module_init.cpp

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/* Copyright (c) 2010 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * helpers for module initialization/shutdown.
 */

#include "precompiled.h"
#include "lib/module_init.h"

#include "lib/sysdep/cpu.h" // cpu_CAS

// not yet initialized, or already shutdown
static const ModuleInitState UNINITIALIZED = 0; // value documented in header
// running user callback - concurrent ModuleInit callers must spin
static const ModuleInitState BUSY = ERR::AGAIN; // never returned
// init succeeded; allow shutdown
static const ModuleInitState INITIALIZED = INFO::SKIPPED;


Status ModuleInit(volatile ModuleInitState* initState, Status (*init)())
{
    for(;;)
    {
        if(cpu_CAS(initState, UNINITIALIZED, BUSY))
        {
            Status ret = init();
            *initState = (ret == INFO::OK)? INITIALIZED : ret;
            COMPILER_FENCE;
            return ret;
        }

        const ModuleInitState latchedInitState = *initState;
        if(latchedInitState == UNINITIALIZED || latchedInitState == BUSY)
        {
            cpu_Pause();
            continue;
        }

        ENSURE(latchedInitState == INITIALIZED || latchedInitState < 0);
        return (Status)latchedInitState;
    }
}


Status ModuleShutdown(volatile ModuleInitState* initState, void (*shutdown)())
{
    for(;;)
    {
        if(cpu_CAS(initState, INITIALIZED, BUSY))
        {
            shutdown();
            *initState = UNINITIALIZED;
            COMPILER_FENCE;
            return INFO::OK;
        }

        const ModuleInitState latchedInitState = *initState;
        if(latchedInitState == INITIALIZED || latchedInitState == BUSY)
        {
            cpu_Pause();
            continue;
        }

        if(latchedInitState == UNINITIALIZED)
            return INFO::SKIPPED;

        ENSURE(latchedInitState < 0);
        return (Status)latchedInitState;
    }
}