_next(&i))) {
01006  *     ... do something on o ...
01007  *     ao2_ref(o, -1);
01008  *  }
01009  *
01010  *  ao2_iterator_destroy(&i);
01011  *
01012  *  \endcode
01013  *
01014  */
01015 
01016 /*! \brief
01017  * The astobj2 iterator
01018  *
01019  * \note You are not supposed to know the internals of an iterator!
01020  * We would like the iterator to be opaque, unfortunately
01021  * its size needs to be known if we want to store it around
01022  * without too much trouble.
01023  * Anyways...
01024  * The iterator has a pointer to the container, and a flags
01025  * field specifying various things e.g. whether the container
01026  * should be locked or not while navigating on it.
01027  * The iterator "points" to the current object, which is identified
01028  * by three values:
01029  *
01030  * - a bucket number;
01031  * - the object_id, which is also the container version number
01032  *   when the object was inserted. This identifies the object
01033  *   uniquely, however reaching the desired object requires
01034  *   scanning a list.
01035  * - a pointer, and a container version when we saved the pointer.
01036  *   If the container has not changed its version number, then we
01037  *   can safely follow the pointer to reach the object in constant time.
01038  *
01039  * Details are in the implementation of ao2_iterator_next()
01040  * A freshly-initialized iterator has bucket=0, version=0.
01041  */
01042 struct ao2_iterator {
01043    /*! the container */
01044    struct ao2_container *c;
01045    /*! operation flags */
01046    int flags;
01047    /*! current bucket */
01048    int bucket;
01049    /*! container version */
01050    unsigned int c_version;
01051    /*! pointer to the current object */
01052    void *obj;
01053    /*! container version when the object was created */
01054    unsigned int version;
01055 };
01056 
01057 /*! Flags that can be passed to ao2_iterator_init() to modify the behavior
01058  * of the iterator.
01059  */
01060 enum ao2_iterator_flags {
01061    /*! Prevents ao2_iterator_next() from locking the container
01062     * while retrieving the next object from it.
01063     */
01064    AO2_ITERATOR_DONTLOCK = (1 << 0),
01065    /*! Indicates that the iterator was dynamically allocated by
01066     * astobj2 API and should be freed by ao2_iterator_destroy().
01067     */
01068    AO2_ITERATOR_MALLOCD = (1 << 1),
01069    /*! Indicates that before the iterator returns an object from
01070     * the container being iterated, the object should be unlinked
01071     * from the container.
01072     */
01073    AO2_ITERATOR_UNLINK = (1 << 2),
01074 };
01075 
01076 /*!
01077  * \brief Create an iterator for a container
01078  *
01079  * \param c the container
01080  * \param flags one or more flags from ao2_iterator_flags
01081  *
01082  * \retval the constructed iterator
01083  *
01084  * \note This function does \b not take a pointer to an iterator;
01085  *       rather, it returns an iterator structure that should be
01086  *       assigned to (overwriting) an existing iterator structure
01087  *       allocated on the stack or on the heap.
01088  *
01089  * This function will take a reference on the container being iterated.
01090  *
01091  */
01092 struct ao2_iterator ao2_iterator_init(struct ao2_container *c, int flags);
01093 
01094 /*!
01095  * \brief Destroy a container iterator
01096  *
01097  * \param i the iterator to destroy
01098  *
01099  * \retval none
01100  *
01101  * This function will release the container reference held by the iterator
01102  * and any other resources it may be holding.
01103  *
01104  */
01105 void ao2_iterator_destroy(struct ao2_iterator *i);
01106 
01107 #ifdef REF_DEBUG
01108 
01109 #define ao2_t_iterator_next(arg1, arg2) __ao2_iterator_next_debug((arg1), (arg2),  __FILE__, __LINE__, __PRETTY_FUNCTION__)
01110 #define ao2_iterator_next(arg1)         __ao2_iterator_next_debug((arg1), "",  __FILE__, __LINE__, __PRETTY_FUNCTION__)
01111 
01112 #else
01113 
01114 #define ao2_t_iterator_next(arg1, arg2) __ao2_iterator_next((arg1))
01115 #define ao2_iterator_next(arg1)         __ao2_iterator_next((arg1))
01116 
01117 #endif
01118 
01119 void *__ao2_iterator_next_debug(struct ao2_iterator *a, char *tag, char *file, int line, const char *funcname);
01120 void *__ao2_iterator_next(struct ao2_iterator *a);
01121 
01122 /* extra functions */
01123 void ao2_bt(void);   /* backtrace */
01124 
01125 #endif /* _ASTERISK_ASTOBJ2_H */

Generated on Wed Apr 6 11:29:40 2011 for Asterisk - The Open Source Telephony Project by  doxygen 1.4.7