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| .\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. |
| .\" * |
| .\" * This software is licensed as described in the file COPYING, which |
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| .\" ************************************************************************** |
| .\" |
| .TH curl_ws_meta 3 "12 Jun 2022" "libcurl" "libcurl" |
| .SH NAME |
| curl_ws_meta - meta data WebSocket information |
| .SH SYNOPSIS |
| .nf |
| #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); |
| .fi |
| .SH DESCRIPTION |
| This function call is EXPERIMENTAL. |
| |
| When the write callback (\fICURLOPT_WRITEFUNCTION(3)\fP) is invoked on |
| received WebSocket traffic, \fIcurl_ws_meta(3)\fP 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 |
| \fIcurl_ws_meta(3)\fP need to pass it on to the callback on its own. |
| |
| .SH "struct fields" |
| .IP age |
| This field specify the age of this struct. It is always zero for now. |
| .IP flags |
| This is a bitmask with individual bits set that describes the WebSocket |
| data. See the list below. |
| .IP offset |
| When this frame is a continuation of fragment data already delivered, this is |
| the offset into the final fragment where this piece belongs. |
| .IP bytesleft |
| If this is not a complete fragment, the \fIbytesleft\fP field informs about |
| how many additional bytes are expected to arrive before this fragment is |
| complete. |
| .SH FLAGS |
| .IP CURLWS_TEXT |
| The buffer contains text data. Note that this makes a difference to WebSocket |
| but libcurl itself will not make any verification of the content or |
| precautions that you actually receive valid UTF-8 content. |
| .IP CURLWS_BINARY |
| This is binary data. |
| .IP CURLWS_CONT |
| This is not the final fragment of the message, it implies that there will be |
| another fragment coming as part of the same message. |
| .IP CURLWS_CLOSE |
| This transfer is now closed. |
| .IP CURLWS_PING |
| This as an incoming ping message, that expects a pong response. |
| .SH EXAMPLE |
| .nf |
| |
| /* 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); |
| } |
| .fi |
| .SH AVAILABILITY |
| Added in 7.86.0. |
| .SH RETURN VALUE |
| This function returns a pointer to a \fIcurl_ws_frame\fP 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. |
| .SH "SEE ALSO" |
| .BR curl_easy_setopt "(3), " curl_easy_getinfo "(3), " |
| .BR curl_ws_send "(3), " curl_ws_recv "(3), " libcurl-ws "(3), " |