Hi, I was going through the pjsip code and found that a lot of linked list is used throughout the code to add new headers,remove and manupulate them. but ,what i am unsure at the moment is the type of linked list used for it (i guess we are using circular linked liist but i am not sure) how i guessed it... in this function of pjsip pjsip_auth_clt_reinit_req the line hdr = rdata->msg_info.msg->hdr.next; while (hdr != &rdata->msg_info.msg->hdr) { tells me that hdr is pointing to the next instance and with the help of hdr ponter we are traversing the entire linked list until we reach the same position from where we started. i would be really great if someone could point out the type of linked list employed. Also,in the same functon i find this line.. cached_auth->is_proxy = (hchal->type == PJSIP_H_PROXY_AUTHENTICATE); i tried to find (const pjsip_www_authenticate_hdr *hchal;) hcal->type i.e to be precise* type* is the member i tried to find but to no avail,also besides *type* i see many extensions such as *slen* and* next* which are not part of the structure and are throughly used throughout the code. I am a beginner so please,overlook my silly questions and help me in understanding the flow. Thanks in Advance. John. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20110206/0d59daab/attachment.html>