mirror of
https://github.com/moparisthebest/curl
synced 2024-11-05 00:55:04 -05:00
104 lines
5.1 KiB
Groff
104 lines
5.1 KiB
Groff
.\" **************************************************************************
|
|
.\" * _ _ ____ _
|
|
.\" * Project ___| | | | _ \| |
|
|
.\" * / __| | | | |_) | |
|
|
.\" * | (__| |_| | _ <| |___
|
|
.\" * \___|\___/|_| \_\_____|
|
|
.\" *
|
|
.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
|
|
.\" *
|
|
.\" * This software is licensed as described in the file COPYING, which
|
|
.\" * you should have received as part of this distribution. The terms
|
|
.\" * are also available at http://curl.haxx.se/docs/copyright.html.
|
|
.\" *
|
|
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
|
|
.\" * copies of the Software, and permit persons to whom the Software is
|
|
.\" * furnished to do so, under the terms of the COPYING file.
|
|
.\" *
|
|
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
|
|
.\" * KIND, either express or implied.
|
|
.\" *
|
|
.\" **************************************************************************
|
|
.TH curl_easy_pause 3 "17 Dec 2007" "libcurl 7.18.0" "libcurl Manual"
|
|
.SH NAME
|
|
curl_easy_pause - pause and unpause a connection
|
|
.SH SYNOPSIS
|
|
.B #include <curl/curl.h>
|
|
|
|
.BI "CURLcode curl_easy_pause(CURL *"handle ", int "bitmask " );"
|
|
|
|
.SH 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
|
|
(\fICURL_READFUNC_PAUSE\fP and \fICURL_WRITEFUNC_PAUSE\fP). 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 (\fICURLOPT_PROGRESSFUNCTION(3)\fP), 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 \fBhandle\fP argument is of course identifying the handle that operates on
|
|
the connection you want to pause or unpause.
|
|
|
|
The \fBbitmask\fP argument is a set of bits that sets the new state of the
|
|
connection. The following bits can be used:
|
|
.IP 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
|
|
(\fICURLOPT_WRITEFUNCTION(3)\fP) won't be called.
|
|
.IP 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
|
|
(\fICURLOPT_READFUNCTION(3)\fP) won't be called.
|
|
.IP CURLPAUSE_ALL
|
|
Convenience define that pauses both directions.
|
|
.IP CURLPAUSE_CONT
|
|
Convenience define that unpauses both directions
|
|
.SH 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
|
|
\fIlibcurl-errors(3)\fP man page for the full list with descriptions.
|
|
.SH 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.
|
|
.SH AVAILABILITY
|
|
This function was added in libcurl 7.18.0. Before this version, there was no
|
|
explicit support for pausing transfers.
|
|
.SH "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.
|
|
.SH "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.
|
|
.SH "SEE ALSO"
|
|
.BR curl_easy_cleanup "(3), " curl_easy_reset "(3)"
|