mongoose/docs/c-api/mg_http_server.h/mg_send_head.md

title	decl_name	symbol_kind	signature
mg_send_head()	mg_send_head	func	void mg_send_head(struct mg_connection *n, int status_code, int64_t content_length, const char *extra_headers);

Sends the response line and headers. This function sends the response line with the status_code, and automatically sends one header: either "Content-Length" or "Transfer-Encoding". If content_length is negative, then "Transfer-Encoding: chunked" header is sent, otherwise, "Content-Length" header is sent.

NOTE: If Transfer-Encoding is chunked, then message body must be sent using mg_send_http_chunk() or mg_printf_http_chunk() functions. Otherwise, mg_send() or mg_printf() must be used. Extra headers could be set through extra_headers. Note extra_headers must NOT be terminated by a new line.