Avoid computing offset twice

mongoose.c

@@ -4785,8 +4785,9 @@ static void http_cb(struct mg_connection *c, int ev, void *ev_data) {
           // contain a Content-length header (unless the body length is 0, in
           // which case it can be omitted). Other requests can also contain a
           // body, but their content has no defined semantics (RFC 7231)
+          // It is a non-chunked request, so the offset (ofs) is updated after
+          // exiting this branch.
           if (hm.body.len != 0) require_content_len = true;
-          ofs += (size_t) n;  // this request has been processed
         } else if (is_response) {
           // HTTP spec 7.2 Entity body: All other responses must include a body
           // or Content-Length header field defined with a value of 0.

src/http.c

@@ -1183,8 +1183,9 @@ static void http_cb(struct mg_connection *c, int ev, void *ev_data) {
           // contain a Content-length header (unless the body length is 0, in
           // which case it can be omitted). Other requests can also contain a
           // body, but their content has no defined semantics (RFC 7231)
+          // It is a non-chunked request, so the offset (ofs) is updated after
+          // exiting this branch.
           if (hm.body.len != 0) require_content_len = true;
-          ofs += (size_t) n;  // this request has been processed
         } else if (is_response) {
           // HTTP spec 7.2 Entity body: All other responses must include a body
           // or Content-Length header field defined with a value of 0.

test/unit_test.c

@@ -1758,6 +1758,14 @@ static void test_http_pipeline(void) {
   for (i = 0; i < 20; i++) mg_mgr_poll(&mgr, 1);
   ASSERT(ok == 1);
   ASSERT(ok2 == 1);
+  // A bodyless POST must not consume the following pipelined request
+  ok = ok2 = 0;
+  c = mg_http_connect(&mgr, url, f6, (void *) &ok2);
+  mg_printf(c, "POST /x HTTP/1.1\r\nHost: h\r\n\r\n"
+               "GET /next HTTP/1.1\r\nHost: h\r\n\r\n");
+  for (i = 0; i < 20; i++) mg_mgr_poll(&mgr, 1);
+  ASSERT(ok == 2);
+  ASSERT(ok2 == 2);
   // MG_INFO(("-----> [%d] [%d]", ok, ok2));
   mg_mgr_free(&mgr);
   ASSERT(mgr.conns == NULL);