mirror of
https://github.com/curl/curl.git
synced 2024-12-09 06:30:06 +08:00
76d6e719d9
- avoid exclamation marks - use consistent number of spaces after periods: one - avoid clichés - avoid using 'very' Closes #8060
113 lines
5.3 KiB
Groff
113 lines
5.3 KiB
Groff
.\" **************************************************************************
|
|
.\" * _ _ ____ _
|
|
.\" * Project ___| | | | _ \| |
|
|
.\" * / __| | | | |_) | |
|
|
.\" * | (__| |_| | _ <| |___
|
|
.\" * \___|\___/|_| \_\_____|
|
|
.\" *
|
|
.\" * Copyright (C) 1998 - 2021, 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 https://curl.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
|
|
.nf
|
|
.B #include <curl/curl.h>
|
|
|
|
.BI "CURLcode curl_easy_pause(CURL *"handle ", int "bitmask ");"
|
|
.fi
|
|
.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 could not take care of any
|
|
data at all, and that data will then be delivered again to the callback when
|
|
the transfer is 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 receiving, the chance is high that you
|
|
will get your write callback called before this function returns.
|
|
|
|
The \fBhandle\fP argument identifies the transfer you want to pause or
|
|
unpause.
|
|
|
|
A paused transfer is excluded from low speed cancels via the
|
|
\fICURLOPT_LOW_SPEED_LIMIT(3)\fP option and unpausing a transfer will reset
|
|
the time period required for the low speed limit to be met.
|
|
|
|
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) will not 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) will not be called.
|
|
.IP CURLPAUSE_ALL
|
|
Convenience define that pauses both directions.
|
|
.IP CURLPAUSE_CONT
|
|
Convenience define that unpauses both directions.
|
|
.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 MULTIPLEXED
|
|
When a connection is used multiplexed, like for HTTP/2, and one of the
|
|
transfers over the connection is paused and the others continue flowing,
|
|
libcurl might end up buffering contents for the paused transfer. It has to do
|
|
this because it needs to drain the socket for the other transfers and the
|
|
already announced window size for the paused transfer will allow the server to
|
|
continue sending data up to that window size amount. By default, libcurl
|
|
announces a 32 megabyte window size, which thus can make libcurl end up
|
|
buffering 32 megabyte of data for a paused stream.
|
|
|
|
When such a paused stream is unpaused again, any buffered data will be
|
|
delivered first.
|
|
.SH EXAMPLE
|
|
.nf
|
|
/* pause a transfer in both directions */
|
|
curl_easy_pause(curl, CURL_READFUNC_PAUSE | CURL_WRITEFUNC_PAUSE);
|
|
.fi
|
|
.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 will have to keep
|
|
it in an allocated buffer until the receiving 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 large data amount needing to be allocated to save the data during the
|
|
pause. This said, you should probably consider not using paused receiving if
|
|
you allow libcurl to uncompress data automatically.
|
|
.SH AVAILABILITY
|
|
Added in 7.18.0.
|
|
.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 "SEE ALSO"
|
|
.BR curl_easy_cleanup "(3), " curl_easy_reset "(3)"
|