db2/os/os_fid.c

   1 /*-
   2  * See the file LICENSE for redistribution information.
   3  *
   4  * Copyright (c) 1996, 1997, 1998
   5  *      Sleepycat Software.  All rights reserved.
   6  */
   7
   8 #include "config.h"
   9
  10 #ifndef lint
  11 static const char sccsid[] = "@(#)os_fid.c      10.11 (Sleepycat) 4/26/98";
  12 #endif /* not lint */
  13
  14 #ifndef NO_SYSTEM_INCLUDES
  15 #include <sys/types.h>
  16 #include <sys/stat.h>
  17
  18 #include <errno.h>
  19 #include <string.h>
  20 #include <time.h>
  21 #endif
  22
  23 #include "db_int.h"
  24 #include "common_ext.h"
  25
  26 /*
  27  * __db_fileid --
  28  *      Return a unique identifier for a file.
  29  *
  30  * PUBLIC: int __db_fileid __P((DB_ENV *, const char *, int, u_int8_t *));
  31  */
  32 int
  33 __db_fileid(dbenv, fname, timestamp, fidp)
  34         DB_ENV *dbenv;
  35         const char *fname;
  36         int timestamp;
  37         u_int8_t *fidp;
  38 {
  39         struct stat sb;
  40         size_t i;
  41         time_t now;
  42         u_int8_t *p;
  43
  44         /* Clear the buffer. */
  45         memset(fidp, 0, DB_FILE_ID_LEN);
  46
  47         /* Check for the unthinkable. */
  48         if (sizeof(sb.st_ino) +
  49             sizeof(sb.st_dev) + sizeof(time_t) > DB_FILE_ID_LEN)
  50                 return (EINVAL);
  51
  52         /* On UNIX, use a dev/inode pair. */
  53         if (stat(fname, &sb)) {
  54                 __db_err(dbenv, "%s: %s", fname, strerror(errno));
  55                 return (errno);
  56         }
  57
  58         /*
  59          * Use the inode first and in reverse order, hopefully putting the
  60          * distinguishing information early in the string.
  61          */
  62         for (p = (u_int8_t *)&sb.st_ino +
  63             sizeof(sb.st_ino), i = 0; i < sizeof(sb.st_ino); ++i)
  64                 *fidp++ = *--p;
  65         for (p = (u_int8_t *)&sb.st_dev +
  66             sizeof(sb.st_dev), i = 0; i < sizeof(sb.st_dev); ++i)
  67                 *fidp++ = *--p;
  68
  69         if (timestamp) {
  70                 (void)time(&now);
  71                 for (p = (u_int8_t *)&now +
  72                     sizeof(now), i = 0; i < sizeof(now); ++i)
  73                         *fidp++ = *--p;
  74         }
  75         return (0);
  76 }