x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
curl_ws_meta(3) libcurl curl_ws_meta(3)
NAME
curl_ws_meta - meta data WebSocket information
SYNOPSIS
#include <curl/easy.h>
struct curl_ws_frame {
int age; /* zero */
int flags; /* See the CURLWS_* defines */
curl_off_t offset; /* the offset of this data into the frame */
curl_off_t bytesleft; /* number of pending bytes left of the payload */
};
const struct curl_ws_frame *curl_ws_meta(CURL *curl);
DESCRIPTION
This function call is EXPERIMENTAL.
When the write callback (CURLOPT_WRITEFUNCTION(3)) is invoked on
received WebSocket traffic, curl_ws_meta(3) can be called from within
the callback to provide additional information about the current frame.
This function only works from within the callback, and only when
receiving WebSocket data.
This function requires an easy handle as input argument for libcurl to
know what transfer the question is about, but as there is no such
pointer provided to the callback by libcurl itself, applications that
want to use curl_ws_meta(3) need to pass it on to the callback on its
own.
struct fields
age This field specify the age of this struct. It is always zero for
now.
flags This is a bitmask with individual bits set that describes the
WebSocket data. See the list below.
offset When this frame is a continuation of fragment data already
delivered, this is the offset into the final fragment where this
piece belongs.
bytesleft
If this is not a complete fragment, the bytesleft field informs
about how many additional bytes are expected to arrive before
this fragment is complete.
FLAGS
CURLWS_TEXT
The buffer contains text data. Note that this makes a difference
to WebSocket but libcurl itself does not make any verification
of the content or precautions that you actually receive valid
UTF-8 content.
CURLWS_BINARY
This is binary data.
CURLWS_CONT
This is not the final fragment of the message, it implies that
there is another fragment coming as part of the same message.
CURLWS_CLOSE
This transfer is now closed.
CURLWS_PING
This as an incoming ping message, that expects a pong response.
EXAMPLE
/* we pass a pointer to this struct to the callback */
struct customdata {
CURL *easy;
void *ptr;
};
static size_t writecb(unsigned char *buffer,
size_t size, size_t nitems, void *p)
{
struct customdata *c = (struct customdata *)p;
const struct curl_ws_frame *m = curl_ws_meta(c->easy);
/* m->flags tells us about the traffic */
}
{
struct customdata custom;
custom.easy = easy;
custom.ptr = NULL;
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writecb);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &custom);
}
AVAILABILITY
Added in 7.86.0.
RETURN VALUE
This function returns a pointer to a curl_ws_frame struct with read-
only information that is valid for this specific callback invocation.
If it cannot return this information, or if the function is called in
the wrong context, it returns NULL.
SEE ALSO
curl_easy_setopt(3), curl_easy_getinfo(3), curl_ws_send(3),
curl_ws_recv(3), libcurl-ws(3)
libcurl 8.4.0 September 26, 2023 curl_ws_meta(3)
Want to link to this manual page? Use this URL:
<http://star2.abcm.com/cgi-bin/bsdi-man?query=curl_ws_meta&sektion=3&manpath=>