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                     22: .TH curl_easy_pause 3 "May 01, 2016" "libcurl 7.70.0" "libcurl Manual"
                     23: 
                     24: .SH NAME
                     25: curl_easy_pause - pause and unpause a connection
                     26: .SH SYNOPSIS
                     27: .B #include <curl/curl.h>
                     28: 
                     29: .BI "CURLcode curl_easy_pause(CURL *"handle ", int "bitmask " );"
                     30: 
                     31: .SH DESCRIPTION
                     32: Using this function, you can explicitly mark a running connection to get
                     33: paused, and you can unpause a connection that was previously paused.
                     34: 
                     35: A connection can be paused by using this function or by letting the read or
                     36: the write callbacks return the proper magic return code
                     37: (\fICURL_READFUNC_PAUSE\fP and \fICURL_WRITEFUNC_PAUSE\fP). A write callback
                     38: that returns pause signals to the library that it couldn't take care of any
                     39: data at all, and that data will then be delivered again to the callback when
                     40: the writing is later unpaused.
                     41: 
                     42: While it may feel tempting, take care and notice that you cannot call this
                     43: function from another thread. To unpause, you may for example call it from the
                     44: progress callback (\fICURLOPT_PROGRESSFUNCTION(3)\fP), which gets called at
                     45: least once per second, even if the connection is paused.
                     46: 
                     47: When this function is called to unpause reading, the chance is high that you
                     48: will get your write callback called before this function returns.
                     49: 
                     50: The \fBhandle\fP argument is of course identifying the handle that operates on
                     51: the connection you want to pause or unpause.
                     52: 
                     53: The \fBbitmask\fP argument is a set of bits that sets the new state of the
                     54: connection. The following bits can be used:
                     55: .IP CURLPAUSE_RECV
                     56: Pause receiving data. There will be no data received on this connection until
                     57: this function is called again without this bit set. Thus, the write callback
                     58: (\fICURLOPT_WRITEFUNCTION(3)\fP) won't be called.
                     59: .IP CURLPAUSE_SEND
                     60: Pause sending data. There will be no data sent on this connection until this
                     61: function is called again without this bit set. Thus, the read callback
                     62: (\fICURLOPT_READFUNCTION(3)\fP) won't be called.
                     63: .IP CURLPAUSE_ALL
                     64: Convenience define that pauses both directions.
                     65: .IP CURLPAUSE_CONT
                     66: Convenience define that unpauses both directions.
                     67: .SH RETURN VALUE
                     68: CURLE_OK (zero) means that the option was set properly, and a non-zero return
                     69: code means something wrong occurred after the new state was set.  See the
                     70: \fIlibcurl-errors(3)\fP man page for the full list with descriptions.
                     71: .SH LIMITATIONS
                     72: The pausing of transfers does not work with protocols that work without
                     73: network connectivity, like FILE://. Trying to pause such a transfer, in any
                     74: direction, will cause problems in the worst case or an error in the best case.
                     75: .SH AVAILABILITY
                     76: This function was added in libcurl 7.18.0. Before this version, there was no
                     77: explicit support for pausing transfers.
                     78: .SH "USAGE WITH THE MULTI-SOCKET INTERFACE"
                     79: Before libcurl 7.32.0, when a specific handle was unpaused with this function,
                     80: there was no particular forced rechecking or similar of the socket's state,
                     81: which made the continuation of the transfer get delayed until next
                     82: multi-socket call invoke or even longer. Alternatively, the user could
                     83: forcibly call for example \fIcurl_multi_socket_all(3)\fP - with a rather hefty
                     84: performance penalty.
                     85: 
                     86: Starting in libcurl 7.32.0, unpausing a transfer will schedule a timeout
                     87: trigger for that handle 1 millisecond into the future, so that a
                     88: curl_multi_socket_action( ... CURL_SOCKET_TIMEOUT) can be used immediately
                     89: afterwards to get the transfer going again as desired.
                     90: .SH "MEMORY USE"
                     91: When pausing a read by returning the magic return code from a write callback,
                     92: the read data is already in libcurl's internal buffers so it'll have to keep
                     93: it in an allocated buffer until the reading is again unpaused using this
                     94: function.
                     95: 
                     96: If the downloaded data is compressed and is asked to get uncompressed
                     97: automatically on download, libcurl will continue to uncompress the entire
                     98: downloaded chunk and it will cache the data uncompressed. This has the side-
                     99: effect that if you download something that is compressed a lot, it can result
                    100: in a very large data amount needing to be allocated to save the data during
                    101: the pause. This said, you should probably consider not using paused reading if
                    102: you allow libcurl to uncompress data automatically.
                    103: .SH "SEE ALSO"
                    104: .BR curl_easy_cleanup "(3), " curl_easy_reset "(3)"