NetBSD/usr.bin/vi/common/exf.c

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1994-08-17 20:17:19 +04:00
/*-
* Copyright (c) 1992, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
1994-08-17 23:19:35 +04:00
static char sccsid[] = "@(#)exf.c 8.97 (Berkeley) 8/17/94";
1994-08-17 20:17:19 +04:00
#endif /* not lint */
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/stat.h>
#include <sys/time.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 <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include "compat.h"
#include <db.h>
#include <regex.h>
#include <pathnames.h>
#include "vi.h"
#include "excmd.h"
/*
* 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.
*/
FREF *
file_add(sp, name)
SCR *sp;
CHAR_T *name;
{
FREF *frp;
/*
* 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 (name != NULL)
for (frp = sp->frefq.cqh_first;
frp != (FREF *)&sp->frefq; frp = frp->q.cqe_next)
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, sizeof(FREF));
msgq(sp, M_SYSERR, NULL);
return (NULL);
}
/* Append into the chain of file names. */
CIRCLEQ_INSERT_TAIL(&sp->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.
*/
int
file_init(sp, frp, rcv_name, force)
SCR *sp;
FREF *frp;
char *rcv_name;
int force;
{
EXF *ep;
RECNOINFO oinfo;
struct stat sb;
size_t psize;
int fd;
char *oname, tname[MAXPATHLEN];
/*
* 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);
/*
* 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));
ep->c_lno = ep->c_nlines = OOBLNO;
ep->rcv_fd = ep->fcntl_fd = -1;
LIST_INIT(&ep->marks);
F_SET(ep, F_FIRSTMODIFY);
/*
* If no name or backing file, 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).
*/
if ((oname = frp->name) == NULL || stat(oname, &sb)) {
(void)snprintf(tname,
sizeof(tname), "%s/vi.XXXXXX", O_STR(sp, O_DIRECTORY));
if ((fd = mkstemp(tname)) == -1) {
msgq(sp, M_SYSERR, "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 = 4 * 1024;
F_SET(frp, FR_NEWFILE);
} else {
/*
* Try to keep it at 10 pages or less per file. This
* isn't friendly on a loaded machine, btw.
*/
if (sb.st_size < 40 * 1024)
psize = 4 * 1024;
else if (sb.st_size < 320 * 1024)
psize = 32 * 1024;
else
psize = 64 * 1024;
ep->mtime = sb.st_mtime;
if (!S_ISREG(sb.st_mode))
msgq(sp, M_ERR,
"Warning: %s is not a regular file", oname);
}
/* Set up recovery. */
memset(&oinfo, 0, sizeof(RECNOINFO));
oinfo.bval = '\n'; /* Always set. */
oinfo.psize = psize;
oinfo.flags = F_ISSET(sp->gp, G_SNAPSHOT) ? R_SNAPSHOT : 0;
if (rcv_name == NULL) {
if (!rcv_tmp(sp, ep, frp->name))
oinfo.bfname = ep->rcv_path;
} else {
if ((ep->rcv_path = strdup(rcv_name)) == NULL) {
msgq(sp, M_SYSERR, NULL);
goto err;
}
oinfo.bfname = ep->rcv_path;
F_SET(ep, F_MODIFIED);
}
/* Open a db structure. */
if ((ep->db = dbopen(rcv_name == NULL ? oname : NULL,
O_NONBLOCK | O_RDONLY, DEFFILEMODE, DB_RECNO, &oinfo)) == NULL) {
msgq(sp, M_SYSERR, rcv_name == NULL ? oname : rcv_name);
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;
/*
* 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.
*/
F_SET(frp, FR_DONTDELETE);
if (sp->ep != NULL && file_end(sp, sp->ep, force)) {
(void)file_end(sp, ep, 1);
goto err;
}
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)
switch (file_lock(oname,
&ep->fcntl_fd, ep->db->fd(ep->db), 0)) {
case LOCK_FAILED:
F_SET(frp, FR_UNLOCKED);
break;
case LOCK_UNAVAIL:
msgq(sp, M_INFO,
"%s already locked, session is read-only", oname);
F_SET(frp, FR_RDONLY);
break;
case LOCK_SUCCESS:
break;
}
/*
* The -R flag, or doing a "set readonly" during a session causes
* all files edited during the session (using an edit command, or
* even using tags) to be marked read-only. Changing the file name
* (see ex/ex_file.c), clears this flag.
*
* 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 (O_ISSET(sp, O_READONLY) || !F_ISSET(frp, FR_NEWFILE) &&
(!(sb.st_mode & (S_IWUSR | S_IWGRP | S_IWOTH)) ||
access(frp->name, W_OK)))
F_SET(frp, FR_RDONLY);
/*
* Set the alternate file name to be the file we've just discarded.
*
* !!!
* If the current file was a temporary file, the call to file_end()
* unlinked it and free'd the name. So, there is no previous file,
* and there is no alternate file name. This matches historical
* practice, although in historical vi it could only happen as the
* result of the initial command, i.e. if vi was executed without a
* file name.
*/
set_alt_name(sp, sp->frp == NULL ? NULL : sp->frp->name);
/*
* Switch...
*
* !!!
* Note, because the EXF structure is examine at interrupt time,
* the underlying DB structures have to be consistent as soon as
* it's assigned to an SCR structure.
*/
++ep->refcnt;
sp->ep = ep;
sp->frp = frp;
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;
}
if (ep->rcv_path != NULL) {
free(ep->rcv_path);
ep->rcv_path = NULL;
}
if (ep->db != NULL)
(void)ep->db->close(ep->db);
FREE(ep, sizeof(EXF));
return (1);
}
/*
* file_end --
* Stop editing a file.
*/
int
file_end(sp, ep, force)
SCR *sp;
EXF *ep;
int force;
{
FREF *frp;
/*
* 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(sp, M_SYSERR, "%s: remove", frp->tname);
free(frp->tname);
frp->tname = NULL;
if (F_ISSET(frp, FR_TMPFILE)) {
CIRCLEQ_REMOVE(&sp->frefq, frp, q);
free(frp->name);
free(frp);
}
sp->frp = NULL;
}
/*
* Clean up the EXF structure.
*
* sp->ep MAY NOT BE THE SAME AS THE ARGUMENT ep, SO DON'T USE IT!
*
* If multiply referenced, just decrement the count and return.
*/
if (--ep->refcnt != 0)
return (0);
/* Close the db structure. */
if (ep->db->close != NULL && ep->db->close(ep->db) && !force) {
msgq(sp, M_ERR, "%s: close: %s", frp->name, strerror(errno));
++ep->refcnt;
return (1);
}
/* 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);
/*
* 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(sp, M_ERR,
"%s: remove: %s", ep->rcv_path, strerror(errno));
if (ep->rcv_mpath != NULL && unlink(ep->rcv_mpath))
msgq(sp, M_ERR,
"%s: remove: %s", ep->rcv_mpath, strerror(errno));
}
if (ep->fcntl_fd != -1)
(void)close(ep->fcntl_fd);
if (ep->rcv_fd != -1)
(void)close(ep->rcv_fd);
if (ep->rcv_path != NULL)
free(ep->rcv_path);
if (ep->rcv_mpath != NULL)
free(ep->rcv_mpath);
FREE(ep, sizeof(EXF));
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.
*/
int
file_write(sp, ep, fm, tm, name, flags)
SCR *sp;
EXF *ep;
MARK *fm, *tm;
char *name;
int flags;
{
struct stat sb;
FILE *fp;
FREF *frp;
MARK from, to;
u_long nlno, nch;
int btear, fd, noname, oflags, rval;
char *msg;
frp = sp->frp;
if (name == NULL) {
noname = 1;
name = frp->name;
} else
noname = 0;
/* Can't write files marked read-only, unless forced. */
if (!LF_ISSET(FS_FORCE) && noname && F_ISSET(frp, FR_RDONLY)) {
if (LF_ISSET(FS_POSSIBLE))
msgq(sp, M_ERR,
"Read-only file, not written; use ! to override");
else
msgq(sp, M_ERR, "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)) {
if (LF_ISSET(FS_POSSIBLE))
msgq(sp, M_ERR,
"%s exists, not written; use ! to override", name);
else
msgq(sp, M_ERR, "%s exists, not written", name);
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)) {
if (LF_ISSET(FS_POSSIBLE))
msgq(sp, M_ERR,
"Use ! to write a partial file");
else
msgq(sp, M_ERR, "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.
*
* If the user is overwriting a file other than the original file, and
* O_WRITEANY was what got us here (neither force nor append was set),
* display the "existing file" messsage. Since the FR_NAMECHANGE flag
* is cleared on a successful write, the message only appears once when
* the user changes a file name. This is historic practice.
*
* One final test. If we're not forcing or appending, and we have a
* saved modification time, stop the user if it's been written since
* we last edited or wrote it, and make them force it.
*/
if (stat(name, &sb))
msg = ": new file";
else {
msg = "";
if (!LF_ISSET(FS_FORCE | FS_APPEND)) {
if (ep->mtime && sb.st_mtime > ep->mtime) {
msgq(sp, M_ERR,
"%s: file modified more recently than this copy%s",
name, LF_ISSET(FS_POSSIBLE) ?
"; use ! to override" : "");
return (1);
}
if (!noname || F_ISSET(frp, FR_NAMECHANGE))
msg = ": existing file";
}
}
/* Set flags to either append or truncate. */
oflags = O_CREAT | O_WRONLY;
if (LF_ISSET(FS_APPEND))
oflags |= O_APPEND;
else
oflags |= O_TRUNC;
/* Open the file. */
if ((fd = open(name, oflags, DEFFILEMODE)) < 0) {
msgq(sp, M_SYSERR, name);
return (1);
}
/* Use stdio for buffering. */
if ((fp = fdopen(fd, "w")) == NULL) {
(void)close(fd);
msgq(sp, M_SYSERR, name);
return (1);
}
/* Build fake addresses, if necessary. */
if (fm == NULL) {
from.lno = 1;
from.cno = 0;
fm = &from;
if (file_lline(sp, ep, &to.lno))
return (1);
to.cno = 0;
tm = &to;
}
/* Turn on the busy message. */
btear = F_ISSET(sp, S_EXSILENT) ? 0 : !busy_on(sp, "Writing...");
rval = ex_writefp(sp, ep, name, fp, fm, tm, &nlno, &nch);
if (btear)
busy_off(sp);
/*
* 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.
*/
ep->mtime = stat(name, &sb) ? 0 : sb.st_mtime;
/* If the write failed, complain loudly. */
if (rval) {
if (!LF_ISSET(FS_APPEND))
msgq(sp, M_ERR, "%s: WARNING: file truncated!", name);
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 clear the modified bit. If the file was
* written back 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 file system, but still keeps them from
* losing their changes by exiting.
*/
if (LF_ISSET(FS_ALL)) {
F_CLR(ep, F_MODIFIED);
if (F_ISSET(frp, FR_TMPFILE))
if (noname)
F_SET(frp, FR_TMPEXIT);
else
F_CLR(frp, FR_TMPEXIT);
}
msgq(sp, M_INFO, "%s%s%s: %lu line%s, %lu characters",
INTERRUPTED(sp) ? "Interrupted write: " : "",
name, msg, nlno, nlno == 1 ? "" : "s", nch);
return (0);
}
/*
* file_m1 --
* First modification check routine. The :next, :prev, :rewind, :tag,
* :tagpush, :tagpop, ^^ modifications check.
*/
int
file_m1(sp, ep, force, flags)
SCR *sp;
EXF *ep;
int force, flags;
{
/*
* 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_write(sp, ep, NULL, NULL, NULL, flags))
return (1);
} else if (ep->refcnt <= 1 && !force) {
msgq(sp, M_ERR,
"File modified since last complete write; write or use %s to override",
LF_ISSET(FS_POSSIBLE) ? "!" : ":edit!");
return (1);
}
return (file_m3(sp, ep, force));
}
/*
* file_m2 --
* Second modification check routine. The :edit, :quit, :recover
* modifications check.
*/
int
file_m2(sp, ep, force)
SCR *sp;
EXF *ep;
int force;
{
/*
* 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,
"File modified since last complete write; write or use ! to override");
return (1);
}
return (file_m3(sp, ep, force));
}
/*
* file_m3 --
* Third modification check routine.
*/
int
file_m3(sp, ep, force)
SCR *sp;
EXF *ep;
int force;
{
/*
* 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,
"File is a temporary; exit will discard modifications");
return (1);
}
return (0);
}
/*
* file_lock --
* Get an exclusive lock on a file.
*
* 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.
*/
enum lockt
file_lock(name, fdp, fd, iswrite)
char *name;
int fd, *fdp, iswrite;
{
#if !defined(USE_FCNTL) && defined(LOCK_EX)
/* 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 || errno == EWOULDBLOCK ?
LOCK_UNAVAIL : LOCK_FAILED : LOCK_SUCCESS);
#else /* 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 (!iswrite) {
if (name == NULL || fdp == NULL)
return (LOCK_FAILED);
if ((fd = open(name, O_RDWR, 0)) == -1)
return (LOCK_FAILED);
*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 || errno == EWOULDBLOCK ?
LOCK_UNAVAIL : LOCK_FAILED);
#endif
}