/*
 * Program:	MBX mail routines
 *
 * Author:	Mark Crispin
 *		Networks and Distributed Computing
 *		Computing & Communications
 *		University of Washington
 *		Administration Building, AG-44
 *		Seattle, WA  98195
 *		Internet: MRC@CAC.Washington.EDU
 *
 * Date:	3 October 1995
 * Last Edited:	12 March 1997
 *
 * Copyright 1997 by the University of Washington
 *
 *  Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted, provided
 * that the above copyright notice appears in all copies and that both the
 * above copyright notice and this permission notice appear in supporting
 * documentation, and that the name of the University of Washington not be
 * used in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission.  This software is made
 * available "as is", and
 * THE UNIVERSITY OF WASHINGTON DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
 * WITH REGARD TO THIS SOFTWARE, INCLUDING WITHOUT LIMITATION ALL IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, AND IN
 * NO EVENT SHALL THE UNIVERSITY OF WASHINGTON BE LIABLE FOR ANY SPECIAL,
 * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, TORT
 * (INCLUDING NEGLIGENCE) OR STRICT LIABILITY, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */


#include <stdio.h>
#include <ctype.h>
#include <errno.h>
extern int errno;		/* just in case */
#include "mail.h"
#include "osdep.h"
#include <pwd.h>
#include <sys/stat.h>
#include <sys/time.h>
#include "mbx.h"
#include "misc.h"
#include "dummy.h"

/* MBX mail routines */


/* Driver dispatch used by MAIL */

DRIVER mbxdriver = {
  "mbx",			/* driver name */
  DR_LOCAL|DR_MAIL,		/* driver flags */
  (DRIVER *) NIL,		/* next driver */
  mbx_valid,			/* mailbox is valid for us */
  mbx_parameters,		/* manipulate parameters */
  mbx_scan,			/* scan mailboxes */
  mbx_list,			/* list mailboxes */
  mbx_lsub,			/* list subscribed mailboxes */
  NIL,				/* subscribe to mailbox */
  NIL,				/* unsubscribe from mailbox */
  mbx_create,			/* create mailbox */
  mbx_delete,			/* delete mailbox */
  mbx_rename,			/* rename mailbox */
  NIL,				/* status of mailbox */
  mbx_open,			/* open mailbox */
  mbx_close,			/* close mailbox */
  mbx_flags,			/* fetch message "fast" attributes */
  mbx_flags,			/* fetch message flags */
  NIL,				/* fetch overview */
  NIL,				/* fetch message envelopes */
  mbx_header,			/* fetch message header */
  mbx_text,			/* fetch message body */
  NIL,				/* fetch partial message text */
  NIL,				/* unique identifier */
  NIL,				/* message number */
  mbx_flag,			/* modify flags */
  mbx_flagmsg,			/* per-message modify flags */
  NIL,				/* search for message based on criteria */
  NIL,				/* sort messages */
  NIL,				/* thread messages */
  mbx_ping,			/* ping mailbox to see if still alive */
  mbx_check,			/* check for new messages */
  mbx_expunge,			/* expunge deleted messages */
  mbx_copy,			/* copy messages to another mailbox */
  mbx_append,			/* append string message to mailbox */
  NIL				/* garbage collect stream */
};

				/* prototype stream */
MAILSTREAM mbxproto = {&mbxdriver};

/* MBX mail validate mailbox
 * Accepts: mailbox name
 * Returns: our driver if name is valid, NIL otherwise
 */

DRIVER *mbx_valid (char *name)
{
  char tmp[MAILTMPLEN];
  return mbx_isvalid (name,tmp) ? &mbxdriver : NIL;
}


/* MBX mail test for valid mailbox
 * Accepts: mailbox name
 *	    scratch buffer
 * Returns: T if valid, NIL otherwise
 */

int mbx_isvalid (char *name,char *tmp)
{
  int fd;
  int ret = NIL;
  char *s,hdr[HDRSIZE];
  struct stat sbuf;
  time_t tp[2];
  errno = EINVAL;		/* assume invalid argument */
  if ((s = mbx_file (tmp,name)) && !stat (s,&sbuf) &&
      ((fd = open (tmp,O_RDONLY,NIL)) >= 0)) {
    errno = -1;			/* bogus format */
    /* I love cretinous C compilers -- don't you? */
    if (read (fd,hdr,HDRSIZE) == HDRSIZE)
      if ((hdr[0] == '*') && (hdr[1] == 'm') && (hdr[2] == 'b') &&
	  (hdr[3] == 'x') && (hdr[4] == '*') && (hdr[5] == '\015') &&
	  (hdr[6] == '\012') && isxdigit (hdr[7]) && isxdigit (hdr[8]))
	if (isxdigit (hdr[9]) && isxdigit (hdr[10]) && isxdigit (hdr[11]) &&
	    isxdigit (hdr[12]) && isxdigit (hdr[13]) && isxdigit (hdr[14]) &&
	    isxdigit (hdr[15]) && isxdigit (hdr[16]))
	  if (isxdigit (hdr[17]) && isxdigit (hdr[18]) &&
	      isxdigit (hdr[19]) && isxdigit (hdr[20]) &&
	      isxdigit (hdr[21]) && isxdigit (hdr[22]) &&
	      (hdr[23] == '\015') && (hdr[24] == '\012')) ret = T;
    close (fd);			/* close the file */
    tp[0] = sbuf.st_atime;	/* preserve atime and mtime */
    tp[1] = sbuf.st_mtime;
    utime (tmp,tp);		/* set the times */
  }
  return ret;			/* return what we should */
}


/* MBX manipulate driver parameters
 * Accepts: function code
 *	    function-dependent value
 * Returns: function-dependent return value
 */

void *mbx_parameters (long function,void *value)
{
  return NIL;
}

/* MBX mail scan mailboxes
 * Accepts: mail stream
 *	    reference
 *	    pattern to search
 *	    string to scan
 */

void mbx_scan (MAILSTREAM *stream,char *ref,char *pat,char *contents)
{
  if (stream) dummy_scan (NIL,ref,pat,contents);
}


/* MBX mail list mailboxes
 * Accepts: mail stream
 *	    reference
 *	    pattern to search
 */

void mbx_list (MAILSTREAM *stream,char *ref,char *pat)
{
  if (stream) dummy_list (NIL,ref,pat);
}


/* MBX mail list subscribed mailboxes
 * Accepts: mail stream
 *	    reference
 *	    pattern to search
 */

void mbx_lsub (MAILSTREAM *stream,char *ref,char *pat)
{
  if (stream) dummy_lsub (NIL,ref,pat);
}

/* MBX mail create mailbox
 * Accepts: MAIL stream
 *	    mailbox name to create
 * Returns: T on success, NIL on failure
 */

long mbx_create (MAILSTREAM *stream,char *mailbox)
{
  char *s,*t,mbx[MAILTMPLEN],tmp[HDRSIZE];
  long ret = NIL;
  int i,fd;
  if (!(s = mbx_file (mbx,mailbox))) {
    sprintf (mbx,"Can't create %s: invalid name",mailbox);
    mm_log (mbx,ERROR);
    return NIL;
  }
				/* create underlying file */
  if (!dummy_create_path (stream,s)) return NIL;
				/* done if made directory */
  if ((s = strrchr (s,'/')) && !s[1]) return T;
  if ((fd = open (mbx,O_WRONLY,
		  (int) mail_parameters (NIL,GET_MBXPROTECTION,NIL))) < 0) {
    sprintf (tmp,"Can't reopen mailbox node %s: %s",mbx,strerror (errno));
    mm_log (tmp,ERROR);
    unlink (mbx);		/* delete the file */
    return NIL;
  }
  memset (tmp,'\0',HDRSIZE);	/* initialize header */
  strcpy (s = tmp,"*mbx*\015\0120000000100000000\015\012");
  for (i = 0; i < NUSERFLAGS; ++i)
    sprintf (s += strlen (s),"%s\015\012",(t = default_user_flag(i)) ? t : "");
  if (write (fd,tmp,HDRSIZE) != HDRSIZE) {
    sprintf (tmp,"Can't initialize mailbox node %s: %s",mbx,strerror (errno));
    mm_log (tmp,ERROR);
    unlink (mbx);		/* delete the file */
    return NIL;
  }
  return close (fd) ? NIL : T;	/* close file */
}


/* MBX mail delete mailbox
 * Accepts: MAIL stream
 *	    mailbox name to delete
 * Returns: T on success, NIL on failure
 */

long mbx_delete (MAILSTREAM *stream,char *mailbox)
{
  return mbx_rename (stream,mailbox,NIL);
}

/* MBX mail rename mailbox
 * Accepts: MAIL stream
 *	    old mailbox name
 *	    new mailbox name (or NIL for delete)
 * Returns: T on success, NIL on failure
 */

long mbx_rename (MAILSTREAM *stream,char *old,char *newname)
{
  long ret = T;
  char *s,tmp[MAILTMPLEN],file[MAILTMPLEN],lock[MAILTMPLEN];
  int ld;
  int fd = open (mbx_file (file,old),O_RDWR,NIL);
				/* lock out non c-client applications */
  if (fd < 0) {			/* open mailbox */
    sprintf (tmp,"Can't open mailbox %s: %s",old,strerror (errno));
    mm_log (tmp,ERROR);
    return NIL;
  }
				/* get parse/append permission */
  if ((ld = lockfd (fd,lock,LOCK_EX)) < 0) {
    mm_log ("Unable to lock rename mailbox",ERROR);
    return NIL;
  }
				/* lock out other users */
  if (flock (fd,LOCK_EX|LOCK_NB)) {
    close (fd);			/* couldn't lock, give up on it then */
    sprintf (tmp,"Mailbox %s is in use by another process",old);
    mm_log (tmp,ERROR);
    unlockfd (ld,lock);		/* release exclusive parse/append permission */
    return NIL;
  }
  if (newname) {		/* want rename? */
    if (!((s = mbx_file (tmp,newname)) && *s)) {
      sprintf (tmp,"Can't rename mailbox %s to %s: invalid name",old,newname);
      mm_log (tmp,ERROR);
      ret = NIL;		/* set failure */
    }
    if (rename (file,s)) {	/* rename the file */
      sprintf (tmp,"Can't rename mailbox %s to %s: %s",old,newname,
	       strerror (errno));
      mm_log (tmp,ERROR);
      ret = NIL;		/* set failure */
    }
  }
  else if (unlink (file)) {
    sprintf (tmp,"Can't delete mailbox %s: %s",old,strerror (errno));
    mm_log (tmp,ERROR);
    ret = NIL;			/* set failure */
  }
  flock (fd,LOCK_UN);		/* release lock on the file */
  unlockfd (ld,lock);		/* release exclusive parse/append permission */
  close (fd);			/* close the file */
				/* recreate file if renamed INBOX */
  if (ret && !strcmp (ucase (strcpy (tmp,old)),"INBOX"))
    mbx_create (NIL,"#mbx/INBOX");
  return ret;			/* return success */
}

/* MBX mail open
 * Accepts: stream to open
 * Returns: stream on success, NIL on failure
 */

MAILSTREAM *mbx_open (MAILSTREAM *stream)
{
  int fd,ld;
  char tmp[MAILTMPLEN];
				/* return prototype for OP_PROTOTYPE call */
  if (!stream) return user_flags (&mbxproto);
  if (LOCAL) {			/* close old file if stream being recycled */
    mbx_close (stream,NIL);	/* dump and save the changes */
    stream->dtb = &mbxdriver;	/* reattach this driver */
    mail_free_cache (stream);	/* clean up cache */
  }
  if (stream->rdonly ||
      (fd = open (mbx_file (tmp,stream->mailbox),O_RDWR,NIL)) < 0) {
    if ((fd = open (mbx_file (tmp,stream->mailbox),O_RDONLY,NIL)) < 0) {
      sprintf (tmp,"Can't open mailbox: %s",strerror (errno));
      mm_log (tmp,ERROR);
      return NIL;
    }
    else if (!stream->rdonly) {	/* got it, but readonly */
      mm_log ("Can't get write access to mailbox, access is readonly",WARN);
      stream->rdonly = T;
    }
  }

  stream->local = fs_get (sizeof (MBXLOCAL));
  LOCAL->buf = (char *) fs_get (MAXMESSAGESIZE + 1);
  LOCAL->buflen = MAXMESSAGESIZE;
				/* note if an INBOX or not */
  LOCAL->inbox = !strcmp (ucase (strcpy (LOCAL->buf,stream->mailbox)),"INBOX");
  fs_give ((void **) &stream->mailbox);
  stream->mailbox = cpystr (tmp);
				/* get parse/append permission */
  if ((ld = lockfd (fd,tmp,LOCK_EX)) < 0) {
    mm_log ("Unable to lock open mailbox",ERROR);
    return NIL;
  }
  flock(LOCAL->fd = fd,LOCK_SH);/* bind and lock the file */
  unlockfd (ld,tmp);		/* release shared parse permission */
  LOCAL->filesize = HDRSIZE;	/* initialize parsed file size */
  LOCAL->filetime = 0;		/* time not set up yet */
  LOCAL->mustcheck = LOCAL->shouldcheck = LOCAL->newkeyword = NIL;
  stream->sequence++;		/* bump sequence number */
				/* parse mailbox */
  stream->nmsgs = stream->recent = 0;
  if (mbx_ping (stream) && !stream->nmsgs)
    mm_log ("Mailbox is empty",(long) NIL);
  if (!LOCAL) return NIL;	/* failure if stream died */
  stream->perm_seen = stream->perm_deleted = stream->perm_flagged =
    stream->perm_answered = stream->perm_draft = stream->rdonly ? NIL : T;
  stream->perm_user_flags = stream->rdonly ? NIL : 0xffffffff;
  stream->kwd_create = (stream->user_flags[NUSERFLAGS-1] || stream->rdonly) ?
    NIL : T;			/* can we create new user flags? */
  return stream;		/* return stream to caller */
}

/* MBX mail close
 * Accepts: MAIL stream
 *	    close options
 */

void mbx_close (MAILSTREAM *stream,long options)
{
  if (stream && LOCAL) {	/* only if a file is open */
    int silent = stream->silent;
    stream->silent = T;		/* note this stream is dying */
    if (options & CL_EXPUNGE) mbx_expunge (stream);
    stream->silent = silent;	/* restore previous status */
    flock (LOCAL->fd,LOCK_UN);	/* unlock local file */
    close (LOCAL->fd);		/* close the local file */
				/* free local text buffer */
    if (LOCAL->buf) fs_give ((void **) &LOCAL->buf);
				/* nuke the local data */
    fs_give ((void **) &stream->local);
    stream->dtb = NIL;		/* log out the DTB */
  }
}


/* MBX mail fetch flags
 * Accepts: MAIL stream
 *	    sequence
 *	    option flags
 * Sniffs at file to see if some other process changed the flags
 */

void mbx_flags (MAILSTREAM *stream,char *sequence,long flags)
{
  long i;
  if (mbx_ping (stream) && 	/* ping mailbox, get new status for messages */
      ((flags & FT_UID) ? mail_uid_sequence (stream,sequence) :
       mail_sequence (stream,sequence)))
    for (i = 1; i <= stream->nmsgs; i++) 
      if (mail_elt (stream,i)->sequence) mbx_elt (stream,i);
}

/* MBX mail fetch message header
 * Accepts: MAIL stream
 *	    message # to fetch
 *	    pointer to returned header text length
 *	    option flags
 * Returns: message header in RFC822 format
 */

char *mbx_header (MAILSTREAM *stream,unsigned long msgno,unsigned long *length,
		  long flags)
{
  *length = 0;			/* default to empty */
  if (flags & FT_UID) return "";/* UID call "impossible" */
				/* get to header position */
  lseek (LOCAL->fd,mbx_hdrpos (stream,msgno,length),L_SET);
				/* is buffer big enough? */
  if (*length > LOCAL->buflen) {
    fs_give ((void **) &LOCAL->buf);
    LOCAL->buf = (char *) fs_get ((LOCAL->buflen = *length) + 1);
  }
  LOCAL->buf[*length] = '\0';	/* tie off string */
				/* slurp the data */
  read (LOCAL->fd,LOCAL->buf,*length);
  return LOCAL->buf;
}

/* MBX mail fetch message text (body only)
 * Accepts: MAIL stream
 *	    message # to fetch
 *	    pointer to returned header text length
 *	    option flags
 * Returns: T, always
 */

long mbx_text (MAILSTREAM *stream,unsigned long msgno,STRING *bs,long flags)
{
  unsigned long i,j;
  MESSAGECACHE *elt;
				/* UID call "impossible" */
  if (flags & FT_UID) return NIL;
  elt = mbx_elt (stream,msgno);	/* get message status */
				/* if message not seen */
  if (!(flags & FT_PEEK) && !elt->seen) {
    elt->seen = T;		/* mark message as seen */
				/* recalculate status */
    mbx_update_status (stream,msgno,T);
  }
				/* find header position */
  i = mbx_hdrpos (stream,msgno,&j);
				/* go to text position */
  lseek (LOCAL->fd,i + j,L_SET);
				/* is buffer big enough? */
  if ((i = elt->rfc822_size - j) > LOCAL->buflen) {
    fs_give ((void **) &LOCAL->buf);
    LOCAL->buf = (char *) fs_get ((LOCAL->buflen = i) + 1);
  }
				/* slurp the data */
  if (read (LOCAL->fd,LOCAL->buf,i) != i) return NIL;
  LOCAL->buf[i] = '\0';		/* tie off string */
				/* set up stringstruct */
  INIT (bs,mail_string,LOCAL->buf,i);
  return T;			/* success */
}

/* MBX mail modify flags
 * Accepts: MAIL stream
 *	    sequence
 *	    flag(s)
 *	    option flags
 */

void mbx_flag (MAILSTREAM *stream,char *sequence,char *flag,long flags)
{
  struct stat sbuf;
  if (!stream->rdonly) {	/* make sure the update takes */
    fsync (LOCAL->fd);
    fstat (LOCAL->fd,&sbuf);	/* get current write time */
    LOCAL->filetime = sbuf.st_mtime;
  }
  if (LOCAL->ffuserflag < NUSERFLAGS && stream->user_flags[LOCAL->ffuserflag])
    LOCAL->newkeyword = T;	/* note if any new keywords appeared */
}


/* MBX mail per-message modify flags
 * Accepts: MAIL stream
 *	    message cache element
 */

void mbx_flagmsg (MAILSTREAM *stream,MESSAGECACHE *elt)
{
  struct stat sbuf;
				/* maybe need to do a checkpoint? */
  if (LOCAL->filetime && !LOCAL->shouldcheck) {
    fstat (LOCAL->fd,&sbuf);	/* get current write time */
    if (LOCAL->filetime < sbuf.st_mtime) LOCAL->shouldcheck = T;
    LOCAL->filetime = 0;	/* don't do this test for any other messages */
  }
				/* recalculate status */
  mbx_update_status (stream,elt->msgno,NIL);
}

/* MBX mail ping mailbox
 * Accepts: MAIL stream
 * Returns: T if stream still alive, NIL if not
 */

long mbx_ping (MAILSTREAM *stream)
{
  long i = 1;
  long r = NIL;
  int ld;
  char lock[MAILTMPLEN];
  struct stat sbuf;
  if (stream && LOCAL) {	/* only if stream already open */
    if (LOCAL->filetime && !(LOCAL->mustcheck || LOCAL->shouldcheck)) {
      fstat (LOCAL->fd,&sbuf);	/* get current write time */
      if (LOCAL->filetime < sbuf.st_mtime) LOCAL->shouldcheck = T;
    }
				/* check for changed message status */
    if (LOCAL->mustcheck || LOCAL->shouldcheck) {
      if (LOCAL->shouldcheck)	/* babble when we do this unilaterally */
	mm_notify (stream,"[CHECK] Checking for flag updates",NIL);
      while (i <= stream->nmsgs) mbx_elt (stream,i++);
      LOCAL->mustcheck = LOCAL->shouldcheck = NIL;
    }
				/* get parse/append permission */
    if ((ld = lockfd (LOCAL->fd,lock,LOCK_EX)) >= 0) {
				/* parse resulting mailbox */
      r = (mbx_parse (stream)) ? T : NIL;
      unlockfd (ld,lock);	/* release shared parse/append permission */
    }
				/* snarf if this is a read-write inbox */
    if (stream && LOCAL && LOCAL->inbox && !stream->rdonly) {
      mbx_snarf (stream);
				/* get parse/append permission */
      if ((ld = lockfd (LOCAL->fd,lock,LOCK_EX)) >= 0) {
				/* parse resulting mailbox */
	r = (mbx_parse (stream)) ? T : NIL;
	unlockfd (ld,lock);	/* release shared parse/append permission */
      }
    }
  }
  return r;			/* return result of the parse */
}


/* MBX mail check mailbox (reparses status too)
 * Accepts: MAIL stream
 */

void mbx_check (MAILSTREAM *stream)
{
				/* mark that a check is desired */
  if (LOCAL) LOCAL->mustcheck = T;
  if (mbx_ping (stream)) mm_log ("Check completed",(long) NIL);
}

/* MBX mail snarf messages from system inbox
 * Accepts: MAIL stream
 */

void mbx_snarf (MAILSTREAM *stream)
{
  unsigned long i = 0;
  unsigned long j,r,hdrlen,txtlen;
  struct stat sbuf;
  char *hdr,*txt,lock[MAILTMPLEN],tmp[MAILTMPLEN];
  MESSAGECACHE *elt;
  MAILSTREAM *sysibx = NIL;
  int ld;
				/* give up if can't get exclusive permission */
  if ((!strcmp (sysinbox (),stream->mailbox)) ||
      ((ld = lockfd (LOCAL->fd,lock,LOCK_EX)) < 0)) return;
  mm_critical (stream);		/* go critical */
  stat (sysinbox (),&sbuf);	/* see if anything there */
  if (sbuf.st_size) {		/* non-empty? */
    fstat (LOCAL->fd,&sbuf);	/* yes, get current file size */
				/* sizes match and can get sysibx mailbox? */
    if ((sbuf.st_size == LOCAL->filesize) && 
	(sysibx = mail_open (sysibx,sysinbox (),OP_SILENT)) &&
	(!sysibx->rdonly) && (r = sysibx->nmsgs)) {
				/* yes, go to end of file in our mailbox */
      lseek (LOCAL->fd,sbuf.st_size,L_SET);
				/* for each message in sysibx mailbox */
      while (r && (++i <= sysibx->nmsgs)) {
				/* snarf message from system INBOX */
	hdr = cpystr (mail_fetchheader_full (sysibx,i,NIL,&hdrlen,NIL));
	txt = mail_fetchtext_full (sysibx,i,&txtlen,FT_PEEK);
	if (j = hdrlen + txtlen) {
				/* calculate header line */
	  mail_date (LOCAL->buf,elt = mail_elt (sysibx,i));
	  sprintf (LOCAL->buf + strlen (LOCAL->buf),
		   ",%lu;00000000%04x-00000000\015\012",j,(fSEEN * elt->seen) +
		   (fDELETED * elt->deleted) + (fFLAGGED * elt->flagged) +
		   (fANSWERED * elt->answered) + (fDRAFT * elt->draft));
				/* copy message */
	  if ((write (LOCAL->fd,LOCAL->buf,strlen (LOCAL->buf)) < 0) ||
	      (write (LOCAL->fd,hdr,hdrlen) < 0) ||
	      (write (LOCAL->fd,txt,txtlen) < 0) || fsync (LOCAL->fd)) r = 0;
	}
	fs_give ((void **) &hdr);
      }
      if (r) {			/* delete all the messages we copied */
	if (r == 1) strcpy (tmp,"1");
	else sprintf (tmp,"%lu:%lu",1,r);
	mail_setflag (sysibx,tmp,"\\Deleted");
	mail_expunge (sysibx);	/* now expunge all those messages */
      }
      else {
	sprintf (LOCAL->buf,"Can't copy new mail: %s",strerror (errno));
	mm_log (LOCAL->buf,ERROR);
	ftruncate (LOCAL->fd,sbuf.st_size);
      }
      fstat (LOCAL->fd,&sbuf);	/* yes, get current file size */
      LOCAL->filetime = sbuf.st_mtime;
    }
    if (sysibx) mail_close (sysibx);
  }
  mm_nocritical (stream);	/* release critical */
  unlockfd (ld,lock);		/* release exclusive parse/append permission */
}

/* MBX mail expunge mailbox
 * Accepts: MAIL stream
 */

void mbx_expunge (MAILSTREAM *stream)
{
  struct stat sbuf;
  off_t pos = HDRSIZE;
  int ld;
  unsigned long i = 1;
  unsigned long j,k,m,recent;
  unsigned long n = 0;
  unsigned long delta = 0;
  char lock[MAILTMPLEN];
  MESSAGECACHE *elt;
				/* do nothing if stream dead */
  if (!mbx_ping (stream)) return;
  if (stream->rdonly) {		/* won't do on readonly files! */
    mm_log ("Expunge ignored on readonly mailbox",WARN);
    return;
  }
  if (LOCAL->filetime && !LOCAL->shouldcheck) {
    fstat (LOCAL->fd,&sbuf);	/* get current write time */
    if (LOCAL->filetime < sbuf.st_mtime) LOCAL->shouldcheck = T;
  }
  /* The cretins who designed flock() created a window of vulnerability in
   * upgrading locks from shared to exclusive or downgrading from exclusive
   * to shared.  Rather than maintain the lock at shared status at a minimum,
   * flock() actually *releases* the former lock.  Obviously they never talked
   * to any database guys.  Fortunately, we have the parse/append permission
   * lock.  If we require this lock before going exclusive on the mailbox,
   * another process can not sneak in and steal the exclusive mailbox lock on
   * us, because it will block on trying to get parse/append permission first.
   */
				/* get parse/append permission */
  if ((ld = lockfd (LOCAL->fd,lock,LOCK_EX)) < 0) {
    mm_log ("Unable to lock expunge mailbox",ERROR);
    return;
  }
				/* get exclusive access */
  if (flock (LOCAL->fd,LOCK_EX|LOCK_NB)) {
    flock (LOCAL->fd,LOCK_SH);	/* recover previous lock */
    mm_log("Can't expunge because mailbox is in use by another process",ERROR);
    unlockfd (ld,lock);		/* release exclusive parse/append permission */
    return;
  }

  mm_critical (stream);		/* go critical */
  recent = stream->recent;	/* get recent now that pinged and locked */
  while (i <= stream->nmsgs) {	/* for each message */
    elt = mbx_elt (stream,i);	/* get cache element */
				/* number of bytes to smash or preserve */
    k = elt->_private_.special.text.size + elt->rfc822_size;
    if (elt->deleted) {		/* if deleted */
      if (elt->recent) --recent;/* if recent, note one less recent message */
      delta += k;		/* number of bytes to delete */
      mail_expunged (stream,i);	/* notify upper levels */
      n++;			/* count up one more expunged message */
    }
    else if (i++ && delta) {	/* preserved message */
				/* first byte to preserve */
      j = elt->_private_.special.offset;
      do {			/* read from source position */
	m = min (k,LOCAL->buflen);
	lseek (LOCAL->fd,j,L_SET);
	read (LOCAL->fd,LOCAL->buf,(unsigned int) m);
	pos = j - delta;	/* write to destination position */
	lseek (LOCAL->fd,pos,L_SET);
	write (LOCAL->fd,LOCAL->buf,m);
	pos += m;		/* new position */
	j += m;			/* next chunk, perhaps */
      } while (k -= m);		/* until done */
				/* note the new address of this text */
      elt->_private_.special.offset -= delta;
    }
				/* preserved but no deleted messages */
    else pos = elt->_private_.special.offset + k;
  }
  if (n) {			/* truncate file after last message */
    if (pos != (LOCAL->filesize -= delta)) {
      sprintf (LOCAL->buf,"Calculated size mismatch %lu != %lu, delta = %lu",
	       pos,LOCAL->filesize,delta);
      mm_log (LOCAL->buf,WARN);
      LOCAL->filesize = pos;	/* fix it then */
    }
    ftruncate (LOCAL->fd,LOCAL->filesize);
    sprintf (LOCAL->buf,"Expunged %lu messages",n);
				/* output the news */
    mm_log (LOCAL->buf,(long) NIL);
  }
  else mm_log ("No messages deleted, so no update needed",(long) NIL);
  fsync (LOCAL->fd);		/* force disk update */
  fstat (LOCAL->fd,&sbuf);	/* get new write time */
  LOCAL->filetime = sbuf.st_mtime;
  mm_nocritical (stream);	/* release critical */
				/* notify upper level of new mailbox size */
  mail_exists (stream,stream->nmsgs);
  mail_recent (stream,recent);
  flock (LOCAL->fd,LOCK_SH);	/* allow sharers again */
  unlockfd (ld,lock);		/* release exclusive parse/append permission */
}

/* MBX mail copy message(s)
 * Accepts: MAIL stream
 *	    sequence
 *	    destination mailbox
 *	    copy options
 * Returns: T if success, NIL if failed
 */

long mbx_copy (MAILSTREAM *stream,char *sequence,char *mailbox,long options)
{
  long i;
  struct stat sbuf;
  MESSAGECACHE *elt;
  if (!(((options & CP_UID) ? mail_uid_sequence (stream,sequence) :
	 mail_sequence (stream,sequence)) &&
	mbx_copy_messages (stream,mailbox))) return NIL;
				/* delete all requested messages */
  if (options & CP_MOVE) for (i = 1; i <= stream->nmsgs; i++)
    if ((elt = mbx_elt (stream,i))->sequence) {
      elt->deleted = T;		/* mark message deleted */
				/* recalculate status */
      mbx_update_status (stream,i,NIL);
    }
  if (!stream->rdonly) {	/* make sure the update takes */
    fsync (LOCAL->fd);
    fstat (LOCAL->fd,&sbuf);	/* get current write time */
    LOCAL->filetime = sbuf.st_mtime;
  }
  return LONGT;
}

/* MBX mail append message from stringstruct
 * Accepts: MAIL stream
 *	    destination mailbox
 *	    stringstruct of messages to append
 * Returns: T if append successful, else NIL
 */

long mbx_append (MAILSTREAM *stream,char *mailbox,char *flags,char *date,
		 STRING *message)
{
  struct stat sbuf;
  int fd,ld;
  char *s,tmp[MAILTMPLEN],file[MAILTMPLEN],lock[MAILTMPLEN];
  time_t tp[2];
  MESSAGECACHE elt;
  long i = 0;
  long size = SIZE (message);
  long ret = LONGT;
  unsigned long uf = 0;
  long f = mail_parse_flags (stream ? stream : user_flags (&mbxproto),
			     flags,&uf);
				/* reverse bits (dontcha wish we had CIRC?) */
  if (date) {			/* want to preserve date? */
				/* yes, parse date into an elt */
    if (!mail_parse_date (&elt,date)) {
      sprintf (tmp,"Bad date in append: %s",date);
      mm_log (tmp,ERROR);
      return NIL;
    }
  }
				/* N.B.: can't use LOCAL->buf for tmp */
				/* make sure valid mailbox */
  if (!mbx_isvalid (mailbox,tmp)) switch (errno) {
  case ENOENT:			/* no such file? */
    mm_notify (stream,"[TRYCREATE] Must create mailbox before append",NIL);
    return NIL;
  case 0:			/* merely empty file? */
    break;
  case EINVAL:
    sprintf (tmp,"Invalid MBX-format mailbox name: %s",mailbox);
    mm_log (tmp,ERROR);
    return NIL;
  default:
    sprintf (tmp,"Not a MBX-format mailbox: %s",mailbox);
    mm_log (tmp,ERROR);
    return NIL;
  }
  if ((fd = open (mbx_file (file,mailbox),O_RDWR|O_CREAT,
		  S_IREAD|S_IWRITE)) < 0) {
    sprintf (tmp,"Can't open append mailbox: %s",strerror (errno));
    mm_log (tmp,ERROR);
    return NIL;
  }
				/* get parse/append permission */
  if ((ld = lockfd (fd,lock,LOCK_EX)) < 0) {
    mm_log ("Unable to lock append mailbox",ERROR);
    return NIL;
  }
  s = (char *) fs_get (size);	/* copy message */
  for (i = 0; i < size; s[i++] = SNX (message));

  mm_critical (stream);		/* go critical */
  fstat (fd,&sbuf);		/* get current file size */
  lseek (fd,sbuf.st_size,L_SET);/* move to end of file */
  if (date) mail_date(tmp,&elt);/* write preseved date */
  else internal_date (tmp);	/* get current date in IMAP format */
				/* add remainder of header */
  sprintf (tmp+26,",%lu;%08lx%04x-00000000\015\012",size,uf,f);
				/* write header */
  if ((write (fd,tmp,strlen (tmp)) < 0) || ((write (fd,s,size)) < 0) ||
      fsync (fd)) {
    sprintf (tmp,"Message append failed: %s",strerror (errno));
    mm_log (tmp,ERROR);
    ftruncate (fd,sbuf.st_size);
    ret = NIL;
  }
  tp[0] = sbuf.st_atime;	/* preserve atime and mtime */
  tp[1] = sbuf.st_mtime;
  utime (file,tp);		/* set the times */
  close (fd);			/* close the file */
  unlockfd (ld,lock);		/* release exclusive parse/append permission */
  mm_nocritical (stream);	/* release critical */
  fs_give ((void **) &s);	/* flush the buffer */
  return ret;
}

/* Internal routines */


/* MBX mail generate file string
 * Accepts: temporary buffer to write into
 *	    mailbox name string
 * Returns: local file string or NIL if failure
 */

char *mbx_file (char *dst,char *name)
{
  char *s = mailboxfile (dst,name);
  return (s && !*s) ? mailboxfile (dst,"~/INBOX") : s;
}

/* MBX mail parse mailbox
 * Accepts: MAIL stream
 * Returns: T if parse OK
 *	    NIL if failure, stream aborted
 */

long mbx_parse (MAILSTREAM *stream)
{
  struct stat sbuf;
  MESSAGECACHE *elt = NIL;
  char c,*s,*t,*x;
  char tmp[MAILTMPLEN];
  unsigned long i,j;
  long curpos = LOCAL->filesize;
  unsigned long nmsgs = stream->nmsgs;
  unsigned long recent = stream->recent;
  unsigned long lastuid = 0;
  short silent = stream->silent;
  fstat (LOCAL->fd,&sbuf);	/* get status */
  if (sbuf.st_size < curpos) {	/* sanity check */
    sprintf (tmp,"Mailbox shrank from %lu to %lu!",curpos,sbuf.st_size);
    mm_log (tmp,ERROR);
    mbx_close (stream,NIL);
    return NIL;
  }
  lseek (LOCAL->fd,0,L_SET);	/* rewind file */
				/* read internal header */
  read (LOCAL->fd,LOCAL->buf,HDRSIZE);
  LOCAL->buf[HDRSIZE] = '\0';	/* tie off header */
  c = LOCAL->buf[15];		/* save first character of last UID */
  LOCAL->buf[15] = '\0';
				/* parse UID validity */
  stream->uid_validity = strtoul (LOCAL->buf + 7,NIL,16);
  LOCAL->buf[15] = c;		/* restore first character of last UID */
				/* parse last UID */
  stream->uid_last = strtoul (LOCAL->buf + 15,NIL,16);
				/* parse user flags */
  for (i = 0, s = LOCAL->buf + 25; i < NUSERFLAGS && (t = strchr (s,'\015'));
       i++, s = t + 2) {
    *t = '\0';			/* tie off flag */
    if (*s && !stream->user_flags[i]) stream->user_flags[i] = cpystr (s);
  }
  LOCAL->ffuserflag = (int) i;	/* first free user flag */

  stream->silent = T;		/* don't pass up mm_exists() events yet */
  while (sbuf.st_size - curpos){/* while there is stuff to parse */
				/* get to that position in the file */
    lseek (LOCAL->fd,curpos,L_SET);
    if ((i = read (LOCAL->fd,LOCAL->buf,64)) <= 0) {
      sprintf (tmp,"Unable to read internal header at %lu, size = %lu: %s",
	       curpos,sbuf.st_size,i ? strerror (errno) : "no data read");
      mm_log (tmp,ERROR);
      mbx_close (stream,NIL);
      return NIL;
    }
    LOCAL->buf[i] = '\0';	/* tie off buffer just in case */
    if (!((s = strchr (LOCAL->buf,'\015')) && (s[1] == '\012'))) {
      sprintf (tmp,"Unable to find CRLF at %lu in %lu bytes, text: %s",
	       curpos,i,LOCAL->buf);
      mm_log (tmp,ERROR);
      mbx_close (stream,NIL);
      return NIL;
    }
    *s = '\0';			/* tie off header line */
    i = (s + 2) - LOCAL->buf;	/* note start of text offset */
    if (!((s = strchr (LOCAL->buf,',')) && (t = strchr (s+1,';')))) {
      sprintf (tmp,"Unable to parse internal header at %lu: %s",curpos,
	       LOCAL->buf);
      mm_log (tmp,ERROR);
      mbx_close (stream,NIL);
      return NIL;
    }
    *s++ = '\0'; *t++ = '\0';	/* tie off fields */

				/* swell the cache */
    mail_exists (stream,++nmsgs);
				/* intantiate an elt for this message */
    (elt = mail_elt (stream,nmsgs))->valid = T;
				/* note file offset of header */
    elt->_private_.special.offset = curpos;
				/* in case error */
    elt->_private_.special.text.size = 0;
				/* header size not known yet */
    elt->_private_.msg.header.text.size = elt->_private_.msg.text.text.size = 0;
				/* parse the header components */
    if (mail_parse_date (elt,LOCAL->buf) &&
	(elt->rfc822_size = strtoul (x = s,&s,10)) && (!(s && *s)))
      if (isxdigit (t[0]) && isxdigit (t[1]) && isxdigit (t[2]) &&
	  isxdigit (t[3]) && isxdigit (t[4]) && isxdigit (t[5]) &&
	  isxdigit (t[6]) && isxdigit (t[7]) && isxdigit (t[8]) &&
	  isxdigit (t[9]) && isxdigit (t[10]) && isxdigit (t[11]))
	if ((t[12] == '-') && isxdigit (t[13]) && isxdigit (t[14]) &&
	    isxdigit (t[15]) && isxdigit (t[16]) && isxdigit (t[17]) &&
	    isxdigit (t[18]) && isxdigit (t[19]) && isxdigit (t[20]))
	  elt->_private_.special.text.size = i;
    else {			/* oops */
      sprintf (tmp,"Unable to parse internal header elements at %lu: %s,%s;%s",
	       curpos,LOCAL->buf,x,t);
      mm_log (tmp,ERROR);
      mbx_close (stream,NIL);
      return NIL;
    }
				/* make sure didn't run off end of file */
    if ((curpos += (elt->rfc822_size + i)) > sbuf.st_size) {
      mm_log ("Last message runs past end of file",ERROR);
      mbx_close (stream,NIL);
      return NIL;
    }
    c = t[8];			/* remember first system flags byte */
    t[8] = t[12] = t[21] = '\0';/* tie off flags */
				/* get user flags value */
    elt->user_flags = strtoul (t,NIL,16);
    t[8] = c;			/* restore first system flags byte */
				/* calculate system flags */
    if ((j = strtoul (t+8,NIL,16)) & fSEEN) elt->seen = T;
    if (j & fDELETED) elt->deleted = T;
    if (j & fFLAGGED) elt->flagged = T;
    if (j & fANSWERED) elt->answered = T;
    if (j & fDRAFT) elt->draft = T;

				/* have a valid UID for this message yet? */
    if ((elt->_private_.uid = strtoul (t+13,NIL,16)) &&
	((elt->_private_.uid <= lastuid) ||
	 (elt->_private_.uid > stream->uid_last))) {
      sprintf (tmp,"Invalid UID %08x in message %lu, rebuilding UIDs",
	       elt->_private_.uid,elt->msgno);
      mm_log (tmp,WARN);
      elt->_private_.uid = 0;	/* lose this UID */
				/* restart UID validity and last UID */
      stream->uid_validity = time (0);
      stream->uid_last = lastuid;
    }
    if (!elt->_private_.uid) {	/* UID assigned yet? */
      elt->recent = T;		/* no, mark as recent */
      recent++;			/* count up a new recent message */
				/* assign new UID */
      elt->_private_.uid = ++stream->uid_last;
      mbx_update_status (stream,elt->msgno,NIL);
    }
    lastuid = elt->_private_.uid;	/* update last parsed UID */
  }
  mbx_update_header (stream);	/* update header */
  fsync (LOCAL->fd);		/* make sure all the UID updates take */
				/* update parsed file size and time */
  LOCAL->filesize = sbuf.st_size;
  fstat (LOCAL->fd,&sbuf);	/* get status again to ensure time is right */
  LOCAL->filetime = sbuf.st_mtime;
  stream->silent = silent;	/* can pass up events now */
  mail_exists (stream,nmsgs);	/* notify upper level of new mailbox size */
  mail_recent (stream,recent);	/* and of change in recent messages */
  return LONGT;			/* return the winnage */
}

/* MBX copy messages
 * Accepts: MAIL stream
 *	    mailbox copy vector
 *	    mailbox name
 * Returns: T if success, NIL if failed
 */

long mbx_copy_messages (MAILSTREAM *stream,char *mailbox)
{
  struct stat sbuf;
  time_t tp[2];
  MESSAGECACHE *elt;
  unsigned long i,j,k;
  long ret = LONGT;
  int fd,ld;
  char file[MAILTMPLEN],lock[MAILTMPLEN];
				/* make sure valid mailbox */
  if (!mbx_isvalid (mailbox,LOCAL->buf)) switch (errno) {
  case ENOENT:			/* no such file? */
    mm_notify (stream,"[TRYCREATE] Must create mailbox before copy",NIL);
    return NIL;
  case 0:			/* merely empty file? */
    break;
  case EINVAL:
    sprintf (LOCAL->buf,"Invalid MBX-format mailbox name: %s",mailbox);
    mm_log (LOCAL->buf,ERROR);
    return NIL;
  default:
    sprintf (LOCAL->buf,"Not a MBX-format mailbox: %s",mailbox);
    mm_log (LOCAL->buf,ERROR);
    return NIL;
  }
				/* got file? */  
  if ((fd=open(mbx_file(file,mailbox),O_RDWR|O_CREAT,S_IREAD|S_IWRITE))<0) {
    sprintf (LOCAL->buf,"Unable to open copy mailbox: %s",strerror (errno));
    mm_log (LOCAL->buf,ERROR);
    return NIL;
  }
  mm_critical (stream);		/* go critical */
				/* get parse/append permission */
  if ((ld = lockfd (fd,lock,LOCK_EX)) < 0) {
    mm_log ("Unable to lock copy mailbox",ERROR);
    return NIL;
  }
  fstat (fd,&sbuf);		/* get current file size */
  lseek (fd,sbuf.st_size,L_SET);/* move to end of file */

				/* for each requested message */
  for (i = 1; ret && (i <= stream->nmsgs); i++) 
    if ((elt = mail_elt (stream,i))->sequence) {
      lseek (LOCAL->fd,elt->_private_.special.offset +
	     elt->_private_.special.text.size,L_SET);
      mail_date(LOCAL->buf,elt);/* build target header */
      sprintf (LOCAL->buf+strlen(LOCAL->buf),",%lu;%08lx%04x-00000000\015\012",
	       elt->rfc822_size,elt->user_flags,(fSEEN * elt->seen) +
	       (fDELETED * elt->deleted) + (fFLAGGED * elt->flagged) +
	       (fANSWERED * elt->answered) + (fDRAFT * elt->draft));
				/* write target header */
      if (ret = (write (fd,LOCAL->buf,strlen (LOCAL->buf)) > 0) && !fsync (fd))
	for (k = elt->rfc822_size; ret && (j = min (k,LOCAL->buflen)); k -= j)
	  ret = (read (LOCAL->fd,LOCAL->buf,j) == j) &&
	    (write (fd,LOCAL->buf,j) == j) && !fsync (fd);
    }
  if (!ret) {			/* if error */
    sprintf (LOCAL->buf,"Unable to write message: %s",strerror (errno));
    mm_log (LOCAL->buf,ERROR);
    ftruncate (fd,sbuf.st_size);
  }
  tp[0] = sbuf.st_atime;	/* preserve atime and mtime */
  tp[1] = sbuf.st_mtime;
  utime (file,tp);		/* set the times */
  close (fd);			/* close the file */
  unlockfd (ld,lock);		/* release exclusive parse/append permission */
  mm_nocritical (stream);	/* release critical */
  return ret;
}

/* MBX get cache element with status updating from file
 * Accepts: MAIL stream
 *	    message number
 * Returns: cache element
 */

MESSAGECACHE *mbx_elt (MAILSTREAM *stream,unsigned long msgno)
{
  MESSAGECACHE *elt = mail_elt (stream,msgno);
  struct {			/* old flags */
    unsigned int seen : 1;
    unsigned int deleted : 1;
    unsigned int flagged : 1;
    unsigned int answered : 1;
    unsigned int draft : 1;
    unsigned long user_flags;
  } old;
  old.seen = elt->seen; old.deleted = elt->deleted; old.flagged = elt->flagged;
  old.answered = elt->answered; old.draft = elt->draft;
  old.user_flags = elt->user_flags;
  mbx_read_flags (stream,elt);
  if ((old.seen != elt->seen) || (old.deleted != elt->deleted) ||
      (old.flagged != elt->flagged) || (old.answered != elt->answered) ||
      (old.draft != elt->draft) || (old.user_flags != elt->user_flags))
    mm_flags (stream,msgno);	/* let top level know */
  return elt;
}


/* MBX read flags from file
 * Accepts: MAIL stream
 * Returns: cache element
 */

void mbx_read_flags (MAILSTREAM *stream,MESSAGECACHE *elt)
{
  unsigned long i;
				/* set the seek pointer */
  lseek (LOCAL->fd,(off_t) elt->_private_.special.offset +
	 elt->_private_.special.text.size - 23,L_SET);
				/* read the new flags */
  if (read (LOCAL->fd,LOCAL->buf,12) < 0) {
    sprintf (LOCAL->buf,"Unable to read new status: %s",strerror (errno));
    fatal (LOCAL->buf);
  }
  LOCAL->buf[12] = '\0';	/* tie off buffer */
				/* calculate system flags */
  i = strtoul (LOCAL->buf+8,NIL,16);
  elt->seen = i & fSEEN ? T : NIL;
  elt->deleted = i & fDELETED ? T : NIL;
  elt->flagged = i & fFLAGGED ? T : NIL;
  elt->answered = i & fANSWERED ? T : NIL;
  elt->draft = i & fDRAFT ? T : NIL;
  LOCAL->buf[8] = '\0';		/* tie off flags */
				/* get user flags value */
  elt->user_flags = strtoul (LOCAL->buf,NIL,16);
}

/* MBX update header
 * Accepts: MAIL stream
 */

void mbx_update_header (MAILSTREAM *stream)
{
  int i;
  char *s = LOCAL->buf;
  memset (s,'\0',HDRSIZE);	/* initialize header */
  sprintf (s,"*mbx*\015\012%08lx%08lx\015\012",
	   stream->uid_validity,stream->uid_last);
  for (i = 0; i < NUSERFLAGS; ++i)
    sprintf (s += strlen (s),"%s\015\012",
	     stream->user_flags[i] ? stream->user_flags[i] : "");
  lseek (LOCAL->fd,0,L_SET);	/* rewind file */
				/* write new header */
  write (LOCAL->fd,LOCAL->buf,HDRSIZE);
}


/* MBX update status string
 * Accepts: MAIL stream
 *	    message number
 *	    flag saying whether or not to sync
 */

void mbx_update_status (MAILSTREAM *stream,unsigned long msgno,long syncflag)
{
  MESSAGECACHE *elt = mail_elt (stream,msgno);
  struct stat sbuf;
				/* readonly */
  if (stream->rdonly) mbx_read_flags (stream,elt);
  else {			/* readwrite */
    if (LOCAL->newkeyword) {	/* defined a new keyword? */
      mbx_update_header (stream);
      LOCAL->newkeyword = NIL;	/* don't do this again */
    }
				/* print new flag string */
    sprintf (LOCAL->buf,"%08lx%04x-%08lx",elt->user_flags,
	     (fSEEN * elt->seen) + (fDELETED * elt->deleted) +
	     (fFLAGGED * elt->flagged) + (fANSWERED * elt->answered) +
	     (fDRAFT * elt->draft),elt->_private_.uid);
				/* get to that place in the file */
    lseek (LOCAL->fd,(off_t) elt->_private_.special.offset +
	   elt->_private_.special.text.size - 23,L_SET);
				/* write new flags and UID */
    write (LOCAL->fd,LOCAL->buf,21);
    if (syncflag) {		/* sync if requested */
      fsync (LOCAL->fd);
      fstat (LOCAL->fd,&sbuf);	/* get new write time */
      LOCAL->filetime = sbuf.st_mtime;
    }
  }
}

/* MBX locate header for a message
 * Accepts: MAIL stream
 *	    message number
 *	    pointer to returned header size
 * Returns: position of header in file
 */

unsigned long mbx_hdrpos (MAILSTREAM *stream,unsigned long msgno,
			  unsigned long *size)
{
  long siz;
  long i = 0;
  int q = 0;
  char *s,tmp[MAILTMPLEN];
  MESSAGECACHE *elt = mbx_elt (stream,msgno);
  unsigned long ret = elt->_private_.special.offset +
    elt->_private_.special.text.size;
				/* is header size known? */
  if (!(*size = elt->_private_.msg.header.text.size)) {
    lseek (LOCAL->fd,ret,L_SET);/* get to header position */
				/* search message for CRLF CRLF */
    for (siz = 1; siz <= elt->rfc822_size; siz++) {
				/* read another buffer as necessary */
      if (--i <= 0)		/* buffer empty? */
	if (read (LOCAL->fd,s = tmp,
		  i = min (elt->rfc822_size - siz,(long) MAILTMPLEN)) < 0)
	  return ret;		/* I/O error? */
      switch (q) {		/* sniff at buffer */
      case 0:			/* first character */
	q = (*s++ == '\015') ? 1 : 0;
	break;
      case 1:			/* second character */
	q = (*s++ == '\012') ? 2 : 0;
	break;
      case 2:			/* third character */
	q = (*s++ == '\015') ? 3 : 0;
	break;
      case 3:			/* fourth character */
	if (*s++ == '\012') {	/* have the sequence? */
				/* yes, note for later */
	  elt->_private_.msg.header.text.size = *size = siz;
	  return ret;
	}
	q = 0;			/* lost... */
	break;
      }
    }
				/* header consumes entire message */
    elt->_private_.msg.header.text.size = *size = elt->rfc822_size;
  }
  return ret;
}
