RTMPDump源代码分析 2：RTMP_ParseURL()
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lenint 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;elsehostlen = 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;elseext = &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;}