nntpfs.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

/*
 * Network news transport protocol (NNTP) file server.
 *
 * Unfortunately, the file system differs from that expected
 * by Charles Forsyth's rin news reader.  This is partially out
 * of my own laziness, but it makes the bookkeeping here
 * a lot easier.
 */

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <auth.h>
#include <fcall.h>
#include <thread.h>
#include <9p.h>

typedef struct Netbuf Netbuf;
typedef struct Group Group;

struct Netbuf {
	Biobuf br;
	Biobuf bw;
	int lineno;
	int fd;
	int code;			/* last response code */
	int auth;			/* Authorization required? */
	char response[128];	/* last response */
	Group *currentgroup;
	char *addr;
	char *user;
	char *pass;
	ulong extended;	/* supported extensions */
};

struct Group {
	char *name;
	Group *parent;
	Group **kid;
	int num;
	int nkid;
	int lo, hi;
	int canpost;
	int isgroup;	/* might just be piece of hierarchy */
	ulong mtime;
	ulong atime;
};

/*
 * First eight fields are, in order: 
 *	article number, subject, author, date, message-ID, 
 *	references, byte count, line count 
 * We don't support OVERVIEW.FMT; when I see a server with more
 * interesting fields, I'll implement support then.  In the meantime,
 * the standard defines the first eight fields.
 */

/* Extensions */
enum {
	Nxover   = (1<<0),
	Nxhdr    = (1<<1),
	Nxpat    = (1<<2),
	Nxlistgp = (1<<3),
};

Group *root;
Netbuf *net;
ulong now;
int netdebug;
int readonly;

void*
erealloc(void *v, ulong n)
{
	v = realloc(v, n);
	if(v == nil)
		sysfatal("out of memory reallocating %lud", n);
	setmalloctag(v, getcallerpc(&v));
	return v;
}

void*
emalloc(ulong n)
{
	void *v;

	v = malloc(n);
	if(v == nil)
		sysfatal("out of memory allocating %lud", n);
	memset(v, 0, n);
	setmalloctag(v, getcallerpc(&n));
	return v;
}

char*
estrdup(char *s)
{
	int l;
	char *t;

	if (s == nil)
		return nil;
	l = strlen(s)+1;
	t = emalloc(l);
	memcpy(t, s, l);
	setmalloctag(t, getcallerpc(&s));
	return t;
}

char*
estrdupn(char *s, int n)
{
	int l;
	char *t;

	l = strlen(s);
	if(l > n)
		l = n;
	t = emalloc(l+1);
	memmove(t, s, l);
	t[l] = '\0';
	setmalloctag(t, getcallerpc(&s));
	return t;
}

char*
Nrdline(Netbuf *n)
{
	char *p;
	int l;

	n->lineno++;
	Bflush(&n->bw);
	if((p = Brdline(&n->br, '\n')) == nil){
		werrstr("nntp eof");
		return nil;
	}
	p[l=Blinelen(&n->br)-1] = '\0';
	if(l > 0 && p[l-1] == '\r')
		p[l-1] = '\0';
if(netdebug)
	fprint(2, "-> %s\n", p);
	return p;
}

int
nntpresponse(Netbuf *n, int e, char *cmd)
{
	int r;
	char *p;

	for(;;){
		p = Nrdline(n);
		if(p==nil){
			strcpy(n->response, "early nntp eof");
			return -1;
		}
		r = atoi(p);
		if(r/100 == 1){	/* BUG? */
			fprint(2, "%s\n", p);
			continue;
		}
		break;
	}

	strecpy(n->response, n->response+sizeof(n->response), p);

	if((r=atoi(p)) == 0){
		close(n->fd);
		n->fd = -1;
		fprint(2, "bad nntp response: %s\n", p);
		werrstr("bad nntp response");
		return -1;
	}

	n->code = r;
	if(0 < e && e<10 && r/100 != e){
		fprint(2, "%s: expected %dxx: got %s\n", cmd, e, n->response);
		return -1;
	}
	if(10 <= e && e<100 && r/10 != e){
		fprint(2, "%s: expected %dx: got %s\n", cmd, e, n->response);
		return -1;
	}
	if(100 <= e && r != e){
		fprint(2, "%s: expected %d: got %s\n", cmd, e, n->response);
		return -1;
	}
	return r;
}

int nntpauth(Netbuf*);
int nntpxcmdprobe(Netbuf*);
int nntpcurrentgroup(Netbuf*, Group*);

/* XXX: bug OVER/XOVER et al. */
static struct {
	ulong n;
	char *s;
} extensions [] = {
	{ Nxover, "OVER" },
	{ Nxhdr, "HDR" },
	{ Nxpat, "PAT" },
	{ Nxlistgp, "LISTGROUP" },
	{ 0, nil }
};

static int indial;

int
nntpconnect(Netbuf *n)
{
	n->currentgroup = nil;
	close(n->fd);
	if((n->fd = dial(n->addr, nil, nil, nil)) < 0){	
		snprint(n->response, sizeof n->response, "dial: %r");
		return -1;
	}
	Binit(&n->br, n->fd, OREAD);
	Binit(&n->bw, n->fd, OWRITE);
	if(nntpresponse(n, 20, "greeting") < 0)
		return -1;
	readonly = (n->code == 201);

	indial = 1;
	if(n->auth != 0)
		nntpauth(n);
//	nntpxcmdprobe(n);
	indial = 0;
	return 0;
}

int
nntpcmd(Netbuf *n, char *cmd, int e)
{
	int tried;

	tried = 0;
	for(;;){
		if(netdebug)
			fprint(2, "<- %s\n", cmd);
		Bprint(&n->bw, "%s\r\n", cmd);
		if(nntpresponse(n, e, cmd)>=0 && (e < 0 || n->code/100 != 5))
			return 0;

		/* redial */
		if(indial || tried++ || nntpconnect(n) < 0)
			return -1;
	}
}

int
nntpauth(Netbuf *n)
{
	char cmd[256];

	snprint(cmd, sizeof cmd, "AUTHINFO USER %s", n->user);
	if (nntpcmd(n, cmd, -1) < 0 || n->code != 381) {
		fprint(2, "Authentication failed: %s\n", n->response);
		return -1;
	}

	snprint(cmd, sizeof cmd, "AUTHINFO PASS %s", n->pass);
	if (nntpcmd(n, cmd, -1) < 0 || n->code != 281) {
		fprint(2, "Authentication failed: %s\n", n->response);
		return -1;
	}

	return 0;
}

int
nntpxcmdprobe(Netbuf *n)
{
	int i;
	char *p;

	n->extended = 0;
	if (nntpcmd(n, "LIST EXTENSIONS", 0) < 0 || n->code != 202)
		return 0;

	while((p = Nrdline(n)) != nil) {
		if (strcmp(p, ".") == 0)
			break;

		for(i=0; extensions[i].s != nil; i++)
			if (cistrcmp(extensions[i].s, p) == 0) {
				n->extended |= extensions[i].n;
				break;
			}
	}
	return 0;
}

/* XXX: searching, lazy evaluation */
static int
overcmp(void *v1, void *v2)
{
	int a, b;

	a = atoi(*(char**)v1);
	b = atoi(*(char**)v2);

	if(a < b)
		return -1;
	else if(a > b)
		return 1;
	return 0;
}

enum {
	XoverChunk = 100,
};

char *xover[XoverChunk];
int xoverlo;
int xoverhi;
int xovercount;
Group *xovergroup;

char*
nntpover(Netbuf *n, Group *g, int m)
{
	int i, lo, hi, mid, msg;
	char *p;
	char cmd[64];

	if (g->isgroup == 0)	/* BUG: should check extension capabilities */
		return nil;

	if(g != xovergroup || m < xoverlo || m >= xoverhi){
		lo = (m/XoverChunk)*XoverChunk;
		hi = lo+XoverChunk;
	
		if(lo < g->lo)
			lo = g->lo;
		else if (lo > g->hi)
			lo = g->hi;
		if(hi < lo || hi > g->hi)
			hi = g->hi;
	
		if(nntpcurrentgroup(n, g) < 0)
			return nil;
	
		if(lo == hi)
			snprint(cmd, sizeof cmd, "XOVER %d", hi);
		else
			snprint(cmd, sizeof cmd, "XOVER %d-%d", lo, hi-1);
		if(nntpcmd(n, cmd, 224) < 0)
			return nil;

		for(i=0; (p = Nrdline(n)) != nil; i++) {
			if(strcmp(p, ".") == 0)
				break;
			if(i >= XoverChunk)
				sysfatal("news server doesn't play by the rules");
			free(xover[i]);
			xover[i] = emalloc(strlen(p)+2);
			strcpy(xover[i], p);
			strcat(xover[i], "\n");
		}
		qsort(xover, i, sizeof(xover[0]), overcmp);

		xovercount = i;

		xovergroup = g;
		xoverlo = lo;
		xoverhi = hi;
	}

	lo = 0;
	hi = xovercount;
	/* search for message */
	while(lo < hi){
		mid = (lo+hi)/2;
		msg = atoi(xover[mid]);
		if(m == msg)
			return xover[mid];
		else if(m < msg)
			hi = mid;
		else
			lo = mid+1;
	}
	return nil;
}

/*
 * Return the new Group structure for the group name.
 * Destroys name.
 */
static int printgroup(char*,Group*);
Group*
findgroup(Group *g, char *name, int mk)
{
	int lo, hi, m;
	char *p, *q;
	static int ngroup;

	for(p=name; *p; p=q){
		if(q = strchr(p, '.'))
			*q++ = '\0';
		else
			q = p+strlen(p);

		lo = 0;
		hi = g->nkid;
		while(hi-lo > 1){
			m = (lo+hi)/2;
			if(strcmp(p, g->kid[m]->name) < 0)
				hi = m;
			else
				lo = m;
		}
		assert(lo==hi || lo==hi-1);
		if(lo==hi || strcmp(p, g->kid[lo]->name) != 0){
			if(mk==0)
				return nil;
			if(g->nkid%16 == 0)
				g->kid = erealloc(g->kid, (g->nkid+16)*sizeof(g->kid[0]));

			/* 
			 * if we're down to a single place 'twixt lo and hi, the insertion might need
			 * to go at lo or at hi.  strcmp to find out.  the list needs to stay sorted.
		 	 */
			if(lo==hi-1 && strcmp(p, g->kid[lo]->name) < 0)
				hi = lo;

			if(hi < g->nkid)
				memmove(g->kid+hi+1, g->kid+hi, sizeof(g->kid[0])*(g->nkid-hi));
			g->nkid++;
			g->kid[hi] = emalloc(sizeof(*g));
			g->kid[hi]->parent = g;
			g = g->kid[hi];
			g->name = estrdup(p);
			g->num = ++ngroup;
			g->mtime = time(0);
		}else
			g = g->kid[lo];
	}
	if(mk)
		g->isgroup = 1;
	return g;
}

static int
printgroup(char *s, Group *g)
{
	if(g->parent == g)
		return 0;

	if(printgroup(s, g->parent))
		strcat(s, ".");
	strcat(s, g->name);
	return 1;
}

static char*
Nreaddata(Netbuf *n)
{
	char *p, *q;
	int l;

	p = nil;
	l = 0;
	for(;;){
		q = Nrdline(n);
		if(q==nil){
			free(p);
			return nil;
		}
		if(strcmp(q, ".")==0)
			return p;
		if(q[0]=='.')
			q++;
		p = erealloc(p, l+strlen(q)+1+1);
		strcpy(p+l, q);
		strcat(p+l, "\n");
		l += strlen(p+l);
	}
}

/*
 * Return the output of a HEAD, BODY, or ARTICLE command.
 */
char*
nntpget(Netbuf *n, Group *g, int msg, char *retr)
{
	char *s;
	char cmd[1024];

	if(g->isgroup == 0){
		werrstr("not a group");
		return nil;
	}

	if(strcmp(retr, "XOVER") == 0){
		s = nntpover(n, g, msg);
		if(s == nil)
			s = "";
		return estrdup(s);
	}

	if(nntpcurrentgroup(n, g) < 0)
		return nil;
	sprint(cmd, "%s %d", retr, msg);
	nntpcmd(n, cmd, 0);
	if(n->code/10 != 22)
		return nil;

	return Nreaddata(n);
}

int
nntpcurrentgroup(Netbuf *n, Group *g)
{
	char cmd[1024];

	if(n->currentgroup != g){
		strcpy(cmd, "GROUP ");
		printgroup(cmd, g);
		if(nntpcmd(n, cmd, 21) < 0)
			return -1;
		n->currentgroup = g;
	}
	return 0;
}

void
nntprefreshall(Netbuf *n)
{
	char *f[10], *p;
	int hi, lo, nf;
	Group *g;

	if(nntpcmd(n, "LIST", 21) < 0)
		return;

	while(p = Nrdline(n)){
		if(strcmp(p, ".")==0)
			break;

		nf = getfields(p, f, nelem(f), 1, "\t\r\n ");
		if(nf != 4){
			int i;
			for(i=0; i<nf; i++)
				fprint(2, "%s%s", i?" ":"", f[i]);
			fprint(2, "\n");
			fprint(2, "syntax error in group list, line %d", n->lineno);
			return;
		}
		g = findgroup(root, f[0], 1);
		hi = strtol(f[1], 0, 10)+1;