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Daniel Stenberg b935fd4a07

docs: make each libcurl man specify protocol(s)

The mandatory header now has a mandatory list of protocols for which the
manpage is relevant.

Most man pages already has a "PROTOCOLS" section, but this introduces a
stricter way to specify the relevant protocols.

cd2nroff verifies that at least one protocol is mentioned (which can be
`*`).

This information is not used just yet, but A) the PROTOCOLS section can
now instead get generated and get a unified wording across all manpages
and B) this allows us to more reliably filter/search for protocol
specific manpages/options.

Closes #13166

2024-03-21 15:27:06 +01:00

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c: Copyright (C) Daniel Stenberg, daniel@haxx.se, et al. SPDX-License-Identifier: curl Title: CURLOPT_IOCTLFUNCTION Section: 3 Source: libcurl Protocol: - * See-also: - CURLOPT_IOCTLDATA (3) - CURLOPT_SEEKFUNCTION (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 cannot 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 an 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 is ignored when seeking.

DEFAULT

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

PROTOCOLS

Used with HTTP

EXAMPLE

#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.

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