mbox.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 <bio.h>
#include <auth.h>
#include "imap4d.h"

static NamedInt	flagChars[NFlags] =
{
	{"s",	MSeen},
	{"a",	MAnswered},
	{"f",	MFlagged},
	{"D",	MDeleted},
	{"d",	MDraft},
	{"r",	MRecent},
};

static	int	fsCtl = -1;

static	void	boxFlags(Box *box);
static	int	createImp(Box *box, Qid *qid);
static	void	fsInit(void);
static	void	mboxGone(Box *box);
static	MbLock	*openImp(Box *box, int new);
static	int	parseImp(Biobuf *b, Box *box);
static	int	readBox(Box *box);
static	ulong	uidRenumber(Msg *m, ulong uid, int force);
static	int	impFlags(Box *box, Msg *m, char *flags);

/*
 * strategy:
 * every mailbox file has an associated .imp file
 * which maps upas/fs message digests to uids & message flags.
 *
 * the .imp files are locked by /mail/fs/usename/L.mbox.
 * whenever the flags can be modified, the lock file
 * should be opened, thereby locking the uid & flag state.
 * for example, whenever new uids are assigned to messages,
 * and whenever flags are changed internally, the lock file
 * should be open and locked.  this means the file must be
 * opened during store command, and when changing the \seen
 * flag for the fetch command.
 *
 * if no .imp file exists, a null one must be created before
 * assigning uids.
 *
 * the .imp file has the following format
 * imp		: "imap internal mailbox description\n"
 * 			uidvalidity " " uidnext "\n"
 *			messageLines
 *
 * messageLines	:
 *		| messageLines digest " " uid " " flags "\n"
 *
 * uid, uidnext, and uidvalidity are 32 bit decimal numbers
 * printed right justified in a field NUid characters long.
 * the 0 uid implies that no uid has been assigned to the message,
 * but the flags are valid. note that message lines are in mailbox
 * order, except possibly for 0 uid messages.
 *
 * digest is an ascii hex string NDigest characters long.
 *
 * flags has a character for each of NFlag flag fields.
 * if the flag is clear, it is represented by a "-".
 * set flags are represented as a unique single ascii character.
 * the currently assigned flags are, in order:
 *	MSeen		s
 *	MAnswered	a
 *	MFlagged	f
 *	MDeleted	D
 *	MDraft		d
 */
Box*
openBox(char *name, char *fsname, int writable)
{
	Box *box;
	MbLock *ml;
	int n, new;

	if(cistrcmp(name, "inbox") == 0)
		name = "mbox";

	fsInit();
	if(fprint(fsCtl, "open /mail/box/%s/%s %s", username, name, fsname) < 0){
//ZZZ
char err[ERRMAX];
errstr(err, sizeof err);
if(strstr(err, "file does not exist") == nil)
	fprint(2, "imap4d at %lud: upas/fs open %s/%s as %s failed: '%s' %s\n", time(nil), username, name, fsname, err, ctime(time(nil)));
		fprint(fsCtl, "close %s", fsname);
		return nil;
	}

	/*
	 * read box to find all messages
	 * each one has a directory, and is in numerical order
	 */
	box = MKZ(Box);
	box->writable = writable;

	n = strlen(name) + 1;
	box->name = emalloc(n);
	strcpy(box->name, name);

	n += STRLEN(".imp");
	box->imp = emalloc(n);
	snprint(box->imp, n, "%s.imp", name);

	n = strlen(fsname) + 1;
	box->fs = emalloc(n);
	strcpy(box->fs, fsname);

	n = STRLEN("/mail/fs/") + strlen(fsname) + 1;
	box->fsDir = emalloc(n);
	snprint(box->fsDir, n, "/mail/fs/%s", fsname);

	box->uidnext = 1;
	new = readBox(box);
	if(new >= 0){
		ml = openImp(box, new);
		if(ml != nil){
			closeImp(box, ml);
			return box;
		}
	}
	closeBox(box, 0);
	return nil;
}

/*
 * check mailbox
 * returns fd of open .imp file if imped.
 * otherwise, return value is insignificant
 *
 * careful: called by idle polling proc
 */
MbLock*
checkBox(Box *box, int imped)
{
	MbLock *ml;
	Dir *d;
	int new;

	if(box == nil)
		return nil;

	/*
	 * if stat fails, mailbox must be gone
	 */
	d = cdDirstat(box->fsDir, ".");
	if(d == nil){
		mboxGone(box);
		return nil;
	}
	new = 0;
	if(box->qid.path != d->qid.path || box->qid.vers != d->qid.vers
	|| box->mtime != d->mtime){
		new = readBox(box);
		if(new < 0){
			free(d);
			return nil;
		}
	}
	free(d);
	ml = openImp(box, new);
	if(ml == nil)
		box->writable = 0;
	else if(!imped){
		closeImp(box, ml);
		ml = nil;
	}
	return ml;
}

/*
 * mailbox is unreachable, so mark all messages expunged
 * clean up .imp files as well.
 */
static void
mboxGone(Box *box)
{
	Msg *m;

	if(cdExists(mboxDir, box->name) < 0)
		cdRemove(mboxDir, box->imp);
	for(m = box->msgs; m != nil; m = m->next)
		m->expunged = 1;
	box->writable = 0;
}

/*
 * read messages in the mailbox
 * mark message that no longer exist as expunged
 * returns -1 for failure, 0 if no new messages, 1 if new messages.
 */
static int
readBox(Box *box)
{
	Msg *msgs, *m, *last;
	Dir *d;
	char *s;
	long max, id;
	int i, nd, fd, new;

	fd = cdOpen(box->fsDir, ".", OREAD);
	if(fd < 0){
		syslog(0, "mail", "imap4d at %lud: upas/fs stat of %s/%s aka %s failed: %r\n", time(nil),
			username, box->name, box->fsDir);
		mboxGone(box);
		return -1;
	}

	/*
	 * read box to find all messages
	 * each one has a directory, and is in numerical order
	 */
	d = dirfstat(fd);
	if(d == nil){
		close(fd);
		return -1;
	}
	box->mtime = d->mtime;
	box->qid = d->qid;
	last = nil;
	msgs = box->msgs;
	max = 0;
	new = 0;
	free(d);
	while((nd = dirread(fd, &d)) > 0){
		for(i = 0; i < nd; i++){
			s = d[i].name;
			id = strtol(s, &s, 10);
			if(id <= max || *s != '\0'
			|| (d[i].mode & DMDIR) != DMDIR)
				continue;

			max = id;

			while(msgs != nil){
				last = msgs;
				msgs = msgs->next;
				if(last->id == id)
					goto continueDir;
				last->expunged = 1;
			}

			new = 1;
			m = MKZ(Msg);
			m->id = id;
			m->fsDir = box->fsDir;
			m->fs = emalloc(2 * (MsgNameLen + 1));
			m->efs = seprint(m->fs, m->fs + (MsgNameLen + 1), "%lud/", id);
			m->size = ~0UL;
			m->lines = ~0UL;
			m->prev = last;
			m->flags = MRecent;
			if(!msgInfo(m))
				freeMsg(m);
			else{
				if(last == nil)
					box->msgs = m;
				else
					last->next = m;
				last = m;
			}
	continueDir:;
		}
		free(d);
	}
	close(fd);
	for(; msgs != nil; msgs = msgs->next)
		msgs->expunged = 1;

	/*
	 * make up the imap message sequence numbers
	 */
	id = 1;
	for(m = box->msgs; m != nil; m = m->next){
		if(m->seq && m->seq != id)
			bye("internal error assigning message numbers");
		m->seq = id++;
	}
	box->max = id - 1;

	return new;
}

/*
 * read in the .imp file, or make one if it doesn't exist.
 * make sure all flags and uids are consistent.
 * return the mailbox lock.
 */
#define IMPMAGIC	"imap internal mailbox description\n"
static MbLock*
openImp(Box *box, int new)
{
	Qid qid;
	Biobuf b;
	MbLock *ml;
	int fd;
//ZZZZ
	int once;

	ml = mbLock();
	if(ml == nil)
		return nil;
	fd = cdOpen(mboxDir, box->imp, OREAD);
	once = 0;
ZZZhack:
	if(fd < 0 || fqid(fd, &qid) < 0){
		if(fd < 0){
			char buf[ERRMAX];

			errstr(buf, sizeof buf);
			if(cistrstr(buf, "does not exist") == nil)
				fprint(2, "imap4d at %lud: imp open failed: %s\n", time(nil), buf);
			if(!once && cistrstr(buf, "locked") != nil){
				once = 1;
				fprint(2, "imap4d at %lud: imp %s/%s %s locked when it shouldn't be; spinning\n", time(nil), username, box->name, box->imp);
				fd = openLocked(mboxDir, box->imp, OREAD);
				goto ZZZhack;
			}
		}
		if(fd >= 0)
			close(fd);
		fd = createImp(box, &qid);
		if(fd < 0){
			mbUnlock(ml);
			return nil;
		}
		box->dirtyImp = 1;
		if(box->uidvalidity == 0)
			box->uidvalidity = box->mtime;
		box->impQid = qid;
		new = 1;
	}else if(qid.path != box->impQid.path || qid.vers != box->impQid.vers){
		Binit(&b, fd, OREAD);
		if(!parseImp(&b, box)){
			box->dirtyImp = 1;
			if(box->uidvalidity == 0)
				box->uidvalidity = box->mtime;
		}
		Bterm(&b);
		box->impQid = qid;
		new = 1;
	}
	if(new)
		boxFlags(box);
	close(fd);
	return ml;
}

/*
 * close the .imp file, after writing out any changes
 */
void
closeImp(Box *box, MbLock *ml)
{
	Msg *m;
	Qid qid;
	Biobuf b;
	char buf[NFlags+1];
	int fd;

	if(ml == nil)
		return;
	if(!box->dirtyImp){
		mbUnlock(ml);
		return;
	}

	fd = cdCreate(mboxDir, box->imp, OWRITE, 0664);
	if(fd < 0){
		mbUnlock(ml);
		return;
	}
	Binit(&b, fd, OWRITE);

	box->dirtyImp = 0;
	Bprint(&b, "%s", IMPMAGIC);
	Bprint(&b, "%.*lud %.*lud\n", NUid, box->uidvalidity, NUid, box->uidnext);
	for(m = box->msgs; m != nil; m = m->next){
		if(m->expunged)
			continue;
		wrImpFlags(buf, m->flags, strcmp(box->fs, "imap") == 0);
		Bprint(&b, "%.*s %.*lud %s\n", NDigest, m->info[IDigest], NUid, m->uid, buf);
	}
	Bterm(&b);

	if(fqid(fd, &qid) >= 0)
		box->impQid = qid;
	close(fd);
	mbUnlock(ml);
}

void
wrImpFlags(char *buf, int flags, int killRecent)
{
	int i;

	for(i = 0; i < NFlags; i++){
		if((flags & flagChars[i].v)
		&& (flagChars[i].v != MRecent || !killRecent))
			buf[i] = flagChars[i].name[0];
		else
			buf[i] = '-';
	}
	buf[i] = '\0';