93 lines
3.7 KiB
Groff
93 lines
3.7 KiB
Groff
.\" **************************************************************************
|
|
.\" * _ _ ____ _
|
|
.\" * Project ___| | | | _ \| |
|
|
.\" * / __| | | | |_) | |
|
|
.\" * | (__| |_| | _ <| |___
|
|
.\" * \___|\___/|_| \_\_____|
|
|
.\" *
|
|
.\" * Copyright (C) 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.
|
|
.\" *
|
|
.\" * SPDX-License-Identifier: curl
|
|
.\" *
|
|
.\" **************************************************************************
|
|
.\"
|
|
.TH CURLOPT_SEEKFUNCTION 3 "April 26, 2023" "ibcurl 8.3.0" libcurl
|
|
|
|
.SH NAME
|
|
CURLOPT_SEEKFUNCTION \- user callback for seeking in input stream
|
|
.SH SYNOPSIS
|
|
.nf
|
|
#include <curl/curl.h>
|
|
|
|
/* These are the return codes for the seek callbacks */
|
|
#define CURL_SEEKFUNC_OK 0
|
|
#define CURL_SEEKFUNC_FAIL 1 /* fail the entire transfer */
|
|
#define CURL_SEEKFUNC_CANTSEEK 2 /* tell libcurl seeking cannot be done, so
|
|
libcurl might try other means instead */
|
|
|
|
int seek_callback(void *clientp, curl_off_t offset, int origin);
|
|
|
|
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SEEKFUNCTION, seek_callback);
|
|
.SH DESCRIPTION
|
|
Pass a pointer to your callback function, which should match the prototype
|
|
shown above.
|
|
|
|
This function gets called by libcurl to seek to a certain position in the
|
|
input stream and can be used to fast forward a file in a resumed upload
|
|
(instead of reading all uploaded bytes with the normal read
|
|
function/callback). It is also called to rewind a stream when data has already
|
|
been sent to the server and needs to be sent again. This may happen when doing
|
|
an HTTP PUT or POST with a multi-pass authentication method, or when an
|
|
existing HTTP connection is reused too late and the server closes the
|
|
connection. The function shall work like fseek(3) or lseek(3) and it gets
|
|
SEEK_SET, SEEK_CUR or SEEK_END as argument for \fIorigin\fP, although libcurl
|
|
currently only passes SEEK_SET.
|
|
|
|
\fIclientp\fP is the pointer you set with \fICURLOPT_SEEKDATA(3)\fP.
|
|
|
|
The callback function must return \fICURL_SEEKFUNC_OK\fP on success,
|
|
\fICURL_SEEKFUNC_FAIL\fP to cause the upload operation to fail or
|
|
\fICURL_SEEKFUNC_CANTSEEK\fP to indicate that while the seek failed, libcurl
|
|
is free to work around the problem if possible. The latter can sometimes be
|
|
done by instead reading from the input or similar.
|
|
|
|
If you forward the input arguments directly to fseek(3) or lseek(3), note that
|
|
the data type for \fIoffset\fP is not the same as defined for curl_off_t on
|
|
many systems!
|
|
.SH DEFAULT
|
|
By default, this is NULL and unused.
|
|
.SH PROTOCOLS
|
|
HTTP, FTP, SFTP
|
|
.SH EXAMPLE
|
|
.nf
|
|
static int seek_cb(void *clientp, curl_off_t offset, int origin)
|
|
{
|
|
struct data *d = (struct data *)clientp;
|
|
lseek(our_fd, offset, origin);
|
|
return CURL_SEEKFUNC_OK;
|
|
}
|
|
|
|
{
|
|
struct data seek_data;
|
|
curl_easy_setopt(CURL *handle, CURLOPT_SEEKFUNCTION, seek_cb);
|
|
curl_easy_setopt(CURL *handle, CURLOPT_SEEKDATA, &seek_data);
|
|
}
|
|
.fi
|
|
.SH AVAILABILITY
|
|
Added in 7.18.0
|
|
.SH RETURN VALUE
|
|
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
|
|
.SH "SEE ALSO"
|
|
.BR CURLOPT_SEEKDATA "(3), " CURLOPT_IOCTLFUNCTION "(3), "
|