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)