CURLOPT_IOCTLFUNCTION(3)

1CURLOPT_IOCTLFUNCTION(3)   curl_easy_setopt options   CURLOPT_IOCTLFUNCTION(3)
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NAME

6       CURLOPT_IOCTLFUNCTION - callback for I/O operations
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SYNOPSIS

9       #include <curl/curl.h>
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11       typedef enum {
12         CURLIOE_OK,            /* I/O operation successful */
13         CURLIOE_UNKNOWNCMD,    /* command was unknown to callback */
14         CURLIOE_FAILRESTART,   /* failed to restart the read */
15         CURLIOE_LAST           /* never use */
16       } curlioerr;
17
18       typedef enum  {
19         CURLIOCMD_NOP,         /* no operation */
20         CURLIOCMD_RESTARTREAD, /* restart the read stream from start */
21         CURLIOCMD_LAST         /* never use */
22       } curliocmd;
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24       curlioerr ioctl_callback(CURL *handle, int cmd, void *clientp);
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26       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IOCTLFUNCTION, ioctl_callback);
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DESCRIPTION

29       Pass a pointer to your callback function, which should match the proto‐
30       type shown above.
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32       This callback function gets called by libcurl  when  something  special
33       I/O-related  needs  to be done that the library can't do by itself. For
34       now, rewinding the read data stream is the only action it can  request.
35       The  rewinding  of  the read data stream may be necessary when doing an
36       HTTP PUT or POST with a multi-pass authentication method.
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38       The callback MUST return CURLIOE_UNKNOWNCMD if the  input  cmd  is  not
39       CURLIOCMD_RESTARTREAD.
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41       The  clientp  argument  to  the callback is set with the CURLOPT_IOCTL‐
42       DATA(3) option.
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44       This option is deprecated! Do not use it.  Use  CURLOPT_SEEKFUNCTION(3)
45       instead  to  provide  seeking!  If CURLOPT_SEEKFUNCTION(3) is set, this
46       parameter will be ignored when seeking.
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DEFAULT

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

52       Used with HTTP
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EXAMPLE

55       static curlioerr ioctl_callback(CURL *handle, int cmd, void *clientp)
56       {
57         struct data *io = (struct data *)clientp;
58         if(cmd == CURLIOCMD_RESTARTREAD) {
59           lseek(fd, 0, SEEK_SET);
60           current_offset = 0;
61           return CURLIOE_OK;
62         }
63         return CURLIOE_UNKNOWNCMD;
64       }
65       {
66         struct data ioctl_data;
67         curl_easy_setopt(curl, CURLOPT_IOCTLFUNCTION, ioctl_callback);
68         curl_easy_setopt(curl, CURLOPT_IOCTLDATA, &ioctl_data);
69       }
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AVAILABILITY

72       Added in 7.12.3
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RETURN VALUE

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