143 lines
3.1 KiB
Markdown
143 lines
3.1 KiB
Markdown
---
|
|
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
|
|
SPDX-License-Identifier: curl
|
|
Title: curl_ws_meta
|
|
Section: 3
|
|
Source: libcurl
|
|
See-also:
|
|
- curl_easy_getinfo (3)
|
|
- curl_easy_setopt (3)
|
|
- curl_ws_recv (3)
|
|
- curl_ws_send (3)
|
|
- libcurl-ws (3)
|
|
---
|
|
|
|
# NAME
|
|
|
|
curl_ws_meta - meta data WebSocket information
|
|
|
|
# SYNOPSIS
|
|
|
|
~~~c
|
|
#include <curl/curl.h>
|
|
|
|
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 curl_ws_frame
|
|
|
|
~~~c
|
|
struct curl_ws_frame {
|
|
int age;
|
|
int flags;
|
|
curl_off_t offset;
|
|
curl_off_t bytesleft;
|
|
};
|
|
~~~
|
|
|
|
## `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
|
|
|
|
~~~c
|
|
|
|
/* 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);
|
|
|
|
printf("flags: %x\n", m->flags);
|
|
}
|
|
|
|
int main(void)
|
|
{
|
|
CURL *curl = curl_easy_init();
|
|
if(curl) {
|
|
struct customdata custom;
|
|
custom.easy = curl;
|
|
custom.ptr = NULL;
|
|
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writecb);
|
|
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &custom);
|
|
|
|
curl_easy_perform(curl);
|
|
|
|
}
|
|
}
|
|
~~~
|
|
|
|
# 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.
|