os_fid.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:4k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1996-2002
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: os_fid.c,v 11.14 2002/08/26 14:37:38 margo Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #include <sys/stat.h>
- #if TIME_WITH_SYS_TIME
- #include <sys/time.h>
- #include <time.h>
- #else
- #if HAVE_SYS_TIME_H
- #include <sys/time.h>
- #else
- #include <time.h>
- #endif
- #endif
- #include <stdlib.h>
- #include <string.h>
- #include <unistd.h>
- #endif
- #include "db_int.h"
- #define SERIAL_INIT 0
- static u_int32_t fid_serial = SERIAL_INIT;
- /*
- * __os_fileid --
- * Return a unique identifier for a file. The structure
- * of a fileid is: ino(4) dev(4) time(4) pid(4) extra(4).
- * For real files, which have a backing inode and device, the first
- * 16 bytes are filled in and the extra bytes are left 0. For
- * temporary files, the inode and device fields are left blank and
- * the extra four bytes are filled in with a random value.
- *
- * PUBLIC: int __os_fileid __P((DB_ENV *, const char *, int, u_int8_t *));
- */
- int
- __os_fileid(dbenv, fname, unique_okay, fidp)
- DB_ENV *dbenv;
- const char *fname;
- int unique_okay;
- u_int8_t *fidp;
- {
- struct stat sb;
- size_t i;
- int ret;
- u_int32_t tmp;
- u_int8_t *p;
- /* Clear the buffer. */
- memset(fidp, 0, DB_FILE_ID_LEN);
- /* On POSIX/UNIX, use a dev/inode pair. */
- retry:
- #ifdef HAVE_VXWORKS
- if (stat((char *)fname, &sb) != 0) {
- #else
- if (stat(fname, &sb) != 0) {
- #endif
- if ((ret = __os_get_errno()) == EINTR)
- goto retry;
- __db_err(dbenv, "%s: %s", fname, strerror(ret));
- return (ret);
- }
- /*
- * Initialize/increment the serial number we use to help avoid
- * fileid collisions. Note that we don't bother with locking;
- * it's unpleasant to do from down in here, and if we race on
- * this no real harm will be done, since the finished fileid
- * has so many other components.
- *
- * We increment by 100000 on each call as a simple way of
- * randomizing; simply incrementing seems potentially less useful
- * if pids are also simply incremented, since this is process-local
- * and we may be one of a set of processes starting up. 100000
- * pushes us out of pid space on most platforms, and has few
- * interesting properties in base 2.
- */
- if (fid_serial == SERIAL_INIT)
- __os_id(&fid_serial);
- else
- fid_serial += 100000;
- /*
- * !!!
- * Nothing is ever big enough -- on Sparc V9, st_ino, st_dev and the
- * time_t types are all 8 bytes. As DB_FILE_ID_LEN is only 20 bytes,
- * we convert to a (potentially) smaller fixed-size type and use it.
- *
- * We don't worry about byte sexing or the actual variable sizes.
- *
- * When this routine is called from the DB access methods, it's only
- * called once -- whatever ID is generated when a database is created
- * is stored in the database file's metadata, and that is what is
- * saved in the mpool region's information to uniquely identify the
- * file.
- *
- * When called from the mpool layer this routine will be called each
- * time a new thread of control wants to share the file, which makes
- * things tougher. As far as byte sexing goes, since the mpool region
- * lives on a single host, there's no issue of that -- the entire
- * region is byte sex dependent. As far as variable sizes go, we make
- * the simplifying assumption that 32-bit and 64-bit processes will
- * get the same 32-bit values if we truncate any returned 64-bit value
- * to a 32-bit value. When we're called from the mpool layer, though,
- * we need to be careful not to include anything that isn't
- * reproducible for a given file, such as the timestamp or serial
- * number.
- */
- tmp = (u_int32_t)sb.st_ino;
- for (p = (u_int8_t *)&tmp, i = sizeof(u_int32_t); i > 0; --i)
- *fidp++ = *p++;
- tmp = (u_int32_t)sb.st_dev;
- for (p = (u_int8_t *)&tmp, i = sizeof(u_int32_t); i > 0; --i)
- *fidp++ = *p++;
- if (unique_okay) {
- /*
- * We want the number of seconds, not the high-order 0 bits,
- * so convert the returned time_t to a (potentially) smaller
- * fixed-size type.
- */
- tmp = (u_int32_t)time(NULL);
- for (p = (u_int8_t *)&tmp, i = sizeof(u_int32_t); i > 0; --i)
- *fidp++ = *p++;
- for (p = (u_int8_t *)&fid_serial, i = sizeof(u_int32_t);
- i > 0; --i)
- *fidp++ = *p++;
- }
- return (0);
- }