[Global]: loading init

deps/curl/docs/libcurl/opts/CURLOPT_IOCTLFUNCTION.md

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+---
+c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_IOCTLFUNCTION
+Section: 3
+Source: libcurl
+See-also:
+  - CURLOPT_IOCTLDATA (3)
+  - CURLOPT_SEEKFUNCTION (3)
+---
+
+# NAME
+
+CURLOPT_IOCTLFUNCTION - callback for I/O operations
+
+# SYNOPSIS
+
+~~~c
+#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
+
+~~~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.