sendfd.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>
#include <auth.h>
#include "httpd.h"
#include "httpsrv.h"

static	void		printtype(Hio *hout, HContent *type, HContent *enc);

/*
 * these should be done better; see the reponse codes in /lib/rfc/rfc2616 for
 * more info on what should be included.
 */
#define UNAUTHED	"You are not authorized to see this area.\n"
#define NOCONTENT	"No acceptable type of data is available.\n"
#define NOENCODE	"No acceptable encoding of the contents is available.\n"
#define UNMATCHED	"The entity requested does not match the existing entity.\n"
#define BADRANGE	"No bytes are avaible for the range you requested.\n"

/*
 * fd references a file which has been authorized & checked for relocations.
 * send back the headers & it's contents.
 * includes checks for conditional requests & ranges.
 */
int
sendfd(HConnect *c, int fd, Dir *dir, HContent *type, HContent *enc)
{
	Qid qid;
	HRange *r;
	HContents conts;
	Hio *hout;
	char *boundary, etag[32];
	long mtime;
	ulong tr;
	int n, nw, multir, ok;
	vlong wrote, length;

	hout = &c->hout;
	length = dir->length;
	mtime = dir->mtime;
	qid = dir->qid;
	free(dir);

	/*
	 * figure out the type of file and send headers
	 */
	n = -1;
	r = nil;
	multir = 0;
	boundary = nil;
	if(c->req.vermaj){
		if(type == nil && enc == nil){
			conts = uriclass(c, c->req.uri);
			type = conts.type;
			enc = conts.encoding;
			if(type == nil && enc == nil){
				n = read(fd, c->xferbuf, HBufSize-1);
				if(n > 0){
					c->xferbuf[n] = '\0';
					conts = dataclass(c, c->xferbuf, n);
					type = conts.type;
					enc = conts.encoding;
				}
			}
		}
		if(type == nil)
			type = hmkcontent(c, "application", "octet-stream", nil);

		snprint(etag, sizeof(etag), "\"%lluxv%lux\"", qid.path, qid.vers);
		ok = checkreq(c, type, enc, mtime, etag);
		if(ok <= 0){
			close(fd);
			return ok;
		}

		/*
		 * check for if-range requests
		 */
		if(c->head.range == nil
		|| c->head.ifrangeetag != nil && !etagmatch(1, c->head.ifrangeetag, etag)
		|| c->head.ifrangedate != 0 && c->head.ifrangedate != mtime){
			c->head.range = nil;
			c->head.ifrangeetag = nil;
			c->head.ifrangedate = 0;
		}

		if(c->head.range != nil){
			c->head.range = fixrange(c->head.range, length);
			if(c->head.range == nil){
				if(c->head.ifrangeetag == nil && c->head.ifrangedate == 0){
					hprint(hout, "%s 416 Request range not satisfiable\r\n", hversion);
					hprint(hout, "Date: %D\r\n", time(nil));
					hprint(hout, "Server: Plan9\r\n");
					hprint(hout, "Content-Range: bytes */%lld\r\n", length);
					hprint(hout, "Content-Length: %d\r\n", STRLEN(BADRANGE));
					hprint(hout, "Content-Type: text/html\r\n");
					if(c->head.closeit)
						hprint(hout, "Connection: close\r\n");
					else if(!http11(c))
						hprint(hout, "Connection: Keep-Alive\r\n");
					hprint(hout, "\r\n");
					if(strcmp(c->req.meth, "HEAD") != 0)
						hprint(hout, "%s", BADRANGE);
					hflush(hout);
					writelog(c, "Reply: 416 Request range not satisfiable\n");
					close(fd);
					return 1;
				}
				c->head.ifrangeetag = nil;
				c->head.ifrangedate = 0;
			}
		}
		if(c->head.range == nil)
			hprint(hout, "%s 200 OK\r\n", hversion);
		else
			hprint(hout, "%s 206 Partial Content\r\n", hversion);

		hprint(hout, "Server: Plan9\r\n");
		hprint(hout, "Date: %D\r\n", time(nil));
		hprint(hout, "ETag: %s\r\n", etag);

		/*
		 * can't send some entity headers if partially responding
		 * to an if-range: etag request
		 */
		r = c->head.range;
		if(r == nil)
			hprint(hout, "Content-Length: %lld\r\n", length);
		else if(r->next == nil){
			hprint(hout, "Content-Range: bytes %ld-%ld/%lld\r\n", r->start, r->stop, length);
			hprint(hout, "Content-Length: %ld\r\n", r->stop - r->start);
		}else{
			multir = 1;
			boundary = hmkmimeboundary(c);
			hprint(hout, "Content-Type: multipart/byteranges; boundary=%s\r\n", boundary);
		}
		if(c->head.ifrangeetag == nil){
			hprint(hout, "Last-Modified: %D\r\n", mtime);
			if(!multir)
				printtype(hout, type, enc);
			if(c->head.fresh_thresh)
				hintprint(c, hout, c->req.uri, c->head.fresh_thresh, c->head.fresh_have);
		}

		if(c->head.closeit)
			hprint(hout, "Connection: close\r\n");
		else if(!http11(c))
			hprint(hout, "Connection: Keep-Alive\r\n");
		hprint(hout, "\r\n");
	}
	if(strcmp(c->req.meth, "HEAD") == 0){
		if(c->head.range == nil)
			writelog(c, "Reply: 200 file 0\n");
		else
			writelog(c, "Reply: 206 file 0\n");
		hflush(hout);
		close(fd);
		return 1;
	}

	/*
	 * send the file if it's a normal file
	 */
	if(r == nil){
		hflush(hout);

		wrote = 0;
		if(n > 0)
			wrote = write(hout->fd, c->xferbuf, n);
		if(n <= 0 || wrote == n){
			while((n = read(fd, c->xferbuf, HBufSize)) > 0){
				nw = write(hout->fd, c->xferbuf, n);
				if(nw != n){
					if(nw > 0)
						wrote += nw;
					break;
				}
				wrote += nw;
			}
		}
		writelog(c, "Reply: 200 file %lld %lld\n", length, wrote);
		close(fd);
		if(length == wrote)
			return 1;
		return -1;
	}

	/*
	 * for multipart/byterange messages,
	 * it is not ok for the boundary string to appear within a message part.
	 * however, it probably doesn't matter, since there are lengths for every part.
	 */
	wrote = 0;
	ok = 1;
	for(; r != nil; r = r->next){
		if(multir){
			hprint(hout, "\r\n--%s\r\n", boundary);
			printtype(hout, type, enc);
			hprint(hout, "Content-Range: bytes %ld-%ld/%lld\r\n", r->start, r->stop, length);
			hprint(hout, "Content-Length: %ld\r\n", r->stop - r->start);
			hprint(hout, "\r\n");
		}
		hflush(hout);

		if(seek(fd, r->start, 0) != r->start){
			ok = -1;
			break;
		}
		for(tr = r->stop - r->start + 1; tr; tr -= n){
			n = tr;
			if(n > HBufSize)
				n = HBufSize;
			if(read(fd, c->xferbuf, n) != n){
				ok = -1;
				goto breakout;
			}
			nw = write(hout->fd, c->xferbuf, n);
			if(nw != n){
				if(nw > 0)
					wrote += nw;
				ok = -1;
				goto breakout;
			}
			wrote += nw;
		}
	}
breakout:;
	if(r == nil){
		if(multir){
			hprint(hout, "--%s--\r\n", boundary);
			hflush(hout);
		}
		writelog(c, "Reply: 206 partial content %lld %lld\n", length, wrote);
	}else
		writelog(c, "Reply: 206 partial content, early termination %lld %lld\n", length, wrote);
	close(fd);
	return ok;
}

static void
printtype(Hio *hout, HContent *type, HContent *enc)
{
	hprint(hout, "Content-Type: %s/%s", type->generic, type->specific);
/*
	if(cistrcmp(type->generic, "text") == 0)
		hprint(hout, ";charset=utf-8");
*/
	hprint(hout, "\r\n");
	if(enc != nil)
		hprint(hout, "Content-Encoding: %s\r\n", enc->generic);
}

int
etagmatch(int strong, HETag *tags, char *e)
{
	char *s, *t;

	for(; tags != nil; tags = tags->next){
		if(strong && tags->weak)
			continue;
		s = tags->etag;
		if(s[0] == '*' && s[1] == '\0')
			return 1;

		t = e + 1;
		while(*t != '"'){
			if(*s != *t)
				break;
			s++;
			t++;
		}

		if(*s == '\0' && *t == '"')
			return 1;
	}
	return 0;
}

static char *
acceptcont(char *s, char *e, HContent *ok, char *which)
{
	char *sep;

	if(ok == nil)
		return seprint(s, e, "Your browser accepts any %s.<br>\n", which);
	s = seprint(s, e, "Your browser accepts %s: ", which);
	sep = "";
	for(; ok != nil; ok = ok->next){
		if(ok->specific)
			s = seprint(s, e, "%s%s/%s", sep, ok->generic, ok->specific);
		else
			s = seprint(s, e, "%s%s", sep, ok->generic);
		sep = ", ";
	}
	return seprint(s, e, ".<br>\n");
}

/*
 * send back a nice error message if the content is unacceptable
 * to get this message in ie, go to tools, internet options, advanced,
 * and turn off Show Friendly HTTP Error Messages under the Browsing category
 */
static int
notaccept(HConnect *c, HContent *type, HContent *enc, char *which)
{
	Hio *hout;
	char *s, *e;

	hout = &c->hout;
	e = &c->xferbuf[HBufSize];
	s = c->xferbuf;
	s = seprint(s, e, "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 Transitional//EN\">\n");
	s = seprint(s, e, "<html>\n<title>Unacceptable %s</title>\n<body>\n", which);
	s = seprint(s, e, "Your browser will not accept this data, %H, because of it's %s.<br>\n", c->req.uri, which);
	s = seprint(s, e, "It's Content-Type is %s/%s", type->generic, type->specific);
	if(enc != nil)
		s = seprint(s, e, ", and Content-Encoding is %s", enc->generic);
	s = seprint(s, e, ".<br>\n\n");

	s = acceptcont(s, e, c->head.oktype, "Content-Type");
	s = acceptcont(s, e, c->head.okencode, "Content-Encoding");
	s = seprint(s, e, "</body>\n</html>\n");

	hprint(hout, "%s 406 Not Acceptable\r\n", hversion);
	hprint(hout, "Server: Plan9\r\n");
	hprint(hout, "Date: %D\r\n", time(nil));
	hprint(hout, "Content-Type: text/html\r\n");
	hprint(hout, "Content-Length: %lud\r\n", s - c->xferbuf);
	if(c->head.closeit)
		hprint(hout, "Connection: close\r\n");
	else if(!http11(c))
		hprint(hout, "Connection: Keep-Alive\r\n");
	hprint(hout, "\r\n");
	if(strcmp(c->req.meth, "HEAD") != 0)
		hwrite(hout, c->xferbuf, s - c->xferbuf);
	writelog(c, "Reply: 406 Not Acceptable\nReason: %s\n", which);
	return hflush(hout);
}

/*
 * check time and entity tag conditions.
 */
int
checkreq(HConnect *c, HContent *type, HContent *enc, long mtime, char *etag)
{
	Hio *hout;
	int m;

	hout = &c->hout;
	if(c->req.vermaj >= 1 && c->req.vermin >= 1 && !hcheckcontent(type, c->head.oktype, "Content-Type", 0))
		return notaccept(c, type, enc, "Content-Type");
	if(c->req.vermaj >= 1 && c->req.vermin >= 1 && !hcheckcontent(enc, c->head.okencode, "Content-Encoding", 0))
		return notaccept(c, type, enc, "Content-Encoding");

	/*
	 * can use weak match only with get or head;
	 * this always uses strong matches
	 */
	m = etagmatch(1, c->head.ifnomatch, etag);

	if(m && strcmp(c->req.meth, "GET") != 0 && strcmp(c->req.meth, "HEAD") != 0
	|| c->head.ifunmodsince && c->head.ifunmodsince < mtime
	|| c->head.ifmatch != nil && !etagmatch(1, c->head.ifmatch, etag)){
		hprint(hout, "%s 412 Precondition Failed\r\n", hversion);
		hprint(hout, "Server: Plan9\r\n");
		hprint(hout, "Date: %D\r\n", time(nil));
		hprint(hout, "Content-Type: text/html\r\n");
		hprint(hout, "Content-Length: %d\r\n", STRLEN(UNMATCHED));
		if(c->head.closeit)
			hprint(hout, "Connection: close\r\n");
		else if(!http11(c))
			hprint(hout, "Connection: Keep-Alive\r\n");
		hprint(hout, "\r\n");
		if(strcmp(c->req.meth, "HEAD") != 0)
			hprint(hout, "%s", UNMATCHED);
		writelog(c, "Reply: 412 Precondition Failed\n");
		return hflush(hout);
	}

	if(c->head.ifmodsince >= mtime
	&& (m || c->head.ifnomatch == nil)){
		/*
		 * can only send back Date, ETag, Content-Location,
		 * Expires, Cache-Control, and Vary entity-headers
		 */
		hprint(hout, "%s 304 Not Modified\r\n", hversion);
		hprint(hout, "Server: Plan9\r\n");
		hprint(hout, "Date: %D\r\n", time(nil));
		hprint(hout, "ETag: %s\r\n", etag);
		if(c->head.closeit)
			hprint(hout, "Connection: close\r\n");
		else if(!http11(c))
			hprint(hout, "Connection: Keep-Alive\r\n");
		hprint(hout, "\r\n");
		writelog(c, "Reply: 304 Not Modified\n");
		return hflush(hout);
	}
	return 1;
}

/*
 * length is the actual length of the entity requested.
 * discard any range requests which are invalid,
 * ie start after the end, or have stop before start.
 * rewrite suffix requests
 */
HRange*
fixrange(HRange *h, long length)
{
	HRange *r, *rr;

	if(length == 0)
		return nil;

	/*
	 * rewrite each range to reflect the actual length of the file
	 * toss out any invalid ranges
	 */
	rr = nil;
	for(r = h; r != nil; r = r->next){
		if(r->suffix){
			r->start = length - r->stop;
			if(r->start >= length)
				r->start = 0;
			r->stop = length - 1;
			r->suffix = 0;
		}
		if(r->stop >= length)
			r->stop = length - 1;
		if(r->start > r->stop){
			if(rr == nil)
				h = r->next;
			else
				rr->next = r->next;
		}else
			rr = r;
	}

	/*
	 * merge consecutive overlapping or abutting ranges
	 *
	 * not clear from rfc2616 how much merging needs to be done.
	 * this code merges only if a range is adjacent to a later starting,
	 * over overlapping or abutting range.  this allows a client
	 * to request wanted data first, followed by other data.
	 * this may be useful then fetching part of a page, then the adjacent regions.
	 */
	if(h == nil)
		return h;
	r = h;
	for(;;){
		rr = r->next;
		if(rr == nil)
			break;
		if(r->start <= rr->start && r->stop + 1 >= rr->start){
			if(r->stop < rr->stop)
				r->stop = rr->stop;
			r->next = rr->next;
		}else
			r = rr;
	}
	return h;
}