CURLOPT_IOCTLFUNCTION(3)

CURLOPT_IOCTLFUNCTION(3curl_easy_setopt optionCURLOPT_IOCTLFUNCTION(3)

NAME

     CURLOPT_IOCTLFUNCTION - callback for I/O operations

SYNOPSIS

     #include <curl/curl.h>

     typedef enum {
       CURLIOE_OK,            /* I/O operation successful */
       CURLIOE_UNKNOWNCMD,    /* command was unknown to callback */
       CURLIOE_FAILRESTART,   /* failed to restart the read */
       CURLIOE_LAST           /* never use */
     } curlioerr;

     typedef enum  {
       CURLIOCMD_NOP,         /* no operation */
       CURLIOCMD_RESTARTREAD, /* restart the read stream from start */
       CURLIOCMD_LAST         /* never use */
     } curliocmd;

     curlioerr ioctl_callback(CURL *handle, int cmd, void *clientp);

     CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IOCTLFUNCTION, ioctl_callback);

DESCRIPTION

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

     This callback function gets called by libcurl when something
     special  I/O-related needs to be done that the library can't
     do by itself. For now, rewinding the read data stream is the
     only  action  it can request. The rewinding of the read data
     stream may be necessary when doing a HTTP PUT or POST with a
     multi-pass authentication method.

     The callback MUST return CURLIOE_UNKNOWNCMD if the input cmd
     is not CURLIOCMD_RESTARTREAD.

     The clientp  argument  to  the  callback  is  set  with  the
     CURLOPT_IOCTLDATA(3) option.

     This  option   is   deprecated!   Do   not   use   it.   Use
     CURLOPT_SEEKFUNCTION(3)   instead  to  provide  seeking!  If
     CURLOPT_SEEKFUNCTION(3)  is  set,  this  parameter  will  be
     ignored when seeking.

DEFAULT

     By default, this parameter is set to NULL. Not used.

PROTOCOLS

     Used with HTTP

libcurl 7.58.0      Last change: May 31, 2017                   1

CURLOPT_IOCTLFUNCTION(3curl_easy_setopt optionCURLOPT_IOCTLFUNCTION(3)

EXAMPLE

     static curlioerr ioctl_callback(CURL *handle, int cmd, void *clientp)
     {
       struct data *io = (struct data *)clientp;
       if(cmd == CURLIOCMD_RESTARTREAD) {
         lseek(fd, 0, SEEK_SET);
         current_offset = 0;
         return CURLIOE_OK;
       }
       return CURLIOE_UNKNOWNCMD;
     }
     {
       struct data ioctl_data;
       curl_easy_setopt(curl, CURLOPT_IOCTLFUNCTION, ioctl_callback);
       curl_easy_setopt(curl, CURLOPT_IOCTLDATA, &ioctl_data);
     }

AVAILABILITY

     Added in 7.12.3

RETURN VALUE

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

SEE ALSO

     CURLOPT_IOCTLDATA(3), CURLOPT_SEEKFUNCTION(3),

libcurl 7.58.0      Last change: May 31, 2017                   2