NAME¶
CURLOPT_SEEKFUNCTION - user callback for seeking in input stream
SYNOPSIS¶
#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 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);
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 doing a HTTP PUT or POST with a multi-pass
authentication method. The function shall work like
fseek(3) or lseek(3) and
it gets SEEK_SET, SEEK_CUR or SEEK_END as argument for
origin, although
libcurl currently only passes SEEK_SET.
userp is the pointer you set with
CURLOPT_SEEKDATA(3).
The callback function must return
CURL_SEEKFUNC_OK on success,
CURL_SEEKFUNC_FAIL to cause the upload operation to fail or
CURL_SEEKFUNC_CANTSEEK 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
offset is not the same as defined for curl_off_t on
many systems!
DEFAULT¶
By default, this is NULL and unused.
PROTOCOLS¶
HTTP, FTP, SFTP
EXAMPLE¶
TODO
AVAILABILITY¶
Added in 7.18.0
RETURN VALUE¶
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
SEE ALSO¶
CURLOPT_SEEKDATA(3),
CURLOPT_IOCTLFUNCTION(3),