curl-w32/docs/libcurl/opts/CURLOPT_IOCTLDATA.md

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---
c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_IOCTLDATA
Section: 3
Source: libcurl
See-also:
- CURLOPT_IOCTLFUNCTION (3)
- CURLOPT_SEEKFUNCTION (3)
---
# NAME
CURLOPT_IOCTLDATA - pointer passed to I/O callback
# SYNOPSIS
~~~c
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IOCTLDATA, void *pointer);
~~~
# DESCRIPTION
Pass the *pointer* that is untouched by libcurl and passed as the 3rd
argument in the ioctl callback set with CURLOPT_IOCTLFUNCTION(3).
# DEFAULT
By default, the value of this parameter is NULL.
# PROTOCOLS
Used with HTTP
# EXAMPLE
~~~c
#include <unistd.h> /* for lseek */
struct data {
int fd; /* our file descriptor */
};
static curlioerr ioctl_callback(CURL *handle, int cmd, void *clientp)
{
struct data *io = (struct data *)clientp;
if(cmd == CURLIOCMD_RESTARTREAD) {
lseek(io->fd, 0, SEEK_SET);
return CURLIOE_OK;
}
return CURLIOE_UNKNOWNCMD;
}
int main(void)
{
struct data ioctl_data;
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_IOCTLFUNCTION, ioctl_callback);
curl_easy_setopt(curl, CURLOPT_IOCTLDATA, &ioctl_data);
}
}
~~~
# AVAILABILITY
Added in 7.12.3. Deprecated since 7.18.0.
# RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.