curlopt_seekfunction(3) [mojave man page]

CURLOPT_SEEKFUNCTION(3) 				     curl_easy_setopt options					   CURLOPT_SEEKFUNCTION(3)

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  data  has
       already	been sent to the server and needs to be sent again. This may happen when doing a 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 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_SEEK-
       FUNC_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),

libcurl 7.54.0							 February 03, 2016					   CURLOPT_SEEKFUNCTION(3)

CURLOPT_SOCKOPTFUNCTION(3)				     curl_easy_setopt options					CURLOPT_SOCKOPTFUNCTION(3)

NAME

       CURLOPT_SOCKOPTFUNCTION - set callback for setting socket options

SYNOPSIS

       #include <curl/curl.h>

       typedef enum  {
	 CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
	 CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
	 CURLSOCKTYPE_LAST    /* never use */
       } curlsocktype;

       #define CURL_SOCKOPT_OK 0
       #define CURL_SOCKOPT_ERROR 1 /* causes libcurl to abort and return
				       CURLE_ABORTED_BY_CALLBACK */
       #define CURL_SOCKOPT_ALREADY_CONNECTED 2

       int sockopt_callback(void *clientp,
			    curl_socket_t curlfd,
			    curlsocktype purpose);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);

DESCRIPTION

       Pass a pointer to your callback function, which should match the prototype shown above.

       When set, this callback function gets called by libcurl when the socket has been created, but before the connect call to allow applications
       to change specific socket options. The callback's purpose argument identifies the exact purpose for this particular socket:

       CURLSOCKTYPE_IPCXN for actively created connections or since 7.28.0  CURLSOCKTYPE_ACCEPT  for  FTP  when  the  connection  was  setup  with
       PORT/EPSV (in earlier versions these sockets weren't passed to this callback).

       Future  versions  of  libcurl  may  support more purposes. libcurl passes the newly created socket descriptor to the callback in the curlfd
       parameter so additional setsockopt() calls can be done at the user's discretion.

       The clientp pointer contains whatever user-defined value set using the CURLOPT_SOCKOPTDATA(3) function.

       Return CURL_SOCKOPT_OK from the callback on success. Return CURL_SOCKOPT_ERROR from the callback function to signal an unrecoverable  error
       to  the	library and it will close the socket and return CURLE_COULDNT_CONNECT.	Alternatively, the callback function can return CURL_SOCK-
       OPT_ALREADY_CONNECTED, to tell libcurl that the socket is already connected and then libcurl will not attempt to connect it. This allows an
       application  to pass in an already connected socket with CURLOPT_OPENSOCKETFUNCTION(3) and then have this function make libcurl not attempt
       to connect (again).

DEFAULT

       By default, this callback is NULL and unused.

PROTOCOLS

       All

EXAMPLE

       TODO

AVAILABILITY

       Added in 7.16.0. The CURL_SOCKOPT_ALREADY_CONNECTED return code was added in 7.21.5.

RETURN VALUE

       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

SEE ALSO

       CURLOPT_SOCKOPTDATA(3), CURLOPT_OPENSOCKETFUNCTION(3),

libcurl 7.54.0							 February 03, 2016					CURLOPT_SOCKOPTFUNCTION(3)