os_id.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2001-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: os_id.c,v 12.15 2005/11/10 18:44:02 bostic Exp $
 */

#include "db_config.h"

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

#include <stdlib.h>
#endif

#include "db_int.h"
#include "dbinc/mutex_int.h"            /* Required to load appropriate
                                           header files for thread functions. */

/*
 * __os_id --
 *      Return the current process ID.
 *
 * PUBLIC: void __os_id __P((DB_ENV *, pid_t *, db_threadid_t*));
 */
void
__os_id(dbenv, pidp, tidp)
        DB_ENV *dbenv;
        pid_t *pidp;
        db_threadid_t *tidp;
{
        /*
         * We can't depend on dbenv not being NULL, this routine is called
         * from places where there's no DB_ENV handle.  It takes a DB_ENV
         * handle as an arg because it's the default DB_ENV->thread_id function.
         *
         * We cache the pid in the DB_ENV handle, it's a fairly slow call on
         * lots of systems.
         */
        if (pidp != NULL) {
                if (dbenv == NULL) {
#if defined(HAVE_VXWORKS)
                        *pidp = taskIdSelf();
#else
                        *pidp = getpid();
#endif
                } else
                        *pidp = dbenv->pid_cache;
        }

        if (tidp != NULL) {
#if defined(DB_WIN32)
                *tidp = GetCurrentThreadId();
#elif defined(HAVE_MUTEX_UI_THREADS)
                *tidp = thr_self();
#elif defined(HAVE_MUTEX_SOLARIS_LWP) || \
        defined(HAVE_MUTEX_PTHREADS) || defined(HAVE_PTHREAD_SELF)
                *tidp = pthread_self();
#else
                /*
                 * Default to just getpid.
                 */
                *tidp = 0;
#endif
        }
}

/*
 * __os_unique_id --
 *      Return a unique 32-bit value.
 *
 * PUBLIC: void __os_unique_id __P((DB_ENV *, u_int32_t *));
 */
void
__os_unique_id(dbenv, idp)
        DB_ENV *dbenv;
        u_int32_t *idp;
{
        static int first = 1;
        pid_t pid;
        db_threadid_t tid;
        u_int32_t id, sec, usec;

        *idp = 0;

        /*
         * Our randomized value is comprised of our process ID, the current
         * time of day and a couple of a stack addresses, all XOR'd together.
         */
        __os_id(dbenv, &pid, &tid);
        __os_clock(dbenv, &sec, &usec);

        id = (u_int32_t)pid ^ sec ^ usec ^ P_TO_UINT32(&pid);

        /*
         * We could try and find a reasonable random-number generator, but
         * that's not all that easy to do.  Seed and use srand()/rand(), if
         * we can find them.
         */
#if HAVE_SRAND
        if (first == 1)
                srand((u_int)id);
#endif
        first = 0;

#if HAVE_RAND
        id ^= (u_int)rand();
#endif

        *idp = id;
}

---