RTMPDump(libRTMP)源代码分析 2:解析RTMP地址——RTMP_ParseURL()

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RTMPdump(libRTMP) 源代码分析系列文章:

RTMPdump 源代码分析 1: main()函数

RTMPDump (libRTMP) 源代码分析2:解析RTMP地址——RTMP_ParseURL()

RTMPdump (libRTMP) 源代码分析3: AMF编码

RTMPdump (libRTMP) 源代码分析4: 连接第一步——握手 (HandShake)

RTMPdump (libRTMP) 源代码分析5: 建立一个流媒体连接  (NetConnection部分)

RTMPdump (libRTMP) 源代码分析6: 建立一个流媒体连接  (NetStream部分 1)

RTMPdump (libRTMP) 源代码分析7: 建立一个流媒体连接  (NetStream部分 2)

RTMPdump (libRTMP) 源代码分析8: 发送消息 (Message)

RTMPdump (libRTMP) 源代码分析9: 接收消息 (Message)  (接收视音频数据)

RTMPdump (libRTMP) 源代码分析10: 处理各种消息 (Message)

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函数调用结构图

RTMPDump (libRTMP)的整体的函数调用结构图如下图所示。

RTMPDump(libRTMP)源代码分析 2:解析RTMP地址——RTMP_ParseURL()_第1张图片

单击查看大图

详细分析

之前分析了一下RTMPDump的Main()函数,其中获取RTMP流媒体数据很重要的前提是RTMP的URL的解析。如果没有这一步,那程序在强大也是白搭。现在来解析一下这个函数吧:RTMP_ParseURL()。

下面首先回顾一下RTMP的URL的格式:

rtmp://localhost/vod/mp4:sample1_1500kbps.f4v

“://”之前的是使用的协议类型,可以是rtmp,rtmpt,rtmps等

之后是服务器地址

再之后是端口号(可以没有,默认1935)

在之后是application的名字,在这里是“vod”

最后是流媒体文件路径。

关于URL就不多说了,可以查看相关文档,下面贴上注释后的代码(整个parseurl.c):

/*
 * 本文件主要包含了对输入URL的解析
 */
#include "stdafx.h"
#include <stdlib.h>
#include <string.h>

#include <assert.h>
#include <ctype.h>

#include "rtmp_sys.h"
#include "log.h"

/*解析URL,得到协议名称(protocol),主机名称(host),应用程序名称(app)
 *
 */
int RTMP_ParseURL(const char *url, int *protocol, AVal *host, unsigned int *port,
	AVal *playpath, AVal *app)
{
	char *p, *end, *col, *ques, *slash;

	RTMP_Log(RTMP_LOGDEBUG, "Parsing...");

	*protocol = RTMP_PROTOCOL_RTMP;
	*port = 0;
	playpath->av_len = 0;
	playpath->av_val = NULL;
	app->av_len = 0;
	app->av_val = NULL;

	/* 字符串解析 */
	/* 查找“://”  */
	//函数原型:char *strstr(char *str1, char *str2);
	//功能:找出str2字符串在str1字符串中第一次出现的位置(不包括str2的串结束符)。
	//返回值:返回该位置的指针,如找不到,返回空指针。
	p = strstr((char *)url, "://");
	if(!p) {
		RTMP_Log(RTMP_LOGERROR, "RTMP URL: No :// in url!");
		return FALSE;
	}
	{
	//指针相减,返回“://”之前字符串长度len
	int len = (int)(p-url);
	//获取使用的协议
	//通过比较字符串的方法
	if(len == 4 && strncasecmp(url, "rtmp", 4)==0)
		*protocol = RTMP_PROTOCOL_RTMP;
	else if(len == 5 && strncasecmp(url, "rtmpt", 5)==0)
		*protocol = RTMP_PROTOCOL_RTMPT;
	else if(len == 5 && strncasecmp(url, "rtmps", 5)==0)
	        *protocol = RTMP_PROTOCOL_RTMPS;
	else if(len == 5 && strncasecmp(url, "rtmpe", 5)==0)
	        *protocol = RTMP_PROTOCOL_RTMPE;
	else if(len == 5 && strncasecmp(url, "rtmfp", 5)==0)
	        *protocol = RTMP_PROTOCOL_RTMFP;
	else if(len == 6 && strncasecmp(url, "rtmpte", 6)==0)
	        *protocol = RTMP_PROTOCOL_RTMPTE;
	else if(len == 6 && strncasecmp(url, "rtmpts", 6)==0)
	        *protocol = RTMP_PROTOCOL_RTMPTS;
	else {
		RTMP_Log(RTMP_LOGWARNING, "Unknown protocol!\n");
		goto parsehost;
	}
	}

	RTMP_Log(RTMP_LOGDEBUG, "Parsed protocol: %d", *protocol);

parsehost:
	//获取主机名称
	//跳过“://”
	p+=3;

	/* 检查一下主机名 */
	if(*p==0) {
		RTMP_Log(RTMP_LOGWARNING, "No hostname in URL!");
		return FALSE;
	}
	//原型:char *strchr(const char *s,char c); 
	//功能:查找字符串s中首次出现字符c的位置
	//说明:返回首次出现c的位置的指针,如果s中不存在c则返回NULL。 
	end   = p + strlen(p);//指向结尾的指针
	col   = strchr(p, ':');//指向冒号(第一个)的指针
	ques  = strchr(p, '?');//指向问号(第一个)的指针
	slash = strchr(p, '/');//指向斜杠(第一个)的指针

	{
	int hostlen;
	if(slash)
		hostlen = slash - p;
	else
		hostlen = end - p;
	if(col && col -p < hostlen)
		hostlen = col - p;

	if(hostlen < 256) {
		host->av_val = p;
		host->av_len = hostlen;
		RTMP_Log(RTMP_LOGDEBUG, "Parsed host    : %.*s", hostlen, host->av_val);
	} else {
		RTMP_Log(RTMP_LOGWARNING, "Hostname exceeds 255 characters!");
	}

	p+=hostlen;
	}

	/* 获取端口号 */
	if(*p == ':') {
		unsigned int p2;
		p++;
		p2 = atoi(p);
		if(p2 > 65535) {
			RTMP_Log(RTMP_LOGWARNING, "Invalid port number!");
		} else {
			*port = p2;
		}
	}

	if(!slash) {
		RTMP_Log(RTMP_LOGWARNING, "No application or playpath in URL!");
		return TRUE;
	}
	p = slash+1;

	{
	/* 获取应用程序(application)
	 *
	 * rtmp://host[:port]/app[/appinstance][/...]
	 * application = app[/appinstance]
	 */

	char *slash2, *slash3 = NULL;//指向第二个斜杠,第三个斜杠的指针
	int applen, appnamelen;

	slash2 = strchr(p, '/');//指向第二个斜杠
	if(slash2)
		slash3 = strchr(slash2+1, '/');//指向第三个斜杠,注意slash2之所以+1是因为让其后移一位

	applen = end-p; /* ondemand, pass all parameters as app */
	appnamelen = applen; /* ondemand length */

	if(ques && strstr(p, "slist=")) { /* whatever it is, the '?' and slist= means we need to use everything as app and parse plapath from slist= */
		appnamelen = ques-p;
	}
	else if(strncmp(p, "ondemand/", 9)==0) {
                /* app = ondemand/foobar, only pass app=ondemand */
                applen = 8;
                appnamelen = 8;
        }
	else { /* app!=ondemand, so app is app[/appinstance] */
		if(slash3)
			appnamelen = slash3-p;
		else if(slash2)
			appnamelen = slash2-p;

		applen = appnamelen;
	}

	app->av_val = p;
	app->av_len = applen;
	RTMP_Log(RTMP_LOGDEBUG, "Parsed app     : %.*s", applen, p);

	p += appnamelen;
	}

	if (*p == '/')
		p++;

	if (end-p) {
		AVal av = {p, end-p};
		RTMP_ParsePlaypath(&av, playpath);
	}

	return TRUE;
}

/*
 * 从URL中获取播放路径(playpath)。播放路径是URL中“rtmp://host:port/app/”后面的部分
 *
 * 获取FMS能够识别的播放路径
 * mp4 流: 前面添加 "mp4:", 删除扩展名
 * mp3 流: 前面添加 "mp3:", 删除扩展名
 * flv 流: 删除扩展名
 */
void RTMP_ParsePlaypath(AVal *in, AVal *out) {
	int addMP4 = 0;
	int addMP3 = 0;
	int subExt = 0;
	const char *playpath = in->av_val;
	const char *temp, *q, *ext = NULL;
	const char *ppstart = playpath;
	char *streamname, *destptr, *p;

	int pplen = in->av_len;

	out->av_val = NULL;
	out->av_len = 0;

	if ((*ppstart == '?') &&
	    (temp=strstr(ppstart, "slist=")) != 0) {
		ppstart = temp+6;
		pplen = strlen(ppstart);

		temp = strchr(ppstart, '&');
		if (temp) {
			pplen = temp-ppstart;
		}
	}

	q = strchr(ppstart, '?');
	if (pplen >= 4) {
		if (q)
			ext = q-4;
		else
			ext = &ppstart[pplen-4];
		if ((strncmp(ext, ".f4v", 4) == 0) ||
		    (strncmp(ext, ".mp4", 4) == 0)) {
			addMP4 = 1;
			subExt = 1;
		/* Only remove .flv from rtmp URL, not slist params */
		} else if ((ppstart == playpath) &&
		    (strncmp(ext, ".flv", 4) == 0)) {
			subExt = 1;
		} else if (strncmp(ext, ".mp3", 4) == 0) {
			addMP3 = 1;
			subExt = 1;
		}
	}

	streamname = (char *)malloc((pplen+4+1)*sizeof(char));
	if (!streamname)
		return;

	destptr = streamname;
	if (addMP4) {
		if (strncmp(ppstart, "mp4:", 4)) {
			strcpy(destptr, "mp4:");
			destptr += 4;
		} else {
			subExt = 0;
		}
	} else if (addMP3) {
		if (strncmp(ppstart, "mp3:", 4)) {
			strcpy(destptr, "mp3:");
			destptr += 4;
		} else {
			subExt = 0;
		}
	}

 	for (p=(char *)ppstart; pplen >0;) {
		/* skip extension */
		if (subExt && p == ext) {
			p += 4;
			pplen -= 4;
			continue;
		}
		if (*p == '%') {
			unsigned int c;
			sscanf(p+1, "%02x", &c);
			*destptr++ = c;
			pplen -= 3;
			p += 3;
		} else {
			*destptr++ = *p++;
			pplen--;
		}
	}
	*destptr = '\0';

	out->av_val = streamname;
	out->av_len = destptr - streamname;
}

rtmpdump源代码(Linux):http://download.csdn.net/detail/leixiaohua1020/6376561

rtmpdump源代码(VC 2005 工程):http://download.csdn.net/detail/leixiaohua1020/6563163


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