NAME

       curl_easy_pause - pause and unpause a connection

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_pause(CURL *handle, int bitmask );

DESCRIPTION

       Using  this  function, you can explicitly mark a running connection to get paused, and you
       can unpause a connection that was previously paused.

       A connection can be paused by using this function or by letting  the  read  or  the  write
       callbacks    return    the    proper    magic   return   code   (CURL_READFUNC_PAUSE   and
       CURL_WRITEFUNC_PAUSE). A write callback that returns pause signals to the library that  it
       couldn't  take  care of any data at all, and that data will then be delivered again to the
       callback when the writing is later unpaused.

       While it may feel tempting, take care and notice that you cannot call this  function  from
       another  thread.  To  unpause,  you  may  for  example  call it from the progress callback
       (CURLOPT_PROGRESSFUNCTION(3)), which gets called at least once per  second,  even  if  the
       connection is paused.

       When this function is called to unpause reading, the chance is high that you will get your
       write callback called before this function returns.

       The handle argument is of course identifying the handle that operates  on  the  connection
       you want to pause or unpause.

       The  bitmask  argument  is  a  set  of bits that sets the new state of the connection. The
       following bits can be used:

       CURLPAUSE_RECV
              Pause receiving data. There will be no data received on this connection until  this
              function   is  called  again  without  this  bit  set.  Thus,  the  write  callback
              (CURLOPT_WRITEFUNCTION(3)) won't be called.

       CURLPAUSE_SEND
              Pause sending data. There will be no  data  sent  on  this  connection  until  this
              function   is   called  again  without  this  bit  set.  Thus,  the  read  callback
              (CURLOPT_READFUNCTION(3)) won't be called.

       CURLPAUSE_ALL
              Convenience define that pauses both directions.

       CURLPAUSE_CONT
              Convenience define that unpauses both directions.

RETURN VALUE

       CURLE_OK (zero) means that the option was set properly, and a non-zero return  code  means
       something  wrong occurred after the new state was set.  See the libcurl-errors(3) man page
       for the full list with descriptions.

LIMITATIONS

       The pausing  of  transfers  does  not  work  with  protocols  that  work  without  network
       connectivity,  like FILE://. Trying to pause such a transfer, in any direction, will cause
       problems in the worst case or an error in the best case.

AVAILABILITY

       This function was added in libcurl 7.18.0. Before this  version,  there  was  no  explicit
       support for pausing transfers.

USAGE WITH THE MULTI-SOCKET INTERFACE

       Before  libcurl  7.32.0, when a specific handle was unpaused with this function, there was
       no particular forced  rechecking  or  similar  of  the  socket's  state,  which  made  the
       continuation  of  the  transfer  get  delayed  until next multi-socket call invoke or even
       longer. Alternatively, the user could forcibly call for example curl_multi_socket_all(3) -
       with a rather hefty performance penalty.

       Starting  in libcurl 7.32.0, unpausing a transfer will schedule a timeout trigger for that
       handle  1  millisecond  into  the  future,  so  that   a   curl_multi_socket_action(   ...
       CURL_SOCKET_TIMEOUT) can be used immediately afterwards to get the transfer going again as
       desired.

MEMORY USE

       When pausing a read by returning the magic return code from a  write  callback,  the  read
       data  is  already  in  libcurl's internal buffers so it'll have to keep it in an allocated
       buffer until the reading is again unpaused using this function.

       If the downloaded data is compressed and is asked to  get  uncompressed  automatically  on
       download,  libcurl  will  continue  to  uncompress the entire downloaded chunk and it will
       cache the data uncompressed. This has the side- effect that if you download something that
       is  compressed a lot, it can result in a very large data amount needing to be allocated to
       save the data during the pause. This said, you should probably consider not  using  paused
       reading if you allow libcurl to uncompress data automatically.

SEE ALSO

       curl_easy_cleanup(3), curl_easy_reset(3)