add a .gitignore file

[nvi.git] / common / exf.c

/*-
 * Copyright (c) 1992, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 1992, 1993, 1994, 1995, 1996
 *      Keith Bostic.  All rights reserved.
 *
 * See the LICENSE file for redistribution information.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "$Id: exf.c,v 10.72 2003/08/10 09:44:01 skimo Exp $ (Berkeley) $Date: 2003/08/10 09:44:01 $";
#endif /* not lint */

#include <sys/param.h>
#include <sys/types.h>          /* XXX: param.h may not have included types.h */
#include <sys/queue.h>
#include <sys/stat.h>

/*
 * We include <sys/file.h>, because the flock(2) and open(2) #defines
 * were found there on historical systems.  We also include <fcntl.h>
 * because the open(2) #defines are found there on newer systems.
 */
#include <sys/file.h>

#include <bitstring.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>

#include "common.h"

static int      file_backup __P((SCR *, char *, char *));
static void     file_cinit __P((SCR *));
static void     file_comment __P((SCR *));
static int      file_spath __P((SCR *, FREF *, struct stat *, int *));

/*
 * file_add --
 *      Insert a file name into the FREF list, if it doesn't already
 *      appear in it.
 *
 * !!!
 * The "if it doesn't already appear" changes vi's semantics slightly.  If
 * you do a "vi foo bar", and then execute "next bar baz", the edit of bar
 * will reflect the line/column of the previous edit session.  Historic nvi
 * did not do this.  The change is a logical extension of the change where
 * vi now remembers the last location in any file that it has ever edited,
 * not just the previously edited file.
 *
 * PUBLIC: FREF *file_add __P((SCR *, char *));
 */
FREF *
file_add(SCR *sp, char *name)
{
        GS *gp;
        FREF *frp, *tfrp;

        /*
         * Return it if it already exists.  Note that we test against the
         * user's name, whatever that happens to be, including if it's a
         * temporary file.
         *
         * If the user added a file but was unable to initialize it, there
         * can be file list entries where the name field is NULL.  Discard
         * them the next time we see them.
         */
        gp = sp->gp;
        if (name != NULL)
                for (frp = gp->frefq.cqh_first;
                    frp != (FREF *)&gp->frefq; frp = frp->q.cqe_next) {
                        if (frp->name == NULL) {
                                tfrp = frp->q.cqe_next;
                                CIRCLEQ_REMOVE(&gp->frefq, frp, q);
                                if (frp->name != NULL)
                                        free(frp->name);
                                free(frp);
                                frp = tfrp;
                                continue;
                        }
                        if (!strcmp(frp->name, name))
                                return (frp);
                }

        /* Allocate and initialize the FREF structure. */
        CALLOC(sp, frp, FREF *, 1, sizeof(FREF));
        if (frp == NULL)
                return (NULL);

        /*
         * If no file name specified, or if the file name is a request
         * for something temporary, file_init() will allocate the file
         * name.  Temporary files are always ignored.
         */
        if (name != NULL && strcmp(name, TEMPORARY_FILE_STRING) &&
            (frp->name = strdup(name)) == NULL) {
                free(frp);
                msgq(sp, M_SYSERR, NULL);
                return (NULL);
        }

        /* Append into the chain of file names. */
        CIRCLEQ_INSERT_TAIL(&gp->frefq, frp, q);

        return (frp);
}

/*
 * file_init --
 *      Start editing a file, based on the FREF structure.  If successsful,
 *      let go of any previous file.  Don't release the previous file until
 *      absolutely sure we have the new one.
 *
 * PUBLIC: int file_init __P((SCR *, FREF *, char *, int));
 */
int
file_init(SCR *sp, FREF *frp, char *rcv_name, int flags)
{
        EXF *ep;
        struct stat sb;
        size_t psize;
        int fd, exists, open_err, readonly, stolen;
        char *oname, tname[MAXPATHLEN];

        stolen = open_err = readonly = 0;

        /*
         * If the file is a recovery file, let the recovery code handle it.
         * Clear the FR_RECOVER flag first -- the recovery code does set up,
         * and then calls us!  If the recovery call fails, it's probably
         * because the named file doesn't exist.  So, move boldly forward,
         * presuming that there's an error message the user will get to see.
         */
        if (F_ISSET(frp, FR_RECOVER)) {
                F_CLR(frp, FR_RECOVER);
                return (rcv_read(sp, frp));
        }

        /*
         * Required FRP initialization; the only flag we keep is the
         * cursor information.
         */
        F_CLR(frp, ~FR_CURSORSET);

        /*
         * Scan the user's path to find the file that we're going to
         * try and open.
         */
        if (file_spath(sp, frp, &sb, &exists))
                return (1);

        /*
         * Check whether we already have this file opened in some
         * other screen.
         */
        if (exists) {
                EXF *exfp;
                for (exfp = sp->gp->exfq.cqh_first;
                    exfp != (EXF *)&sp->gp->exfq; exfp = exfp->q.cqe_next) {
                        if (exfp->mdev == sb.st_dev &&
                            exfp->minode == sb.st_ino && 
                            (exfp != sp->ep || exfp->refcnt > 1)) {
                                ep = exfp;
                                goto postinit;
                        }
                }
        }

        /*
         * Required EXF initialization:
         *      Flush the line caches.
         *      Default recover mail file fd to -1.
         *      Set initial EXF flag bits.
         */
        CALLOC_RET(sp, ep, EXF *, 1, sizeof(EXF));
        CIRCLEQ_INIT(&ep->scrq);
        sp->c_lno = ep->c_nlines = OOBLNO;
        ep->rcv_fd = ep->fcntl_fd = -1;
        F_SET(ep, F_FIRSTMODIFY);

        /*
         * If no name or backing file, for whatever reason, create a backing
         * temporary file, saving the temp file name so we can later unlink
         * it.  If the user never named this file, copy the temporary file name
         * to the real name (we display that until the user renames it).
         */
        oname = frp->name;
        if (LF_ISSET(FS_OPENERR) || oname == NULL || !exists) {
                if (opts_empty(sp, O_TMP_DIRECTORY, 0))
                        goto err;
                (void)snprintf(tname, sizeof(tname),
                    "%s/vi.XXXXXX", O_STR(sp, O_TMP_DIRECTORY));
                if ((fd = mkstemp(tname)) == -1) {
                        msgq(sp, M_SYSERR,
                            "237|Unable to create temporary file");
                        goto err;
                }
                (void)close(fd);

                if (frp->name == NULL)
                        F_SET(frp, FR_TMPFILE);
                if ((frp->tname = strdup(tname)) == NULL ||
                    (frp->name == NULL && 
                     (frp->name = strdup(tname)) == NULL)) {
                        if (frp->tname != NULL) {
                                free(frp->tname);
                        }
                        msgq(sp, M_SYSERR, NULL);
                        (void)unlink(tname);
                        goto err;
                }
                oname = frp->tname;
                psize = 1024;
                if (!LF_ISSET(FS_OPENERR))
                        F_SET(frp, FR_NEWFILE);

                time(&ep->mtime);
        } else {
                /*
                 * XXX
                 * A seat of the pants calculation: try to keep the file in
                 * 15 pages or less.  Don't use a page size larger than 10K
                 * (vi should have good locality) or smaller than 1K.
                 */
                psize = ((sb.st_size / 15) + 1023) / 1024;
                if (psize > 10)
                        psize = 10;
                if (psize == 0)
                        psize = 1;
                psize *= 1024;

                F_SET(ep, F_DEVSET);
                ep->mdev = sb.st_dev;
                ep->minode = sb.st_ino;

                ep->mtime = sb.st_mtime;

                if (!S_ISREG(sb.st_mode))
                        msgq_str(sp, M_ERR, oname,
                            "238|Warning: %s is not a regular file");
        }

        /* Set up recovery. */
        if (rcv_name == NULL) {
                /* ep->rcv_path NULL if rcv_tmp fails */
                rcv_tmp(sp, ep, frp->name);
        } else {
                if ((ep->rcv_path = strdup(rcv_name)) == NULL) {
                        msgq(sp, M_SYSERR, NULL);
                        goto err;
                }
                F_SET(ep, F_MODIFIED);
        }

        if (db_init(sp, ep, rcv_name, oname, psize, &open_err)) {
                if (open_err && !LF_ISSET(FS_OPENERR))
                        goto oerr;
                goto err;
        }

        /*
         * Do the remaining things that can cause failure of the new file,
         * mark and logging initialization.
         */
        if (mark_init(sp, ep) || log_init(sp, ep))
                goto err;

postinit:
        /*
         * Set the alternate file name to be the file we're discarding.
         *
         * !!!
         * Temporary files can't become alternate files, so there's no file
         * name.  This matches historical practice, although it could only
         * happen in historical vi as the result of the initial command, i.e.
         * if vi was executed without a file name.
         */
        if (LF_ISSET(FS_SETALT))
                set_alt_name(sp, sp->frp == NULL ||
                    F_ISSET(sp->frp, FR_TMPFILE) ? NULL : sp->frp->name);

        /*
         * Close the previous file; if that fails, close the new one and run
         * for the border.
         *
         * !!!
         * There's a nasty special case.  If the user edits a temporary file,
         * and then does an ":e! %", we need to re-initialize the backing
         * file, but we can't change the name.  (It's worse -- we're dealing
         * with *names* here, we can't even detect that it happened.)  Set a
         * flag so that the file_end routine ignores the backing information
         * of the old file if it happens to be the same as the new one.
         *
         * !!!
         * Side-effect: after the call to file_end(), sp->frp may be NULL.
         */
        if (sp->ep != NULL) {
                F_SET(frp, FR_DONTDELETE);
                if (file_end(sp, NULL, LF_ISSET(FS_FORCE))) {
                        (void)file_end(sp, ep, 1);
                        goto err;
                }
                sp->ep = NULL;
                F_CLR(frp, FR_DONTDELETE);
        }

        /*
         * Lock the file; if it's a recovery file, it should already be
         * locked.  Note, we acquire the lock after the previous file
         * has been ended, so that we don't get an "already locked" error
         * for ":edit!".
         *
         * XXX
         * While the user can't interrupt us between the open and here,
         * there's a race between the dbopen() and the lock.  Not much
         * we can do about it.
         *
         * XXX
         * We don't make a big deal of not being able to lock the file.  As
         * locking rarely works over NFS, and often fails if the file was
         * mmap(2)'d, it's far too common to do anything like print an error
         * message, let alone make the file readonly.  At some future time,
         * when locking is a little more reliable, this should change to be
         * an error.
         */
        if (rcv_name == NULL && ep->refcnt == 0) {
                if ((ep->fd = open(oname, O_RDWR)) == -1)
                    goto no_lock;

                switch (file_lock(sp, oname, &ep->fcntl_fd, ep->fd, 1)) {
                case LOCK_FAILED:
no_lock:
                        F_SET(frp, FR_UNLOCKED);
                        break;
                case LOCK_UNAVAIL:
                        readonly = 1;
                        msgq_str(sp, M_INFO, oname,
                            "239|%s already locked, session is read-only");
                        break;
                case LOCK_SUCCESS:
                        break;
                }
        }

        /*
         * Historically, the readonly edit option was set per edit buffer in
         * vi, unless the -R command-line option was specified or the program
         * was executed as "view".  (Well, to be truthful, if the letter 'w'
         * occurred anywhere in the program name, but let's not get into that.)
         * So, the persistant readonly state has to be stored in the screen
         * structure, and the edit option value toggles with the contents of
         * the edit buffer.  If the persistant readonly flag is set, set the
         * readonly edit option.
         *
         * Otherwise, try and figure out if a file is readonly.  This is a
         * dangerous thing to do.  The kernel is the only arbiter of whether
         * or not a file is writeable, and the best that a user program can
         * do is guess.  Obvious loopholes are files that are on a file system
         * mounted readonly (access catches this one on a few systems), or
         * alternate protection mechanisms, ACL's for example, that we can't
         * portably check.  Lots of fun, and only here because users whined.
         *
         * !!!
         * Historic vi displayed the readonly message if none of the file
         * write bits were set, or if an an access(2) call on the path
         * failed.  This seems reasonable.  If the file is mode 444, root
         * users may want to know that the owner of the file did not expect
         * it to be written.
         *
         * Historic vi set the readonly bit if no write bits were set for
         * a file, even if the access call would have succeeded.  This makes
         * the superuser force the write even when vi expects that it will
         * succeed.  I'm less supportive of this semantic, but it's historic
         * practice and the conservative approach to vi'ing files as root.
         *
         * It would be nice if there was some way to update this when the user
         * does a "^Z; chmod ...".  The problem is that we'd first have to
         * distinguish between readonly bits set because of file permissions
         * and those set for other reasons.  That's not too hard, but deciding
         * when to reevaluate the permissions is trickier.  An alternative
         * might be to turn off the readonly bit if the user forces a write
         * and it succeeds.
         *
         * XXX
         * Access(2) doesn't consider the effective uid/gid values.  This
         * probably isn't a problem for vi when it's running standalone.
         */
        if (readonly || F_ISSET(sp, SC_READONLY) ||
            (!F_ISSET(frp, FR_NEWFILE) &&
            (!(sb.st_mode & (S_IWUSR | S_IWGRP | S_IWOTH)) ||
            access(frp->name, W_OK))))
                O_SET(sp, O_READONLY);
        else
                O_CLR(sp, O_READONLY);

        /* Switch... */
        ++ep->refcnt;
        CIRCLEQ_INSERT_HEAD(&ep->scrq, sp, eq);
        sp->ep = ep;
        sp->frp = frp;

        /* Set the initial cursor position, queue initial command. */
        file_cinit(sp);

        /* Report conversion errors again. */
        F_CLR(sp, SC_CONV_ERROR);

        /* Redraw the screen from scratch, schedule a welcome message. */
        F_SET(sp, SC_SCR_REFORMAT | SC_STATUS);

        if (frp->lno == OOBLNO)
                F_SET(sp, SC_SCR_TOP);

        /* Append into the chain of file structures. */
        if (ep->refcnt == 1)
                CIRCLEQ_INSERT_TAIL(&sp->gp->exfq, ep, q);

        return (0);

err:    if (frp->name != NULL) {
                free(frp->name);
                frp->name = NULL;
        }
        if (frp->tname != NULL) {
                (void)unlink(frp->tname);
                free(frp->tname);
                frp->tname = NULL;
        }

oerr:   if (F_ISSET(ep, F_RCV_ON))
                (void)unlink(ep->rcv_path);
        if (ep->rcv_path != NULL) {
                free(ep->rcv_path);
                ep->rcv_path = NULL;
        }
        if (ep->db != NULL) {
                (void)db_close(ep->db);
                ep->db = NULL;
        }
        free(ep);

        return (open_err && !LF_ISSET(FS_OPENERR) ?
            file_init(sp, frp, rcv_name, flags | FS_OPENERR) : 1);
}

/*
 * file_spath --
 *      Scan the user's path to find the file that we're going to
 *      try and open.
 */
static int
file_spath(SCR *sp, FREF *frp, struct stat *sbp, int *existsp)
{
        CHAR_T savech;
        size_t len;
        int found;
        char *name, *p, *t, path[MAXPATHLEN];

        /*
         * If the name is NULL or an explicit reference (i.e., the first
         * component is . or ..) ignore the O_PATH option.
         */
        name = frp->name;
        if (name == NULL) {
                *existsp = 0;
                return (0);
        }
        if (name[0] == '/' || (name[0] == '.' &&
            (name[1] == '/' || (name[1] == '.' && name[2] == '/')))) {
                *existsp = !stat(name, sbp);
                return (0);
        }

        /* Try . */
        if (!stat(name, sbp)) {
                *existsp = 1;
                return (0);
        }

        /* Try the O_PATH option values. */
        for (found = 0, p = t = O_STR(sp, O_PATH);; ++p)
                if (*p == ':' || *p == '\0') {
                        if (t < p - 1) {
                                savech = *p;
                                *p = '\0';
                                len = snprintf(path,
                                    sizeof(path), "%s/%s", t, name);
                                *p = savech;
                                if (!stat(path, sbp)) {
                                        found = 1;
                                        break;
                                }
                        }
                        t = p + 1;
                        if (*p == '\0')
                                break;
                }

        /* If we found it, build a new pathname and discard the old one. */
        if (found) {
                MALLOC_RET(sp, p, char *, len + 1);
                memcpy(p, path, len + 1);
                free(frp->name);
                frp->name = p;
        }
        *existsp = found;
        return (0);
}

/*
 * file_cinit --
 *      Set up the initial cursor position.
 */
static void
file_cinit(SCR *sp)
{
        GS *gp;
        MARK m;
        size_t len;
        int nb;
        CHAR_T *wp;
        size_t wlen;

        /* Set some basic defaults. */
        sp->lno = 1;
        sp->cno = 0;

        /*
         * Historically, initial commands (the -c option) weren't executed
         * until a file was loaded, e.g. "vi +10 nofile", followed by an
         * :edit or :tag command, would execute the +10 on the file loaded
         * by the subsequent command, (assuming that it existed).  This
         * applied as well to files loaded using the tag commands, and we
         * follow that historic practice.  Also, all initial commands were
         * ex commands and were always executed on the last line of the file.
         *
         * Otherwise, if no initial command for this file:
         *    If in ex mode, move to the last line, first nonblank character.
         *    If the file has previously been edited, move to the last known
         *        position, and check it for validity.
         *    Otherwise, move to the first line, first nonblank.
         *
         * This gets called by the file init code, because we may be in a
         * file of ex commands and we want to execute them from the right
         * location in the file.
         */
        nb = 0;
        gp = sp->gp;
        if (gp->c_option != NULL && !F_ISSET(sp->frp, FR_NEWFILE)) {
                if (db_last(sp, &sp->lno))
                        return;
                if (sp->lno == 0) {
                        sp->lno = 1;
                        sp->cno = 0;
                }
                CHAR2INT(sp, gp->c_option, strlen(gp->c_option) + 1,
                         wp, wlen);
                if (ex_run_str(sp, "-c option", wp, wlen - 1, 1, 1))
                        return;
                gp->c_option = NULL;
        } else if (F_ISSET(sp, SC_EX)) {
                if (db_last(sp, &sp->lno))
                        return;
                if (sp->lno == 0) {
                        sp->lno = 1;
                        sp->cno = 0;
                        return;
                }
                nb = 1;
        } else {
                if (F_ISSET(sp->frp, FR_CURSORSET)) {
                        sp->lno = sp->frp->lno;
                        sp->cno = sp->frp->cno;

                        /* If returning to a file in vi, center the line. */
                         F_SET(sp, SC_SCR_CENTER);
                } else {
                        if (O_ISSET(sp, O_COMMENT))
                                file_comment(sp);
                        else
                                sp->lno = 1;
                        nb = 1;
                }
                if (db_get(sp, sp->lno, 0, NULL, &len)) {
                        sp->lno = 1;
                        sp->cno = 0;
                        return;
                }
                if (!nb && sp->cno > len)
                        nb = 1;
        }
        if (nb) {
                sp->cno = 0;
                (void)nonblank(sp, sp->lno, &sp->cno);
        }

        /*
         * !!!
         * The initial column is also the most attractive column.
         */
        sp->rcm = sp->cno;

        /*
         * !!!
         * Historically, vi initialized the absolute mark, but ex did not.
         * Which meant, that if the first command in ex mode was "visual",
         * or if an ex command was executed first (e.g. vi +10 file) vi was
         * entered without the mark being initialized.  For consistency, if
         * the file isn't empty, we initialize it for everyone, believing
         * that it can't hurt, and is generally useful.  Not initializing it
         * if the file is empty is historic practice, although it has always
         * been possible to set (and use) marks in empty vi files.
         */
        m.lno = sp->lno;
        m.cno = sp->cno;
        (void)mark_set(sp, ABSMARK1, &m, 0);
}

/*
 * file_end --
 *      Stop editing a file.
 *
 * PUBLIC: int file_end __P((SCR *, EXF *, int));
 */
int
file_end(SCR *sp, EXF *ep, int force)
{
        FREF *frp;

        /*
         * !!!
         * ep MAY NOT BE THE SAME AS sp->ep, DON'T USE THE LATTER.
         * (If argument ep is NULL, use sp->ep.)
         *
         * If multiply referenced, just decrement the count and return.
         */
        if (ep == NULL)
                ep = sp->ep;
        CIRCLEQ_REMOVE(&ep->scrq, sp, eq);
        if (--ep->refcnt != 0)
                return (0);

        /*
         *
         * Clean up the FREF structure.
         *
         * Save the cursor location.
         *
         * XXX
         * It would be cleaner to do this somewhere else, but by the time
         * ex or vi knows that we're changing files it's already happened.
         */
        frp = sp->frp;
        frp->lno = sp->lno;
        frp->cno = sp->cno;
        F_SET(frp, FR_CURSORSET);

        /*
         * We may no longer need the temporary backing file, so clean it
         * up.  We don't need the FREF structure either, if the file was
         * never named, so lose it.
         *
         * !!!
         * Re: FR_DONTDELETE, see the comment above in file_init().
         */
        if (!F_ISSET(frp, FR_DONTDELETE) && frp->tname != NULL) {
                if (unlink(frp->tname))
                        msgq_str(sp, M_SYSERR, frp->tname, "240|%s: remove");
                free(frp->tname);
                frp->tname = NULL;
                if (F_ISSET(frp, FR_TMPFILE)) {
                        CIRCLEQ_REMOVE(&sp->gp->frefq, frp, q);
                        if (frp->name != NULL)
                                free(frp->name);
                        free(frp);
                }
                sp->frp = NULL;
        }

        /*
         * Clean up the EXF structure.
         *
         * Close the db structure.
         */
        if (ep->db->close != NULL) {
                if ((sp->db_error = db_close(ep->db)) != 0 && 
                    !force) {
                        msgq_str(sp, M_DBERR, frp->name, "241|%s: close");
                        CIRCLEQ_INSERT_HEAD(&ep->scrq, sp, eq);
                        ++ep->refcnt;
                        return (1);
                }
                ep->db = NULL;
        }

        /* COMMITTED TO THE CLOSE.  THERE'S NO GOING BACK... */

        /* Stop logging. */
        (void)log_end(sp, ep);

        /* Free up any marks. */
        (void)mark_end(sp, ep);

        if (ep->env) {
                DB_ENV *env;

                db_env_close(ep->env, 0);
                ep->env = 0;
                if ((sp->db_error = db_env_create(&env, 0)))
                        msgq(sp, M_DBERR, "env_create");
                if ((sp->db_error = db_env_remove(env, ep->env_path, 0)))
                        msgq(sp, M_DBERR, "env->remove");
                if (ep->env_path != NULL && rmdir(ep->env_path))
                        msgq_str(sp, M_SYSERR, ep->env_path, "242|%s: remove");
        }

        /*
         * Delete recovery files, close the open descriptor, free recovery
         * memory.  See recover.c for a description of the protocol.
         *
         * XXX
         * Unlink backup file first, we can detect that the recovery file
         * doesn't reference anything when the user tries to recover it.
         * There's a race, here, obviously, but it's fairly small.
         */
        if (!F_ISSET(ep, F_RCV_NORM)) {
                if (ep->rcv_path != NULL && unlink(ep->rcv_path))
                        msgq_str(sp, M_SYSERR, ep->rcv_path, "242|%s: remove");
                if (ep->rcv_mpath != NULL && unlink(ep->rcv_mpath))
                        msgq_str(sp, M_SYSERR, ep->rcv_mpath, "243|%s: remove");
        }
        CIRCLEQ_REMOVE(&sp->gp->exfq, ep, q);
        if (ep->fd != -1)
                (void)close(ep->fd);
        if (ep->fcntl_fd != -1)
                (void)close(ep->fcntl_fd);
        if (ep->rcv_fd != -1)
                (void)close(ep->rcv_fd);
        if (ep->env_path != NULL)
                free(ep->env_path);
        if (ep->rcv_path != NULL)
                free(ep->rcv_path);
        if (ep->rcv_mpath != NULL)
                free(ep->rcv_mpath);

        free(ep);
        return (0);
}

/*
 * file_write --
 *      Write the file to disk.  Historic vi had fairly convoluted
 *      semantics for whether or not writes would happen.  That's
 *      why all the flags.
 *
 * PUBLIC: int file_write __P((SCR *, MARK *, MARK *, char *, int));
 */
int
file_write(SCR *sp, MARK *fm, MARK *tm, char *name, int flags)
{
        enum { NEWFILE, OLDFILE } mtype;
        struct stat sb;
        EXF *ep;
        FILE *fp;
        FREF *frp;
        MARK from, to;
        size_t len;
        u_long nlno, nch;
        int fd, nf, noname, oflags, rval;
        char *p, *s, *t, buf[MAXPATHLEN + 64];
        const char *msgstr;

        ep = sp->ep;
        frp = sp->frp;

        /*
         * Writing '%', or naming the current file explicitly, has the
         * same semantics as writing without a name.
         */
        if (name == NULL || !strcmp(name, frp->name)) {
                noname = 1;
                name = frp->name;
        } else
                noname = 0;

        /* Can't write files marked read-only, unless forced. */
        if (!LF_ISSET(FS_FORCE) && noname && O_ISSET(sp, O_READONLY)) {
                msgq(sp, M_ERR, LF_ISSET(FS_POSSIBLE) ?
                    "244|Read-only file, not written; use ! to override" :
                    "245|Read-only file, not written");
                return (1);
        }

        /* If not forced, not appending, and "writeany" not set ... */
        if (!LF_ISSET(FS_FORCE | FS_APPEND) && !O_ISSET(sp, O_WRITEANY)) {
                /* Don't overwrite anything but the original file. */
                if ((!noname || F_ISSET(frp, FR_NAMECHANGE)) &&
                    !stat(name, &sb)) {
                        msgq_str(sp, M_ERR, name,
                            LF_ISSET(FS_POSSIBLE) ?
                            "246|%s exists, not written; use ! to override" :
                            "247|%s exists, not written");
                        return (1);
                }

                /*
                 * Don't write part of any existing file.  Only test for the
                 * original file, the previous test catches anything else.
                 */
                if (!LF_ISSET(FS_ALL) && noname && !stat(name, &sb)) {
                        msgq(sp, M_ERR, LF_ISSET(FS_POSSIBLE) ?
                            "248|Partial file, not written; use ! to override" :
                            "249|Partial file, not written");
                        return (1);
                }
        }

        /*
         * Figure out if the file already exists -- if it doesn't, we display
         * the "new file" message.  The stat might not be necessary, but we
         * just repeat it because it's easier than hacking the previous tests.
         * The information is only used for the user message and modification
         * time test, so we can ignore the obvious race condition.
         *
         * One final test.  If we're not forcing or appending the current file,
         * and we have a saved modification time, object if the file changed
         * since we last edited or wrote it, and make them force it.
         */
        if (stat(name, &sb))
                mtype = NEWFILE;
        else {
                if (noname && !LF_ISSET(FS_FORCE | FS_APPEND) &&
                    ((F_ISSET(ep, F_DEVSET) &&
                    (sb.st_dev != ep->mdev || sb.st_ino != ep->minode)) ||
                    sb.st_mtime != ep->mtime)) {
                        msgq_str(sp, M_ERR, name, LF_ISSET(FS_POSSIBLE) ?
"250|%s: file modified more recently than this copy; use ! to override" :
"251|%s: file modified more recently than this copy");
                        return (1);
                }

                mtype = OLDFILE;
        }

        /* Set flags to create, write, and either append or truncate. */
        oflags = O_CREAT | O_WRONLY |
            (LF_ISSET(FS_APPEND) ? O_APPEND : O_TRUNC);

        /* Backup the file if requested. */
        if (!opts_empty(sp, O_BACKUP, 1) &&
            file_backup(sp, name, O_STR(sp, O_BACKUP)) && !LF_ISSET(FS_FORCE))
                return (1);

        /* Open the file. */
        SIGBLOCK;
        if ((fd = open(name, oflags,
            S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)) < 0) {
                msgq_str(sp, M_SYSERR, name, "%s");
                SIGUNBLOCK;
                return (1);
        }
        SIGUNBLOCK;

        /* Try and get a lock. */
        if (!noname && file_lock(sp, NULL, NULL, fd, 0) == LOCK_UNAVAIL)
                msgq_str(sp, M_ERR, name,
                    "252|%s: write lock was unavailable");

#if __linux__
        /*
         * XXX
         * In libc 4.5.x, fdopen(fd, "w") clears the O_APPEND flag (if set).
         * This bug is fixed in libc 4.6.x.
         *
         * This code works around this problem for libc 4.5.x users.
         * Note that this code is harmless if you're using libc 4.6.x.
         */
        if (LF_ISSET(FS_APPEND) && lseek(fd, (off_t)0, SEEK_END) < 0) {
                msgq(sp, M_SYSERR, name);
                return (1);
        }
#endif

        /*
         * Use stdio for buffering.
         *
         * XXX
         * SVR4.2 requires the fdopen mode exactly match the original open
         * mode, i.e. you have to open with "a" if appending.
         */
        if ((fp = fdopen(fd, LF_ISSET(FS_APPEND) ? "a" : "w")) == NULL) {
                msgq_str(sp, M_SYSERR, name, "%s");
                (void)close(fd);
                return (1);
        }

        /* Build fake addresses, if necessary. */
        if (fm == NULL) {
                from.lno = 1;
                from.cno = 0;
                fm = &from;
                if (db_last(sp, &to.lno))
                        return (1);
                to.cno = 0;
                tm = &to;
        }

        rval = ex_writefp(sp, name, fp, fm, tm, &nlno, &nch, 0);

        /*
         * Save the new last modification time -- even if the write fails
         * we re-init the time.  That way the user can clean up the disk
         * and rewrite without having to force it.
         */
        if (noname) {
                if (stat(name, &sb))
                        time(&ep->mtime);
                else {
                        F_SET(ep, F_DEVSET);
                        ep->mdev = sb.st_dev;
                        ep->minode = sb.st_ino;

                        ep->mtime = sb.st_mtime;
                }
        }

        /*
         * If the write failed, complain loudly.  ex_writefp() has already
         * complained about the actual error, reinforce it if data was lost.
         */
        if (rval) {
                if (!LF_ISSET(FS_APPEND))
                        msgq_str(sp, M_ERR, name,
                            "254|%s: WARNING: FILE TRUNCATED");
                return (1);
        }

        /*
         * Once we've actually written the file, it doesn't matter that the
         * file name was changed -- if it was, we've already whacked it.
         */
        F_CLR(frp, FR_NAMECHANGE);

        /*
         * If wrote the entire file, and it wasn't by appending it to a file,
         * clear the modified bit.  If the file was written to the original
         * file name and the file is a temporary, set the "no exit" bit.  This
         * permits the user to write the file and use it in the context of the
         * filesystem, but still keeps them from discarding their changes by
         * exiting.
         */
        if (LF_ISSET(FS_ALL) && !LF_ISSET(FS_APPEND)) {
                F_CLR(ep, F_MODIFIED);
                if (F_ISSET(frp, FR_TMPFILE)) {
                        if (noname)
                                F_SET(frp, FR_TMPEXIT);
                        else
                                F_CLR(frp, FR_TMPEXIT);
                }
        }

        p = msg_print(sp, name, &nf);
        switch (mtype) {
        case NEWFILE:
                msgstr = msg_cat(sp,
                    "256|%s: new file: %lu lines, %lu characters", NULL);
                len = snprintf(buf, sizeof(buf), msgstr, p, nlno, nch);
                break;
        case OLDFILE:
                msgstr = msg_cat(sp, LF_ISSET(FS_APPEND) ?
                    "315|%s: appended: %lu lines, %lu characters" :
                    "257|%s: %lu lines, %lu characters", NULL);
                len = snprintf(buf, sizeof(buf), msgstr, p, nlno, nch);
                break;
        default:
                abort();
        }

        /*
         * There's a nasty problem with long path names.  Cscope and tags files
         * can result in long paths and vi will request a continuation key from
         * the user.  Unfortunately, the user has typed ahead, and chaos will
         * result.  If we assume that the characters in the filenames only take
         * a single screen column each, we can trim the filename.
         */
        s = buf;
        if (len >= sp->cols) {
                for (s = buf, t = buf + strlen(p); s < t &&
                    (*s != '/' || len >= sp->cols - 3); ++s, --len);
                if (s == t)
                        s = buf;
                else {
                        *--s = '.';             /* Leading ellipses. */
                        *--s = '.';
                        *--s = '.';
                }
        }
        msgq(sp, M_INFO, s);
        if (nf)
                FREE_SPACE(sp, p, 0);
        return (0);
}

/*
 * file_backup --
 *      Backup the about-to-be-written file.
 *
 * XXX
 * We do the backup by copying the entire file.  It would be nice to do
 * a rename instead, but: (1) both files may not fit and we want to fail
 * before doing the rename; (2) the backup file may not be on the same
 * disk partition as the file being written; (3) there may be optional
 * file information (MACs, DACs, whatever) that we won't get right if we
 * recreate the file.  So, let's not risk it.
 */
static int
file_backup(SCR *sp, char *name, char *bname)
{
        struct dirent *dp;
        struct stat sb;
        DIR *dirp;
        EXCMD cmd;
        off_t off;
        size_t blen;
        int flags, maxnum, nr, num, nw, rfd, wfd, version;
        char *bp, *estr, *p, *pct, *slash, *t, *wfname, buf[8192];
        CHAR_T *wp;
        size_t wlen;
        size_t nlen;
        char *d = NULL;

        rfd = wfd = -1;
        bp = estr = wfname = NULL;

        /*
         * Open the current file for reading.  Do this first, so that
         * we don't exec a shell before the most likely failure point.
         * If it doesn't exist, it's okay, there's just nothing to back
         * up.
         */
        errno = 0;
        if ((rfd = open(name, O_RDONLY, 0)) < 0) {
                if (errno == ENOENT)
                        return (0);
                estr = name;
                goto err;
        }

        /*
         * If the name starts with an 'N' character, add a version number
         * to the name.  Strip the leading N from the string passed to the
         * expansion routines, for no particular reason.  It would be nice
         * to permit users to put the version number anywhere in the backup
         * name, but there isn't a special character that we can use in the
         * name, and giving a new character a special meaning leads to ugly
         * hacks both here and in the supporting ex routines.
         *
         * Shell and file name expand the option's value.
         */
        ex_cinit(sp, &cmd, 0, 0, 0, 0, 0);
        if (bname[0] == 'N') {
                version = 1;
                ++bname;
        } else
                version = 0;
        CHAR2INT(sp, bname, strlen(bname) + 1, wp, wlen);
        if (argv_exp2(sp, &cmd, wp, wlen - 1))
                return (1);

        /*
         *  0 args: impossible.
         *  1 args: use it.
         * >1 args: object, too many args.
         */
        if (cmd.argc != 1) {
                msgq_str(sp, M_ERR, bname,
                    "258|%s expanded into too many file names");
                (void)close(rfd);
                return (1);
        }

        /*
         * If appending a version number, read through the directory, looking
         * for file names that match the name followed by a number.  Make all
         * of the other % characters in name literal, so the user doesn't get
         * surprised and sscanf doesn't drop core indirecting through pointers
         * that don't exist.  If any such files are found, increment its number
         * by one.
         */
        if (version) {
                GET_SPACE_GOTOC(sp, bp, blen, cmd.argv[0]->len * 2 + 50);
                INT2SYS(sp, cmd.argv[0]->bp, cmd.argv[0]->len + 1,
                         p, nlen); 
                d = strdup(p);
                p = d;
                for (t = bp, slash = NULL;
                     p[0] != '\0'; *t++ = *p++)
                        if (p[0] == '%') {
                                if (p[1] != '%')
                                        *t++ = '%';
                        } else if (p[0] == '/')
                                slash = t;
                pct = t;
                *t++ = '%';
                *t++ = 'd';
                *t = '\0';

                if (slash == NULL) {
                        dirp = opendir(".");
                        p = bp;
                } else {
                        *slash = '\0';
                        dirp = opendir(bp);
                        *slash = '/';
                        p = slash + 1;
                }
                if (dirp == NULL) {
                        INT2SYS(sp, cmd.argv[0]->bp, cmd.argv[0]->len + 1,
                                estr, nlen);
                        goto err;
                }

                for (maxnum = 0; (dp = readdir(dirp)) != NULL;)
                        if (sscanf(dp->d_name, p, &num) == 1 && num > maxnum)
                                maxnum = num;
                (void)closedir(dirp);

                /* Format the backup file name. */
                (void)snprintf(pct, blen - (pct - bp), "%d", maxnum + 1);
                wfname = bp;
        } else {
                bp = NULL;
                INT2SYS(sp, cmd.argv[0]->bp, cmd.argv[0]->len + 1,
                        wfname, nlen);
        }
        
        /* Open the backup file, avoiding lurkers. */
        if (stat(wfname, &sb) == 0) {
                if (!S_ISREG(sb.st_mode)) {
                        msgq_str(sp, M_ERR, bname,
                            "259|%s: not a regular file");
                        goto err;
                }
                if (sb.st_uid != getuid()) {
                        msgq_str(sp, M_ERR, bname, "260|%s: not owned by you");
                        goto err;
                }
                if (sb.st_mode & (S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)) {
                        msgq_str(sp, M_ERR, bname,
                           "261|%s: accessible by a user other than the owner");
                        goto err;
                }
                flags = O_TRUNC;
        } else
                flags = O_CREAT | O_EXCL;
        if ((wfd = open(wfname, flags | O_WRONLY, S_IRUSR | S_IWUSR)) < 0) {
                estr = bname;
                goto err;
        }

        /* Copy the file's current contents to its backup value. */
        while ((nr = read(rfd, buf, sizeof(buf))) > 0)
                for (off = 0; nr != 0; nr -= nw, off += nw)
                        if ((nw = write(wfd, buf + off, nr)) < 0) {
                                estr = wfname;
                                goto err;
                        }
        if (nr < 0) {
                estr = name;
                goto err;
        }

        if (close(rfd)) {
                estr = name;
                goto err;
        }
        if (close(wfd)) {
                estr = wfname;
                goto err;
        }
        if (bp != NULL)
                FREE_SPACE(sp, bp, blen);
        return (0);

alloc_err:
err:    if (rfd != -1)
                (void)close(rfd);
        if (wfd != -1) {
                (void)unlink(wfname);
                (void)close(wfd);
        }
        if (estr)
                msgq_str(sp, M_SYSERR, estr, "%s");
        if (d != NULL)
                free(d);
        if (bp != NULL)
                FREE_SPACE(sp, bp, blen);
        return (1);
}

/*
 * file_comment --
 *      Skip the first comment.
 */
static void
file_comment(SCR *sp)
{
        db_recno_t lno;
        size_t len;
        CHAR_T *p;

        for (lno = 1; !db_get(sp, lno, 0, &p, &len) && len == 0; ++lno);
        if (p == NULL)
                return;
        if (p[0] == '#') {
                F_SET(sp, SC_SCR_TOP);
                while (!db_get(sp, ++lno, 0, &p, &len))
                        if (len < 1 || p[0] != '#') {
                                sp->lno = lno;
                                return;
                        }
        } else if (len > 1 && p[0] == '/' && p[1] == '*') {
                F_SET(sp, SC_SCR_TOP);
                do {
                        for (; len > 1; --len, ++p)
                                if (p[0] == '*' && p[1] == '/') {
                                        sp->lno = lno;
                                        return;
                                }
                } while (!db_get(sp, ++lno, 0, &p, &len));
        } else if (len > 1 && p[0] == '/' && p[1] == '/') {
                F_SET(sp, SC_SCR_TOP);
                while (!db_get(sp, ++lno, 0, &p, &len))
                        if (len < 1 || p[0] != '/' || p[1] != '/') {
                                sp->lno = lno;
                                return;
                        }
        }
}

/*
 * file_m1 --
 *      First modification check routine.  The :next, :prev, :rewind, :tag,
 *      :tagpush, :tagpop, ^^ modifications check.
 *
 * PUBLIC: int file_m1 __P((SCR *, int, int));
 */
int
file_m1(SCR *sp, int force, int flags)
{
        EXF *ep;

        ep = sp->ep;

        /* If no file loaded, return no modifications. */
        if (ep == NULL)
                return (0);

        /*
         * If the file has been modified, we'll want to write it back or
         * fail.  If autowrite is set, we'll write it back automatically,
         * unless force is also set.  Otherwise, we fail unless forced or
         * there's another open screen on this file.
         */
        if (F_ISSET(ep, F_MODIFIED)) {
                if (O_ISSET(sp, O_AUTOWRITE)) {
                        if (!force && file_aw(sp, flags))
                                return (1);
                } else if (ep->refcnt <= 1 && !force) {
                        msgq(sp, M_ERR, LF_ISSET(FS_POSSIBLE) ?
"262|File modified since last complete write; write or use ! to override" :
"263|File modified since last complete write; write or use :edit! to override");
                        return (1);
                }
        }

        return (file_m3(sp, force));
}

/*
 * file_m2 --
 *      Second modification check routine.  The :edit, :quit, :recover
 *      modifications check.
 *
 * PUBLIC: int file_m2 __P((SCR *, int));
 */
int
file_m2(SCR *sp, int force)
{
        EXF *ep;

        ep = sp->ep;

        /* If no file loaded, return no modifications. */
        if (ep == NULL)
                return (0);

        /*
         * If the file has been modified, we'll want to fail, unless forced
         * or there's another open screen on this file.
         */
        if (F_ISSET(ep, F_MODIFIED) && ep->refcnt <= 1 && !force) {
                msgq(sp, M_ERR,
"264|File modified since last complete write; write or use ! to override");
                return (1);
        }

        return (file_m3(sp, force));
}

/*
 * file_m3 --
 *      Third modification check routine.
 *
 * PUBLIC: int file_m3 __P((SCR *, int));
 */
int
file_m3(SCR *sp, int force)
{
        EXF *ep;

        ep = sp->ep;

        /* If no file loaded, return no modifications. */
        if (ep == NULL)
                return (0);

        /*
         * Don't exit while in a temporary files if the file was ever modified.
         * The problem is that if the user does a ":wq", we write and quit,
         * unlinking the temporary file.  Not what the user had in mind at all.
         * We permit writing to temporary files, so that user maps using file
         * system names work with temporary files.
         */
        if (F_ISSET(sp->frp, FR_TMPEXIT) && ep->refcnt <= 1 && !force) {
                msgq(sp, M_ERR,
                    "265|File is a temporary; exit will discard modifications");
                return (1);
        }
        return (0);
}

/*
 * file_aw --
 *      Autowrite routine.  If modified, autowrite is set and the readonly bit
 *      is not set, write the file.  A routine so there's a place to put the
 *      comment.
 *
 * PUBLIC: int file_aw __P((SCR *, int));
 */
int
file_aw(SCR *sp, int flags)
{
        if (!F_ISSET(sp->ep, F_MODIFIED))
                return (0);
        if (!O_ISSET(sp, O_AUTOWRITE))
                return (0);

        /*
         * !!!
         * Historic 4BSD vi attempted to write the file if autowrite was set,
         * regardless of the writeability of the file (as defined by the file
         * readonly flag).  System V changed this as some point, not attempting
         * autowrite if the file was readonly.  This feels like a bug fix to
         * me (e.g. the principle of least surprise is violated if readonly is
         * set and vi writes the file), so I'm compatible with System V.
         */
        if (O_ISSET(sp, O_READONLY)) {
                msgq(sp, M_INFO,
                    "266|File readonly, modifications not auto-written");
                return (1);
        }
        return (file_write(sp, NULL, NULL, NULL, flags));
}

/*
 * set_alt_name --
 *      Set the alternate pathname.
 *
 * Set the alternate pathname.  It's a routine because I wanted some place
 * to hang this comment.  The alternate pathname (normally referenced using
 * the special character '#' during file expansion and in the vi ^^ command)
 * is set by almost all ex commands that take file names as arguments.  The
 * rules go something like this:
 *
 *    1: If any ex command takes a file name as an argument (except for the
 *       :next command), the alternate pathname is set to that file name.
 *       This excludes the command ":e" and ":w !command" as no file name
 *       was specified.  Note, historically, the :source command did not set
 *       the alternate pathname.  It does in nvi, for consistency.
 *
 *    2: However, if any ex command sets the current pathname, e.g. the
 *       ":e file" or ":rew" commands succeed, then the alternate pathname
 *       is set to the previous file's current pathname, if it had one.
 *       This includes the ":file" command and excludes the ":e" command.
 *       So, by rule #1 and rule #2, if ":edit foo" fails, the alternate
 *       pathname will be "foo", if it succeeds, the alternate pathname will
 *       be the previous current pathname.  The ":e" command will not set
 *       the alternate or current pathnames regardless.
 *
 *    3: However, if it's a read or write command with a file argument and
 *       the current pathname has not yet been set, the file name becomes
 *       the current pathname, and the alternate pathname is unchanged.
 *
 * If the user edits a temporary file, there may be times when there is no
 * alternative file name.  A name argument of NULL turns it off.
 *
 * PUBLIC: void set_alt_name __P((SCR *, char *));
 */
void
set_alt_name(SCR *sp, char *name)
{
        if (sp->alt_name != NULL)
                free(sp->alt_name);
        if (name == NULL)
                sp->alt_name = NULL;
        else if ((sp->alt_name = strdup(name)) == NULL)
                msgq(sp, M_SYSERR, NULL);
}

/*
 * file_lock --
 *      Get an exclusive lock on a file and set close-on-exec flag
 *
 * XXX
 * The default locking is flock(2) style, not fcntl(2).  The latter is
 * known to fail badly on some systems, and its only advantage is that
 * it occasionally works over NFS.
 *
 * Furthermore, the semantics of fcntl(2) are wrong.  The problems are
 * two-fold: you can't close any file descriptor associated with the file
 * without losing all of the locks, and you can't get an exclusive lock
 * unless you have the file open for writing.  Someone ought to be shot,
 * but it's probably too late, they may already have reproduced.  To get
 * around these problems, nvi opens the files for writing when it can and
 * acquires a second file descriptor when it can't.  The recovery files
 * are examples of the former, they're always opened for writing.  The DB
 * files can't be opened for writing because the semantics of DB are that
 * files opened for writing are flushed back to disk when the DB session
 * is ended. So, in that case we have to acquire an extra file descriptor.
 *
 * PUBLIC: lockr_t file_lock __P((SCR *, char *, int *, int, int));
 */
lockr_t
file_lock(SCR *sp, char *name, int *fdp, int fd, int iswrite)
{
        fcntl(fd, F_SETFD, 1);

        if (!O_ISSET(sp, O_LOCKFILES))
                return (LOCK_SUCCESS);
        
#ifdef HAVE_LOCK_FLOCK                  /* Hurrah!  We've got flock(2). */
        /*
         * !!!
         * We need to distinguish a lock not being available for the file
         * from the file system not supporting locking.  Flock is documented
         * as returning EWOULDBLOCK; add EAGAIN for good measure, and assume
         * they are the former.  There's no portable way to do this.
         */
        errno = 0;
        return (flock(fd, LOCK_EX | LOCK_NB) ? errno == EAGAIN
#ifdef EWOULDBLOCK
            || errno == EWOULDBLOCK
#endif
            ? LOCK_UNAVAIL : LOCK_FAILED : LOCK_SUCCESS);
#endif
#ifdef HAVE_LOCK_FCNTL                  /* Gag me.  We've got fcntl(2). */
{
        struct flock arg;
        int didopen, sverrno;

        arg.l_type = F_WRLCK;
        arg.l_whence = 0;               /* SEEK_SET */
        arg.l_start = arg.l_len = 0;
        arg.l_pid = 0;

        /*
         * If the file descriptor isn't opened for writing, it must fail.
         * If we fail because we can't get a read/write file descriptor,
         * we return LOCK_SUCCESS, believing that the file is readonly
         * and that will be sufficient to warn the user.
         */
        if (!iswrite) {
                if (name == NULL || fdp == NULL)
                        return (LOCK_FAILED);
                if ((fd = open(name, O_RDWR, 0)) == -1)
                        return (LOCK_SUCCESS);
                *fdp = fd;
                didopen = 1;
        }

        errno = 0;
        if (!fcntl(fd, F_SETLK, &arg))
                return (LOCK_SUCCESS);
        if (didopen) {
                sverrno = errno;
                (void)close(fd);
                errno = sverrno;
        }

        /*
         * !!!
         * We need to distinguish a lock not being available for the file
         * from the file system not supporting locking.  Fcntl is documented
         * as returning EACCESS and EAGAIN; add EWOULDBLOCK for good measure,
         * and assume they are the former.  There's no portable way to do this.
         */
        return (errno == EACCES || errno == EAGAIN
#ifdef EWOULDBLOCK
        || errno == EWOULDBLOCK
#endif
        ?  LOCK_UNAVAIL : LOCK_FAILED);
}
#endif
#if !defined(HAVE_LOCK_FLOCK) && !defined(HAVE_LOCK_FCNTL)
        return (LOCK_SUCCESS);
#endif
}