/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *      Sleepycat Software.  All rights reserved.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)os_fid.c      10.12 (Sleepycat) 7/21/98";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <sys/stat.h>

#include <errno.h>
#include <string.h>
#include <time.h>
#endif

#include "db_int.h"
#include "common_ext.h"

/*
 * __os_fileid --
 *      Return a unique identifier for a file.
 *
 * PUBLIC: int __os_fileid __P((DB_ENV *, const char *, int, u_int8_t *));
 */
int
__os_fileid(dbenv, fname, timestamp, fidp)
        DB_ENV *dbenv;
        const char *fname;
        int timestamp;
        u_int8_t *fidp;
{
        struct stat sb;
        size_t i;
        time_t now;
        u_int8_t *p;

        /* Clear the buffer. */
        memset(fidp, 0, DB_FILE_ID_LEN);

        /* Check for the unthinkable. */
        if (sizeof(sb.st_ino) +
            sizeof(sb.st_dev) + sizeof(time_t) > DB_FILE_ID_LEN)
                return (EINVAL);

        /* On UNIX, use a dev/inode pair. */
        if (stat(fname, &sb)) {
                __db_err(dbenv, "%s: %s", fname, strerror(errno));
                return (errno);
        }

        /*
         * Use the inode first and in reverse order, hopefully putting the
         * distinguishing information early in the string.
         */
        for (p = (u_int8_t *)&sb.st_ino +
            sizeof(sb.st_ino), i = 0; i < sizeof(sb.st_ino); ++i)
                *fidp++ = *--p;
        for (p = (u_int8_t *)&sb.st_dev +
            sizeof(sb.st_dev), i = 0; i < sizeof(sb.st_dev); ++i)
                *fidp++ = *--p;

        if (timestamp) {
                (void)time(&now);
                for (p = (u_int8_t *)&now +
                    sizeof(now), i = 0; i < sizeof(now); ++i)
                        *fidp++ = *--p;
        }
        return (0);
}