typedef struct Client Client;typedef struct Ctl Ctl;typedef struct Ibuf Ibuf;typedef struct Url Url; /* simple buffered i/o for network connections; shared by http, ftp */struct Ibuf{	int fd;	Ioproc *io;	char buf[4096];	char *rp, *wp;}; struct Ctl{	int	acceptcookies;	int	sendcookies;	int	redirectlimit;	char	*useragent;}; struct Client{	Url	*url;	Url	*baseurl;	Ctl ctl;	Channel *creq;	/* chan(Req*) */	int num;	int plumbed;	char *contenttype;	char *postbody;	char *redirect;	char *authenticate;	char *ext;	int npostbody;	int havepostbody;	int iobusy;	int bodyopened;	Ioproc *io;	int ref;	void *aux;}; /* * If ischeme is USunknown, then the given URL is a relative * URL which references the "current document" in the context of the base. * If this is the case, only the "fragment" and "url" members will have * meaning, and the given URL structure may not be used as a base URL itself. */enum{	USunknown,	UShttp,	UShttps,	USftp,	USfile,	UScurrent,}; struct Url{	int		ischeme;	char*	url;	char*	scheme;	int		(*open)(Client*, Url*);	int		(*read)(Client*, Req*);	void		(*close)(Client*);	char*	schemedata;	char*	authority;	char*	user;	char*	passwd;	char*	host;	char*	port;	char*	path;	char*	query;	char*	fragment;	union {		struct {			char *page_spec;		} http;		struct {			char *path_spec;			char *type;		} ftp;	};}; enum{	STACK = 16384,}; extern	Client**	client;extern	int		cookiedebug;extern	Srv		fs;extern	int		fsdebug;extern	Ctl		globalctl;extern	int		nclient;extern	int		urldebug;extern	int		httpdebug;extern	char*	status[];