/*
?*?proxy.c?-?CS:APP?Web?proxy
?*
?*?
?*?IMPORTANT:?Give?a?high?level?description?of?your?code?here.?You
?*?must?also?provide?a?header?comment?at?the?beginning?of?each
?*?function?that?describes?what?that?function?does.
?*/?

#include?“csapp.h“

struct?arg
{
????int?fd;
????struct?sockaddr_in?sock;
};

FILE?*log_file;
sem_t?sem_log;
sem_t?sem_dns;

/*
?*?Function?prototypes
?*/
int?parse_uri（char?*uri?char?*target_addr?char?*path?int??*port）;
void?format_log_entry（char?*logstring?struct?sockaddr_in?*sockaddr?char?*uri?int?size）;
void?*proxy（void?*）;
void?Rio_writen_w（int?fd?void?*usrbuf?size_t?n）;
ssize_t?Rio_readlineb_w（rio_t?*rp?void?*usrbuf?size_t?maxlen）;
int?Open_clientfd_w（char?*hostname?int?port）;

/*?
?*?main?-?Main?routine?for?the?proxy?program?
?*/
int?main（int?argc?char?**argv）
{
????Signal（SIGPIPE?SIG_IGN）;

????int?port?=?atoi（argv[1]）;

????sem_init（&sem_log?0?1）;
????sem_init（&sem_dns?0?1）;
?
????log_file?=?fopen（“./proxy.log“?“a“）;

????int?connfd;
????int?listenfd?=?Open_listenfd（port）;
????struct?sockaddr_in?clientaddr;
????int?clientlen;
????pthread_t?tid;
????struct?arg?g;

????while?（1）
????{
????????clientlen=?sizeof（clientaddr）;
????????struct?arg?*g?=?（struct?arg?*）malloc（sizeof（struct?arg））;
????????connfd?=?Accept（listenfd?（SA?*）（&（g->sock））?&clientlen）;
????????g->fd?=?connfd;
????????Pthread_create（&tid?NULL?proxy?（void?*）g）;
????}

????exit（0）;
}

/*
?*?Thread
?*/
void?*proxy（void?*ptr）
{
????Pthread_detach（pthread_self（））;

????struct?arg?*g?=?（struct?arg?*）ptr;
????int?connfd?=?g->fd;
????struct?sockaddr_in?sock;
????memcpy（&sock?&（g->sock）?sizeof（struct?sockaddr_in））;
????free（g）;

????char?buf[MAXLINE]?method[MAXLINE]?uri[MAXLINE]?version[MAXLINE]
	hostname[MAXLINE]?pathname[MAXLINE]?content[MAXLINE];
????int?port?server_fd?content_len;
????rio_t?rio_client?rio_server;

????Rio_readinitb（&rio_client?connfd）;
????Rio_readlineb_w（&rio_client?content?MAXLINE）;

????sscanf（content?“%s?%s?%s“?method?uri?version）;

????parse_uri（uri?hostname?pathname?&port）;

????//send?content?to?server
????int?retval?=?0;
????server_fd?=?Open_clientfd_w（hostname?port）;
????if?（server_fd==0）?return;
????Rio_readinitb（&rio_server?server_fd）;??
????Rio_writen_w（server_fd?content?strlen（content））;
????while?（Rio_readlineb_w（&rio_client?content?MAXLINE）>2）
????{
????????if?（strstr（content?“Proxy-Connection“））
????????????strcpy（content?“Proxy-Connection:?close\r\n“）;
????????else?if?（strstr（content?“Connection“））
????????????strcpy（content?“Connection:?close\r\n“）;?
????????Rio_writen_w（server_fd?content?strlen（content））;
????}
????Rio_writen_w（server_fd?“\r\n“?2）;

????//?receive?content?from?server
????int?found?=?0;
????while?（Rio_readlineb_w（&rio_server?buf?MAXLINE）>2）?{
????????char?*index?=?strstr（buf?“Content-Length“）;
????????if?（index）?{
????????????found?=?1;
????????????content_len?=?atoi（index+16）;
????????}
????????
????????Rio_writen_w（connfd?buf?strlen（buf））;
?