os_seek.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1997-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: os_seek.c,v 12.2 2005/08/10 15:47:27 bostic Exp $
 */

#include "db_config.h"

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

#include <stdlib.h>
#include <string.h>
#endif

#include "db_int.h"

/*
 * __os_seek --
 *      Seek to a page/byte offset in the file.
 *
 * PUBLIC: int __os_seek __P((DB_ENV *,
 * PUBLIC:      DB_FH *, u_int32_t, db_pgno_t, u_int32_t, int, DB_OS_SEEK));
 */
int
__os_seek(dbenv, fhp, pgsize, pageno, relative, isrewind, db_whence)
        DB_ENV *dbenv;
        DB_FH *fhp;
        u_int32_t pgsize;
        db_pgno_t pageno;
        u_int32_t relative;
        int isrewind;
        DB_OS_SEEK db_whence;
{
        off_t offset;
        int ret, whence;

        /* Check for illegal usage. */
        DB_ASSERT(F_ISSET(fhp, DB_FH_OPENED) && fhp->fd != -1);

        switch (db_whence) {
        case DB_OS_SEEK_CUR:
                whence = SEEK_CUR;
                break;
        case DB_OS_SEEK_END:
                whence = SEEK_END;
                break;
        case DB_OS_SEEK_SET:
                whence = SEEK_SET;
                break;
        default:
                return (EINVAL);
        }

        offset = (off_t)pgsize * pageno + relative;
        if (isrewind)
                offset = -offset;

        if (DB_GLOBAL(j_seek) != NULL)
                ret = DB_GLOBAL(j_seek)(fhp->fd, offset, whence);
        else
                RETRY_CHK((lseek(fhp->fd, offset, whence) == -1 ? 1 : 0), ret);

        if (ret == 0) {
                fhp->pgsize = pgsize;
                fhp->pgno = pageno;
                fhp->offset = relative;
        } else
                __db_err(dbenv, "seek: %lu %d %d: %s",
                    (u_long)pgsize * pageno + relative,
                    isrewind, db_whence, strerror(ret));

        return (ret);
}

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