Programmer 7500/MAX_PROGRAMMERS.iso/INFO/EDITOR/ME39SRC2.ZIP/DOLOCK.C

C/C++ Source or Header | 1987-07-07 | 4.5 KB | 222 lines

#if    0
/*    dolock:    MDBS specific Unix 4.2BSD file locking mechinism
        this is not to be distributed generally        */

#include    <mdbs.h>
#include    <mdbsio.h>
#include    <sys/types.h>
#include    <sys/stat.h>

/* included by port.h: mdbs.h, mdbsio.h, sys/types.h, sys/stat.h */


#ifndef bsdunix
char *dolock(){return(NULL);}
char *undolock(){return(NULL);}
#else

#include <pwd.h>
#include <errno.h>

extern int errno;

#define LOCKDIR ".xlk"

#define LOCKMSG "LOCK ERROR -- "
#define LOCKMSZ sizeof(LOCKMSG)
#define LOCKERR(s) { strcat(lmsg,s); oldumask = umask(oldumask); return(lmsg); }

/**********************
 *
 * dolock -- lock the file fname
 *
 * if successful, returns NULL
 * if file locked, returns username of person locking the file
 * if other error, returns "LOCK ERROR: explanation"
 *
 * Jon Reid, 2/19/86
 *
 *********************/

BOOL parent = FALSE;
BOOL tellall = FALSE;

char *gtname(filespec)        /* get name component of unix-style filespec */
char *filespec;
{
    char *rname, *rindex();

    rname = rindex(filespec,'/');

    if (rname != NULL)
        return(rname);
    else
        return(filespec);
}

char *getpath(filespec)
char *filespec;
{
    char rbuff[LFILEN];
    char *rname, *rindex();

    strcpy(rbuff,filespec);
    rname = rindex(rbuff,'/');

    if (rname == NULL)
        return(NULL);
    else
    {
        *(++rname) = '\0';
        return(rbuff);
    }

}

char *dolock(fname)
    char *fname;
{
    static char lockname[LFILEN] = LOCKDIR;
    static char username[12];
    static char lmsg[40] = LOCKMSG;
    char *pathfmt;
    struct stat statblk;
    struct passwd *pblk;
    long pid, getpid();
    FILE *lf, *fopen();
    int oldumask;

    oldumask = umask(0);    /* maximum access allowed to lock files */


      if (*fname != '/')
       pathfmt = "./%s%s";
      else
       pathfmt = "%s/%s";
      sprintf(lockname,pathfmt,getpath(fname), LOCKDIR);

      if (tellall) printf("checking for existence of %s\n",lockname);

      if (stat(lockname,&statblk))
      {
         if (tellall) printf("making directory %s\n",lockname);
         mkdir(lockname,0777);
      }

      sprintf(lockname,"%s/%s",lockname,gtname(fname));

      if (tellall) printf("checking for existence of %s\n",lockname);

      if (stat(lockname,&statblk))
      {
makelock:      if (tellall) printf("creating %s\n",lockname);

        if ((lf = fopen(lockname,FOP_TW)) == NULL)
          LOCKERR("could not create lock file")
            else
          {
            if (parent)
             pid = getppid();    /* parent pid */
            else
             pid = getpid();    /* current pid */

             if (tellall)
              printf("pid is %ld\n",pid);

             fprintf(lf,"%ld",pid); /* write pid to lock file */

            fclose(lf);
            oldumask = umask(oldumask);
            return(NULL);
        }
      }
      else
      {
        if (tellall) printf("reading lock file %s\n",lockname);
        if ((lf = fopen(lockname,FOP_TR)) == NULL)
          LOCKERR("could not read lock file")
            else
          {
            fscanf(lf,"%ld",&pid); /* contains current pid */
            fclose(lf);
            if (tellall)
             printf("pid in %s is %ld\n",lockname, pid);
            if (tellall)
             printf("signaling process %ld\n", pid);
            if (kill(pid,0))
                switch (errno)
                {
                  case ESRCH:    /* process not found */
                        goto makelock;
                        break;
                  case EPERM:    /* process exists, not yours */
                         if (tellall)
                         puts("process exists");
                        break;
                  default:
                    LOCKERR("kill was bad")
                    break;
                }
            else
             if (tellall) puts("kill was good; process exists");
        }
        if ((pblk = getpwuid(statblk.st_uid)) == NULL)
          sprintf(username,"uid %d",atoi(statblk.st_uid));
        else
          strcpy(username,pblk->pw_name);

        oldumask = umask(oldumask);
        return(username);
      }
}

/**********************
 *
 * undolock -- unlock the file fname
 *
 * if successful, returns NULL
 * if other error, returns "LOCK ERROR: explanation"
 *
 * Jon Reid, 2/19/86
 *
 *********************/

char *undolock(fname)
    char *fname;
{
    static char lockname[LFILEN] = LOCKDIR;
    static char lmsg[40] = LOCKMSG;
    char *pathfmt;

      if (*fname != '/')
       pathfmt = "./%s%s";
      else
       pathfmt = "%s/%s";
      sprintf(lockname,pathfmt,getpath(fname), LOCKDIR);

      sprintf(lockname,"%s/%s",lockname,gtname(fname));

      if (tellall) printf("attempting to unlink %s\n",lockname);

      if (unlink(lockname))
      {
        strcat(lmsg,"could not remove lock file");
        return(lmsg);
      }
      else
            return(NULL);
}

#endif

/******************
 * end dolock module
 *******************/

#else
dolhello()
{
}
#endif