isc/win32/once.c

	once.c revision cb73e2bfacb60eed27a3e4940f6dbe0c0580fc18
/*
 * Copyright (C) 1999  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

/* $Id: once.c,v 1.1 1999/09/23 18:14:16 tale Exp $ */

/* Principal Authors: DCL */

#ifdef ISC_ONCE_USE_MUTEX
#include <stdio.h>
#include <process.h>
#endif

#include <windows.h>

#include <isc/once.h>
#include <isc/assertions.h>

#ifdef ISC_ONCE_USE_MUTEX

/*
 * XXXDCL someone (me? bob?) should decide which method to use,
 * the mutex method or the InterlockedDecrement method.
 */

isc_result_t
isc_once_do(isc_once_t *controller, void(*function)(void))

{
    char mutex_name[64];
    HANDLE mutex;

    REQUIRE(controller != NULL && function != NULL);

    if (controller->status == ISC_ONCE_INIT_NEEDED) {

        /*
         * Create a name that is associated only with this process
         * and controller.
         */
        sprintf(mutex_name, "__isc_once_do_%ld:%p",
            getpid(), controller);

        /*
         * Create the mutex (or attach to the existing mutex)
         * and lock it.
         */
        mutex = CreateMutex(NULL, FALSE, mutex_name);
        if (mutex == NULL)
            return (ISC_R_UNEXPECTED);
        if (WaitForSingleObject(mutex, INFINITE) == WAIT_FAILED)
            return (ISC_R_UNEXPECTED);

        /*
         * Recheck need for initialization now that
         * the controller is locked.
         */
        if (controller->status == ISC_ONCE_INIT_NEEDED) {
            function();
            controller->status = ISC_ONCE_INIT_DONE;
        }

        ReleaseMutex(mutex);
        CloseHandle(mutex);
    }

    return (ISC_R_SUCCESS);
}

#else /* not ISC_ONCE_USE_MUTEX, use InterlockedDecrement instead */

isc_result_t
isc_once_do(isc_once_t *controller, void(*function)(void))

{
    REQUIRE(controller != NULL && function != NULL);

    if (controller->status == ISC_ONCE_INIT_NEEDED) {

        if (InterlockedDecrement(&controller->counter) == 0) {
            if (controller->status == ISC_ONCE_INIT_NEEDED) {
                function();
                controller->status = ISC_ONCE_INIT_DONE;
            }
        } else {
            while (controller->status == ISC_ONCE_INIT_NEEDED) {
                /*
                 * Spin wait.
                 */
            }
        }
    }

    return (ISC_R_SUCCESS);
}

#endif /* ISC_ONCE_USE_MUTEX */