2009-04-18 19:00:33 +02:00
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/* Copyright (C) 2009 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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2009-04-18 19:51:05 +02:00
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/*
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* helpers for module initialization/shutdown.
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2009-04-18 18:14:48 +02:00
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*/
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#include "precompiled.h"
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#include "module_init.h"
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#include "lib/sysdep/cpu.h" // cpu_CAS, cpu_AtomicAdd
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// notes:
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// - value must be 0 to allow users to just define uninitialized static
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// variables (they don't have access to our MODULE_* symbols)
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// - unlike expected in-game operation, the self-tests require repeated
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// sequences of init/shutdown pairs. we therefore allow this in general
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// (resetting back to MODULE_UNINITIALIZED after shutdown) because
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// there's no real disadvantage other than loss of strictness.
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static const ModuleInitState MODULE_UNINITIALIZED = 0u;
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// (1..N = reference count)
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static const ModuleInitState MODULE_ERROR = ~(uintptr_t)1u;
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bool ModuleShouldInitialize(volatile ModuleInitState* pInitState)
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{
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// currently uninitialized, so give the green light.
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if(cpu_CAS(pInitState, MODULE_UNINITIALIZED, 1))
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return true;
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// increment reference count - unless already in a final state.
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retry:
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ModuleInitState latchedInitState = *pInitState;
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if(latchedInitState == MODULE_ERROR)
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return false;
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if(!cpu_CAS(pInitState, latchedInitState, latchedInitState+1))
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goto retry;
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return false;
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}
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bool ModuleShouldShutdown(volatile ModuleInitState* pInitState)
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{
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// decrement reference count - unless already in a final state.
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retry:
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ModuleInitState latchedInitState = *pInitState;
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if(latchedInitState == MODULE_UNINITIALIZED || latchedInitState == MODULE_ERROR)
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return false;
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if(!cpu_CAS(pInitState, latchedInitState, latchedInitState-1))
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goto retry;
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// refcount reached zero => allow shutdown.
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if(latchedInitState-1 == MODULE_UNINITIALIZED)
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return true;
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return false;
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}
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void ModuleSetError(volatile ModuleInitState* pInitState)
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{
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*pInitState = MODULE_ERROR;
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}
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bool ModuleIsError(volatile ModuleInitState* pInitState)
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{
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return (*pInitState == MODULE_ERROR);
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}
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