Wed Oct 28 11:53:30 2009

Asterisk developer's documentation

ao2_iterator Struct Reference

When we need to walk through a container, we use an ao2_iterator to keep track of the current position. More...

#include <astobj2.h>

Collaboration diagram for ao2_iterator:

Collaboration graph

Data Fields

int bucket
struct ao2_containerc
unsigned int c_version
int flags
void * obj
unsigned int version

Detailed Description

When we need to walk through a container, we use an ao2_iterator to keep track of the current position.

Because the navigation is typically done without holding the lock on the container across the loop, objects can be inserted or deleted or moved while we work. As a consequence, there is no guarantee that we manage to touch all the elements in the container, and it is possible that we touch the same object multiple times.

However, within the current hash table container, the following is true:

An iterator must be first initialized with ao2_iterator_init(), then we can use o = ao2_iterator_next() to move from one element to the next. Remember that the object returned by ao2_iterator_next() has its refcount incremented, and the reference must be explicitly released when done with it.

In addition, ao2_iterator_init() will hold a reference to the container being iterated, which will be freed when ao2_iterator_destroy() is called to free up the resources used by the iterator (if any).


  struct ao2_container *c = ... // the container we want to iterate on
  struct ao2_iterator i;
  struct my_obj *o;

  i = ao2_iterator_init(c, flags);

  while ( (o = ao2_iterator_next(&i)) ) {
     ... do something on o ...
     ao2_ref(o, -1);


The astobj2 iterator

You are not supposed to know the internals of an iterator! We would like the iterator to be opaque, unfortunately its size needs to be known if we want to store it around without too much trouble. Anyways... The iterator has a pointer to the container, and a flags field specifying various things e.g. whether the container should be locked or not while navigating on it. The iterator "points" to the current object, which is identified by three values:

Details are in the implementation of ao2_iterator_next() A freshly-initialized iterator has bucket=0, version=0.

Definition at line 1007 of file astobj2.h.

Field Documentation

int bucket

current bucket

Definition at line 1013 of file astobj2.h.

Referenced by __ao2_iterator_next().

struct ao2_container* c [read]

unsigned int c_version

container version

Definition at line 1015 of file astobj2.h.

Referenced by __ao2_iterator_next().

int flags

operation flags

Definition at line 1011 of file astobj2.h.

Referenced by __ao2_iterator_next(), _ao2_iterator_next(), _ao2_iterator_next_debug(), and ao2_iterator_init().

void* obj

pointer to the current object

Definition at line 1017 of file astobj2.h.

Referenced by __ao2_iterator_next().

unsigned int version

container version when the object was created

Definition at line 1019 of file astobj2.h.

Referenced by __ao2_iterator_next().

The documentation for this struct was generated from the following file:

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