如何使用libcurl实现http流

Question

I am trying to use CURL to implement Microsoft's EWS Streaming Notifications ie HTTP Streaming where the request is sent once and the server responds with a header with "Transfer Encoding: chunked". The server will send multiple keepalive or notification chunks before the final packet. The chunks are terminated with cr lf.

If I create a standard CURL client then curl_easy_perform will not return until the final chunk is received whereas I need curl_easy_perform to return upon receipt of each chunk whereupon the application will process the received chunk and call curl_easy_perform to wait for the next chunk.

I realize that I could process the chunk in the CURLOPT_WRITEFUNCTION callback but the architecture of the application doesn't allow for that (this is a GSOAP plugin)

Any suggestions other than switching to CURLOPT_CONNECT_ONLY and handling the write all subsequent reads with curl_easy_send and curl_easy_recv? Which seems a shame as I will have to duplicate CURL's formatting and parsing.

Alan

Answer 1

curl_easy_perform is completely synchronous and will return only once the entire transfer is done. There's really no way around that (you already mentioned CURLOPT_CONNECT_ONLY and I wouldn't recommend that either) with this API.

If you want control back in the same thread before the entire transfer is done, which your question suggests, you probably rather want to use the multi interface.

Using that interface, curl_multi_perform will only do as much as it can right now without blocking and return control back to your function. It does however put the responsibility over to your code to wait for socket activity and call libcurl again when there is.

(Sorry, but I don't know what restrictions a "GSOAP plugin" has and you didn't state them here, so maybe this is all crap)