Страницы справочника OS X

Эта страница руководства является частью версии 5.0 Инструментов XCode

Читать страницы руководства

curl_multi_socket_action(3)                    libcurl Manual                    curl_multi_socket_action(3)



NAME
       curl_multi_socket_action - reads/writes available data given an action

SYNOPSIS
       #include <curl/curl.h>

       CURLMcode curl_multi_socket_action(CURLM * multi_handle,
                                          curl_socket_t sockfd, int ev_bitmask,
                                          int *running_handles);

DESCRIPTION
       When  the  application  has  detected  action  on  a  socket  handled  by  libcurl,  it  should  call
       curl_multi_socket_action(3) with the sockfd argument set to the socket  with  the  action.  When  the
       events  on  a  socket  are known, they can be passed as an events bitmask ev_bitmask by first setting
       ev_bitmask to 0, and then adding using bitwise OR (|) any combination of events  to  be  chosen  from
       CURL_CSELECT_IN,  CURL_CSELECT_OUT or CURL_CSELECT_ERR. When the events on a socket are unknown, pass
       0 instead, and libcurl  will  test  the  descriptor  internally.  It  is  also  permissible  to  pass
       CURL_SOCKET_TIMEOUT  to the sockfd parameter in order to initiate the whole process or when a timeout
       occurs.

       At return, the integer running_handles points to will contain the  number  of  running  easy  handles
       within  the  multi  handle.  When this number reaches zero, all transfers are complete/done. When you
       call curl_multi_socket_action(3) on a specific socket and the counter decreases by one, it  DOES  NOT
       necessarily   mean   that   this   exact   socket/transfer   is   the   one   that   completed.   Use
       curl_multi_info_read(3) to figure out which easy handle that completed.

       The curl_multi_socket_action(3) functions inform the application about updates in  the  socket  (file
       descriptor) status by doing none, one, or multiple calls to the socket callback function set with the
       CURLMOPT_SOCKETFUNCTION option to curl_multi_setopt(3). They update the status with changes since the
       previous time the callback was called.

       Get  the  timeout  time  by setting the CURLMOPT_TIMERFUNCTION option with curl_multi_setopt(3). Your
       application will then get called with information on how long to wait  for  socket  actions  at  most
       before  doing the timeout action: call the curl_multi_socket_action(3) function with the sockfd argu-ment argument
       ment set to CURL_SOCKET_TIMEOUT. You can also use the  curl_multi_timeout(3)  function  to  poll  the
       value  at any given time, but for an event-based system using the callback is far better than relying
       on polling the timeout value.

CALLBACK DETAILS
       The socket callback function uses a prototype like this

         int curl_socket_callback(CURL *easy,      /* easy handle */
                                  curl_socket_t s, /* socket */
                                  int action,      /* see values below */
                                  void *userp,    /* private callback pointer */
                                  void *socketp); /* private socket pointer,
                                                     NULL if not
                                                     previously assigned with
                                                     curl_multi_assign(3) */

       The callback MUST return _.

       The easy argument is a pointer to the easy handle that deals with this particular socket. Note that a
       single handle may work with several sockets simultaneously.

       The s argument is the actual socket value as you use it within your system.

       The action argument to the callback has one of five values:

              CURL_POLL_NONE (_)
                     register, not interested in readiness (yet)

              CURL_POLL_IN (1)
                     register, interested in read readiness

              CURL_POLL_OUT (2)
                     register, interested in write readiness

              CURL_POLL_INOUT (3)
                     register, interested in both read and write readiness

              CURL_POLL_REMOVE (4)
                     unregister

       The  socketp  argument  is  a private pointer you have previously set with curl_multi_assign(3) to be
       associated with the s socket. If no pointer has been set, socketp will be NULL. This argument  is  of
       course  a service to applications that want to keep certain data or structs that are strictly associ-ated associated
       ated to the given socket.

       The userp argument is a private pointer you have previously set  with  curl_multi_setopt(3)  and  the
       CURLMOPT_SOCKETDATA option.

RETURN VALUE
       CURLMcode type, general libcurl multi interface error code.

       Before  version 7.20.0: If you receive CURLM_CALL_MULTI_PERFORM, this basically means that you should
       call curl_multi_socket_action(3) again before you wait for more actions  on  libcurl's  sockets.  You
       don't  have to do it immediately, but the return code means that libcurl may have more data available
       to return or that there may be more data to send off before it is "satisfied".

       The return code from this function is for the whole multi stack.  Problems still might have  occurred
       on individual transfers even when one of these functions return OK.

TYPICAL USAGE
       1. Create a multi handle

       2. Set the socket callback with CURLMOPT_SOCKETFUNCTION

       3.  Set  the  timeout  callback with CURLMOPT_TIMERFUNCTION, to get to know what timeout value to use
       when waiting for socket activities.

       4. Add easy handles with curl_multi_add_handle()

       5. Provide some means to manage the sockets libcurl is using, so you can  check  them  for  activity.
       This  can be done through your application code, or by way of an external library such as libevent or
       glib.

       6. Call curl_multi_socket_action(..., CURL_SOCKET_TIMEOUT, 0, ...)  to kickstart everything.  To  get
       one or more callbacks called.

       7.  Wait for activity on any of libcurl's sockets, use the timeout value your callback has been told.

       8, When activity is detected, call curl_multi_socket_action() for the socket(s) that got  action.  If
       no   activity   is   detected   and   the  timeout  expires,  call  curl_multi_socket_action(3)  with
       CURL_SOCKET_TIMEOUT.

AVAILABILITY
       This function was added in libcurl 7.15.4, and is deemed stable since 7.16.0.

SEE ALSO
       curl_multi_cleanup(3), curl_multi_init(3), curl_multi_fdset(3), curl_multi_info_read(3),  the  hiper-fifo.c hiperfifo.c
       fifo.c example



libcurl 7.16.0                                   9 Jul 2006                      curl_multi_socket_action(3)