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Diffstat (limited to 'storage/bdb/os/os_fid.c')
| -rw-r--r-- | storage/bdb/os/os_fid.c | 148 |
1 files changed, 148 insertions, 0 deletions
diff --git a/storage/bdb/os/os_fid.c b/storage/bdb/os/os_fid.c new file mode 100644 index 00000000000..125e6f0712c --- /dev/null +++ b/storage/bdb/os/os_fid.c @@ -0,0 +1,148 @@ +/*- + * 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); +} |