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Diffstat (limited to 'docs/libcurl/opts/GNURLOPT_SEEKFUNCTION.3')
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diff --git a/docs/libcurl/opts/GNURLOPT_SEEKFUNCTION.3 b/docs/libcurl/opts/GNURLOPT_SEEKFUNCTION.3 new file mode 100644 index 000000000..85eca1d68 --- /dev/null +++ b/docs/libcurl/opts/GNURLOPT_SEEKFUNCTION.3 @@ -0,0 +1,89 @@ +.\" ************************************************************************** +.\" * _ _ ____ _ +.\" * Project ___| | | | _ \| | +.\" * / __| | | | |_) | | +.\" * | (__| |_| | _ <| |___ +.\" * \___|\___/|_| \_\_____| +.\" * +.\" * Copyright (C) 1998 - 2017, 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.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 GNURLOPT_SEEKFUNCTION 3 "16 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options" +.SH NAME +CURLOPT_SEEKFUNCTION \- user callback for seeking in input stream +.SH SYNOPSIS +.nf +#include <gnurl/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 can't be done, so + libcurl might try other means instead */ + +int seek_callback(void *userp, 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. + +\fIuserp\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 *userp, curl_off_t offset, int origin) +{ + struct data *d = (struct data *)userp; + 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), " |