http: Implement trailing headers for chunked transfers

This adds the CURLOPT_TRAILERDATA and CURLOPT_TRAILERFUNCTION
options that allow a callback based approach to sending trailing headers
with chunked transfers.

The test server (sws) was updated to take into account the detection of the
end of transfer in the case of trailing headers presence.

Test 1591 checks that trailing headers can be sent using libcurl.

Closes #3350

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/http.h b/lib/http.h
index 21fa701ab..7fa0471ad 100644
--- a/lib/http.h
+++ b/lib/http.h
@@ -74,6 +74,9 @@ CURLcode Curl_add_timecondition(struct Curl_easy *data,
 CURLcode Curl_add_custom_headers(struct connectdata *conn,
                                  bool is_connect,
                                  Curl_send_buffer *req_buffer);
+CURLcode Curl_http_compile_trailers(struct curl_slist *trailers,
+                                    Curl_send_buffer *buffer,
+                                    struct Curl_easy *handle);
 
 /* protocol-specific functions set up to be called by the main engine */
 CURLcode Curl_http(struct connectdata *conn, bool *done);