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cb73e2bfac
should be decided on; it is kind of a toss-up to me personally. One method is slightly more complicated but the other uses a spin lock. See once.c for details.
111 lines
2.7 KiB
C
111 lines
2.7 KiB
C
/*
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* Copyright (C) 1999 Internet Software Consortium.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
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* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
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* CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
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* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
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* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
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* SOFTWARE.
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*/
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/* $Id: once.c,v 1.1 1999/09/23 18:14:16 tale Exp $ */
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/* Principal Authors: DCL */
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#ifdef ISC_ONCE_USE_MUTEX
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#include <stdio.h>
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#include <process.h>
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#endif
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#include <windows.h>
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#include <isc/once.h>
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#include <isc/assertions.h>
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#ifdef ISC_ONCE_USE_MUTEX
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/*
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* XXXDCL someone (me? bob?) should decide which method to use,
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* the mutex method or the InterlockedDecrement method.
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*/
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isc_result_t
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isc_once_do(isc_once_t *controller, void(*function)(void))
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{
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char mutex_name[64];
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HANDLE mutex;
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REQUIRE(controller != NULL && function != NULL);
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if (controller->status == ISC_ONCE_INIT_NEEDED) {
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/*
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* Create a name that is associated only with this process
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* and controller.
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*/
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sprintf(mutex_name, "__isc_once_do_%ld:%p",
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getpid(), controller);
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/*
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* Create the mutex (or attach to the existing mutex)
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* and lock it.
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*/
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mutex = CreateMutex(NULL, FALSE, mutex_name);
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if (mutex == NULL)
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return (ISC_R_UNEXPECTED);
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if (WaitForSingleObject(mutex, INFINITE) == WAIT_FAILED)
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return (ISC_R_UNEXPECTED);
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/*
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* Recheck need for initialization now that
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* the controller is locked.
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*/
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if (controller->status == ISC_ONCE_INIT_NEEDED) {
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function();
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controller->status = ISC_ONCE_INIT_DONE;
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}
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ReleaseMutex(mutex);
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CloseHandle(mutex);
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}
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return (ISC_R_SUCCESS);
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}
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#else /* not ISC_ONCE_USE_MUTEX, use InterlockedDecrement instead */
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isc_result_t
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isc_once_do(isc_once_t *controller, void(*function)(void))
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{
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REQUIRE(controller != NULL && function != NULL);
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if (controller->status == ISC_ONCE_INIT_NEEDED) {
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if (InterlockedDecrement(&controller->counter) == 0) {
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if (controller->status == ISC_ONCE_INIT_NEEDED) {
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function();
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controller->status = ISC_ONCE_INIT_DONE;
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}
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} else {
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while (controller->status == ISC_ONCE_INIT_NEEDED) {
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/*
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* Spin wait.
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*/
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}
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}
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}
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return (ISC_R_SUCCESS);
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}
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#endif /* ISC_ONCE_USE_MUTEX */
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