InfoMagic Internet Tools 1993 July/Internet Tools.iso/RockRidge/mail/mush-7.1.1/lock.c

C/C++ Source or Header | 1990-05-02 | 4.5 KB | 225 lines

/*
 * lock.c -- deal with file locking on various architectures and UNIXs.
 * dot_lock() creates a file with the same name as the parameter passed
 * with the appendage ".lock" -- this is to be compatible with certain
 * systems that don't use flock or lockf or whatever they have available
 * that they don't use.
 */

#ifdef USG
#include <unistd.h>
#endif /* USG */
#include "mush.h"
#if defined(SYSV) && !defined(USG)
#include <sys/locking.h>
#endif /* SYSV && !USG */

#ifdef DOT_LOCK
extern int sgid;
#ifdef BSD
extern int rgid;
#endif /* BSD */

dot_lock(filename)
char *filename;
{
    char buf[MAXPATHLEN];
    int lockfd, cnt = 0;
    SIGRET (*oldint)(), (*oldquit)();

#ifdef SYSV
    /* Only the spoolfile needs to be dot_locked -- other files are
     * handled by lock_fopen, below.  To avoid collisions with 14-char
     * file name limits, we allow dot_locking ONLY of the spoolfile.
     */
    if (strcmp(spoolfile, filename) != 0)
    return 0;
#endif
#ifdef BSD
    setregid(rgid, sgid);
#else /* BSD */
    setgid(sgid);
#endif /* BSD */
#ifdef M_XENIX
    (void) sprintf(buf, "/tmp/%.10s.mlk", login);
#else /* M_XENIX */
    (void) sprintf(buf, "%s.lock", filename);
#endif /* M_XENIX */
    on_intr();
    while ((lockfd = open(buf, O_CREAT|O_WRONLY|O_EXCL, 0444)) == -1) {
    if (errno != EEXIST) {
        error("unable to lock %s", filename);
        break;
    }
    if (cnt++ == 0)
        print("%s already locked, waiting", filename);
    else
        print_more(".");
    sleep(1);
    if (ison(glob_flags, WAS_INTR)) {
        print_more("\nAborted.\n");
        break;
    }
    }
    off_intr();
    if (lockfd != -1) {
    if (cnt)
        print("done.\n");
    (void) close(lockfd);
    }
#ifdef BSD
    setregid(sgid, rgid);
#else
    setgid(getgid());
#endif /* BSD */
    return lockfd == -1? -1 : 0;
}
#endif /* DOT_LOCK */

#ifdef SYSV

/*
 * Define some BSD names for the SYSV world
 */
#ifdef USG
#define LOCK_SH F_RDLCK
#define LOCK_EX F_WRLCK
#define LOCK_UN F_UNLCK
#else /* USG */
#define LOCK_SH LK_LOCK
#define LOCK_EX LK_LOCK
#define LOCK_UN LK_UNLCK
#endif /* USG */
#define LOCK_NB 0    /* Always non-blocking in this case */

#ifdef HPUX
#undef EWOULDBLOCK
#endif /* HPUX */
#define EWOULDBLOCK    EAGAIN

flock(fd, op)
int fd, op;
{
#ifndef USG
    (void) locking(fd, op, 0); /* old xenix (sys III) */
    return 0;
#else
    struct flock l;

    l.l_len = 0L;
    l.l_start = 0L;
    l.l_whence = 1;
    l.l_type = op;

    return fcntl(fd, F_SETLK, &l);
#endif /* USG */
}

#endif /* SYSV */

FILE *
lock_fopen(filename, mode)
char *filename;
char *mode;
{
    FILE *mail_fp = NULL_FILE;
#ifndef LCKDFLDIR
    int fd, lk;
    int cnt = 0;
    SIGRET (*oldint)(), (*oldquit)();
#else /* LCKDFLDIR */
    extern FILE *lk_fopen();
#endif /* !LCKDFLDIR */

    if (debug && do_set(set_options, "deadlock")) {
    (void) un_set(&set_options, "deadlock");
    return NULL_FILE;
    }

#ifdef LCKDFLDIR
    return lk_fopen(filename, mode, NULL, NULL, 0);
#else /* !LCKDFLDIR */

#ifdef DOT_LOCK
    if (dot_lock(filename) == 0)
#endif /* DOT_LOCK */
    mail_fp = mask_fopen(filename, mode);
    if (!mail_fp)
    return NULL_FILE;
    fd = fileno(mail_fp);

    if (mode[0] != 'r' || mode[1] == '+')
    lk = LOCK_EX | LOCK_NB;
    else
    lk = LOCK_SH | LOCK_NB;

    on_intr();
    while (isoff(glob_flags, WAS_INTR) && flock(fd, lk)) {
    if (errno == EWOULDBLOCK) {
        if (isoff(glob_flags, REDIRECT))
        if (!cnt++)
            print("\nwaiting to lock");
        else
            print(".");
    } else {
        error("Unable to lock \"%s\"", filename);
        (void) fclose(mail_fp);
        off_intr();
        return NULL_FILE;
    }
    (void) fflush(stdout);
    sleep(1);
    }
    if (cnt)
    print("\n");
    cnt = (ison(glob_flags, WAS_INTR) != 0);
    off_intr();
    if (cnt) {
    (void) fclose(mail_fp);
    return NULL_FILE;
    }
    return mail_fp;
#endif /* LCKDFLDIR */
}

/*ARGSUSED*/
close_lock(filename, fp)
char *filename;
FILE *fp;
#ifdef LCKDFLDIR
{
    return lk_fclose(fp, filename, NULL, NULL);
}
#else /* !LCKDFLDIR */
{
#ifdef DOT_LOCK
    char buf[MAXPATHLEN];
#endif /* DOT_LOCK */

    fflush(fp);
#ifdef DOT_LOCK
#ifdef BSD
    setregid(rgid, sgid);
#else
    setgid(sgid);
#endif /* BSD */
#ifdef SYSV
    if (strcmp(spoolfile, filename) == 0)
#endif /* SYSV */
#ifdef M_XENIX
    (void) unlink(sprintf(buf, "/tmp/%.10s.mlk", login));
#else /* M_XENIX */
    (void) unlink(sprintf(buf, "%s.lock", filename));
#endif /* M_XENIX */
#ifdef BSD
    setregid(sgid, rgid);
#else
    setgid(getgid());
#endif /* BSD */
#endif /* DOT_LOCK */

    (void) flock(fileno(fp), LOCK_UN);
    return fclose(fp);
}
#endif /* LCKDFLDIR */