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Annotation of researchv10no/lbin/Mail/olock.c, revision 1.1.1.1

1.1       root        1: #include <stdio.h>
                      2: #include <sys/types.h>
                      3: #include <dir.h>
                      4: #include <sys/stat.h>          /* mjm <stat.h> --> <sys/stat.h> */
                      5: #include "string.h"
                      6: 
                      7: /* imports */
                      8: extern char *mktemp();
                      9: extern long time();
                     10: extern unsigned int sleep();
                     11: 
                     12: #define LOCKPREFIX "/tmp/L."
                     13: static char    lockname[DIRSIZ+sizeof(LOCKPREFIX)] = { 0 };
                     14: 
                     15: /* Lock the given file.  The parameter "file" must contain at least one '/'. */
                     16: extern void
                     17: lock(file)
                     18: char *file;
                     19: {
                     20: #      define TMPLNAME "/tmp/mlXXXXX"
                     21: #      define LOCKPREFIX "/tmp/L."
                     22:        char tmplname[sizeof(TMPLNAME)*2];
                     23:        struct stat stbuf;
                     24:        int fd;
                     25: 
                     26:        /* return if we are already in the middle of a lock */
                     27:        if (*lockname != '\0')
                     28:                return;
                     29: 
                     30:        /* create a temporary file */
                     31:        (void)strcpy(tmplname, TMPLNAME);
                     32:        (void)mktemp(tmplname);
                     33:        if ((fd=creat(tmplname, 0444))<0)
                     34:                return;
                     35:        close(fd);
                     36: 
                     37:        /* Make a link to it with the lock file name.  This will fail only
                     38:         * if it already exists.
                     39:         */
                     40:        (void)strcpy(lockname, LOCKPREFIX);
                     41:        (void)strcat(lockname, strrchr(file, '/')+1);
                     42:        lockname[DIRSIZ+sizeof("/tmp/")-1] = '\0';
                     43:        while (link(tmplname, lockname) < 0) {
                     44:                long now;
                     45: 
                     46:                /* File is already locked.  Break it if the lock is old. */
                     47:                sleep(2);
                     48:                now = time((long *)0);
                     49:                if (stat(lockname, &stbuf)==0 && stbuf.st_ctime+60 < now) {
                     50:                        if (stat(file, &stbuf)==0 && stbuf.st_mtime+60 >= now)
                     51:                                continue;
                     52:                        fprintf(stderr, "mail: breaking lock\n");
                     53:                        unlink(lockname);
                     54:                }
                     55:        }
                     56:        unlink(tmplname);
                     57:        return;
                     58: }
                     59: 
                     60: extern void
                     61: unlock()
                     62: {
                     63:        if (*lockname != '\0') {
                     64:                unlink(lockname);
                     65:                *lockname = '\0';
                     66:        }
                     67: }
                     68: 

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