Libevent+bufferevent Summary

Libevent+bufferevent Summary 1 Study reference URL

Libevent Study Website: http://blog.csdn.net/feitianxuxue/article/details/9372535

Http://www.cnblogs.com/hustcat/archive/2010/08/31/1814022.html

Http://www.cppblog.com/mysileng/archive/2013/02/04/197719.html

Bufferevent Study Website: http://blog.csdn.net/feitianxuxue/article/details/9386843

http://blog.csdn.net/feitianxuxue/article/details/9386843

2 basic knowledge of libevent and Bufferevent 2.1 event_base

struct Event_base { const struct EVENTOP *evsel; void *evbase; int event_count; /* Total number of events */ int event_count_active; /* Total number of active events */ int event_gotterm; /* Set the terminating event loop */ int event_break; /* Set immediately terminate event loop */ /* Active Event Management */ struct Event_list **activequeues; Array of pointers, array indexes are priority priorities int nactivequeues; /* Signal Processing information */ struct Evsignal_info sig; struct Event_list eventqueue; List of registered events struct Timeval event_tv; struct MIN_HEAP timeheap; struct Timeval tv_cache; };

The structure of Event_base is as follows:

2.2 Bufferevent_new ()

bufferevent_new (int fd, EVBUFFERCB READCB, EVBUFFERCBWRITECB,EVERRORCB errorcb, void *cbarg)

The function of bufferevent_new in CDN/CLS code is simply to initialize the parameters. Libevent's bufferevent maintains a buffer on the basis of the event, which has the following structure: its own read-write event, read-write buffer, and read-write callback function.

struct Bufferevent { struct Event_base *ev_base; struct event ev_read; struct event ev_write; struct Evbuffer *input; struct Evbuffer *output; struct Event_watermark wm_read; struct Event_watermark wm_write; EVBUFFERCB READCB; EVBUFFERCB WRITECB; EVERRORCB ERRORCB; void *cbarg; int timeout_read; /* units are seconds * / int timeout_write; /* units are seconds * / Short enabled; /* whether the event is available * / };

2.3 Event_base_set (struct event_base *base, struct event *ev)

Modifies the Structevent event structure to which the event_base belongs to the specified event_base. The libevnet contains a global event_base structure. In multiple thread applications, if multiple threads require a libevent event loop, you need to call Event_base_set to modify the event structure based on the event_base. Bufferevent_base_set () is to place read and write events as specified values.

2.4 Event_base_loopexit (M_pevbase, &TV);

Event_base_loopexit () lets event_base stop looping after a given time. It will not return until the end of the event that is being done.

2.5 event_base_loop (m_pevbase, 0)

int Event_base_loop (struct event_base *, int);

Wait for the event to be triggered, and then call their callback function. This is a more flexible version of Event_base_dispatch. By default, the loop runs until there are no events added, or until Event_base_loopbreak () or Evenet_base_loopexit () is called. You can modify this behavior by using the flags parameter.

The parameter 1:eb represents the Event_base struct body.

Parameter 2:flags is Evloop_once | A combination of evloop_nonblock.

The return value: 0 indicates success, 1 indicates an error has occurred, and 1 indicates that no event has been registered.

Evloop_once: Blocks until an active event is executed and then exits with a callback for the active events.

Evloop_nonblock: Do not block, check which event is ready, call the highest priority one, and then exit.

3 Instructions for use

The main functions that Libevent uses to implement the main functions require:

Event_new (); Initialize an event

Event_base_set (); Point the event pointer to an event that you want to use now

Event_base_loop () Listener event, execute callback function

The representation in the code is as follows:

Bufferevent_new (Ssockethead.ifd,cb_read, Cb_write, Cb_error, (void*) this);

The initialization of the parameters is realized;

Bufferevent_base_set (M_pevbase, Psocketmsg->pbufev); Point the event pointer to the event you want to run, in fact the pointer to the corresponding read-write event points to the event that needs to be run.

Event_base_loop (m_pevbase, 0);

Listens for events and executes callback functions.

Libevent+bufferevent Summary