/*------------------------------------------------------------------------- * rtprecv.c - rtprecv *------------------------------------------------------------------------- */#include <ipOS.h>#include <ipHAL.h>#include <ipStack.h>#include <ipEthernet.h>#include "hust_rtp.h"#include "hust_hash.h"#include "hust_event.h"#include "hust_rtplibcommon.h"////#include <unistd.h>/*------------------------------------------------------------------------ * rtprecv - 接收一個rtp包，并將包放到所屬源的stream中 	     把stream中的rtp包解析成為連續的TS流的操作 	     將是在stream中積累一定量的連續序列號的rtp包之后 *------------------------------------------------------------------------ */intrtprecv(struct session *psn){	struct rtpln		*pln;	////隊列節點上的rtp包		u32_t	from;	///rtp包的源地址		int			fromlen, len;	///地址長度		struct rtp		*prtp;	struct stream		*pstm;	bool			head;	int			rv;	pln = (struct rtpln *) bufpoolgetbuf(&psn->sn_bpool);	///獲得固定大小的緩沖區	if (pln ==  NULL) {		rtppostevent(psn, EVENT_NOBUFS, 0, NULL, 0);		return ERROR;	}	////處理緩沖區用完的情況	fromlen = sizeof(from);///	len = recvfrom(psn->sn_rtpfd, (char *) &pln->rln_rtp, psn->sn_bpool.bp_size - sizeof(struct rtpln), 0, (struct sockaddr *) &from, &fromlen);///用來接收遠程主機指定的soket傳來的數據，數據存放在pln->rln_trp里面	if (len < 1) {		bufpoolfreebuf(pln);		return ERROR;	}	////接收失敗的情況	pln->rln_len = len;	/*	 * Extract source address as RTCP destination for unicast session 	 * if the RTCP destination has not already been learned.	 */	if (psn->sn_rtcpto== RTP_INADDRUNINITIALIZED) {		psn->sn_rtcpto = from;	}	////必要時，給rtcp賦目的地址	/*	 * Get pointer to RTP header.	 */	prtp = &pln->rln_rtp;  	////prtp作為指向rtp頭部的指針	/*	 * Convert header byte order and check version.	 */	////rtpntoh(prtp);	////這里不考慮字節的位的順序問題	if (prtp->rtp_ver != RTP_CURRVERS) {		bufpoolfreebuf(pln);		return ERROR;	}	///檢查版本	/*	 * Lookup stream by SSRC.	 */	pstm = rtpgetstream(psn, prtp->rtp_ssrc);	/* 	 * Create new stream if newly discovered source.	 */	if (pstm == NULL) {		if ((pstm = rtpnewstream(psn, prtp->rtp_ssrc)) == NULL) {			bufpoolfreebuf(pln);			return ERROR;		}	}	///如果是新的源，就要為這個源創建一個stream	else {		if (RTP_INACTIVE(pstm->stm_inactive)) {			rtpreleasestream(psn, pstm);			bufpoolfreebuf(pln);			return ERROR;		}	}  	if (pstm->stm_ip== RTP_INADDRUNINITIALIZED)		pstm->stm_ip = from;////stream.stm_ip是數據源的地址	/*	 * Update stream's statistics and check if stream is still	 * on probation.	 */	if (rtpupdate(psn, pstm, prtp) == ERROR) {		rtpreleasestream(psn, pstm);		bufpoolfreebuf(pln);		return ERROR;	}	/*	 * Enqueue the packet if stream is ``on''.	 */	if (pstm->stm_enqueue == TRUE) {		/* 		 * Tag packet with *extended* sequence number.		 */		pln->rln_seq = ((pstm->stm_roll) << 16) | prtp->rtp_seq;		////pthread_mutex_lock(&pstm->stm_queue.rq_mutex);		rv = _rtpqinsert(&pstm->stm_queue, pln, &head);		////pthread_mutex_unlock(&pstm->stm_queue.rq_mutex);		/*		 * Post event if packet added at front of queue.		 * Doing so will notify a thread waiting on an		 * empty queue.		 */		if (rv == OK) {			rtppostevent(psn, (head == TRUE ? EVENT_RTP_HEAD : EVENT_RTP), pstm->stm_ssrc, NULL, 0);			rtpreleasestream(psn, pstm);			return OK;		}		else {			/* 			 * Free packet and return error if 			 * enqueue operation failed.			 */			rtpreleasestream(psn, pstm);			bufpoolfreebuf(pln);			return ERROR;		}	}	rtpreleasestream(psn, pstm);	/*	 * Post an RTP-packet-received event.	 */	rtppostevent(psn, EVENT_RTP, prtp->rtp_ssrc, NULL, 0);	bufpoolfreebuf(pln);	return OK;}